Faba bean and pea harvest index estimations using aerial-based multimodal data and machine learning algorithms.

Early and high-throughput estimations of the crop harvest index (HI) are essential for crop breeding and field management in precision agriculture; however, traditional methods for measuring HI are time-consuming and labor-intensive. The development of unmanned aerial vehicles (UAVs) with onboard sensors offers an alternative strategy for crop HI research. In this study, we explored the potential of using low-cost, UAV-based multimodal data for HI estimation using red-green-blue (RGB), multispectral (MS), and thermal infrared (TIR) sensors at 4 growth stages to estimate faba bean (Vicia faba L.) and pea (Pisum sativum L.) HI values within the framework of ensemble learning. The average estimates of RGB (faba bean: coefficient of determination [R2] = 0.49, normalized root-mean-square error [NRMSE] = 15.78%; pea: R2 = 0.46, NRMSE = 20.08%) and MS (faba bean: R2 = 0.50, NRMSE = 15.16%; pea: R2 = 0.46, NRMSE = 19.43%) were superior to those of TIR (faba bean: R2 = 0.37, NRMSE = 16.47%; pea: R2 = 0.38, NRMSE = 19.71%), and the fusion of multisensor data exhibited a higher estimation accuracy than those obtained using each sensor individually. Ensemble Bayesian model averaging provided the most accurate estimations (faba bean: R2 = 0.64, NRMSE = 13.76%; pea: R2 = 0.74, NRMSE = 15.20%) for whole growth stage, and the estimation accuracy improved with advancing growth stage. These results indicate that the combination of low-cost, UAV-based multimodal data and machine learning algorithms can be used to estimate crop HI reliably, therefore highlighting a promising strategy and providing valuable insights for high spatial precision in agriculture, which can help breeders make early and efficient decisions.

Genotypic composition and performance of pea-nodulating rhizobia from soils outside the native plant-host range.

Cultivated soils need to shelter suitable rhizobia for legume cropping, especially in areas outside of the plant-host native range, where soils may lack efficient symbiotic partners. We analyzed the distribution patterns and traits of native rhizobia associated with Pisum sativum L. in soils of Hebei Province, a region that has recently experienced an expansion of pea production in China. A total of 43 rhizobial isolates were obtained from root-nodules and characterized genetically and symbiotically. The isolates discriminated into 12 genotypes as defined by PCR-RFLP of IGS DNA. Multiple locus sequence analysis (MLSA) based on the 16S rRNA, recA, atpD and gyrB of representative strains placed them into five clusters of four defined species (R. sophorae, R. indicum, R. changzhiense, and R. anhuiense) and a novel Rhizobium genospecies. R. sophorae was the dominant group (58%) followed by R. indicum (23%). The other groups composed of R. changzhiense (14%), R. anhuiense (1 isolate) and the new genospecies (1 isolate), were minor and site-specific. Based on nodC phylogeny, all representatives were intermingled within the symbiovar viciae with R. sophorae and R. changzhiense being a new record. All the tested strains showed efficient symbiotic fixation on pea plants, with half of them exhibiting better plant biomass performance. This suggests that the pea-nodulating rhizobia in Hebei Province form a specific community of efficient symbiotic rhizobia on pea, distinct from those reported in other countries.

Chromosome-length genome assemblies of six legume species provide insights into genome organization, evolution, and agronomic traits for crop improvement.

INTRODUCTION: Legume crops are an important source of protein and oil for human health and in fixing atmospheric N2 for soil enrichment. With an objective to accelerate much-needed genetic analyses and breeding applications, draft genome assemblies were generated in several legume crops; many of them are not high quality because they are mainly based on short reads. However, the superior quality of genome assembly is crucial for a detailed understanding of genomic architecture, genome evolution, and crop improvement. OBJECTIVES: Present study was undertaken with an objective of developing improved chromosome-length genome assemblies in six different legumes followed by their systematic investigation to unravel different aspects of genome organization and legume evolution. METHODS: We employed in situ Hi-C data to improve the existing draft genomes and performed different evolutionary and comparative analyses using improved genome assemblies. RESULTS: We have developed chromosome-length genome assemblies in chickpea, pigeonpea, soybean, subterranean clover, and two wild progenitor species of cultivated groundnut (A. duranensis and A. ipaensis). A comprehensive comparative analysis of these genome assemblies offered improved insights into various evolutionary events that shaped the present-day legume species. We highlighted the expansion of gene families contributing to unique traits such as nodulation in legumes, gravitropism in groundnut, and oil biosynthesis in oilseed legume crops such as groundnut and soybean. As examples, we have demonstrated the utility of improved genome assemblies for enhancing the resolution of "QTL-hotspot" identification for drought tolerance in chickpea and marker-trait associations for agronomic traits in pigeonpea through genome-wide association study. Genomic resources developed in this study are publicly available through an online repository, 'Legumepedia'. CONCLUSION: This study reports chromosome-length genome assemblies of six legume species and demonstrates the utility of these assemblies in crop improvement. The genomic resources developed here will have significant role in accelerating genetic improvement applications of legume crops.

