Evaluation of underutilized Ethiopian potato (Plectranthus edulis (Vatke) Agnew) accessions in Oromia regional state, central Ethiopia

Abstract

Ethiopian potato (P. edulis) is an endemic tuber crop species, which belongs to the Lamiaceae family, locally known as Ethiopian potato as the common name, and Oromo Dinch as a vernacular name in the Oromia region. The study aimed to evaluate P. edulis accessions to identify better physical adaptability potential and high yielding in the central highland of Ethiopia. Twenty promising P. edulis accessions were planted in a 3.5 m × 3 m plot area by using a randomized complete block design (RCBD) with three replication. In the present study, the measured agronomic parameters of individual accession were varied in the range of plant height (59.10–95.12 cm), number of stems per hill (2.24–4.73), stem girth (2.0–3.25 cm), number of node per plant (18.13–26.16), stem internode length (2.95–4.26 cm), number of branch/plant (13.53–23.94), leaf length (8.5–12.89 cm), leaf width (2.3–3.70 cm), leaf area (20.15–47.12 cm²), days to flower initiation (110.20–158.40), days to flowering (124.30–168.60), flower length (9.50–18.24 cm), number of tuber/hill (28.40–143.26), tuber diameter (13.57–22.38 cm), tuber length (13.18–17.39 cm), tuber weight/hill (0.30–1.64 kg), tuber yield (9.94–54.69 tonne/ha), and marketable tuber weight (9.49–54.4 tonne/ha) were recorded. From this study, eight accessions: PE001, PE003, PE005, PE006, E007, PE009, PE010, and PE011 were identified as those that revealed better physical adaptation and produced the highest tuber yields (>40 tonne/ha), and the highest marketable tuber yield (>40 tonne/ha). Therefore, these accessions are suggested for production and scale-up by producers in the central highland of Ethiopia, and other similar areas of agroecological zones.

1. Introduction

The larger part of the Ethiopian population depends generally on cereal crops as a food source. The food capacity of root and tuber crops has not still been fully exploited and used despite their important contributions toward food security, financial source improvement, delivery of food energy, and asset base conservation [1]. The low agrarian productivity, recurrent drought, and socio-political factors have importantly contributed to critical food scarcities in Ethiopia mainly because of the over-dependence on limited cereal crops without integration of root and tuber crops into the food system [2,3]. Generally, root and tuber crops are an underutilized species of food crops that are grown as homestead/home gardens which are usually produced and taken care of by women farmers in Ethiopia [4,5].

Plectranthus edulis is an endemic tuber crop species of Ethiopia, which belongs to the Lamiaceae family, locally known as Ethiopian potato as the common name, and Oromo Dinch as a vernacular name in the Oromia region. Ethiopian potato (Plectranthus edulis) is an old Ethiopian tuber crop cultivated in mid and high-altitude regions in the north, south, and west parts of Ethiopia. The genus Plectranthus encompasses over 350 non-tuber and tuber-bearing species that develop predominantly in Africa, Asia, and Australia [5]. Plectranthus edulis is native to Ethiopia and known by different local names depending on the place of cultivation such as Oromo potato in Oromia, Gurage potato in the Gurage zone, Agew potato in Awi zone, and Wolaita potato in Wolaita zone [2,6]. The crop is widely grown in the South and Southwestern parts of the country [3]. Plectranthus edulis is a native annual tuber crop cultivated widely in the central, southern, western, northwestern, and southwestern areas of Ethiopia [2,7]. The Plectranthus edulis plant produced main stems and primary, secondary, and tertiary branches, and their leaves constituted the main part of the canopy. Plant components are the seed tuber pieces, sprouts, main stems, branches, leaves, flowers, fruits, seeds, roots, stolons, and tubers [3,8].

The Plectranthus edulis plants grown or propagated mainly from the edible tuber pieces were ascending, herbaceous, and bushy with the highest height of 1.50 m length. Plectranthus edulis produces tubers on stolons initiating from the stems [3,9]. Stolons were formed on main stems and primary branches and initiated below ground or above ground (aerial stolons). Aerial stolons originated later than below-ground stolons and were much longer (up to 2.5 m). Tubers usually were produced as a swelling on the tip of the stolon and sometimes as a swelling of the middle part of the stolons. Tubers were stem tubers with pairs of ‘‘eyes’’ being arranged in the same pattern as the axillary buds on stolons and stem [3]. Plectranthus edulis is cultivated primarily for its tubers and is consumed after cooking [8]. To some extent, also, the leaves are used as a cooked vegetable in some western Ethiopian regions [8,6]. The raw tuber is rich in carbohydrate energy. The boiled tuber has a slightly higher carbohydrate concentration than the Irish potato, but both have comparable low protein and fat concentrations. The leaves of P. edulis are frequently used as medicines to treat a range of ailments, particularly skin, infectious and respiratory problems, and digestive problems [8].

Practices of agronomy and utilization of Plectranthus edulis have been passed from the past generation to the current generation through oral tradition with very slight recorded information. Due to the lower care given to the research and development of Plectranthus edulis, there is no variety up to now developed and released. Traditional selection practices are existence followed by local producers to grow Plectranthus edulis types of desirable better yields and local adaptation performance based on a specific agroecology concern a larger tuber size [2,6]. Beyond the old-style experience, there is limited scientific information access on the selection of more yielders in quantity & quality, and better adaptive performance of Plectranthus edulis accessions in a region leads to limiting further scaling up progress in production yields intensively and extensively (area expansion). The objective study was conducted to collect and evaluate the underutilized crop species of Ethiopian potato (Plectranthus edulis) accessions to identify better physical adaptability potential and high-yielding accession (s) in the west Shewa zone, central highland of Ethiopia.

2. Materials and methods

2.1. Description of the study area

2.1.1. Location

The research was conducted in the west Shewa zone, Oromia regional state, central Ethiopia, which zone is located at 8°57′N latitude and 38°07′E longitude and with elevation ranges between 1380 and 3300 m.a.s.l. Fig. [1(A-B)] shows the map of Ethiopia.

Fig. 1.

Images represent: (A) Map of Ethiopia with Administrative Regions & Zones, and (B) Map of West Shewa with Administrative Districts.

The study was conducted at Ambo University Guder Mammo Mezemir Campus research center, in the Toke Kutaye district of the West Shewa zone; Fig. [1(B)]. The district is located about 126 km away from Addis Ababa to the western and 12 km away from the perspective Zone Town of Ambo [10]. Specifically, Toke Kutaye district is located at 37° 26‟ 0‟’ to 37° 57‟30‟ E longitude and 8° 49‟0‟ to 9°5‟30‟ N latitude with an elevation of 1580–3190 m. a. s. l [11].

