Abstract
Maize (Zea may L.) is one of the most important crops worldwide, but ear rot poses a significant threat to its production. Diverse pathogens cause ear rot in China, with Fusarium spp. being predominant, especially Fusarium graminearum and Fusarium verticillioides. Current methods for the control of ear rot are limited, making the use of resistant germplasm resources an effective and economical management strategy. Earlier research focused on resistance to Fusarium ear rot (FER; caused by F. verticillioides) and Gibberella ear rot (GER; caused by F. graminearum), but assessing maize resistance to multiple major Fusarium spp. is critical in ensuring maize production. Thus, the resistance of 343 maize germplasm resources to ear rot caused by six Fusarium spp. (F. verticillioides, F. graminearum, F. proliferatum, F. meridionale, F. subglutinans, and F. temperatum) was evaluated in this study. Over three years, 69 and 77 lines resistant to six and five ear rot diseases, respectively, and 139 lines resistant to both FER and GER were identified. Moreover, the 343 germplasm resources were divided into eight heterotic groups, of which PH4CV was the most resistant one, whereas NSS and Pioneer Female were the least resistant ones. These findings provide a basis for the development of maize cultivars with broad-spectrum ear rot resistance.
Keywords: maize germplasm, Fusarium species, ear rot, resistance, precise identification
1. Introduction
Maize (Zea mays L.) is one of the main crops in terms of both planting area and yield. With a total production volume of 12.14 billion tons and a planting area of 161.7 million hectares in 2024, according to USDA data, maize is the most significant grain crop worldwide, with substantial contributions to the global food supply and agriculture-based economies. It has critical roles associated with feed and food production and industrial processing, thereby directly affecting food security and sustainable development [1].
Maize ear rot represents the most severe disease complex in maize-growing regions worldwide [2], primarily infecting kernels, along with significant yield and quality losses. This complex encompasses distinct diseases, such as Fusarium ear rot (FER), Gibberella ear rot (GER), and Aspergillus ear rot (AER), each caused by specific fungal pathogens. In China, its prevalence is severe, with infection rates generally ranging from 10% to 20%, and they can reach 40–50% during epidemics. Continuous rainy conditions during the grain-filling stage exacerbate maize ear rot outbreaks, leading to yield losses of 30–40%. In severe cases, the infection rates can reach 40–100% for some susceptible varieties [3]. Globally, more than 70 species have been identified as causal agents of maize ear rot, including Fusarium spp., Aspergillus spp., Penicillium spp., Trichoderma spp., Stenocarpella maydis, Trichoderma atroviride, Sarocladium zeae, Lecanicillium lecanii, and Trichothecium roseum. These fungi contribute significantly to maize ear rot severity and mycotoxin contamination, with detrimental effects on both crop yields and safety. Among these species, Fusarium spp. are the most prominent pathogens worldwide [4]. Moreover, they are primarily transmitted through soil, plant residues, or infected seeds, often overwintering as mycelia or spores. Maize ear rot spreads via soil, insect vectors, or rainwater, with the field temperature and humidity playing key roles in disease development. Favorable temperatures and high humidity are particularly conducive to the outbreak and spread of this disease [5,6,7].
Pathogens causing maize ear rot can decrease maize yields, while also producing various harmful toxins that significantly affect grain quality. Fusarium spp., the primary pathogens, produce different toxins during infection, with deoxynivalenol (DON) and fumonisins being the most common. For example, F. verticillioides predominantly produces fumonisins, which are highly toxic to animals, causing delayed growth, disease, or even death. In humans, fumonisins are linked to esophageal, liver, and stomach cancers [8]. The F. graminearum species complex primarily produces zearalenone (ZEN), nivalenol, and DON. ZEN exposure can cause multiple symptoms, including weakness, dizziness, diarrhea, and severe disruptions to the central nervous system. DON has highly cytotoxic and immunosuppressive effects, posing significant risks to human and livestock health. Ingesting DON-contaminated food can lead to acute poisoning symptoms, including vomiting, diarrhea, fever, unsteady gait, and delayed reactions, with severe cases causing hematopoietic system damage and death [9,10].
In China, Fusarium spp. are the primary pathogens causing maize ear rot, with significant diversity in pathogens and regional distributions [11,12]. Duan collected 239 maize ear rot samples from 18 provinces in 2009–2014, revealing that F. verticillioides and F. graminearum represented 95.1% of the identified Fusarium isolates. Other Fusarium spp. included F. culmorum, F. oxysporum, F. proliferatum, F. subglutinans, and F. solani [9]. In a previous study involving 14 provinces, Ren identified Fusarium spp. as the dominant pathogens, with F. verticillioides and F. graminearum being the most common. In addition to F. verticillioides and F. graminearum, the other isolated Fusarium spp. included F. proliferatum, F. oxysporum, F. subglutinans, F. culmorum, F. solani, and F. semitectum, which were sorted according to the number of detected isolates [13]. In a study conducted by Zhou et al. from 2014 to 2015 in Chongqing and the surrounding areas, 10 Fusarium spp. were isolated from maize ear rot samples (F. verticillioides, F. proliferatum, F. graminearum species complex, F. oxysporum species complex, F. fujikuroi, F. equiseti, F. culmorum, F. incarnatum, F. kyushuense, and F. solani); the dominant pathogens were F. verticillioides, the F. graminearum species complex, and F. proliferatum [14]. In a study by Sun et al., Fusarium spp. were isolated from maize ear rot samples collected in Hainan in 2016; five species were identified, including F. verticillioides, F. subglutinans, F. equiseti, and F. andiyazi [15]. In 2018, Wang collected 143 typical ear rot samples from 21 maize-producing counties in Heilongjiang. From 200 single-spore isolates, 12 Fusarium spp. were identified. The species, listed in descending order of frequency, were F. graminearum, F. verticillioides, F. subglutinans, F. proliferatum, F. boothii, F. temperatum, F. andiyazi, F. incarnatum, F. sporotrichioides, F. poae, F. commune, and F. asiaticum [16]. Chai et al. collected 254 maize ear rot samples across Jilin Province during 2020–2021. Sixteen pathogenic Fusarium species were isolated, with F. verticillioides and F. graminearum exhibiting the highest isolation frequencies. Subdominant species included F. proliferatum, F. boothii, F. subglutinans, F. temperatum, F. asiaticum, F. chlamydosporum, F. fujikuroi, F. equiseti, and F. subglutinans (in descending order of prevalence) [17,18]. Wang et al. collected 36 maize ear rot samples in Gansu Province in 2020–2021, isolating eight pathogenic Fusarium species. Their isolation frequencies were as follows: F. verticillioides (68.49%), F. proliferatum (19.18%), F. subglutinans (6.85%), F. boothii (2.40%), F. graminearum (1.71%), F. temperatum (0.69%), F. poae (0.34%), and F. andiyazi (0.34%) [19].