Large-Scale Heat-Tolerance Screening and Genetic Diversity of Pea (Pisum sativum L.) Germplasms.

Pea (Pisum sativum L.) is an important legume crop. However, the yield of pea is adversely affected by heat stress in China. In this study, heat-tolerant germplasms were screened and evaluated in the field under multi-conditions. The results showed that heat stress could significantly affect pea yield. On the basis of grain weight per plant, 257 heat-tolerant and 175 heat-sensitive accessions were obtained from the first year's screening, and 26 extremely heat-tolerant and 19 extremely heat-sensitive accessions were finally obtained in this study. Based on SNaPshot technology, two sets of SNP markers, including 46 neutral and 20 heat-tolerance-related markers, were used to evaluate the genetic diversity and population genetic structure of the 432 pea accessions obtained from the first year's screening. Genetic diversity analysis showed that the average polymorphic information content was lower using heat-tolerance-related markers than neutral markers because of the selective pressure under heat stress. In addition, population genetic structure analysis showed that neutral markers divided the 432 pea accessions into two subpopulations associated with sowing date type and geographical origin, while the heat-tolerance-related markers divided these germplasms into two subpopulations associated with heat tolerance and sowing date type. Overall, we present a comprehensive resource of heat-tolerant and heat-sensitive pea accessions through heat-tolerance screenings in multi-conditions, which could help genetic improvements of pea in the future.

Improved pea reference genome and pan-genome highlight genomic features and evolutionary characteristics.

Complete and accurate reference genomes and annotations provide fundamental resources for functional genomics and crop breeding. Here we report a de novo assembly and annotation of a pea cultivar ZW6 with contig N50 of 8.98 Mb, which features a 243-fold increase in contig length and evident improvements in the continuity and quality of sequence in complex repeat regions compared with the existing one. Genome diversity of 118 cultivated and wild pea demonstrated that Pisum abyssinicum is a separate species different from P. fulvum and P. sativum within Pisum. Quantitative trait locus analyses uncovered two known Mendel's genes related to stem length (Le/le) and seed shape (R/r) as well as some candidate genes for pod form studied by Mendel. A pan-genome of 116 pea accessions was constructed, and pan-genes preferred in P. abyssinicum and P. fulvum showed distinct functional enrichment, indicating the potential value of them as pea breeding resources in the future.

Construction of A GBS-Based High-Density Genetic Map and Flower Color-Related Loci Mapping in Grasspea (Lathyrus sativus L.).

Grasspea (Lathyrus sativus L.), a legume crop with excellent resistance to a broad array of environmental stressors, has, to this point, been poorly genetically characterized. High-density genetic linkage maps are critical for draft genome assembly, quantitative trait loci (QTLs) analysis, and gene mining. The lack of a high-density genetic linkage map has limited both genomic studies and selective breeding in grasspea. Here, we developed a high-density genetic linkage map of grasspea using genotyping-by-sequencing (GBS) to sequence 154 grasspea plants, comprising 2 parents and 152 F2 progeny. In all, 307.74 Gb of data was produced, including 2,108,910,938 paired-end reads, as well as 3536 SNPs mapped to seven linkage groups (LG1-LG7). With an average length of 996.52 cM per LG, the overall genetic distance was 6975.68 cM. Both the χ2 test and QTL analysis, based on the Kruskal-Wallis (KW) test and interval mapping (IM) analysis, revealed the monogenic inheritance of flower color in grasspea, with the responsible QTL located between 308.437 cM and 311.346 cM in LG4. The results can aid grasspea genome assembly and accelerate the selective breeding of new grasspea germplasm resources.

Estimation of plant height and yield based on UAV imagery in faba bean (Vicia faba L.).

