Abstract
Edible podded peas viz., snow pea (Pisum sativum var. saccharatum) and sugar snap pea (Pisum sativum var. macrocarpon) are valued for their tender, parchment-free pods and sweet flavor. In present study, morphologically 26 diverse genotypes were characterized based on pod colour, flower colour, seed colour and pod type. Among these, four morphologically and phenotypically diverse genotypes viz., ‘Royal Snow’, ‘Punjab Mithi Phali-3’, ‘Honey Snap’ and ‘Mithi Phali’ were identified and utilized for developing reciprocal segregating populations between snow and sugar snap peas (Mithi Phali × Honey Snap, Honey Snap × Mithi phali, Royal Snow × Punjab Mithi Phali-3, Punjab Mithi Phali-3 × Royal Snow) to study the maternal/cytoplasmic inheritance. Phenotypically first generation hybrids across all reciprocal crosses indicated dominance of purple flower colour over white, green pod colour over yellow and purple pigmented pods, brown/light brown seeds over green colour seeds and snow-type over sugar snap pods without showing maternal/cytoplasmic inheritance. Segregating F2 populations followed expected Mendelian inheritance with chi-square (χ2) analysis confirming 3:1 best fit ratio, indicating single dominant gene inheritance for these traits in edible podded peas. These findings provide valuable insights for the genetic improvement of edible podded peas.
Keywords: Edible podded, F2 population, Chi-square (χ2) analysis, Maternal/cytoplasmic inheritance, Reciprocal crosses
Subject terms: Genetics, Plant sciences
Introduction
Pea (Pisum sativum L., 2n = 2x = 14) is a highly self-pollinated crop with cleistogamous flower structure and belongs to third-largest angiosperm family Leguminosae comprising 18,000 species over 650 genera1,2. Pea primarily originated in the Mediterranean region whereas Ethiopia and Near East Asia are considered as secondary centers of origin3. Peas are grown globally on 7.41 million hectares for dry pea seeds and 2.66 million hectares for green pea seeds4. Asia produces 87% of the world’s green peas, indicating its dominance over European nations5. Pea is traditionally classified into four botanical varieties, namely garden pea (Pisum sativum var. hortense), field pea (Pisum sativum var. arvense), snow pea (Pisum sativum var. saccharatum) and sugar snap pea (Pisum sativum var. macrocarpon) based on their utility and morphological traits such as pod and seed characteristics as well as their end-use6. Garden pea (Pisum sativum var. hortense) generally has white flowers and their seeds are round or wrinkled in shape with green, yellow or brown colour seed coat. Contrarily, field pea (Pisum sativum var. arvense) has white, purple, lavender or coloured flowers and their seeds are round in shape with yellow or green colour seed coat. Seeds of garden and field peas are shelled from the pods before consumption as the pod wall is inedible due to presence of parchment layer (transparent layer) on the internal surface of pod wall and fibers along the suture lines. Snow peas (Pisum sativum var. saccharatum) and sugar snap peas (Pisum sativum var. macrocarpon) known as edible-podded types, lack membranous coating (parchment layer) on inner pod wall surface leading to whole pod consumption with zero wastage7. Edible podded peas have white, purple or light purple flowers and seeds round or wrinkled in shape with yellow, green or brown colour seed coat. The pods of field and garden pea are generally green in colour but edible podded peas (snow pea and sugar snap pea) are of different colours i.e. green, pruple or yellow. Among these edible podded types, Pisum sativum var. saccharatum is characterized by flat pods having thin pod wall and picked before pod swelling as well as string development, whereas Pisum sativum var. macrocarpon (a cross between snow pea and tightly-podded pea mutant) have thick pod wall and allowed to mature fully before picking6. Although all these groups show distinct phenotypic characteristics, but are not genetically isolated and share a common gene pool with free intercrossing potential. Therefore, studying inheritance patterns within and between these groups remains relevant, particularly for traits where limited genetic information is available.