The geographic distribution and ecological dominance of the main Fusarium species in China are presented in Table 1. F. verticillioides and F. graminearum are the dominant pathogens causing maize ear rot across China [20], being more prevalent in the northeastern regions than in other areas. F. subglutinans and F. temperatum are more commonly found in Northern China, while there is considerable diversity in the Fusarium spp. in the central and southern regions. F. proliferatum is mainly found in central provinces, whereas the F. graminearum species complex is often isolated in southern regions [21]. Additionally, F. proliferatum, F. subglutinans, and F. temperatum have been detected in various regions and are becoming secondary dominant pathogens. Because of the diversity of these pathogens, crop rotations and fungicide applications have had limited effects in preventing maize ear rot [22], highlighting the importance of strengthening maize resistance through the selection of stable, multi-resistant germplasm, which is key for long-term disease management and breeding.
Table 1.
Geographic distribution and ecological dominance of Fusarium species in China.
| Fusarium sp. | Geographic Distribution | Ecological Status |
|---|---|---|
| F. verticillioides | All primary maize agroecological zones | Dominant species |
| F. graminearum | All primary maize agroecological zones | Dominant species |
| F. proliferatum | Northeast, northwest, southwest | Regionally dominant species |
| F. meridionale | Southwest, southeast | Regionally dominant species |
| F. subglutinans | Northeast, northwest | Regionally dominant species |
| F. temperatum | Northeast | Regionally dominant species |
| F. oxysporum | Geographically undifferentiated distribution | Endemic species |
| F. culmorum | Geographically undifferentiated distribution | Endemic species |
| F. solani | Geographically undifferentiated distribution | Endemic species |
| F. semitectum | Geographically undifferentiated distribution | Endemic species |
| F. fujikuroi | Geographically undifferentiated distribution | Endemic species |
From 2006 to 2009, Duan et al. evaluated the resistance of 836 superior maize resources to FER, identifying 5 highly resistant, 71 resistant, and 388 moderately resistant germplasm resources [23]. Between 2006 and 2012, Duan et al. evaluated 1647 maize germplasm resources for resistance to FER, identifying 27 highly resistant, 352 resistant, and 784 moderately resistant lines [24]. Between 2009 and 2011, Guo et al. used a natural field infection method to assess maize resistance to Fusarium ear rot and identified 74 highly resistant, 55 resistant, and 275 moderately resistant maize lines [25]. From 2018 to 2020, Han et al. analyzed the resistance of 10,524 maize germplasm resources to FER and GER, identifying 191 highly resistant lines, which were evaluated further, ultimately revealing 59 lines with stable resistance [26]. Zhang et al. screened 44 maize inbred lines for resistance to both FER and GER and identified three highly resistant lines [27]. Zhao et al. precisely evaluated 48 maize inbred lines and selected five lines resistant to GER [28]. In 2018–2020, Duan et al. examined 690 representative maize germplasm resources resistant to FER, identifying 35 germplasm resources with stable resistance to FER [29]. Xia et al. screened 346 maize inbred lines, identifying 45 lines that were at least moderately resistant to both FER and GER [30]. The dominant pathogens in different regions can change over time [14,31]. To address the potential risks from shifts in predominant pathogens, in addition to focusing on FER and GER, attention should be paid to ear rot caused by F. proliferatum, F. subglutinans, and F. temperatum, which are emerging threats to maize cultivation [32]. A shift from F. culmorum to F. graminearum and F. verticillioides in Heilongjiang is an example of a change in the dominant pathogens over time. Additionally, multiple dominant pathogens may coexist within the same province. For example, in Shandong, F. verticillioides is widely distributed, but F. poae and F. graminearum are major pathogens in the central, eastern, and southwestern regions [33].
Current evaluations of maize germplasm resistance to ear rot are largely focused on resistance to F. verticillioides and F. graminearum, leaving broad-spectrum resistance to multi-Fusarium systems critically underexplored. Although F. proliferatum, F. moniliforme, F. subglutinans, and F. temperatum are also primary pathogenic fungi, their geographic distribution varies significantly across regions. Therefore, there is a critical need for analyses of resistance to multiple Fusarium spp. to ensure safe maize production. To address this gap, we conducted China’s first systematic screening of 343 maize inbred lines against six economically impactful Fusarium species (F. verticillioides, F. graminearum, F. proliferatum, F. subglutinans, F. temperatum, and F. meridionale) across three years (2022–2024), with the objectives of identifying multi-resistant germplasm and quantifying pathogen correlation networks.
2. Results
From 2022 to 2024, 343 maize inbred lines were evaluated for resistance to ear rot caused by six Fusarium species. The resistance level was assessed in visual and machine-assisted surveys. With the exception of 2023, where extreme weather events resulted in significantly lower disease incidence, all other years exhibited epidemiologically effective infection pressure for each Fusarium species (Table 2).
Table 2.
The mean disease severity for ear rot caused by six Fusarium species in three years.
| F. verticillioides Ear Rot | F. graminearum Ear Rot | F. proliferatum Ear Rot | F. temperatum Ear Rot | F. meridionale Ear Rot | F. subglutinans Ear Rot | |
|---|---|---|---|---|---|---|
| 2022 | 5.76 | 5.28 | 5.86 | 5.47 | 5.79 | 6.07 |
| 2023 | 3.56 | 3.61 | 4.53 | 3.03 | 3.69 | 4.24 |
| 2024 | 6.55 | 6.59 | 6.26 | 6.10 | 6.89 | 6.36 |
Figure 1 illustrates the typical field symptoms of ear rot caused by the six species considered in this study. Maize infected with F. graminearum developed purplish red lesions on ear tissues. In contrast, an infection by F. temperatum resulted in pale blue lesions, whereas an infection by F. subglutinans mostly induced black necrotic lesions on infected ears. The main symptoms of infections by the remaining three Fusarium spp. were white or whitish lesions at infection sites. These distinct disease symptoms provide critical diagnostic markers for the identification of ear rot pathogens under field conditions.
Figure 1.