BACKGROUND: Faba bean is an important legume crop in the world. Plant height and yield are important traits for crop improvement. The traditional plant height and yield measurement are labor intensive and time consuming. Therefore, it is essential to estimate these two parameters rapidly and efficiently. The purpose of this study was to provide an alternative way to accurately identify and evaluate faba bean germplasm and breeding materials. RESULTS: The results showed that 80% of the maximum plant height extracted from two-dimensional red-green-blue (2D-RGB) images had the best fitting degree with the ground measured values, with the coefficient of determination (R2), root-mean-square error (RMSE), and normalized root-mean-square error (NRMSE) were 0.9915, 1.4411 cm and 5.02%, respectively. In terms of yield estimation, support vector machines (SVM) showed the best performance (R2 = 0.7238, RMSE = 823.54 kg ha-1, NRMSE = 18.38%), followed by random forests (RF) and decision trees (DT). CONCLUSION: The results of this study indicated that it is feasible to monitor the plant height of faba bean during the whole growth period based on UAV imagery. Furthermore, the machine learning algorithms can estimate the yield of faba bean reasonably with the multiple time points data of plant height.

Genetic diversity of Lathyrus sp collected from different geographical regions.

BACKGROUND: The demand for grass peas (Lathyrus sativus L.) had increased as high nutritional safe food, but most of the accessions of South Asia and Africa had low grain harvest. Therefore, this study had been undertaken to collect grass pea germplasm for boosting yields and quality improvement. METHODS AND RESULTS: In this study, 400 accessions of grass pea from different geographical regions had characterized by using 56 Simple Sequences Repeat (SSRs) markers. In total 253 alleles were detected, the maximum and minimum polymorphic information content (PIC) indices were 0.70 and 0.34 found in markers G17922 and G18078, correspondingly. The germplasm was split into two main and one sub-group by cluster assay, by SSR assay, and three populations by model-based population structure analysis (Pop1, Pop2 and admixed). Neighbors joining tree assay showed the tested germplasm highly diverse in structure. Three-dimensional principal components analysis (PCA) and two dimensional principles coordinate analysis (PCoA) exhibited two main and one admixed group (P1, P2 and P1P2). In addition, FST population value of pairwise mean and analysis of molecular variance (AMOVA) showed high population structure across all pairs of populations on an average 0.1710 advocating all population structure categories varied significantly. The average predictable heterozygosity distant was 0.4472-0.4542 in same cluster for the individuals. CONCLUSION: Discovery from this study revealed SSR markers based polymorphic bands showed in the diversified grasspea germplasm which might be utilized as genetic resource of a breeding scheme and prospective uses for mapping analyses of recombinant inbred lines (RIL).

Rhizobium sophorae is the dominant rhizobial symbiont of Vicia faba L. In North China.

Faba bean (Vicia faba L.) is a major introduced grain-legume crop cultivated in China. In this study, rhizobia that nodulated faba bean grown in soils from three sites in North China (Hebei Province) were isolated and characterized. Firstly, isolates were categorized into genotypes by ribosomal IGS PCR-RFLP analysis, then representatives of the different IGS genotypes were further identified by phylogenetic analyses of 16S rRNA, housekeeping (atpD, recA) and nodulation (nodC) gene sequences. Rhizobial distribution based on the IGS genotype was related to the different soil physicochemical features by redundancy analysis. IGS typing and phylogenetic analyses of 16S rRNA and concatenated housekeeping gene sequences affiliated the 103 rhizobial strains isolated into four Rhizobium species/genospecies. A total of 69 strains of 3 IGS types were assigned to R. sophorae, 20 isolates of 5 IGS types to R. changzhiense and 9 isolates of 3 IGS types to R. indicum. The representative strain of the five remaining isolates (1 IGS type) was clearly separated from all Rhizobium type strains and was most closely related to defined genospecies according to the recently described R. leguminosarum species complex. Rhizobium sophorae strains (67% of total isolates) were common in all sites and shared an identical nodC sequence typical of faba bean symbionts belonging to symbiovar viciae. In this first study of rhizobia nodulating faba bean in Hebei Province, China, R. sophorae was found to be the dominant symbiont in contrast to other countries.

Development and application of the Faba_bean_130K targeted next-generation sequencing SNP genotyping platform based on transcriptome sequencing.