The garden pea genetics study has been a foundation in the development of classical genetics and plant breeding. Dr. Gregor Mendel revolutionized genetics by discovering the laws of inheritance in garden pea and examined seven characteristics viz., flower colour, pod colour, seed shape, seed colour, pod shape, flower position and stem height8,9. In 1866, Mendel observed that the gene responsible for green pod colour (GP) is dominant over the gene for yellow pods (gp). However, did not mention about green pods with purple-pigmentation in these studies. Further advancements in genetic studies led to the identification of the GP/gp gene on chromosome 3 (linkage group V)10,11, providing deeper insights into pod colour inheritance in peas. For pod shape, Mendel reported that inflated pods (P or V) are dominant over constricted pods (p or v) and mapped these genes on chromosome 5 (linkage group III) in garden peas12–14, but no information is available on inheritance of pod shape in edible podded types. Likewise, purple flowers (A) were found dominant over white flowers (a) and mapped to a single locus on chromosome 6 (linkage group II) but present days genotypes have lot of variation for flower colour. Additionally, yellow seed colour (I) showed dominance over green seed colour (i) in garden peas15.
Despite extensive genetic studies in garden pea, the inheritance of key morphological traits in edible-podded peas (Pisum sativum var. saccharatum and Pisum sativum var. macrocarpon) remains relatively less explored under diverse genetic backgrounds, particularly regarding the inheritance of pod colour, flower colour, seed colour, and pod type. Although several genes controlling these traits have been identified in garden pea, their expression and inheritance patterns in edible-podded pea backgrounds require further validation. To know the genetics and cytoplasmic or maternal effects of above mentioned traits, reciprocal crosses were developed between genotypes with different flower colours (white and purple), pod colours (green with purple pigmentation, yellow, and green), seed colours (light brown, brown, and green) and pod types (snow and sugar snap). The objective of this study was to determine the mode of inheritance of pod colour, flower colour, seed colour, and pod type in edible-podded peas and to test for the presence of maternal or cytoplasmic effects using reciprocal crosses. As edible-podded peas (snow and sugar snap types) differ markedly from garden peas in pod morphology, utilization, and market preference, they represent valuable targets for breeding aimed at enhancing pod quality and yield. However, systematic genetic studies on these types remain limited. Therefore, a focused investigation into the inheritance of key morphological traits is essential to support effective breeding strategies and to deepen our understanding of genetic behaviour across diverse pea types.
Material and methods
Location and climatic conditions
The present study was conducted at Punjab Agricultural University (PAU), Ludhiana, Punjab and PAU, Regional Research Station, Keylong, Himachal Pradesh. PAU, Ludhiana is located at 30° 53′ 57.7″ N latitude, 75° 47′ 37.7″ E longitude and 245 m above mean sea level altitude. The average rainfall in Ludhiana was 726 mm with hot and dry summers (April to June) followed by a hot and humid monsoon period and cold winters during December–January. The PAU research station at Keylong, Himachal Pradesh, has a high-altitude climate with cold winters, snowfall, and mild summers, characterized by significantly lower temperatures due to its high elevation at around 10,500 feet above sea level. Two locations were used to facilitate different stages of the experiment, with hybridization carried out at Ludhiana during the winter season and generation advancement (F1 to F2) at Keylong during the summer season. The use of contrasting locations was primarily to overcome seasonal limitations and ensure continuous generation advancement, rather than to evaluate genotype × environment interactions. During the experimental period, Ludhiana experienced temperatures ranging from approximately 10–25 °C during the rabi season, while Keylong had cooler summer conditions with temperatures ranging from 5 to 20 °C. These environments provided suitable conditions for pea cultivation and generation advancement.
Morphological characterization of germplasm
Based on previous year’s performances, 26 diverse and horticulturally superior edible podded pea genotypes viz., Pisum sativum var. saccharatum and Pisum sativum var. macrocarpon (Table 1) from germplasm collection were selected and morphologically characterized for flower colour, pod colour, seed colur and pod type. All these genotypes were sown at Vegetable Research Farm, PAU, Ludhiana during October, 2022. The genotypes were sown on flat beds (at proper soil moisture) having plot size of 1 × 1 m2 during the second fortnight of October using Randomized Block Design having three replications (plots) with a row-to-row spacing of 30 cm and plant-to-plant spacing of 10.0 cm. Each plot accommodated approximately 30–35 plants, and all plants in each replication were considered for phenotypic evaluation. Thus, observations were recorded on approximately 90–105 plants per genotype across three replications. The seeds of all the genotypes were treated with Captan @ 2 g/kg of seeds before sowing. The 45 kg Urea and 155 kg Superphosphate per acre were applied before sowing. For weed control, Stomp 30 EC (pendimethalin) @1.0 L per acre was applied within 1 day of sowing by dissolving in 150–200 L of water. The second and third weeding was done manually 1 and 2 months after sowing. The standard cultural and practices were followed as per PAU Package of Practices were followed (https://www.pau.edu/content/ccil/pf/pp_veg.pdf).