Symptoms of maize ear rot caused by Fusarium spp. in the field. (a) Ear rot caused by F. graminearum; (b) ear rot caused by F. temperatum; (c) ear rot caused by F. subglutinans; (d) ear rot caused by F. proliferatum; (e) ear rot caused by F. verticillioides; (f) ear rot caused by F. meridionale. Scale bar: 5 cm.
Of the 343 germplasm resources evaluated over 3 years, 69 and 77 lines were resistant to six and five ear rot types caused by Fusarium species, respectively, whereas 139 lines were resistant to both FER and GER. Some lines were highly resistant to all six ear rot diseases caused by Fusarium species, including K21HZD2610, K21HZD0611, K21HZD2374, K21HZD6018, K21HZD0057, K21HZD2879, K21HZD2596, and K21HZD5342. Selected highly resistant materials are presented in Figure 2.
Figure 2.
Selected materials highly resistant to six ear rot pathogens. (a) K21HZD2596; (b) K21HZD5342. From left to right: maize ears infected with F. graminearum, F. proliferatum, F. subglutinans, F. temperatum, F. verticillioides, and F. meridionale. Scale bar: 5 cm.
Correlations among the resistances of the tested germplasm resources to six ear rot pathogens exhibited marked interannual variability between 2022 and 2024. In 2022, the resistance correlations (r-values) ranged from 0.18 to 0.51 (Figure 3a), with the r-values for most pairwise comparisons exceeding 0.4, indicating moderate correlations. Exceptions included the resistance to GER, which had a relatively weak association with the resistance to ear rot caused by F. temperatum or F. proliferatum. However, in 2023, the r-values decreased to −0.01–0.21 (Figure 3b), likely because of extreme environmental stressors, including sustained high temperatures (>40 °C) and unseasonal late rainfall, which suppressed uniform disease development and obscured intrinsic resistance relationships. By 2024, the correlations rebounded robustly, with r-values between 0.36 and 0.71 (Figure 3c). Resistance correlations increased significantly, with the r-values for all comparisons, except those involving ear rot caused by F. proliferatum, exceeding 0.62. Notably, GER resistance was highly correlated with the resistance to FER and ear rot caused by F. subglutinans, suggesting that there may be shared resistance mechanisms under certain environmental conditions. A heatmap of the correlations between the resistance of the tested materials to the six ear rot pathogens from 2022 to 2024 revealed a general lack of strong correlations among the resistance to most Fusarium spp. (r-values of 0.16 to 0.54) (Figure 3d). However, the r-value for the resistance of the tested materials to FER and ear rot caused by F. temperatum or F. proliferatum was approximately 0.5, indicating a moderate correlation.
Figure 3.
Heatmap of correlations between the resistance of tested materials to six ear rot pathogens between 2022 and 2024. (a) 2022; (b) 2023; (c) 2024; (d) 2022–2024. (FV: FER, FG: GER, FP: F. proliferatum ear rot, FT: F. temperatum ear rot, FM: F. meridionale ear rot, FS: F. subglutinans ear rot), data markers indicate statistical significance (*: p < 0.05; **: p < 0.01; ***: p < 0.001).
The evaluation of the resistance to the six ear rot pathogens indicated that 51.99% of the tested germplasm resources were moderately resistant, 28.47% were susceptible, 16.52% were resistant, 2.24% were highly susceptible, and only 0.78% were highly resistant. Thus, most of the tested materials were moderately resistant to the six ear rot pathogens, whereas highly susceptible or highly resistant accessions were relatively rare.
According to an analysis of germplasm resistance to FER and GER, four and three accessions were highly resistant, 62 and 66 were resistant, and 175 and 172 were moderately resistant to FER and GER, respectively. Five accessions were highly susceptible to FER (Figure 4a), but 16 accessions were highly susceptible to GER (Figure 4b), representing the highest number of accessions highly susceptible to one of the six ear rot pathogens included in this study. The number of susceptible accessions was the highest for ear rot caused by F. proliferatum (119 accessions; 34.6%) (Figure 4c), followed by ear rot caused by F. subglutinans (118 accessions; 34.3%) (Figure 4f). In terms of the smallest number of resistant accessions, only 29 accessions (8.4%) were resistant to ear rot caused by F. proliferatum, which was in contrast to the 45 accessions resistant to ear rot caused by F. subglutinans. A total of 66 (19.1%) accessions were highly susceptible or susceptible to ear rot caused by F. temperatum (Figure 4d), which was smaller than the number of accessions highly susceptible or susceptible to ear rot caused by the other pathogens. No accession was highly resistant to ear rot caused by F. meridionale (Figure 4e). Overall, the tested accessions were most resistant to ear rot caused by F. temperatum, followed by FER and GER. Accessions resistant to ear rot caused by F. subglutinans or F. meridionale were generally moderately resistant. The poorest resistance performance was observed for ear rot caused by F. proliferatum.
Figure 4.
Distribution of germplasm resistance to ear rot caused by six pathogens. (a) FER; (b) GER; (c) ear rot caused by F. proliferatum; (d) ear rot caused by F. temperatum; (e) ear rot caused by F. meridionale; (f) ear rot caused by F. subglutinans.
An analysis of variance (ANOVA) across three years revealed significant genotypic variance (p-value < 0.05) for resistance to all six Fusarium species, indicating stable and heritable differences in ear rot resistance among the 343 maize inbred lines. The largest genotypic variances (genotypic variance > 1.6) were observed for GER and FER, suggesting that these two species are the most suitable targets for resistance breeding (Table 3).
Table 3.
Significance of genotypic variance and heritability values among six Fusarium ear rot types.
| Fusarium Ear Rot | Genotypic Variance | F-Value | Broad Sense Heritability Value | p-Value |
|---|---|---|---|---|
| F. graminearum ear rot | 1.85 ± 0.21 | 24.37 | 0.86 | <0.001, *** |
| F. verticillioides ear rot | 1.62 ± 0.18 | 19.83 | 0.83 | <0.001, *** |
| F. proliferatum ear rot | 1.28 ± 0.15 | 15.02 | 0.54 | <0.001, *** |
| F. temperatum ear rot | 0.97 ± 0.11 | 10.45 | 0.32 | 0.003, ** |
| F. meridionale ear rot | 0.89 ± 0.10 | 9.12 | 0.31 | 0.008, ** |
| F. subglutinans ear rot | 0.75 ± 0.09 | 7.85 | 0.29 | 0.021, * |
Data markers indicate statistical significance (*: p < 0.05; **: p < 0.01; ***: p < 0.001).