KEY MESSAGE: Large-scale faba bean transcriptome data are available, and the first genotyping platform based on liquid-phase probe targeted capture technology was developed for genetic and molecular breeding studies. Faba bean (Vicia faba L., 2n = 12) is an important food legume crop that is widely grown for multiple uses worldwide. However, no reference genome is currently available due to its very large genome size (approximately 13 Gb) and limited single nucleotide polymorphism (SNP) markers as well as highly efficient genotyping tools have been reported for faba bean. In this study, 16.7 billion clean reads were obtained from transcriptome libraries of flowers and leaves of 102 global faba bean accessions. A total of 243,120 unigenes were de novo assembled and functionally annotated. Moreover, a total of 1,579,411 SNPs were identified and further filtered according to a selection pipeline to develop a high-throughput, flexible, low-cost Faba_bean_130K targeted next-generation sequencing (TNGS) genotyping platform. A set of 69 Chinese faba bean accessions were genotyped with the TNGS genotyping platform, and the average mapping rate of captured reads to reference transcripts was 93.14%, of which 53.23% were located in the targeted regions. The TNGS genotyping results were validated by Sanger sequencing and the average consistency rate reached 93.6%. Comprehensive population genetic analysis was performed on the 69 Chinese faba bean accessions and identified four genetic subgroups correlated with the geographic distribution. This study provides valuable genomic resources and a reliable genotyping tool that could be implemented in genetic and molecular breeding studies to accelerate new cultivar development and improvement in faba bean.

Genetic diversity analysis for narrow-leafed lupin (Lupinus angustifolius L.) by SSR markers.

Narrow-leafed lupin (Lupinus angustifolius L.) is used as grain legumes, fodder for livestock and green manure in the world and has a great potential to be developed as a new crop in China. In this study, we assessed the genetic diversity among a set of 109 newly introduced accessions of narrow-leafed lupin using 76 genomic SSR markers. Data analysis suggested that the average gene diversity index and average polymorphism information content (PIC) were 0.4758 and 0.4328, respectively. The mean allele number per loci (Na) was 6.3816. The population structure analysis identified two subgroups based on delta K (ΔK) values. This result is in accordance with that of a PCA. The AMOVA analysis showed that most of molecular variance were within population. These results will be useful to guide the genetic improvement of the narrow-leafed lupin crop in China.

Effects of multiple N, P, and K fertilizer combinations on adzuki bean (Vigna angularis) yield in a semi-arid region of northeastern China.

Nitrogen (N), phosphorus (P), and potassium (K) exert various effects on adzuki bean yields. Our research was conducted in a semi-arid area, and four test sites were established in environments that have chernozem or sandy loam soils. During a five-year period, the effects of N, P, and K fertilizers on yield were comprehensively investigated in field trials (2014-2016) and for model-implementation trials (2017-2018), with models established prior to the latter. In the field trials, 23 treatments comprising different N, P, and K combinations significantly affected both yield and yield components, and regression analysis indicated that the experimental results were suitable for model establishment. The model subsequently demonstrated that the yield and the yield components were more sensitive to N and K fertilizer than to P fertilizer. Moreover, the yield and yield components increased. These yield increases were intense in response to the 0.5 to 1.34 levels in terms of the single effects; interaction effects; and the effects of combinations of N, P, and K fertilizers. Moreover, the effects of combinations of N, P, and K fertilizers were more significant on yield than were the single or interaction effects of N, P, and K fertilizers. The optimal fertilizer combination that resulted in high yields (≥1941.53 kg ha-1) comprised 57.23-68.43 kg ha-1 N, 36.04-47.32 kg ha-1 P2O5 and 50.29-61.27 kg ha-1 K2O. The fertilizer combination that resulted in the maximum yield was 62.98 kg ha-1 N, 47.04 kg ha-1 P2O5 and 59.95 kg ha-1 K2O (N:P2O5:K2O = 1:0.75:0.95), which produced the model-expected yield in trials at multiple sites. An economical fertilizer combination was determined on the basis of the best fertilizer measures in consideration of the cost of fertilizer and seed; this combination achieved yields of 2236.17 kg ha-1, the profit was 15,653.16 Yuan ha-1, and the corresponding rates were 57.60 kg ha-1 N, 47.03 kg ha-1 P2O5, and 31.64 kg ha-1 K2O (N:P2O5:K2O = 1:0.82:0.55).