Table 1.
List of edible podded pea genotypes used for morphological characterization.
| Sr. no. | Genotypes | Origin | Sr. no. | Genotypes | Origin |
|---|---|---|---|---|---|
| 1. | Him Palam Mithi Phali-1 | CSKHPKV, Palampur | 14. | Tarvedo Sugar | PAU, Ludhiana |
| 2. | Him Palam Mithi Phali-2 | CSKHPKV, Palampur | 15. | PED-18-1 | PAU, Ludhiana |
| 3. | Honey Snap | USA | 16. | PED-18-6 | PAU, Ludhiana |
| 4. | Punjab Mithi Phali-3 | PAU, Ludhiana | 17. | PED-18-7 | PAU, Ludhiana |
| 5. | Airtel | USA | 18. | PED-18-8 | PAU, Ludhiana |
| 6. | Tardio | PAU, Ludhiana | 19. | PED-21-1 | PAU, Ludhiana |
| 7. | Oregon Sugar Pod | USA | 20. | PED-21-2 | PAU, Ludhiana |
| 8. | Sugar Daddy | USA | 21. | PED-21-3 | PAU, Ludhiana |
| 9. | Dwarf Grey Sugar | PAU, Ludhiana | 22. | PED-21-4 | PAU, Ludhiana |
| 10. | Cascatia | USA | 23. | PED-21-5 | PAU, Ludhiana |
| 11. | Royal Snow | USA | 24. | PED-21-6 | PAU, Ludhiana |
| 12. | Sugar Bon | USA | 25. | PED-21-7 | PAU, Ludhiana |
| 13. | Arka Sampoorna | IIHR, Bangalore | 26. | Mithi Phali | PAU, Ludhiana |
Genetics of different traits
Hybridization and segregating population development
Based on the morphological characterization four genetically diverse parents viz., Royal Snow (Pisum sativum var. saccharatum), Punjab Mithi Phali-3 (Pisum sativum var. macrocarpon), Honey Snap (Pisum sativum var. macrocarpon) and Mithi Phali (Pisum sativum var. saccharatum) were identified (Fig. 1) and used in hybridization programme. To study the genetics of flower colour, pod colour, seed colour and pod type, reciprocal crosses were attempted among Pisum sativum var. saccharatum and Pisum sativum var. macrocarpon (Mithi Phali × Honey Snap; Honey Snap × Mithi; Royal Snow × Punjab Mithi Phali-3; Punjab Mithi Phali-3 × Royal Snow) to develop F1 hybrids during January–February, 2023 at Vegetable Research Farm, PAU, Ludhiana. The F1’s of each cross were selfed to produce F2 populations from May to September 2023 at PAU, Regional Research Station, Keylong, Himachal Pradesh. Seeds of all four F2 populations were sown at Vegetable Research Farm, PAU, Ludhiana during the second fortnight of October 2023. The standard cultural and practices were followed as per PAU Package of Practices (https://www.pau.edu/content/ccil/pf/pp_veg.pdf). The size of each F2 population varied among crosses, ranging from 119 to 146 plants, and the number of individuals evaluated for each cross and its reciprocal is presented in Tables 3 and 4.
Fig. 1.
Parental genotypes of edible podded pea used for hybridization. Four genetically diverse genotypes namely Royal Snow and Mithi Phali (snow pea types) and Honey Snap and Punjab Mithi Phali-3 (sugar snap pea types) showing distinct variation in pod colour, seed colour, flower colour and pod type were selected for reciprocal crossing to study inheritance patterns and maternal effects.
Table 3.