2.1.2. Climate

The Agroecology of the district covers 23% high land, 60% mid-highland, and 17% low land. The area obtains the maximum rainfall during the rainy period between June and September and followed by March and April Months in every year. Generally, the area has bimodal rainfall patterns, but it has one separate crop growing season (main season). The annual mean maximum and minimum rainfalls are 1900 mm and 600 mm, respectively. The mean minimum and maximum air temperatures of the area are 11.7 °C and 27.4°, respectively [12].

2.2. Materials used in the experiment

The materials used for Ethiopian Potato (Plectranthus edulis) accessions growth, yield, and yield component performance evaluation of the collected accessions in west Shewa Zone agroecological conditions. For the present study, a total of 20 Ethiopian Potato (Plectranthus edulis) accessions were collected from different provenance sites in the country by the Institute of Biodiversity Conservation (Table 1). The research was conducted for three consecutive main rain-fed cropping seasons 2018–2020 between April and October Months. The accessions were planted at the ambo university Guder Mamo Mezemir Campus on-farm research site.

Table 1.

Twenty (20) Ethiopian Potato (Plectranthus edulis) accessions materials used and their area of collections.

S/n	Acc. Number	Collection Region	Zone	Woreda	Kebele	M.a.s.l	UTM
						Altitude (m)	Lat	Long
1	PE001	Oromia	S.W.Shewa	Goro	Gambela Goro	1835	374792	927865
2	PE003	Oromia	S.W.Shewa	Woliso	Foduna Gora	1972	386105	940381
3	PE005	Oromia	East Wollega	Limmu	Warso	2156	222300	1089267
4	PE006	Oromia	East Wollega	Kiramu	Babo	2172	266764	1103908
5	PE007	SNNP	Gurage	Endegagn	Shawura	2261	371729	867217
6	PE009	SNNP	Gurage	Gumer	Isenina Dangeso	2863	395550	879979
7	PE010	SNNP	Hadiya	Lemo	Jawe	2121	365839	830439
8	PE011	SNNP	Hadiya	Sesh Duna	Sesh Duna	2195	370720	832265
9	PE012	SNNP	K. Tembaro	Doyu Gena	Wagebeta Eba	2293	363184	813164
10	PE013	Oromiya	Ilu Aba Bora	Alle	Yubo Mari	1794	781347	900009
11	PE014	Oromia	Ilu Aba Bora	Darimu	Wale	1650	775026	943622
12	PE015	Oromia	Ilu Aba Bora	Kumbabe	Guji	1923	183276	927973
13	PE016	Oromia	Ilu Aba Bora	Didessa	Yembero	2096	219193	900059
14	PE017	Oromia	West Shewa	Dandi	Golole Bolo	2469	390882	991969
15	PE018	Oromia	Jimma	Gera	Gure Ganji	1975	197673	855091
16	PE019	Oromia	Jimma	Goma	Andode Mari	1848	240990	875481
17	PE020	Oromia	Jimma	Sokoru	Yero Sokru	1719	262234	846752
18	PE022	Oromia	West Shewa	Cheliya	Ale Hula Dabi	2924	324020	1007305
19	PE024	Oromia	West Shewa	TokeKutaye	Toke Kombolcha	2249	340335	990271
20	PE025	Oromia	Jimma	Goma	Balto	1605	234630	870448

Source: Institute of Biodiversity Conservation (2017)

2.3. Treatment and experimental design

The adaptation trial research design was focused on the evaluation of Ethiopian Potato (Plectranthus edulis) accessions adaptation performance and yield production. The field experimental design was arranged in a randomized complete block design (RCBD) with three replications (i.e. 20 accessions x 3 replications = 60 treatment combinations plots).

2.4. Experimental procedures

The experimental site area was cleared and plowed using oxen according to local farmers’ practice to a depth of about 25–30 cm and the plot was leveled off manually before planting. The entire field was divided into three replication blocks, each of which included twenty (20) different accession plots. The plot size was fixed at 3.5 m long and 3 m in width (i.e. 3.5 m × 3 m = 10.5 m² plot size). The individual plot consists of six rows and 6 plants per row (i.e. 6 rows × 6 plants/row = 36 plants/plot). The tubers were planted with a spacing of 60 cm between rows, and 50 cm between plants. The spacing distance between adjacent plots and blocks was 1 m and 1.5 m, respectively.

Tubers that had just started sprouting were used as planting material. Planting was done at the beginning of the rainy season (April) in well-drained, loose soil on flat ground. Tubers were used as planting material for all accessions. In the designed plot two uniforms medium size (35–45) mm long and (18–22) mm diameter and well-sprouted seed tubers were planted per hill at a depth of 5–7 cm. The planting hole was dug with a hoe in a smooth flatbed during planting, and the hill was made in the period of the first and second cultivation time. One hundred eight (108) good-performance planted seedlings of each accession were grown for this research to evaluate accession adaptability and better yields in a study area.

2.4.1. Management activities and fertilizer application

The appropriate recommended intercultural agronomic activities such as field planning, land clearing, land preparation, planting, weeding, and harvesting were carried out during the cropping season for Ethiopian Potato (Plectranthus edulis) production. ‘Fertilizers were applied at planting (Di-Ammonium Phosphate (DAP) at 195 kg/ha and urea at 82.5 kg/ha) with a second application of urea (82.5 kg/ha) at flowering [13].

2.5. Sampling techniques and data collection methods

2.5.1. Sampling method

Quantitative variables were recorded on a total of 18 randomly selected Ethiopian Potato accession plants per plot (3 plants randomly at the center/middle of each accession planting row x 6 rows per plot). For sampling techniques, the International Plant Genetic Resources Institute descriptor list for potato [14] and cucurbit species [15]was adopted with some modifications to suit the Ethiopian Potato crop performance to record the quantitative morphological growth, yield components, and yield variables.

2.5.2. Data collected method

Both pre-harvest and post-harvest data from randomly selected eighteen (18) plants from each plot for each response morphological growth, yield components, and yield variables were recorded at different growth stages; Fig. [2(A-F)]. The pre-harvest data of morphological growth variables of sample plants were collected during the flower initiation days to each accession within the 110–158 days range after planting. However, the days to flowering initiation of individual accession varied among them due to their genetic variation, and study area ecological adaptation capacity (See Table 2). Additionally, the post-harvest tuber yield data were collected after fully matured individual accession at different times.

Fig. 2.

Images represent Ethiopian potato (P. edulis) plant vegetative growth stages: (A) seedlings stage, (B) saplings stage, (C) young stage, (D) flower initiation stage, (E) fully flowering stage, and (F) Edible root.

Table 2.

Vegetative growth variables of Ethiopian Potato as influenced by accessions collected from different provenances of Ethiopia.