Two Novel er1 Alleles Conferring Powdery Mildew (Erysiphe pisi) Resistance Identified in a Worldwide Collection of Pea (Pisum sativum L.) Germplasms.

Powdery mildew caused by Erysiphe pisi DC. severely affects pea crops worldwide. The use of resistant cultivars containing the er1 gene is the most effective way to control this disease. The objectives of this study were to reveal er1 alleles contained in 55 E. pisi-resistant pea germplasms and to develop the functional markers of novel alleles. Sequences of 10 homologous PsMLO1 cDNA clones from each germplasm accession were used to determine their er1 alleles. The frame shift mutations and various alternative splicing patterns were observed during transcription of the er1 gene. Two novel er1 alleles, er1-8 and er1-9, were discovered in the germplasm accessions G0004839 and G0004400, respectively, and four known er1 alleles were identified in 53 other accessions. One mutation in G0004839 was characterized by a 3-bp (GTG) deletion of the wild-type PsMLO1 cDNA, resulting in a missing valine at position 447 of the PsMLO1 protein sequence. Another mutation in G0004400 was caused by a 1-bp (T) deletion of the wild-type PsMLO1 cDNA sequence, resulting in a serine to leucine change of the PsMLO1 protein sequence. The er1-8 and er1-9 alleles were verified using resistance inheritance analysis and genetic mapping with respectively derived F2 and F2:3 populations. Finally, co-dominant functional markers specific to er1-8 and er1-9 were developed and validated in populations and pea germplasms. These results improve our understanding of E. pisi resistance in pea germplasms worldwide and provide powerful tools for marker-assisted selection in pea breeding.

An RNA Sequencing Transcriptome Analysis of Grasspea (Lathyrus sativus L.) and Development of SSR and KASP Markers.

Grasspea (Lathyrus sativus L., 2n = 14) has great agronomic potential because of its ability to survive under extreme conditions, such as drought and flood. However, this legume is less investigated because of its sparse genomic resources and very slow breeding process. In this study, 570 million quality-filtered and trimmed cDNA sequence reads with total length of over 82 billion bp were obtained using the Illumina NextSeqTM 500 platform. Approximately two million contigs and 142,053 transcripts were assembled from our RNA-Seq data, which resulted in 27,431 unigenes with an average length of 1,250 bp and maximum length of 48,515 bp. The unigenes were of high-quality. For example, the stay-green (SGR) gene of grasspea was aligned with the SGR gene of pea with high similarity. Among these unigenes, 3,204 EST-SSR primers were designed, 284 of which were randomly chosen for validation. Of these validated unigenes, 87 (30.6%) EST-SSR primers produced polymorphic amplicons among 43 grasspea accessions selected from different geographical locations. Meanwhile, 146,406 SNPs were screened and 50 SNP loci were randomly chosen for the kompetitive allele-specific PCR (KASP) validation. Over 80% (42) SNP loci were successfully transformed to KASP markers. Comparison of the dendrograms according to the SSR and KASP markers showed that the different marker systems are partially consistent with the dendrogram constructed in our study.

Marker-trait association analysis of frost tolerance of 672 worldwide pea (Pisum sativum L.) collections.

Frost stress is one of the major abiotic stresses causing seedling death and yield reduction in winter pea. To improve the frost tolerance of pea, field evaluation of frost tolerance was conducted on 672 diverse pea accessions at three locations in Northern China in three growing seasons from 2013 to 2016 and marker-trait association analysis of frost tolerance were performed with 267 informative SSR markers in this study. Sixteen accessions were identified as the most winter-hardy for their ability to survive in all nine field experiments with a mean survival rate of 0.57, ranging from 0.41 to 0.75. Population structure analysis revealed a structured population of two sub-populations plus some admixtures in the 672 accessions. Association analysis detected seven markers that repeatedly had associations with frost tolerance in at least two different environments with two different statistical models. One of the markers is the functional marker EST1109 on LG VI which was predicted to co-localize with a gene involved in the metabolism of glycoproteins in response to chilling stress and may provide a novel mechanism of frost tolerance in pea. These winter-hardy germplasms and frost tolerance associated markers will play a vital role in marker-assisted breeding for winter-hardy pea cultivar.

Soil Fertility Map for Food Legumes Production Areas in China.