In contrast, F. proliferatum ear rot, F. temperatum ear rot, F. meridionale ear rot, and F. subglutinans ear rot showed strong genotype-by-environment interactions, with G × E effects accounting for over 32% of the total phenotypic variation. This indicates that resistance to these species is highly influenced by environmental factors, particularly in the case of F. temperatum ear rot, which exhibited the strongest environmental dependency. GER and FER had comparatively lower G × E effects (<21%), reflecting more stable resistance performance across different environments (Table 4).
Table 4.
Contribution of genotype × environment interaction to phenotypic variance in ear rot caused by six Fusarium species.
| Fusarium Ear Rot | G × E Interaction Variance | Percentage of Total Variance |
|---|---|---|
| F. graminearum ear rot | 0.38 ± 0.05 | 17.2% |
| F. verticillioides ear rot | 0.42 ± 0.06 | 20.6% |
| F. proliferatum ear rot | 0.61 ± 0.08 | 32.3% |
| F. temperatum ear rot | 0.75 ± 0.09 | 43.6% |
| F. meridionale ear rot | 0.68 ± 0.08 | 43.3% |
| F. subglutinans ear rot | 0.59 ± 0.07 | 44.0% |
STRUCTURE 2.2 was used for the heterotic group classification of 294 of 343 accessions. An analysis of the population structure revealed that the ΔK value was the highest when K was 8, indicative of eight major heterotic groups (Figure 5). These groups were as follows: Pioneer Male (79 accessions), subdivided into Pioneer Male A (23 accessions) and Pioneer Male B (56 accessions), and Pioneer Female (62 accessions).
Figure 5.
Heterotic group classification of maize germplasm resources. NSS (34 accessions); SS (27 accessions); TSPT (31 accessions); PB (31 accessions); and PH4CV (30 accessions). According to the observed resistance to six ear rot pathogens, the germplasm resources were categorized as follows: highly resistant accessions (resistant to five or six Fusarium species), moderately resistant accessions (resistant to two to four Fusarium species), and susceptible accessions (susceptible to five or six Fusarium species).
The SS group had the most accessions resistant to all six Fusarium species (17 accessions), followed by the PH4CV group (14 accessions) and the Pioneer Male B group (12 accessions). By contrast, the NSS group consisted of only two accessions resistant to all six Fusarium species (Figure 6a). The Pioneer Male B group had the most accessions resistant to FER and GER (23 accessions). The other groups had similar resistance levels, with approximately 14 resistant accessions per group (Figure 6b).
Figure 6.
Classification of maize germplasm resources on the basis of different hierarchies. (a) Accessions resistant to six ear rot pathogens; (b) accessions resistant to FER and GER.
The Pioneer Male A group was most strongly resistant to ear rot caused by F. temperatum (with 87% of the tested accessions being moderately resistant or resistant), followed by ear rot caused by F. subglutinans and FER. This group exhibited partial resistance to ear rot caused by F. proliferatum and GER. However, it was poorly resistant to ear rot caused by F. meridionale (as 34% of the tested accessions were susceptible) (Figure 7a). The Pioneer Male B group was most resistant to ear rot caused by F. temperatum (85.7% of the tested accessions were moderately resistant or resistant), but it was also moderately resistant to FER and GER. However, its resistance was weakest for ear rot caused by F. subglutinans (where 37.5% of the tested accessions were susceptible) (Figure 7b). The SS group was most resistant to ear rot caused by F. temperatum (where 88.4% of the tested accessions were resistant or moderately resistant), followed by GER and ear rot caused by F. subglutinans, with intermediate resistance to FER and ear rot caused by F. meridionale or F. proliferatum (Figure 7c). The TSPT group was resistant or moderately resistant to four Fusarium spp. (with more than 75% resistant materials), but it also exhibited intermediate resistance to FER and ear rot caused by F. subglutinans (Figure 7d). The PB group was similarly resistant to GER and ear rot caused by F. temperatum or F. meridionale (where 83% of the tested accessions were moderately resistant or resistant), but 33% of the accessions in this group were susceptible to ear rot caused by F. verticillioides, F. subglutinans, or F. proliferatum (Figure 7e). The PH4CV group had the highest overall resistance, with 93%, 87%, 83%, and 80% of the tested accessions being moderately resistant or resistant to ear rot caused by F. temperatum, F. subglutinans, F. meridionale, and F. verticillioides (Figure 7f). By contrast, the NSS group was effectively resistant to only ear rot caused by F. temperatum (where 90% of the tested accessions were moderately resistant or resistant) or F. meridionale (87%), with 30% of the tested accessions being susceptible to ear rot caused by the other four Fusarium species (Figure 7g). The Pioneer Female group exhibited the poorest resistance, with 34–42% of the tested accessions susceptible to all six Fusarium species (Figure 7h).
Figure 7.
Distribution of resistance to six Fusarium species across heterotic groups. (a) Pioneer Male A group; (b) Pioneer Male B group; (c) SS group; (d) TSPT group; (e) PB group; (f) PH4CV group; (g) NSS group; (h) Pioneer Female group.
A comprehensive evaluation revealed that PH4CV was the group that was most resistant to ear rot, followed by the Pioneer Male and SS groups, which exhibited moderate, but statistically significant, resistance. By contrast, the TSPT and PB groups had intermediate resistance profiles, whereas NSS and Pioneer Female were consistently the groups with the least effective resistance to all tested Fusarium species.
3. Discussion
Maize ear rot caused by fungal pathogens is one of the most significant threats to maize production [2,34]. It severely affects the yield, and the associated production of various toxins depending on the pathogens poses a risk to human and animal safety. Therefore, controlling maize ear rot is crucial in ensuring economic stability.
Although certain fungicide formulations may be useful in controlling ear rot under controlled conditions [35], the diversity of pathogens and the complexity of environmental factors in the field are major challenges to their widespread application. Enhancing the inherent disease resistance of maize remains the most effective and economical approach to protecting against ear rot. Both domestic and international studies have extensively focused on screening for germplasm resources resistant to FER and GER, resulting in the identification of numerous superior resistant germplasm resources [36,37]. However, there has been limited research on resistance to multiple ear rot pathogens. In the current study, 343 germplasm resources were precisely evaluated for resistance to ear rot caused by six Fusarium spp. over three years (2022–2024). Promising resources, critical for breeding broadly adaptive, multi-resistant maize varieties, were identified.