Acc. Code	PH	NSPH	SG	NNPP	SIL	NBPP	LL	LW	LA	DFI	DF	FL
PE001	80.73d	3.2gf	3.18ba	18.92ij	4.07ba	20.03ef	11.57 cb	3.5bac	38.77c	155.70ba	160.90cd	12.8de
PE003	79.68edf	3.69edf	3.04ebdac	24.4bdc	3.6fhedcg	21.46c	11.758b	3.5bac	41.15bc	157.20a	162.40cd	16.03b
PE005	95.12a	4.08bdc	3.25a	24.04bdc	4.26a	23.94a	12.89a	3.7a	47.12a	158.40a	168.60a	18.24a
PE006	76.58egf	4.42ba	2.66gfh	24.65ba	4.01bac	23.39a	11.773b	3.6ba	44.18ba	155.10b	164.20b	15.57b
PE007	76.36gf	3.8edc	2.47gih	21.65fgh	3.21hij	20.64ed	11.2cd	3.5bac	38.13c	141.70d	159.90cd	13.96dc
PE009	77.34edf	3.06g	2.82edfc	23.84bedc	3.17hij	20.7d	11.17cd	3.37bdc	38.12c	148.90c	157.90d	11.35gf
PE010	80.21ed	3.12g	3.10bac	20.48igh	3.78fbedc	15.43j	11.1ed	3.36bedc	38c	146.90c	153.80e	13.01dce
PE011	91.11b	4.73a	2.88ebdfc	26.16a	3.83bdc	19.5f	10.84ed	3.36bedc	37.7c	147.40c	154.10e	13.53dce
PE012	76.29gf	4.34bac	2.70gf	19.95ih	4.1ba	19.53f	10.72e	3.34edc	34d	147.80c	150.30f	10.53gh
PE013	59.10k	3.72 edf	2.794edf	18.13j	2.95j	18.65g	9.92f	3.2fed	31.27ed	143.30d	149.70f	9.56i
PE014	71.32hi	3.4egf	3.09bdac	22.66 fed	3.82bedc	18.54g	9.90f	3.1feg	30.7ed	140.70d	145.30gh	12.61e
PE015	84.87c	3.68edf	2.49gih	18.79ij	3.4fheig	18.51g	9.68gf	3.05 fg	30.38ed	137.10e	147.70gf	14.09c
PE016	67.95ji	2.9 hg	2.75egf	24.55bac	3.72fbedc	17.21h	9.59gfh	3.04 fg	29.99e	135.10e	142.70ih	12.53fe
PE017	76.49gf	2.4hi	3.03ebdac	22.67fed	3.13ij	17.75h	9.53gfh	2.94 fg	29.4e	137.20e	145.20gh	13.51dce
PE018	79.20edf	3.72edf	2.62gfh	22.02 fg	3.31hijg	16.46i	9.5gh	2.93 fg	28.25e	110.30i	135.70k	10.80gh
PE019	71.hi	3.73edf	2.40gih	25.1ba	3.02ij	16.43i	9.2ih	2.92g	27.8e	136.30e	139.10j	11.26g
PE020	73.63 hg	3.12g	2.49gih	22.61 fe	3.36fhijg	16.35i	9.ji	2.6h	22.95f	124.20g	140.60ij	9.8hi
PE022	73.47 hg	3.04g	2.22gik	19.71ij	3.39 fheig	15.58j	8.8jik	2.52h	21.96f	116.70h	127.80l	11.31g
PE024	78.71edf	3.06g	2.14k	22.79fedc	3.57fhedg	14.2k	8.7jk	2.5h	21.4f	131.30f	130.20k	16.48b
PE025	66.17ji	2.24i	2.k	18.84ij	3.29hijg	13.53l	8.5k	2.3i	20.15f	110.20i	124.30 m	14.04c
Mean	76.76	3.47	2.7	22	3.55	18.7	10.27	3.1	32.57	136.90	148.02	13
LSD	3.68	0.77	0.30	1.76	0.43	0.64	0.42	0.26	3.53	11.38	3.08	1.21
CV (%)	4.17	13.64	9.53	6.91	10.56	2.97	3.56	7.33	9.41	1.96	1.81	8.08
Sign	***	**	***	***	***	***	***	***	***	*	**	***

PH= Plant height (cm), NSPH= Number of stem per hill, SG= Stem girth (cm), NNPP= Number of node per plant, SIL= Stem internode length (cm), NBPP= Number of branch per plant, LL = leaf length (cm), LW = leaf width (cm), LA = Leaf Area (cm²), DFI = Days to flower initiation(days), DF = days to flowering (days), and flower length (cm).

The pre-harvest and post-harvest plant data variables include plant height, number of stems per hill, stem diameter (girth), leaf area, internodes length, leaf length, leaf width, number of nodes per plant, days to flower initiation, days to flowering, flower length, number of tubers per hill, tuber length, tuber diameter, tuber weight per hill, and tuber weight per hectare. These plant data were collected according to the following procedure:

Plant height (cm): the height of the plant was measured from the base of the main shoot/mounding to the apex/tip of the plant at the maturity stage.

The number of stems per hill: recorded as the number of stems counts per hill at the maturity stage.

The stem diameter (girth) of the main stem was measured at the fourth internode from the mound at 50% flowering;

Number of nodes per plant: the number of nodes on the main stem counted at 50% flowering; Internodes length (cm): the length of nodes on the main stem measured at 50% flowering;

Number of primary branches: number of primary branches on the main stem counted at crop maturity;

Leaf length (cm): length of the leaf on the main stem originating at the fourth node below the main stem inflorescence;

Leaf width (cm): width of the leaf on the main stem originating at the fourth node below the main stem inflorescence.

Leaf area (cm²): was measured from the middle parts of the plant by selecting 18 leaves at random from each plot and then the average was done at the full maturity stage from 18 sampled plants, i.e., Leaf area (cm²) = Leaf length (cm) x leaf width (cm).

Days to flower initiation: number of days from planting until the appearance of the first open flower on a plot basis was recorded;

Days to 50% flowering: determined by the number of days from the date of planting to the date at which 50% of the plants produce flowers.

Flower length (cm): length of flowers was measured from eighteen plants at the 50% flowering stage.

Number of tubers per hill: the actual count of the number of tubers at harvest per hill;

Tuber diameter (cm): the average diameter of eighteen tubers measured per hill at harvest.

Tuber length (cm): length of the tuber was measured from eighteen tubers per hill at harvest.

Tuber weight per hill (kg): the total weight of tubers per hill (tuber yield per hill) was taken from eighteen plants from the central row.

Total Tuber weight per hectare (tonne): The total root yield measured in tonne per hectare from the sampled plants to the overall plots.

Marketable tubers per hectare (tonne/ha): average weight of marketable tubers per ha was calculated from the plot area based on the harvest.

Unmarketable tubers per hectare (tonne/ha): average weight of tubers that were infected, and over or undersized tubers that were not marketable.