Genetic analysis of segregating F2 populations from cross ‘Honey Snap × Mithi Phali’ and their reciprocal using Chi-square test.
| Population/parents | Total number of plants | Flower colour | Pod colour | Pod type | Seed colour | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Observed phenotype | Expected phenotype | χ2 value (p value) |
Observed phenotype | Expected phenotype | χ2 value (p value) |
Observed phenotype | Expected phenotype | χ2 value (p value) |
Observed phenotype | Expected phenotype | χ2 value | ||||||||||
| Purple | White | Purple | White | Yellow | Green | Yellow | Green | Sugar Snap | Snow | Sugar Snap | Snow | Light brown | Green | Light brown | Green | ||||||
| Honey Snap | 20 | 20 | – | – | – | – | 20 | – | – | – | – | 20 | – | – | – | – | 20 | – | – | – | – |
| Mithi Phali | 20 | – | 20 | – | – | – | – | 20 | – | – | – | – | 20 | – | – | – | – | 20 | – | – | – |
| F1 (Honey Snap × Mithi Phali) | 56 | 56 | – | – | – | – | – | 56 | – | – | – | – | 56 | – | – | – | 56 | – | – | – | – |
| F1 (Mithi phali × Honey Snap) | 47 | 47 | – | – | – | – | – | 47 | – | – | – | – | 47 | – | – | – | 47 | – | – | – | – |
| F2 (Honey Snap × Mithi Phali) | 146 | 112 | 34 | 109.5 | 36.5 |
0.23* (0.63) |
39 | 107 | 36.5 | 109.5 |
0.23* (0.63) |
40 | 106 | 36.5 | 109.5 |
0.45* (0.50) |
105 | 41 | 109.5 | 36.5 |
0.74* (0.38) |
| F2 (Mithi phali × Honey Snap) | 130 | 98 | 32 | 97.5 | 32.5 |
0.01* (0.92) |
35 | 95 | 32.5 | 97.5 |
0.25* (0.61) |
36 | 94 | 32.5 | 97.5 |
0.50* (0.47) |
94 | 36 | 97.5 | 32.5 |
0.50* (0.47) |
Expected values were calculated based on Mendelian 3:1 segregation ratio.
Chi-square (χ2) tests were performed for each cross and its reciprocal with 1 degree of freedom (df = 1).
χ2 values lower than the critical value (3.84 at p = 0.05) indicate conformity to the expected Mendelian ratio.
*Non-significant at p = 0.05.
Table 4.
Genetic analysis of segregating F2 populations from cross ‘Royal Snow × Punjab Mithi Phali-3’ and their reciprocal using Chi-square test.
| Population/parents | Total number of plants | Flower colour | Pod colour | Pod type | Seed colour | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Observed phenotype | Expected phenotype | χ2 value (p value) |
Observed phenotype | Expected phenotype | χ2 value (p value) |
Observed phenotype | Expected phenotype | χ2 value (p value) |
Observed phenotype | Expected phenotype | χ2 value | ||||||||||
| Purple | White | Purple | White | Green with purple pigmentation | Green | Green with purple pigmentation | Green | Snow | Sugar snap | Snow | Sugar snap | Brown | Green | Brown | Green | ||||||
| Royal snow | 20 | 20 | – | – | – | – | 20 | – | – | – | – | 20 | – | – | – | – | 20 | – | – | – | – |
| Punjab Mithi Phali-3 | 20 | – | 20 | – | – | – | – | 20 | – | – | – | – | 20 | – | – | – | – | 20 | – | – | – |
| F1 (Royal Snow × Punjab Mithi Phali-3) | 51 | 51 | – | – | – | – | – | 51 | – | – | – | 51 | – | – | – | – | 51 | – | – | – | – |
| F1 (Punjab Mithi Phali-3 × Royal Snow) | 39 | 39 | – | – | – | – | – | 39 | – | – | – | 39 | – | – | – | – | 39 | – | – | – | – |
| F2 (Royal Snow × Punjab Mithi Phali-3) | 129 | 99 | 30 | 96.75 | 32.25 |
0.21* (0.64) |
26 | 103 | 32.25 | 96.75 |
1.61* (0.20) |
95 | 34 | 96.75 | 32.25 |
0.13* (0.71) |
100 | 29 | 96.75 | 32.25 |
0.44* (0.51) |
| F2 (Punjab Mithi Phali-3 × Royal Snow) | 119 | 83 | 36 | 89.25 | 29.75 |
1.75* (0.18) |
34 | 85 | 29.75 | 89.25 |
0.81* (0.36) |
84 | 35 | 89.25 | 29.75 |
1.23* (0.26) |
83 | 36 | 89.25 | 29.75 |
1.75* (0.18) |
Expected values were calculated based on Mendelian 3:1 segregation ratio.
Chi-square (χ2) tests were performed for each cross and its reciprocal with 1 degree of freedom (df = 1).