Maize ear rot resistance is a genetically complex, polygenic quantitative trait [38]. The evaluation of ear rot resistance is influenced by several factors, including the field planting methods, cultivation systems, geography, temperature, annual rainfall, and other pests and diseases. Consequently, there may be discrepancies in the results obtained from different locations and years [39,40]. The epidemiological significance of the six studied Fusarium species also varies across years. F. graminearum and F. verticillioides were consistently detected at high frequencies. In contrast, species such as F. temperatum and F. meridionale were more sporadic, likely influenced by specific climatic conditions. These fluctuations may partially explain the year-to-year variation in disease severity and genotype performance. Thus, the resistance observed in this study may reflect both broad-spectrum resistance and species-specific responses shaped by the annual pathogen composition.
In the present study, the correlation coefficients for the resistance of the tested accessions to six ear rot pathogens ranged from −0.01 to 0.21 in 2023; this range was significantly influenced by the climate conditions. Temperature and humidity play crucial roles in disease development. In 2023, the overall disease incidence remained relatively low because of high temperatures (>40 °C) and drought in July, which not only hindered disease development but also affected maize growth. The climate in 2022 and 2024 was more conducive to ear rot, resulting in relatively consistent correlation coefficients among the infections by the six Fusarium spp.
In 2022, the r-values for the resistance of the tested accessions to six ear rot pathogens ranged from 0.18 to 0.51. Excluding GER, the r-values for the resistance of the tested accessions to ear rot caused by the other pathogens exceeded 0.4 (i.e., moderate correlations). In 2024, the r-values for the resistance of the tested accessions to the six ear rot pathogens ranged from 0.36 to 0.71, with most r-values greater than 0.62 (i.e., strong correlations), including those for the resistance of the tested accessions to FER and ear rot caused by F. proliferatum or F. subglutinans. An analysis of the data compiled over the three-year study period revealed correlations between the resistance of the tested accessions to the six ear rot pathogens (r-values between 0.16 and 0.54), suggesting that certain materials might share similar ear rot resistance mechanisms, but this possibility will need to be experimentally validated. The correlations for the resistance of the tested accessions to other ear rot pathogens were relatively low. The response of each accession to different Fusarium spp. may vary significantly. According to previous research involving maize, resistance to FER is significantly correlated with resistance to GER [41,42]. In the current study, the r-values for the resistance to these two Fusarium species in 2022 and 2024 were 0.46 and 0.71, respectively, confirming a certain level of association. However, resistance correlations for the other Fusarium spp. have not been reported. This study detected moderate correlations in the resistance to ear rot caused by most of the tested pathogens, with the exception of resistance to ear rot caused by F. proliferatum, which was not highly correlated with resistance to ear rot caused by the other pathogens. These findings may need to be further validated in future studies.
Currently, the two main methods of evaluating maize ear rot are visual and machine-assisted surveys. Visual surveys remain the primary method for large-scale field evaluations [43]. Their advantages include their affordability, speed, and the fact that they can be conducted in all locations, but they are highly influenced by surveyor expertise and tend to have some inherent errors. Data from visual surveys typically represent the average disease scale across all ears of the same material, rather than the actual average diseased area. Although ears with 50% and 100% disease-affected areas are classified as highly susceptible (disease scale of 9), their actual resistance differs substantially. The correlation between the two methods was exceptionally strong (Pearson’s r = 0.65), indicating a moderately strong linear relationship. Machine-based phenotyping captured a broader phenotypic spectrum, demonstrating a superior resolution for extreme phenotypes—particularly in highly susceptible materials (Figure 8). Quantifying resistance levels on the basis of the mean disease-affected areas may be more precise than methods involving a conventional mean disease scale. Accordingly, the mean disease-affected area is crucial in quantifying the disease resistance of materials. Machine-assisted surveys rely on specialized imaging equipment and algorithms, thereby decreasing the need for expert knowledge among operators. These surveys produce consistent and precise results, eliminating human error, and are increasingly used for accurate ear rot resistance evaluations. However, issues regarding these surveys persist, including difficulties in distinguishing Fusarium ear rot lesions from other lesions (i.e., not caused by Fusarium spp.), which may lead to overestimations. Additionally, mechanical damage to kernels may lead to inflated readings. Continually optimizing algorithms is expected to lead to increased accuracy (i.e., data that match actual disease levels).
Figure 8.
Scatter plot of visual and machine-assisted phenotyping for Fusarium ear rot. X-axis: machine-assisted survey, Y-axis: visual survey. Black line: y = 0.435x + 2.83.
Survey methods should be selected according to specific needs. For the large-scale screening of materials in fields or assessments of varietal resistance where quantitative analyses of ear rot resistance are not required, visual surveys are clearly more suitable. However, for the precise gene mapping of ear rot resistance or accurate examinations of varietal resistance, machine surveys are more appropriate because of their accuracy and lack of human error. Future research should aim to apply machine learning and algorithms to screen for maize ear rot.
4. Materials and Methods
4.1. Test Materials
A total of 343 representative maize inbred lines with rich genetic diversity were used in this study. These lines were sourced from various institutions (e.g., Henan Academy of Agricultural Sciences, Heilongjiang Academy of Agricultural Sciences, Liaoning Academy of Agricultural Sciences, Beijing Academy of Agriculture and Forestry, Chinese Academy of Agricultural Sciences, Sichuan Agricultural University, and China Agricultural University). A list of the germplasm resources evaluated in this study is included in Table A1.
4.2. Pathogen and Inoculum Preparation
The six highly pathogenic Fusarium spp. (F. verticillioides, F. graminearum, F. proliferatum, F. meridionale, F. subglutinans, and F. temperatum) used in this experiment were isolated, identified, preserved, and cultured in our laboratory [14]. For inoculation, we used a single isolate per species. Figure 9 presents the colony and spore morphologies of these six isolates.
Figure 9.
Colony and spore morphologies of six Fusarium spp. (a) F. graminearum; (b) F. proliferatum; (c) F. subglutinans; (d) F. temperatum; (e) F. verticillioides; (f) F. meridionale.
4.3. Disease Identification Plot
Maize resistance to ear rot was precisely evaluated in plots with environmental conditions conducive to disease development. These plots were located in the Changping (40°10′ N, 116°14′ E) and Shunyi (40°13′ N, 116°65′ E) districts of Beijing. The resistance of the germplasm resources was assessed in Changping in 2022–2023 and in both Changping and Shunyi in 2024. All materials were planted in mid-May consistently from 2022 to 2024. Experimental materials were randomly arranged, with each material planted in two rows (one row in Changping and one in Shunyi in 2024). Each row was 5.0 m long, with row spacing of 0.6 m and 25 plants per row. Susceptible and resistant control materials (B73 and X178, respectively) were included at every 100 rows. To prevent pollination disruption by pests, Ostrinia furnacalis and Mythimna separata were controlled with 5% emamectin benzoate spray during the seedling (V3) and bell (V12) stages, respectively.