2.6. Data analysis

The data were subjected to analysis of variance (ANOVA) according to RCBD for the random effects model for the factorial experiment [16]. Based on the significant difference in ANOVA, mean separation was carried out using the LSD method at 5% level of significance. All the statistical analyses were carried out using the statistical software (SAS) package Version 9.4.

3. Results and discussions

3.1. Analysis of variance

Analysis of variance was computed for plant physical characteristics of growths, yield components, and yield. A total of 19 quantitative morphological traits were recorded on 18 selected sample plant basis per plot for each P. edulis accession. Days to flower initiation and days to 50% flowering were recorded on a field plot basis. The average of eighteen (18) plant traits data per plot was used for statistical analysis. The analysis of variance for each growth parameter revealed a very high significant (P < 0.001) difference among the accessions for all the characters examined, except for days to flower initiation, and days to flowering, significant differences (P < 0.5) were observed (Table 2). The P. edulis accession tested results showed a differential response to west Shewa central highland environmental conditions. The variation response in growth, yield, and yield component parameters among the selected 20 Ethiopian potato (Plectranthus edulis) accessions could be attributed due to the genetic variability, and potential of adaptation to the local environmental conditions (soil, water, and climate) of the study area. Similar to the present findings [17,18], observed the variation values of plant morphological traits/characters among different accessions in potato and cassava tuber crops, respectively. The coefficients of variation (CV) for morphological growth characters ranged from 1.81 (days to 50% flowering) to 13.64 (number of stems per hill), whereas coefficients of variation (CV) for yield components and yields parameters ranged from 4.32 (Unmarketable tuber weight) to 8.59 (tuber yield tonne/ha) (Table 1, Table 2). This variation occurred due to the existence of high genetic variability among the accessions for effective adaptation.

3.2. Growth parameters of Ethiopian potato (Plectranthus edulis) accessions

The majority of growth parameters of the Ethiopian potato (Plectranthus edulis) were determined from 20 different accessions including plant height, number of stems per hill, stem girth (diameter), numbers of nodes per hill, stem internode length, number of branches per plant, leaf length, leaf width, leaf area, days to flower initiation, days to flowering and, flower length (Table 2).

3.2.1. Plant height, number of stems per hill, and stem girth (diameter)

Plant height: analysis of variance shows that there is a very highly significant difference (p < 0.001) in plant height among accessions. The overall recorded mean values of plant height ranged between 59.10 and 95.12 cm. The tallest plant height (95.12 cm) was obtained from accession no. PE005, followed by accession no. PE011 (91.11 cm) which was collected from the East Wollega zone, Limmu district, and Hadiya zone, Sesh Duna district, respectively. The plant height was recorded at accession no. PE005 (95.12), PE011 (91.11), PE015 (84.87), PE010 (80.21), and PE001 (80.73) were higher than the overall mean value of 76.76 cm. While the shortest plant height (59.10 cm) was recorded from accession no. PE013, followed by accession no. PE025 those brought from Ilu Aba Bora zone, Alle district, and Jimma zone, Goma district, respectively. General the overall plant height values showed a wide variation among accessions. The variation in plant height could be due to the genetic make-up of the accession, and the difference in the capacity of accession to adapt to the study area of agroecology. This result agrees with the previous research on Plectranthus edulis accessions which report the existence of growth variation among different accession collected from different agro-ecology of Ethiopia [19,20]. Similarly, other workers also observed the variations in plant height [21] in 25 potato genotypes [22], in eight potato varieties [23], in eight potato varieties, and [24] in eight potato varieties in different sites in Ethiopia.

3.2.2. The number of stems per hill

The analysis of variance revealed that there were very highly significant differences (p < 0.001) in the number of stems per hill among the tested Ethiopian potato accessions at the Guder Mammo Mezemir campus research site (Table 2). The results revealed that numerically the number of stems per hill ranges from 2.24 at accession no. PE025 to 4.73 at accession no. PE011. Among the accessions, the maximum mean value of the number of stems per hill (4.73) was observed in accession no. PE011, followed by accession no. PE006 (4.42), PE012 (4.34), and PE005 (4.08), statistically without significant difference among them. While the lowest number of stems per hill was recorded from accession no. PE025, followed by accession no. PE017 (2.4), and PE016 (2.9), which were collected from Jimma zone, Goma district, West Shewa zone, Dandi district, and Ilu Aba Bora zone, Didessa district, respectively. This variation shows the existence of high genetic variation among Ethiopian potatoes used for this experiment. The reason for the number of stems per hill variation happening among accession is probably related to the variation of local environmental conditions among individual accession original condition and study area environmental situation (water, soil, climate change, which influence the adaptation potential of accession growing performance. In line with the present finding [[21], [22], [23],25] reported the wide variation mean values of the number of stems per hill in different potato varieties in different study sites of Ethiopia. Similarly [20], reported that the mean values of the number of stems per hill were laid between 1.40 and 4.10 stems/hill of Plectranthus edulis at Jimma Agricultural Research Centre.

Stem girth (diameter): analysis of variance reveals that there is a very highly significant difference (p < 0.001) in stem girth among accessions. In the present finding, the mean values of plant stem girth was found numerically between the 2 cm and 3.25 cm ranges. The highest stem girth (3.25 cm) was obtained from accession no. PE005, followed by accession numbers PE001 (3.18 cm), PE010 (3.10), and PE014 (3.09), statistically without significant variation among them. While the smallest stem girth (2 cm) was recorded from PE025 followed by accession no. PE024 (2.14 cm) without a significant difference between them. The variation of plant stem girth probably occurred due to genetic variation among accession; and the high vegetative growth nature of accession. However, in comparison to the present findings, numerical [20] reported the lower mean values of stem girth/diameter range between 1.01 and 2.06 among 36 P. edulis germplasm accessions.

3.2.3. Number of nodes per plant, stem internode length, and number of branches per plant

The number of nodes per plant: Mean squares from the combined ANOVA revealed a very highly significant variation (P < 0.001) among the accessions for the number of nodes per plant. The mean values of the number of nodes per plant varied between 18.13 and 26.16. The maximum mean value of the number of nodes per plant was observed at accession no. PE011 (26.16), followed by accession no. PE019 (25.10), PE006 (24.65), and PE016 (24.55) without significant differences among them. The minimum mean value of the number of nodes per plant was observed at accession no. PE013 (18.13), followed by accession no. PE015 (18.79), and PE025 (18.84) statistically without significant differences among them, and these accessions were collected Ilu Aba Bora zone, Alle district, Jimma zone, Gera district, and Jimma zone, Goma district, respectively. The variability in the number of nodes per plant among accessions could be due to the effect of genetic differences among accession, and environmental conditions (soils, temperature, moisture) factors of the study area to these accessions. Similarly, the wide variations of the number of nodes per plant (15.65–27.00) among different 36 P. edulis germplasm accessions were reported by Ref. [20].