χ2 values lower than the critical value (3.84 at p = 0.05) indicate conformity to the expected Mendelian ratio.
*Non-significant at p = 0.05.
Phenotyping of segregating population
Phenotypic data of parents and F1 populations was recorded to investigate the role of cytoplasmic gene(s) in the inheritance of different traits understudy. Furthermore, from all the four F2 populations, phenotypically flower colour was recorded at the full bloom stage when the plants were at peak flowering. While at pod developmental stage, pod colour and pod type were recorded for all plants separately. Finally, at harvesting stage when the seeds were fully matured, seed colour was recorded and seeds from each plant were harvested separately to ensure precise data collection. All qualitative traits such as flower colour, pod colour, seed colour and pod type were recorded based on visual assessment following standard descriptors for pea. Observations were made at appropriate growth stages using consistent scoring criteria to ensure uniformity across populations.
Statistical analysis
Chi-square (χ2) analysis was performed separately for each cross and its reciprocal to test the goodness-of-fit of observed segregation ratios with expected Mendelian ratios16. The calculated χ2 values were compared with tabulated values at appropriate degrees of freedom to determine the significance of deviation at the 5% probability level. The F2 population sizes were adequate for chi-square (χ2) analysis, as expected frequencies for all phenotypic classes exceeded the minimum requirement of five.
 |
where O = Observed frequency of plants; E = Expected frequency of plants; n = Number of phenotypic class.
Null hypothesis (Ho) is no difference between observed and expected frequency. Degrees of freedom (d.f.) represents the number of independent phenotypic classes that can vary freely after the total is fixed. When the calculated χ2 value was less than tabulated value for (n − 1) degrees of freedom (d.f.) at p = 0.05, Ho was accepted, while Ho was rejected when the calculated value of χ2 was more than tabulated value. The present study was designed to investigate inheritance patterns of qualitative traits; therefore, genotype × environment interactions were not analyzed. Phenotypic observations were primarily used to assess segregation patterns within each population.
Results
Morphological characterization
Morphological characterization of 26 edible podded pea genotypes based on flower colour, pod colour, seed colour and pod types showed a substantial degree of genetic variation among the studied genotypes (Table 2, Fig. 2). Two different flower colour viz., white and purple were observed among the genotypes. Five genotypes viz., Honey Snap, Sugar Daddy, Dwarf Grey Sugar, PED-18-1 and Royal Snow produced purple coloured flowers while remaining genotypes showed white colour flowers. Similarly, distinct classes of pod colour (green, yellow and green colour with purple pigmentation) and seed colour (green, brown, yellow, cream and light brown) were observed among the genotypes. Yellow colour pods were observed in Honey Snap and Sugar Daddy, green colour pods with purple pigmentation in Royal Snow and rest of the genotypes showed green colour pods. The genetic differences influencing chlorophyll retention and pigment synthesis are responsible for different colour seeds. Among these 26 genotypes, Honey Snap showed light brown seeds while, four genotypes viz., Sugar Daddy, Dwarf Grey Sugar, Royal Snow and PED-18-1 showed brown seeds. Three genotypes viz., Sugar Bon, Arka Sampoorna and PED-18-7 had yellow seeds, five genotypes viz., Airtel, Tardio, PED-21-1, PED-21-3, and PED-21-5 showed cream seed colour while, the remaining genotypes showed green colour seeds. Different pigment deposition and influence of genetic loci contributed for seed coat colour variation. In edible podded peas two distinct pod types viz., snow and sugar snap were observed. The 17 genotypes viz., Him Palam Mithi Phali-1, Him Palam Mithi Phali-2, Airtel, Tardio, Oregon Sugar Pod, Royal Snow, Sugar Daddy, Arka Sampoorna, Mithi Phali, PED-18-6, PED-18-7, PED-18-8, PED-21-1, PED-21-2, PED-21-3, PED-21-6, and PED-21-7 belongs to snow pea pod type whereas remaining nine genotypes viz., Punjab Mithi Phali-3, Honey Snap, Dwarf Grey Sugar, Cascatia, Sugar Bon, Tarvedo Sugar, PED-18-1, PED-21-4 and PED-21-5 fell into the sugar snap category. Out of 26 edible podded pea genotypes, four genotypes viz., Mithi Phali and Royal Snow from snow peas and Honey Snap and Punjab Mithi Phali-3 from sugar snap peas (Table 2) were identified genetically diverse for flower colour, pod colour, seed colour, and pod type along with superior horticulturally traits. Thus, these genotypes were selected for developing segregating populations to study the gene(s) governing inheritance of different traits.