4.4. Inoculum Preparation
Preparation of pea broth: A volume of 40 g/L dried peas was boiled in 1 L water for 30 min. The suspension was filtered through a cheesecloth, after which the volume was adjusted to 1 L, and it was autoclaved at 121 °C for 30 min.
Preparation of spore suspension: Six highly pathogenic Fusarium spp. activated from PDA medium in plates were cut into small pieces and added to sterile liquid pea broth. The culture was incubated at 25 °C in darkness, with shaking at 180 rpm, for 7–10 days. The mycelium was filtered and the spore suspension was collected and prepared for a concentration of 1 × 106 spores/mL.
4.5. Inoculation Method
Duan et al. and Wang et al. compared the efficacy of two major inoculation methods, namely silk channel injection and ear injection (traumatic inoculation), for the evaluation of maize ear rot resistance; the results obtained from both methods were highly consistent (correlation coefficients > 0.90) [29,44]. The silk channel injection method, which more closely mimics the natural infection of maize ears by Fusarium spp., was selected for this study. At 3–5 days post-silking or when silks attained 5–10 cm in length, a calibrated continuous syringe was laterally inserted into the hollow central cavity of the silk channel. Each ear was inoculated with 2 mL of spore suspension via injection, with only the primary ear per plant being inoculated. Each type of ear rot was inoculated in two rows, with a total of 50 plants.
4.6. Disease Resistance Survey and Evaluation
Disease resistance was evaluated at the full maturity stage. For each accession, husk leaves were removed from the ears and the first ears were collected. Disease resistance was assessed using a machine-assisted system (maize ear rot image recognition and automated imaging system). The following describes the general working principles of the machine-assisted system used for disease evaluation. To ensure clear visualization, excess silks and husk leaves adhering to the maize ears were carefully removed prior to imaging. Each ear from the same genotype was sequentially placed into a machine equipped with rolling rollers and an overhead camera. Under computer control, the camera captured 12 evenly spaced images of each ear as it rotated within the rollers. A custom algorithm (the algorithm resembled that of “The Ear Unwrapper” [45] and the image system used by Wen et al. [46]) was then used to calculate the diseased area from the 12 images of each ear. The average diseased area of all ears from the same line was calculated to represent the disease severity of that line. The diseased area was then converted to a disease severity grade for an evaluation of resistance (Table 5). A visual survey was also conducted to generate supplementary data. Specifically, the diseased area was visually inspected and classified according to the percentage of the ear with disease symptoms. The average disease severity score was calculated and used for the final evaluation of resistance.
Table 5.
Classification of disease severity levels and criteria for evaluation of ear rot resistance.
| Scale | Description | Ear Rot Score | Resistance |
|---|---|---|---|
| 1 | 0~1% of the diseased ear surface | ≤1.5 | Highly resistant (HR) |
| 3 | 2~10% of the diseased ear surface | 1.6~3.5 | Resistant (R) |
| 5 | 11~25% of the diseased ear surface | 3.6~5.5 | Moderately resistant (MR) |
| 7 | 26~50% of the diseased ear surface | 5.6~7.5 | Susceptible (S) |
| 9 | 51~100% of the diseased ear surface | 7.6~9.0 | Highly susceptible (HS) |
4.7. Statistical Analysis of Genotypic Variance and G × E Interaction
To assess the genetic variation and genotype-by-environment interactions for resistance to ear rot, a two-way analysis of variance (ANOVA) was conducted across three consecutive years for each Fusarium species. The model included the genotype, year, and their interaction as fixed effects. Genotypic variance and the proportion of variance explained by G × E interaction were estimated. The significance of genotype effects was tested using F-statistics (p < 0.05). The relative magnitude of the G × E interaction was calculated as the percentage of the total phenotypic variation attributed to the interaction term. All statistical analyses were performed using R (v4.2.0) or SAS (v9.4).
4.8. Heterotic Group Classification
A total of 294 maize inbred lines were genotyped by sequencing. The population structure was inferred using STRUCTURE v2.3.4, with the following settings [47]: admixture model and correlated allele frequencies; 50,000 iterations for Markov Chain Monte Carlo (MCMC) stabilization in the burn-in period; 100,000 iterations for MCMC replicates for the post-burn-in period. The number of clusters (K) was tested from 1 to 10, with 10 independent runs per K. The most probable number of genetic clusters (K) was identified using the ΔK method [48] implemented in STRUCTURE HARVESTER v0.6.94. Population structure bar plots were generated using Distruct v1.1, with individuals ordered according to Q-values (ancestry coefficients) [49,50]. A threshold of 0.65 was set to classify individuals into clusters after STRUCTURE analysis; individuals with Q-values greater than or equal to 0.65 were assigned to the corresponding group.
5. Conclusions
In this study, we evaluated the resistance of 343 maize germplasm resources to ear rot caused by six major Fusarium species over three consecutive years. A total of 69 and 77 lines were resistance to six and five ear rot diseases, respectively, while 139 lines were resistant to both FER and GER. These results highlight the presence of valuable broad-spectrum resistance within the tested germplasm. Furthermore, heterotic group analysis revealed significant variation in resistance, with the PH4CV group exhibiting the highest level of resistance. This work provides important genetic resources and insights for the breeding of maize cultivars with enhanced and durable ear rot resistance.
Appendix A
Table A1.