Internode length (cm): The analysis of variance revealed a very highly significant (p ≤ 0.001) difference among 20 accessions of Ethiopian potato for inters node length per plant (Table 2). In the present study, the mean values of inters node length per plant ranged between 2.95 and 4.26 cm. The longest internode length per plant was recorded from plant accession no. PE005 (4.26 cm) followed by accession no. PE001 (4.10), PE006 (4.01), and PE012 (4.07) without significant difference among them, and these accessions were collected from East Wollega zone, Limmu district, S.W.Shewa zone, Goro district, East Wollega zone, Kiramu district, and K. Tembaro zone, Doyu Gena district, respectively. However, the shortest internode length was recorded from accession no. PE013 (2.95 cm) followed by accessions PE017 (3.13), and PE019 (3.02) without significant difference, which was collected from Ilu Aba Bora zone, Alle district, West Shewa zone, Dandi district, and Jimma zone, Goma district, respectively. The variability in internode length among accessions could be due to the effect of genetic differences among accession, and local environmental conditions (soils, climate, and moisture) influence plants. This also occurred in Ethiopian potato accessions having long main vines that are directly translated to internodes length. The present findings agree with [20,[22], [23], [24]] reported on the variation of internode length means values among different tuber crop varieties and accessions.

3.2.4. Number of branches per plant

The number of branches per plant was significantly (P < 0.001) affected by accessions (Table 2). The number of branches per plant among the Plectranthus edulis accessions varied from 13.53 to 23.94 in PE025 and PE005 accessions, respectively. The higher number of branches per plant was recorded from accession no. PE005 (23.94), followed by accession no. PE006 (23.39), which was brought from the East Wollega zone, Limmu, and Kiramu districts, respectively. While the lowest number of branches per plant was recorded at accession no. PE025 (13.53) followed by accession no. PE024 (14.2) those collected from Jimma zone, Goma district, and West Shewa zone, Toke Kutaye district, respectively. The variation of these results among accessions could be attributed due to the existence of genetic variation in vegetative growth among the accession and the environmental influences. Similar findings were reported by Ref. [20] in 36 P. edulis germplasm accessions, and [22] in eight potato varieties stated that the variation of genetics contributed by location effect on the number of branches per plant variations.

3.2.5. Leaf length, leaf width, and leaf area

Analysis of variance shows a highly significant difference (P < 0.001) for Leaf length, leaf width, and leaf area among different accession of Ethiopian potatoes (Table 2). The overall mean value of leaf length varied between 8.5 cm and 12.89 cm. The longest leaf length was recorded from accession no.PE005 (12.89 cm) followed by accession no.PE006 (11.77 cm) with a significant difference, which was collected from the East Wollega zone, Limmu, and Kiramu districts, respectively, while the shortest leaf length was recorded from accession no. PE025 (8.5 cm), followed by accession no. PE022 (8.80), and PE024 (8.70) without significant variation among them, those brought from Jimma zone, Goma district, West Shewa zone Cheliya district, and West Shewa zone TokeKutaye district, respectively.

The overall mean value of leaf width varied between 2.30 cm and 3.70 cm. The wider leaf width was recorded from accession no.PE005 (3.7 cm) followed by accession no.PE006 (3.6 cm) without significant difference, which was collected from the East Wollega zone, Kiramu, and Limmu districts, respectively. While the narrowest leaf length was recorded from accession no. PE025 (2.3 cm), followed by accession no. PE024 (2.50), PE022 (2.60(, and PE020 (2.52) without significant variations among them, those collected from the Jimma zone, Goma district, West Shewa zone Toke Kutaye district, West Shewa zone Cheliya district, and Jimma zone, Goma district, respectively. The variation in mean values of leaf length and leaf width among Ethiopian potato accessions tested could be attributed due to heritability, and local environmental influence. This finding is in agreement with studies at Jimma University which indicated the difference in vegetative growth among different accession collected from different growing environments in Ethiopia [20]. The present findings also agreed with other workers of [[22], [23], [24]].

The overall mean value of leaf area varied between 20.15 cm² to 47.12 cm². The larger leaf area was recorded from accession no.PE005 (47.12 cm²) followed by accession no.PE006 (44.18 cm²) without significant difference, those brought from the East Wollega zone, Limmu, and Kiramu districts, respectively. However, the smallest leaf areas were recorded from accession no. PE025 (20.15 cm²) followed by accession no. PE024 (21.40), PE022 (21.96), and PE020 (22.95) statistically without significant differences among them, which were collected from the Jimma zone, Goma district, West Shewa zone TokeKutaye district, West Shewa zone Cheliya district, and Jimma zone, Sokoru district, respectively. This leaf area variation could be happened due to the variation of length, and leave width, because leaf area is the product of leaf dimension. The accession used for this field experiment shows a wide range of variability. Generally, the various sizes of leave length, width, and leave surface area among different accessions could be attributed due to the genetic makeup, and local research trial experimental site environmental adaptation potential variations. However, among the evaluated Ethiopian Potato (Plectranthus edulis) accessions adaptability in the central highland of Ethiopia, accession no. PE001, PE003, PE005, PE006, PE007, and PE009 achieved better performance than other collected accessions. This shows that the agro-ecology of the central highland of Ethiopia, particularly, the West Shewa zone, Guder province is conducive for this crop. According to Ref. [26], pronounced variability in leaf traits is observed between cultivated accessions Ethiopia potatoes collected from different provinces of Ethiopia. Similarly, the 20 Ethiopia potato accessions also portrayed a wide range of diversity in leaf quantitative character. The result was also consistent with the results of [20] for different accession of Ethiopian potatoes [17,18]. also reported similar results for leaf and leaf-related characters in potato and cassava, respectively.

3.2.6. Days to flower initiation, days to flowering, and, flower length

Analysis of variance showed that very high significant (P < 0.001) variation for flower length, highly significant (P < 0.01) variation for days to flowering, and significant (P < 0.05) difference for days to flower initiation among different accession of Ethiopian potato (Table 2). The overall mean value of Days to flower initiation varied between 110.20 and 158.40 days. The largest days to flower initiation were recorded from accession no.PE005 (158.40 days) followed by accession no. PE003 (157.20 days), statistically without a significant difference which brought from East Wollega zone, Limmu district, S.W.Shewa zone, Waliso district, while the shortest Days to flower initiation were recorded from accession no. PE025 (110.20 days) followed by PE018 (110.30), and PE022 (116.70) accession numbers collected from Jimma zone, Goma district, Jimma zone, Gera district, and West Shewa zone Cheliya district, respectively.