Table 2.
Morphological description of 26 edible podded pea genotypes.
| S. no | Genotypes | Flower colour | Pod colour | Seed colour | Pod type |
|---|---|---|---|---|---|
| 1. | Him Palam Mithi Phali-1 | White | Green | Green | Snow |
| 2. | Him Palam Mithi Phali-2 | White | Green | Green | Snow |
| 3. | Honey Snap | Purple | Yellow | Light brown | Sugar snap |
| 4. | Punjab Mithi Phali-3 | White | Green | Green | Sugar snap |
| 5. | Airtel | White | Green | Cream | Snow |
| 6. | Tardio | White | Green | Cream | Snow |
| 7. | Oregon Sugar Pod | White | Green | Green | Snow |
| 8. | Sugar Daddy | Purple | Yellow | Brown | Snow |
| 9. | Dwarf Grey Sugar | Purple | Green | Brown | Sugar snap |
| 10. | Cascatia | White | Green | Green | Sugar snap |
| 11. | Royal Snow | Purple | Green with purple pigmentation | Brown | Snow |
| 12. | Sugar Bon | White | Green | Yellow | Sugar snap |
| 13. | Arka Sampoorna | White | Green | Yellow | Snow |
| 14. | Tarvedo Sugar | White | Green | Green | Sugar snap |
| 15. | PED-18-1 | Purple | Green | Brown | Sugar snap |
| 16. | PED-18-6 | White | Green | Green | Snow |
| 17. | PED-18-7 | White | Green | Yellow | Snow |
| 18. | PED-18-8 | White | Green | Green | Snow |
| 19. | PED-21-1 | White | Green | Cream | Snow |
| 20. | PED-21-2 | White | Green | Green | Snow |
| 21. | PED-21-3 | White | Green | Cream | Snow |
| 22. | PED-21-4 | White | Green | Green | Sugar snap |
| 23. | PED-21-5 | White | Green | Cream | Sugar snap |
| 24. | PED-21-6 | White | Green | Green | Snow |
| 25. | PED-21-7 | White | Green | Green | Snow |
| 26. | Mithi Phali | White | Green | Green | Snow |
Fig. 2.
Morphological variation observed among 26 edible podded pea genotypes. (a) Variation in flower colour showing white and purple flowered genotypes; (b) Variation in pod colour and pod type depicting green pods, yellow pods, and green pods with purple pigmentation, along with snow and sugar snap pod types, (c) Variation in seed colour illustrating green, yellow, cream, light brown and brown seed coat colour among studied genotypes.
Genetic studies
Flower colour
Genetics of flower colour was studied in four distinct crosses including their reciprocals especially to study the cytoplasmic inheritance of flower colour. The F1 hybrids of all reciprocal crosses produced purple flowers, indicating dominance of purple over white flower colour. The F2 populations of Honey Snap × Mithi Phali and its reciprocal cross segregated into 112 purple and 34 white flowers, and 98 purple and 32 white flowers, respectively (Table 3). Similarly, Royal Snow × Punjab Mithi Phali-3 and its reciprocal cross segregated into 99 purple and 30 white flowers, and 83 purple and 36 white flowers, respectively (Table 4). The segregation ratios in all crosses showed good agreement with the expected Mendelian 3:1 ratio as confirmed by chi-square analysis, indicating single-gene inheritance for flower colour.
Pod colour
The F1 hybrid obtained from Honey Snap × Mithi Phali and its reciprocal cross showed the green pods dominance over yellow pods. The genetic study of pod colour clearly demonstrated that there was no role of maternal inheritance for this trait. Total 146 F2 plants of Honey Snap × Mithi Phali produced 107 green and 39 yellow pods while, 95 green and 35 yellow pods were produced in its reciprocal cross i.e. Mithi Phali × Honey Snap (Table 3). Further inheritance of pod colour was studied using F2 population of ‘Royal Snow × Punjab Mithi Phali-3’ and observed 103 plants with green and 26 plants with green purple pigmentation pods from the total population of 129 plants which showed the single dominant gene control the inheritance for green pod colour. Similarly in the F2 population of cross ‘Punjab Mithi Phali-3 × Royal Snow’ it was observed that 85 plants produce green and 34 plants produce green purple-pigmented pods which clearly showed best fit in 3:1 goodness of fit ratio (Table 4).