Codes and heterotic groups of maize inbred lines used in this study.
| Code | Heterotic Group | Code | Heterotic Group | Code | Heterotic Group |
|---|---|---|---|---|---|
| K21HZD0021 | NSS | K21HZD1517 | Pioneer Female | K21HZD5457 | Pioneer Male B |
| K21HZD0044 | NSS | K21HZD1548 | Pioneer Female | K21HZD5461 | Pioneer Male B |
| K21HZD0071 | NSS | K21HZD1550 | Pioneer Female | K21HZD5970 | Pioneer Male B |
| K21HZD0187 | NSS | K21HZD1558 | Pioneer Female | K21HZD5973 | Pioneer Male B |
| K21HZD0271 | NSS | K21HZD1978 | Pioneer Female | K21HZD5976 | Pioneer Male B |
| K21HZD0275 | NSS | K21HZD1983 | Pioneer Female | K21HZD6054 | Pioneer Male B |
| K21HZD0375 | NSS | K21HZD2118 | Pioneer Female | K21HZD6057 | Pioneer Male B |
| K21HZD0394 | NSS | K21HZD2123 | Pioneer Female | K21HZD6063 | Pioneer Male B |
| K21HZD0395 | NSS | K21HZD2124 | Pioneer Female | K21HZD0012 | SS |
| K21HZD0401 | NSS | K21HZD2130 | Pioneer Female | K21HZD0105 | SS |
| K21HZD0402 | NSS | K21HZD2131 | Pioneer Female | K21HZD0452 | SS |
| K21HZD0482 | NSS | K21HZD2228 | Pioneer Female | K21HZD0611 | SS |
| K21HZD0566 | NSS | K21HZD2239 | Pioneer Female | K21HZD0700 | SS |
| K21HZD0751 | NSS | K21HZD2253 | Pioneer Female | K21HZD0736 | SS |
| K21HZD0759 | NSS | K21HZD2258 | Pioneer Female | K21HZD0762 | SS |
| K21HZD0766 | NSS | K21HZD2278 | Pioneer Female | K21HZD1623 | SS |
| K21HZD0777 | NSS | K21HZD2357 | Pioneer Female | K21HZD1693 | SS |
| K21HZD0792 | NSS | K21HZD2365 | Pioneer Female | K21HZD1786 | SS |
| K21HZD0847 | NSS | K21HZD2415 | Pioneer Female | K21HZD1971 | SS |
| K21HZD0850 | NSS | K21HZD2588 | Pioneer Female | K21HZD1985 | SS |
| K21HZD1131 | NSS | K21HZD2598 | Pioneer Female | K21HZD2127 | SS |
| K21HZD1133 | NSS | K21HZD4687 | Pioneer Female | K21HZD2146 | SS |
| K21HZD1145 | NSS | K21HZD4698 | Pioneer Female | K21HZD2199 | SS |
| K21HZD1172 | NSS | K21HZD4705 | Pioneer Female | K21HZD2388 | SS |
| K21HZD1214 | NSS | K21HZD4731 | Pioneer Female | K21HZD2405 | SS |
| K21HZD1463 | NSS | K21HZD4757 | Pioneer Female | K21HZD2442 | SS |
| K21HZD1465 | NSS | K21HZD5217 | Pioneer Female | K21HZD2612 | SS |
| K21HZD1467 | NSS | K21HZD5267 | Pioneer Female | K21HZD3969 | SS |
| K21HZD1979 | NSS | K21HZD5274 | Pioneer Female | K21HZD4182 | SS |
| K21HZD2550 | NSS | K21HZD5279 | Pioneer Female | K21HZD4303 | SS |
| K21HZD4741 | NSS | K21HZD5290 | Pioneer Female | K21HZD4790 | SS |
| K21HZD5318 | NSS | K21HZD5291 | Pioneer Female | K21HZD5082 | SS |
| K21HZD5376 | NSS | K21HZD5375 | Pioneer Female | K21HZD5296 | SS |
| K21HZD5988 | NSS | K21HZD5946 | Pioneer Female | K21HZD5454 | SS |
| K21HZD0010 | PB | K21HZD5949 | Pioneer Female | K21HZD5650 | SS |
| K21HZD0018 | PB | K21HZD5952 | Pioneer Female | K21HZD0051 | TSPT |
| K21HZD0334 | PB | K21HZD5955 | Pioneer Female | K21HZD0103 | TSPT |
| K21HZD0471 | PB | K21HZD5958 | Pioneer Female | K21HZD0761 | TSPT |
| K21HZD0569 | PB | K21HZD5991 | Pioneer Female | K21HZD0844 | TSPT |
| K21HZD0715 | PB | K21HZD6006 | Pioneer Female | K21HZD0871 | TSPT |
| K21HZD0897 | PB | K21HZD6018 | Pioneer Female | K21HZD1179 | TSPT |
| K21HZD1854 | PB | K21HZD6021 | Pioneer Female | K21HZD1380 | TSPT |
| K21HZD1948 | PB | K21HZD6027 | Pioneer Female | K21HZD1410 | TSPT |
| K21HZD1967 | PB | K21HZD0074 | Pioneer Male A | K21HZD1429 | TSPT |
| K21HZD1993 | PB | K21HZD0095 | Pioneer Male A | K21HZD1485 | TSPT |
| K21HZD2220 | PB | K21HZD0224 | Pioneer Male A | K21HZD1499 | TSPT |
| K21HZD2417 | PB | K21HZD0236 | Pioneer Male A | K21HZD1634 | TSPT |
| K21HZD2473 | PB | K21HZD0279 | Pioneer Male A | K21HZD2154 | TSPT |
| K21HZD2475 | PB | K21HZD0341 | Pioneer Male A | K21HZD2177 | TSPT |
| K21HZD2595 | PB | K21HZD0397 | Pioneer Male A | K21HZD2243 | TSPT |
| K21HZD2596 | PB | K21HZD0398 | Pioneer Male A | K21HZD2423 | TSPT |
| K21HZD2779 | PB | K21HZD0444 | Pioneer Male A | K21HZD2425 | TSPT |
| K21HZD2817 | PB | K21HZD0511 | Pioneer Male A | K21HZD2429 | TSPT |
| K21HZD2839 | PB | K21HZD0562 | Pioneer Male A | K21HZD2439 | TSPT |
| K21HZD2844 | PB | K21HZD0691 | Pioneer Male A | K21HZD2509 | TSPT |
| K21HZD2879 | PB | K21HZD0731 | Pioneer Male A | K21HZD2555 | TSPT |
| K21HZD3076 | PB | K21HZD1027 | Pioneer Male A | K21HZD2556 | TSPT |
| K21HZD3156 | PB | K21HZD1132 | Pioneer Male A | K21HZD3945 | TSPT |
| K21HZD3435 | PB | K21HZD1155 | Pioneer Male A | K21HZD5342 | TSPT |
| K21HZD4242 | PB | K21HZD1344 | Pioneer Male A | K21HZD5629 | TSPT |
| K21HZD4690 | PB | K21HZD1970 | Pioneer Male A | K21HZD5961 | TSPT |
| K21HZD5166 | PB | K21HZD2373 | Pioneer Male A | K21HZD5964 | TSPT |
| K21HZD5459 | PB | K21HZD2374 | Pioneer Male A | K21HZD5967 | TSPT |