The overall mean value of days to flowering varied between 124.30 and 168.60 days. The largest days to flowering were recorded from accession no. PE005 (168.60 days) followed by accession no.PE006 (164.20 days) statistically with a significant difference, which brought from East Wollega zone, Limmu, and Kiramu districts, whereas, the smallest days to flowering were recorded from accession no.PE025 (124.30 days) followed by accession no. PE022 (127.80 days), and PE024 (130.20 days) those collected from the Jimma zone, Goma district, West Shewa zone Cheliya district, and West Shewa zone Toke Kutaye district, respectively. This shows high genetic variation and adaptation to the agroecology or environments of the growing area among accession days to flower initiation and days to flowering. In line with the present finding [20], in 36 P. edulis germplasm accessions [21], in 25 potato genotypes [23], in three potato varieties [25], in 21 potato varieties reported the wide variation mean values of days to flower initiation, days to flowering and, flower length in the different study area in Ethiopia.

The overall mean value of flower length of the Ethiopian potato accession tested varied between 9.56 and 18.24 cm. The longest flower length was observed in accession no. PE005 (18.24 cm), followed by accession no. PE024 (16.48), PE003 (16.03), and PE006 (15.57) those collected from the East Wollega zone, Limmu district, West Shewa zone TokeKutaye district, S.W.Shewa zone, Waliso district, East Wollega zone, Kiramu district, respectively. While the shortest flower length was recorded in accession no. PE013(9.56), followed by PE020 (9.80), PE012 (10.53), and PE018 (10.80) accession numbers, which were collected from the provenance areas of Ilu Aba Bora zone, Alle district, Jimma zone, Sokoru district, Kembata Tembaro zone, Doyu Gena district, and Jimma zone, Gera district, respectively. The variation in flower length size might be attributed due to the genetic variation and local environmental (soil, moisture, climate) influence. In line with the present findings [21,23] reported the different sizes of flower lengths in different potato varieties.

3.3. Yield and yield components of Ethiopian Potato (Plectranthus edulis) accessions

The common yields and yield components parameters of Ethiopian potato (Plectranthus edulis) were examined based on the number of tubers per hill, tuber diameter, tuber length, tuber weight per hill (kg), tuber weight per ha (tonne/ha), marketable tuber weight and unmarketable tuber weight.

3.3.1. Number of tuber per hill, tuber diameter, and tuber length

Number of tubers per hill: Analysis of variance showed a highly significant difference (P < 0.001) in the number of tubers per hill among different accession of Ethiopian potatoes (Table 3). The overall mean value of the number of tubers per hill varied between 28.4 and 143.26. The highest numbers of tubers per hill were recorded from accession no.PE011 (143.26) followed by accession no.PE007 (125.74) and PE003 (106.49) statistically with significant differences among them collected from Hadiya zone, Sesh Duna district, Gurage zone, Endegagn district, and S.W.Shewa zone, Woliso district, respectively. While the lowest number of tubers per hill was recorded from accession no. PE025 (28.4) followed by accession no. PE024 (31.66) without significant difference, which brought from Jimma zone, Goma district, and West Shewa zone, Toke Kutaye district, respectively. The wide variation of the number of tubers per hill from smallest to highest mean values could be attributed due to genetic makeup, and local environmental adaptation potential variation. In line with the present finding [20], in 36 P. edulis accessions [21], in 25 potato genotypes [22], in eight potato varieties, and [25] in 21 potato varieties reported the wide variation mean values of the number of tubers per hill in different study sites of Ethiopia (see Table 4).

Table 3.

Yield and yield component variables of Ethiopian Potato as influenced by accessions from different provenances.

Accession Code	Number of tuber per hill	Tuber diameter (cm)	Tuber length (cm)	Tuber weight/hill (kg)	Tuber yield (tonne/ha)	Marketable tuber weight (tonne/ha)	Unmarketable tuber weight (tonne/ha)
PE001	104.46dc	22.08a	17.04a	1.60a	53.37a	53.11a	0.26f
PE003	106.49c	19.49dce	15.66bc	1.48bc	49.40b	49.01b	0.31e
PE005	62.34h	22.38a	17.38a	1.64a	54.69a	54.4a	0.29e
PE006	106.07dc	21.7ba	15 becd	1.36dc	46.50 cb	46.16c	0.34de
E007	125.74b	21.26ba	17.14a	1.32cd	44.12cd	43.87dc	0.25f
PE009	53.4i	19.35dce	17.04a	1.27ed	42.20ed	42.02d	0.18g
PE010	56.25i	14.69kjl	17.39a	1.25ed	41.75ed	41.23de	0.52c
PE011	143.26a	18.33dfe	15.20bcd	1.24edf	41.45ed	41.02de	0.43d
PE012	101.3d	19.63dc	16.09ba	1.20ef	40.30ef	39.92e	0.38de
PE013	106.11dc	20.29bc	13.18f	1.19ef	39.78ef	39.16e	0.62bc
PE014	62.42h	16.86gifh	17.37a	1.15gf	38.16gf	37.88ef	0.28e
PE015	64h	18.2gfe	17.29a	1.08g	36.00g	35.83f	0.17g
PE016	73.70g	17.52gfh	15.61bc	0.97h	32.30h	31.93g	0.37de
PE017	85.58f	15.78kij	14.28fed	0.94h	31.44h	30.87g	0.57c
PE018	69.94g	16.34ih	13.38f	0.78i	26.10i	25.17h	0.93ba
PE019	94.15e	13.57l	13.75fe	0.65j	21.80j	20.77i	1.03a
PE020	69.51g	14.32 kl	13.78fe	0.58j	19.35j	18.37ij	0.98a
PE022	63.68h	17.08gifh	14.47fecd	0.49k	15.80k	15.13k	0.67bc
PE024	31.66j	16.2ijh	13.50f	0.39lk	12.90lk	12.15 kl	0.75b
PE025	28.40j	16.60gih	15.52bcd	0.30l	9.94l	9.49l	0.45d
Mean	80.42	18	15.5	1.046	34.87	34.38	0.49
LSD	1.54	1.54	1.31	0.10	3.40	3.25	0.17
CV (%)	5.56	7.41	7.30	8.51	8.59	8.17	4.32
Sign	***	***	***	***	***	***	***

Note: Means for Ethiopian Potato (Plectranthus edulis) accessions within a column followed by the same letter are not significantly different from each other at p < 0.05. Keys: *, **, ***, and ns = significant at P < 0.05, high significant at P < 0.01, very high significant at P < 0.001, and non-significant at P > 0.05, respectively.

Table 4.

Combined correlation coefficients among vegetative growth parameters, yields, and yield components of Ethiopian Potato (Plectranthus edulis) accessions evaluated at central highland, West Shewa zone, Guder site, Ethiopia.