Seed colour
In four distinct crosses, first-generation hybrids (F1) obtained for seed colour inheritance in all the cross combinations including reciprocal crosses exhibited brown or light brown seed colour, confirming the monogenic gene control of brown seed colour over green seeds. The absence of differences between seed colour in F1’s of all crosses including reciprocal crosses showed the absence of maternal/cytoplasmic gene effects, suggesting the presence of only nuclear genes in the inheritance of seed clour. Further, chi-square analysis of F2 populations showed best fit to the expected Mendelian 3:1 segregation ratio, confirming monogenic inheritance. In cross combination ‘Honey Snap × Mithi Phali’, 146 F2 seeds segregated into light brown (No: 105) and green seeds (No: 41), while its reciprocal cross showed 94 light brown and 36 green seeds (Table 3). Similarly 129 F2 plants of cross ‘Royal Snow × Punjab Mithi Phali-3’ produced 100 brown and 29 green seeds while, 83 brown and 36 green seeds were produced in its reciprocal cross (Table 4). These finding indicated single gene recessive inheritance of green seed colour in edible podded peas.
Pod type
The inheritance pattern of pod type in all the four cross combination including their reciprocal crosses showed monogenic inheritance where, snow type pods were dominant over the sugar snap types. The F1 plants of all the crosses showed snow-type pod without involvement of maternal or cytoplasmic genes. Further chi-square analysis of F2 generations showed a segregation ratio that best fit the expected Mendelian 3:1 pattern. The F2 population segregated by showing 106 snow and 40 sugar snap pods in Honey Snap × Mithi Phali cross and 94 snow and 36 sugar snap pods in Mithi Phali × Honey Snap cross (Table 3). The another independent cross ‘Royal Snow × Punjab Mithi Phali-3’ was used for studying inheritance of pod type and its F2 populations (No: 129), produced 95 snow type pods and 34 sugar snap type pods while its reciprocal cross resulted in 84 snow type pods and 35 sugar snap type pods (Table 4). These results of F2 population of all the four cross combinations including their reciprocal crosses indicate that a dominant allele controls snow-type pods and the recessive allele results in sugar snap type pods.
Discussion
Edible podded peas are classified into two distinct types, namely snow pea (Pisum sativum var. saccharatum) and sugar snap pea (Pisum sativum var. macrocarpon), which differ primarily in flower, pod and seed characteristics6. These are economically important yet comparatively underexplored segments of Pisum sativum. Unlike garden and field peas, where extensive genetic and genomic studies have been conducted, edible podded types have received limited attention despite their increasing demand in fresh vegetable markets. Therefore, understanding the key morphological traits in these types is importance as per breeding programme targeting pod quality, market prefernces and yield attributes. In the present study, reciprocal crosses were performed between genetically contrasting genotypes to examine the possible involvement of maternal or cytoplasmic inheritance. Sugar snap pea cv. Punjab Mithi Phali-3 (green pods, white flowers, sugar snap type pods and green seeds) was crossed with snow pea cv. Royal Snow (purple pigmented pods, purple flowers, snow type pods and brown seeds) and vice versa. Similarly, another reciprocal cross was made between snow pea cv. Mithi Phali (green pods, white flowers, snow type pods and green seeds) and sugar snap pea cv. Honey Snap (green pods, purple flowers, snap type pods and brown seeds). The uniform phenotypic expression observed in F1 hybrids, along with comparable segregation patterns in F2 populations of both reciprocal crosses for flower colour, pod colour, seed colour and pod type, consistently indicated that these traits are governed by nuclear genes and most likely controlled by single major genes exhibiting dominant inheritance, with no detectable cytoplasmic or maternal influence. This confirms that inheritance follows classical Mendelian patterns1,8,16,17, a finding of particular significance in edible-podded pea types where such genetic information remains limited. The absence of maternal effects further suggests that trait expression is stable irrespective of the direction of hybridization, thereby simplifying genetic analysis and facilitating more efficient breeding strategies. Therefore, breeders can slect parents based on trait complementarity without considering maternal lineage effects.