| K21HZD5982 | PB | K21HZD2376 | Pioneer Male A | K21HZD5979 | TSPT |
| K21HZD5985 | PB | K21HZD2377 | Pioneer Male A | K21HZD6042 | TSPT |
| K21HZD0057 | PH4CV | K21HZD4780 | Pioneer Male A | K21HZD6048 | TSPT |
| K21HZD0171 | PH4CV | K21HZD0025 | Pioneer Male B | 2021S0915 | |
| K21HZD0196 | PH4CV | K21HZD0068 | Pioneer Male B | 2021S0919 | |
| K21HZD0197 | PH4CV | K21HZD0072 | Pioneer Male B | 2021S0925 | |
| K21HZD0210 | PH4CV | K21HZD0214 | Pioneer Male B | 2021S0926 | |
| K21HZD0390 | PH4CV | K21HZD0512 | Pioneer Male B | 2021S0928 | |
| K21HZD0415 | PH4CV | K21HZD0526 | Pioneer Male B | 2021S0929 | |
| K21HZD0749 | PH4CV | K21HZD0730 | Pioneer Male B | 2021S0931 | |
| K21HZD0904 | PH4CV | K21HZD0836 | Pioneer Male B | 2021S0933 | |
| K21HZD1193 | PH4CV | K21HZD0842 | Pioneer Male B | 2021S0935 | |
| K21HZD1205 | PH4CV | K21HZD0852 | Pioneer Male B | 2021S0940 | |
| K21HZD1208 | PH4CV | K21HZD0857 | Pioneer Male B | 2021S0941 | |
| K21HZD1210 | PH4CV | K21HZD0866 | Pioneer Male B | 2021S0943 | |
| K21HZD1237 | PH4CV | K21HZD0868 | Pioneer Male B | 2021S0945 | |
| K21HZD1245 | PH4CV | K21HZD0885 | Pioneer Male B | 2021S0960 | |
| K21HZD1514 | PH4CV | K21HZD0898 | Pioneer Male B | 2021S0961 | |
| K21HZD1526 | PH4CV | K21HZD0899 | Pioneer Male B | 22NHRB001 | |
| K21HZD1617 | PH4CV | K21HZD0903 | Pioneer Male B | 22NHRB016 | |
| K21HZD1636 | PH4CV | K21HZD1149 | Pioneer Male B | 22NHRB039 | |
| K21HZD1637 | PH4CV | K21HZD1182 | Pioneer Male B | 22NHRB048 | |
| K21HZD1640 | PH4CV | K21HZD1183 | Pioneer Male B | 22NHRB066 | |
| K21HZD1944 | PH4CV | K21HZD1200 | Pioneer Male B | 22NHRB081 | |
| K21HZD1987 | PH4CV | K21HZD1217 | Pioneer Male B | 22NHRB105 | |
| K21HZD2300 | PH4CV | K21HZD1520 | Pioneer Male B | 22NHRB108 | |
| K21HZD2567 | PH4CV | K21HZD1573 | Pioneer Male B | 22NHRB155 | |
| K21HZD2578 | PH4CV | K21HZD1581 | Pioneer Male B | 22NHRB214 | |
| K21HZD2581 | PH4CV | K21HZD1590 | Pioneer Male B | 22NHRB315 | |
| K21HZD2602 | PH4CV | K21HZD1598 | Pioneer Male B | 22NHRB322 | |
| K21HZD2610 | PH4CV | K21HZD1615 | Pioneer Male B | CNH3323 | |
| K21HZD4732 | PH4CV | K21HZD1962 | Pioneer Male B | CY103 | |
| K21HZD0170 | Pioneer Female | K21HZD1965 | Pioneer Male B | CY105 | |
| K21HZD0226 | Pioneer Female | K21HZD2234 | Pioneer Male B | CY109 | |
| K21HZD0296 | Pioneer Female | K21HZD2244 | Pioneer Male B | K21HXY045 | |
| K21HZD0400 | Pioneer Female | K21HZD2260 | Pioneer Male B | K21HXY085 | |
| K21HZD0742 | Pioneer Female | K21HZD2274 | Pioneer Male B | K21HXY145 | |
| K21HZD0786 | Pioneer Female | K21HZD2350 | Pioneer Male B | K21HXY221 | |
| K21HZD0804 | Pioneer Female | K21HZD2371 | Pioneer Male B | K21HXY259 | |
| K21HZD0849 | Pioneer Female | K21HZD2398 | Pioneer Male B | K21HZD0276 | |
| K21HZD0861 | Pioneer Female | K21HZD2463 | Pioneer Male B | K21HZD0887 | |
| K21HZD0915 | Pioneer Female | K21HZD2482 | Pioneer Male B | K21HZD1353 | |
| K21HZD1261 | Pioneer Female | K21HZD2534 | Pioneer Male B | K21HZD1470 | |
| K21HZD1295 | Pioneer Female | K21HZD2553 | Pioneer Male B | K21HZD1521 | |
| K21HZD1302 | Pioneer Female | K21HZD2616 | Pioneer Male B | K21HZD1528 | |
| K21HZD1307 | Pioneer Female | K21HZD2618 | Pioneer Male B | K21HZD2219 | |
| K21HZD1309 | Pioneer Female | K21HZD3093 | Pioneer Male B | K21HZD4411 | |
| K21HZD1323 | Pioneer Female | K21HZD4339 | Pioneer Male B | K21HZD4653 | |
| K21HZD1370 | Pioneer Female | K21HZD4737 | Pioneer Male B | K21HZD4739 | |
| K21HZD1418 | Pioneer Female | K21HZD5309 | Pioneer Male B | K21HZD5266 | |
| K21HZD1511 | Pioneer Female | K21HZD5366 | Pioneer Male B | K21HZD5308 | |
| K21HZD5467 |
Author Contributions
C.D., S.L. and Z.C. conceived and designed the study; S.L., L.Z., Y.G., Y.Z. and C.H. performed the experiments; L.Z., S.L. and Y.L. analyzed the data; W.W. and S.S. participated in some experiments; S.L., L.Z., Z.C. and C.D. wrote the manuscript; S.L., C.D. and Z.C. revised the manuscript; and C.D. obtained funding and was responsible for this article. All authors have read and agreed to the published version of the manuscript.
Data Availability Statement
The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.
Conflicts of Interest
The authors declare no conflicts of interest.
Funding Statement
This work was supported by grants from the National Key Research & Development Program of China (2021YFD1200700) and the Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences (01-ICS-02).
Footnotes
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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 datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.