	PH	SG	NNPP	IL	NSPH	NB	LL	LW	DFI	DF	FL	TL	TN	TD	TWPHi	TWPH
PH	1
SG	0.36***	1
NNPP	0.45***	0.34***	1
IL	0.29***	0.29***	0.30***	1
NSPH	0.32***	0.17**	0.38***	0.05***	1
NB	0.06ns	0.37**	0.20***	0.4***	−0.13*	1
LL	0.27**	0.28**	0.19***	0.51***	−0.16*	0.45***	1
LW	0.27**	0.30***	0.11***	0.48***	−0.16*	0.58***	0.70***	1
DFI	0.19*	0.13ns	0.41***	0.10ns	0.37***	−0.25**	−0.18**	−0.45***	1
DF	0.25**	0.10***	0.37***	0.38***	0.39***	−0.29**	−0.14**	−0.4***	0.95***	1
FL	0.27**	0.27**	0.07***	0.43***	0.27**	0.48***	0.59***	0.59***	−0.44**	−0.43**	1
TL	0.27**	0.38***	0.16***	0.25**	0.144ns	0.40***	0.24**	0.36**	−0.16*	−0.12*	0.4**	1
TN	0.15*	0.33***	0.22**	0.26**	0.052ns	0.02ns	0.06ns	0.08ns	0.37**	0.34***	−0.17*	0.11ns	1
TD	0.17*	0.45***	0.10***	0.31***	−0.08*	0.61***	0.28**	0.50**	−0.17	−0.25**	0.38***	0.27**	−0.03**
TWPHi	0.37***	0.61***	0.16***	0.38***	0.18*	0.32***	0.17**	0.33***	0.15*	0.13ns	0.12ns	0.40**	0.58***	0.58***	1
TWPH	0.37***	0.61***	0.16***	0.38***	0.18*	0.32***	0.17**	0.33***	0.16ns	0.13ns	0.12ns	0.40***	0.58***	0.58***	0.87***	1

*, **, ***, ns represent significant at 0.05, high significant at 0.01, very highly significant at 0.001, and non-significant, respectively.

Key: PH = plant height, SG = stem girth (cm), NNPP = number of node per plant, IL = inter node length, NSPH = number stem per hill, NB = number of branch per plant, LL = leaf length, LW = leaf with width, DFI = days to flower initiation, DF = days to flowering, FL = flower length, TL = tuber length, TN = Tuber number, TD = tuber diameter, TWPHi = tuber weight per hill, and TWPH = tuber weight per hectare.

Tuber diameter: Analysis of variance revealed a highly significant difference (P < 0.001) for tuber diameter among different accession of Ethiopian potato (Table 3). The overall mean value of tuber diameter varied between 13.57 cm and 22.38 cm. The largest tuber diameter was recorded from accession no.PE005 (22.38 cm) followed by accession no. PE001 (22.08), PE006 (21.70), and E007 (21.26) without significant variation among them, which brought from East Wollega zone, Limmu district, S.W.Shewa zone, Goro district, East Wollega zone, Kiramu district, and Gurage zone, Endegagn district, respectively. However, the smallest tuber diameter was recorded from accession no. PE019 (13.57 cm) followed by accession no. PE020 (14.32) which was collected from the Jimma zone, Goma, and Sokoru districts, respectively. The wide variation from the smallest to the largest tuber diameter size might be due to the performance adaptability of different accessions of the same crop to different environments. The present study results agreed with [20,21,24] finding reports in different sites of Ethiopia.

Tuber length: The analysis of variance (ANOVA) for tuber length (cm) revealed that there were significant differences (P < 0.001) among accessions (Table 3). The overall mean value of tuber length varied between 13.18 cm and 17.39 cm. The overall mean value of tuber length (cm) was 15.50 cm in the study area. Among the accessions, the maximum length means the value of tuber length (cm) was observed in accession no. PE010 (17.39 cm) followed by accession no. PE005 (17.38 cm), PE014 (17.37), PE015 (17.29), E007 (17.14), PE001 (17.04), and PE009 (17.04) without significant difference, which were collected from the Hadiya zone, Lemo district, East Wollega zone, Limmu district, Ilu Aba Bora zone, Darimu district, Ilu Aba Bora zone, Kumbabe district, Gurage zone, Endegagn district, and S.W.Shewa zone, Goro district, and Gurage zone, Gumer district, respectively. However, the shortest mean value of tuber length (cm) was recorded in PE013 (13.18), followed by accession no. PE018 (13.38), and PE024 (13.50) without significant variations among them, those brought from Ilu Aba Bora zone, Alle district, Jimma zone, Gera district, and West Shewa zone Toke Kutaye district, respectively. The main reasons for the variation of tuber length (cm) from the shortest 13.18 cm to the longest 17.39 cm could be attributed due to local environmental influence and hereditability variation among accessions. Similarly [20,22,24], observed different mean values of tuber length (cm) among different tuber crops of potato varieties.

3.3.2. Tuber weight per hill, and tuber yield

Tuber weight per hill (kg) Analysis of ANOVA revealed that very highly significant difference (P < 0.001) in tuber weight per hill among different accession of Ethiopian potatoes (Table 3). The overall mean value of tuber length varied between 0.30 kg and 1.64 kg. The largest tuber weight per hill was recorded from accession no.PE005 (1.64 kg) followed by accession no. PE001 (1.60) statistical without significance difference, those collected from East Wollega zone, Limmu district, and S.W. Shewa zone, Goro district, respectively. However, the smallest tuber weight per hill was recorded from accession no. PE025 (0.30 kg) followed by accession PE024 (0.39) without significant difference. This tuber weight per hill yield variation from 0.30 kg/hill to 1.64 kg/hill among accessions occurred probably due to genetic and local environmental adaptation potential variations [20]. also found that tuber yield per hill; dry matter content and number of tubers per hill had the greatest direct effect on tuber yield per unit area in their order of magnitude in potatoes [18]. also reported that average tuber weight had the maximum positive direct effect followed by tuber number per plant, leaf area, days to maturity, tuber dry matter content, and plant height on tuber yield per plant on potato.

3.3.3. Tuber weight per hectare (tonne/ha)

Analysis of ANOVA showed that very highly significant difference (P < 0.001) for tuber weight per hectare among different accession of Ethiopian potato (Table 3). The overall mean value of tuber weight per hectare varied from 9.94 tonne/ha to 54.69 tonne/ha. The largest tuber weight per hectare was recorded from accession no.PE005 (54.69 tonne/ha) which was followed by accession no.PE001 (53.37 tonne/ha) statistical without significance difference, those collected from East Wollega zone, Limmu district, and S.W. Shewa zone, Goro district, respectively. However, the smallest tuber weight per hectare was recorded from accession no. PE025 (9.94 tonne/ha) followed by accession no. PE024 (12.90). This shows the existence of genetic diversity among the accession for tuber and tuber-related characters. A supporting result was reported by Weyessa et al. (2013) who observed that the variation in tuber weight per hectare of Ethiopian potato accession was collected from different regions of the country. Similar to the present findings other workers also observed the various mean values of tuber weight per hectare in 36 P. edulis accessions [20], in 25 potato genotypes [21], in eight potato varieties [27], in seven potato varieties [24], and 21 potato varieties [25].