Furthermore, the dominance relationships observed in the present study are consistent with earlier reports describing inheritance patterns of colour and pod traits in pea17–19. Previous studies have also reported dominance of purple flower colour and green pod colour in crosses involving contrasting parental lines20, indicating that pod type does not influence the inheritance of colour-related traits. Seed coat colour inheritance in the present study revealed dominance of light brown and brown seed coats over green seeds, which agrees with earlier findings where pigmented grey seeds exhibited dominant inheritance when crossed with white-seeded plants18. Similar dominance of grey, grey-brown or leather-brown seed coat colour associated with violet-red flowers and reddish spotting in leaf axils has also been reported in pea21,22. These traits have been previously associated with the pleiotropic A gene in pea, which influences seed coat colour, flower colour, and pigmentation patterns, as reported in earlier studies13. The A gene encodes a transcription factor regulating anthocyanin biosynthesis, resulting in purple flower pigmentation and coloured seed coats. Additionally, mapping studies on pod colour in pea have identified candidate genes such as Psat0s4355g0080 and Psat0s4355g0120, which are closely associated with loci originally described by Mendel20. therefore, present work validates that these genetic mechansims remain conserved across different utilization groups because genetic interactions and expression patterns might varies sometime across backgrounds and such validation strengthens the classical genetic knowledge in diverse breeding materials.
The present study further confirmed the dominance of snow-type pods over sugar snap pods supporting earlier reports that attribute pod type differentiation to the dominant N gene, where the dominant allele confers thin-walled edible pods characteristic of snow peas, while the recessive condition results in thick-walled pods typical of sugar snap peas23. Therefore, monogenic and dominant inheritance of these traits provide a strong foundation for integrating molecular tools. Traits governed by single major genes are highly amenable to marker assiseted selection. Absence of cytoplasmic effects combined with simple inheritance patterns makes these traits suitable targets for genomic selection models to improve prediction accuracy. In conclusion, the present findings provides novel evidence for for the absence of cytoplasmic effects. By bridging classical genetics with modern molecular approaches, the findings establish a strong foundation for further linkage/QTL mapping studies to identify tightly linked markers and validate candidate genes in diverse genetic backgrounds.
Acknowledgements
The authors acknowledge the Punjab Agricultural University, Ludhiana, for providing the necessary infrastructure to conduct the research.
Author contributions
Conceptualization, R.K.D.; methodology, R.K.D. and Har.S.; software, S.Y., M.K. and N.V.; validation, R.K.D., Har.S. and S.Y.; formal analysis, Har.S, Han.S. and N,V.; investigation, R.K.D; resources, R.K.D. ; data curation, Han.S, M.K. and S.Y.; writing—original draft preparation, Har.S and N.V.; writing—review and editing, R.K.D, and P.S; supervision, R.K.D.; project administration, R.K.D.; funding acquisition, R.K.D. and P.S.; All authors have read and agreed to the published version of the manuscript.
Funding
The work is supported by the Ministry of Science and Technology, Department of Biotechnology, Government of India under the Scheme “Centre of Excellence – Development and Integration of Advanced Genomic Technologies for Targeted Breeding” (No: BT/Ag/CoE/PAU-GSKIG/2020-21) and CSS 52 (PC-6372).
Data availability
The data associated with the study has already been given in the manuscript. Besides, the Master’s thesis of first author (Har.S.) has been uploaded on Krishikosh website by Punjab Agricultural University, Ludhiana.
Declarations
Competing interests
The authors declare no competing interests.
Ethics approval and consent to participate
The germplasm used in the present study was developed, collected or introduced by the breeder (Dr. Rajinder Kumar Dhall) at Punjab Agricultural University, Ludhiana, Punjab, India. All the guidelines were followed as per the University research ethics for development, characterisation and documentation of germplasm accessions. The proper breeding procedure was followed during field experiments and its details were mentioned in material and methods section. Punjab Agricultural University, Ludhiana, Punjab, India has been established in 1962 by an act of legislature and is the custodian of crop biodiversity. As a faculty member of the University and Principal Olericulturist at Vegetable Science department, Corresponding author (RKD) is fully authorised to develop, conserve and characterise the germplasm for breeding improved varieties.
Consent to participate
This article does not contain any studies with human participants or animals performed by any of authors.
Consent for publication
All authors have read the manuscript and consented to publish.
Footnotes
Publisher’s note
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data associated with the study has already been given in the manuscript. Besides, the Master’s thesis of first author (Har.S.) has been uploaded on Krishikosh website by Punjab Agricultural University, Ludhiana.