3.3.4. Marketable tuber weight (tonne/ha)

Statistically, the marketable tuber weight (tonne/ha) showed a significant variation as a function of accession (p < 0.001). The overall mean value of the marketable tuber weight (tonne/ha) of 20 different Ethiopia potato accessions were felled between 9.49 and 54.4 tonne/ha ranges (Table 3). Among the tested accessions, the maximum mean value of marketable tuber weight (tonne/ha) was recorded in accession no. PE005 (54.4), and followed with accession no. PE001 (53.11), which come from East Wollega zone, Limmu district, and S.W.Shewa zone, Goro district provenances, respectively. While the minimum mean value of marketable tuber weight (tonne/ha) was recorded in accession no. PE025 (9.49), followed by accession no. PE024 (12.15), those brought from the Jimma zone, Goma district, and West Shewa zone TokeKutaye district, respectively. The main reasons for the higher marketable tuber weight (tonne/ha) among the majority of accessions, particularly, in accession no. PE005 (54.4), PE001 (53.11), PE003 (49.01), PE006 (46.16), E007 (43.87), PE009 (42.02), PE010 (41.23), and PE011 (41.02) probably due to the size of the majority tubers felled in the medium normal standard size in both diameter and length and the tubers free from infected disease and insects. Similar studies results were reported by Ref. [20] in 36 P. edulis accessions [22], in eight potato varieties [28], in five orange-fleshed sweet potato varieties [23], in three improved potato varieties, and [25] in 21 potato varieties for the various values of marketable tuber weight (tonne/ha) among different tuber crops accessions and varieties in different sites of Ethiopia.

3.3.5. Unmarketable tuber weight (tonne/ha)

The analysis of variance for unmarketable tuber weight (tonne/ha) revealed a significant difference as a function of different accession (p < 001). The overall mean value of the unmarketable tuber weight (tonne/ha) under the 20 different Ethiopia potato accessions varied between 0.17 and 1.03 (tonne/ha). Among the collected accessions, the highest unmarketable tuber weight (tonne/ha) was observed in accession no. PE019 (1.03) followed by accession no. PE020 (0.98) those collected from the Jimma zone, Goma, and Sokoru districts, respectively. Whereas, on the contrary, the lowest unmarketable tuber weight (tonne/ha) was observed in the Ilu Aba Bora zone, Kumbabe district, and Gurage zone, Gumer district, respectively (Table 1, and Table 3). The main reason for the highest unmarketable tuber weight (tonne/ha) recorded in some of the accessions was attributed due to the undersized tubers in both diameter and length and partial infection by disease and insects. Other researchers have also observed a higher unmarketable tuber weight (tonne/ha) in some potato accessions than in other accessions in different study sites in Ethiopia [21,28].

3.4. Correlation analysis among variables

Simple correlation coefficients show the relationships (express as positive, negative, and no relation) between some vegetative growth parameters, yields, and yield components of Ethiopian Potato (Plectranthus edulis) accessions. It is important to understand the magnitude and the interrelationship of the Ethiopian Potato (Plectranthus edulis) accessions measured variables among themselves and with the target tuber yields. Among the measured Ethiopian Potato (Plectranthus edulis) accessions, plant height, stem girth, number of nodes per plant, and internode length characters revealed a positive correlation relationship with all variables measured in the study(Table 4).

The majority of Ethiopian Potato vegetative growth parameters, yields, and yield component variables plant height, stem girth number of nodes per plant, internode length, number of branches per plant, and leaf width were shown very highly significant (p < 0.001), and strong positive correlation relationships to P. edulis tuber weight yields (tonne/ha). This revealed that the association of these characters was attributed to the increase in P. edulis tuber weight yields (tonne/ha) in the study area. Similar study results were reported by Ref. [20] in 36 P. edulis accessions, and [21], in 25 potato genotypes for the positive relationships of the stated variables to P. edulis tuber weight (tonne/ha) in different sites in Ethiopia. This is in agreement with [29] who also reported positive correlations of tuber yield per plant with plant height, tuber number per hill, and tuber diameter in potatoes.

4. Conclusion

Ethiopian Potato (Plectranthus edulis) has been cultivated and used as a major supply of food in different parts of Ethiopia. The present study was initiated to evaluate the agronomic performance of Ethiopian Potato (Plectranthus edulis) accessions by analyzing data on plant vegetative growth, yield, and yield component variables. Accordingly, the Ethiopian Potato (P. edulis) accession tested results showed a different response to the west zone, central highland environmental conditions. The variation response could be attributed due to the genetic variability, and potential of adaptation to the demonstration environmental conditions (soil, moisture, and climate) of the study area.

This study exemplified the existence of a wide range of differences among the P. edulis accessions collected from different areas of Ethiopia. The physical characters attribute of all accessions were evaluated plant height, number of stems per hill, stem girth, number of nodes per plant, stem internode length, number of branches per plant, leaf length, leaf width, leaf area, days to flower initiation, days to flowering, flower length, number of tubers per hill, tuber diameter, tuber length, tuber weight per hill, tuber yield marketable tuber weight, and unmarketable tuber weight. This indicates the presence of a considerable amount of variability for the different characters. From this study, we concluded that eight (8) accessions of PE001, PE003, PE005, PE006, E007, PE009, PE010, and PE011 were identified, which revealed that better adaptation in the majority of physical vegetative growth characters, and produced higher tuber yields (>40 tonne/ha), and higher marketable tuber yield (>40 tonne/ha) in the study area, which indicates good performance and adaptation in west Shewa zone, central highland of Ethiopia. Therefore, these accessions are suggested to produce and scale up by farmers in the central highland of Ethiopia, particularly the west Shewa zone, and other areas of similar agro-ecological zones.

Author contribution statement

Zinash Teferi Abdena: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data; and Wrote the paper.

Chala Begna Bedassa: Contributed reagents, materials, analysis tools or data.

Data availability statement

Data included in article/supp. material/referenced in article.

Additional information

No additional information is available for this paper.

Declaration of competing interest

We, the authors hereby declare that： we have no known significant pecuniary competing interest or other personal relationships directly or indirectly, in any matter that raises or may raise a conflict on our manuscript, which could have appeared to influence the results or interpretation of the work reported in this manuscript for publication in Heliyon Journal.

Abbreviations

%

Percent

m. a.s.l.

The meter above sea level

cm

Centimeter

CV

Coefficient of variation

kg

Kilogram

ha

Hectare