Given the limited resources of fossil energy, and the environmental risks of excess fertilizer on crops, it is time to reappraise the potential role of food legume biological nitrogen fixation (BNF) as sources of nitrogen for cropping systems in China. 150 soil samples across 17 provinces and 2 municipalities of China were collected and analyzed. A distribution map of the soil fertilities and their patterns of distribution was constructed. The pH results indicated that soils were neutral to slightly alkaline overall. The soil organic matter (SOM) and the available nitrogen (AN) content were relatively low, while the available phosphorus (AP) and available potassium (AK) contents were from moderate to high. Production areas of food legumes (faba bean, pea, adzuki bean, mung bean and common bean) were clearly separated into 4 soil fertility type clusters. In addition, regions with SOM, AN, AP and AK deficiency, high acidity and high alkalinity were listed as target areas for further soil improvement. The potential was considered for biological nitrogen fixation to substitute for the application of mineral nitrogen fertiliser.

Discovery of a Novel er1 Allele Conferring Powdery Mildew Resistance in Chinese Pea (Pisum sativum L.) Landraces.

Pea powdery mildew, caused by Erysiphe pisi D.C., is an important disease worldwide. Deployment of resistant varieties is the main way to control this disease. This study aimed to screen Chinese pea (Pisum sativum L.) landraces resistant to E. pisi, and to characterize the resistance gene(s) at the er1 locus in the resistant landraces, and to develop functional marker(s) specific to the novel er1 allele. The 322 landraces showed different resistance levels. Among them, 12 (3.73%), 4 (1.24%) and 17 (5.28%) landraces showed immunity, high resistance and resistance to E. pisi, respectively. The other landraces appeared susceptible or highly susceptible to E. pisi. Most of the immune and highly resistant landraces were collected from Yunnan province. To characterize the resistance gene at the er1 locus, cDNA sequences of PsMLO1 gene were determined in 12 immune and four highly resistant accessions. The cDNAs of PsMLO1 from the immune landrace G0005576 produced three distinct transcripts, characterized by a 129-bp deletion, and 155-bp and 220-bp insertions, which were consistent with those of er1-2 allele. The PsMLO1 cDNAs in the other 15 resistant landraces produced identical transcripts, which had a new point mutation (T→C) at position 1121 of PsMLO1, indicating a novel er1 allele, designated as er1-6. This mutation caused a leucine to proline change in the amino acid sequence. Subsequently, the resistance allele er1-6 in landrace G0001778 was confirmed by resistance inheritance analysis and genetic mapping on the region of the er1 locus using populations derived from G0001778 × Bawan 6. Finally, a functional marker specific to er1-6, SNP1121, was developed using the high-resolution melting technique, which could be used in pea breeding via marker-assisted selection. The results described here provide valuable genetic information for Chinese pea landraces and a powerful tool for pea breeders.

A novel er1 allele and the development and validation of its functional marker for breeding pea (Pisum sativum L.) resistance to powdery mildew.

KEY MESSAGE: A novel er1 allele, er1 -7, conferring pea powdery mildew resistance was characterized by a 10-bp deletion in PsMLO1 cDNA, and its functional marker was developed and validated in pea germplasms. Pea powdery mildew caused by Erysiphe pisi DC is a major disease worldwide. Pea cultivar 'DDR-11' is an elite germplasm resistant to E. pisi. To identify the gene conferring resistance in DDR-11, the susceptible Bawan 6 and resistant DDR-11 cultivars were crossed to produce F1, F2, and F(2:3) populations. The phenotypic segregation patterns in the F2 and F(2:3) populations fit the 3:1 (susceptible:resistant) and 1:2:1 (susceptible homozygotes:heterozygotes:resistant homozygotes) ratios, respectively, indicating that resistance was controlled by a single recessive gene. Analysis of er1-linked markers in the F2 population suggested that the recessive resistance gene in DDR-11 was an er1 allele, which was mapped between markers ScOPE16-1600 and c5DNAmet. To further characterize er1 allele, the cDNA sequences of PsMLO1 from the parents were obtained and a novel er1 allele in DDR-11 was identified and designated as er1-7, which has a 10-bp deletion in position 111-120. The er1-7 allele caused a frame-shift mutation, resulting in a premature termination of translation of PsMLO1 protein. A co-dominant functional marker specific for er1-7 was developed, InDel111-120, which co-segregated with E. pisi resistance in the mapping population. The marker was able to distinguish between pea germplasms with and without the er1-7. Of 161 pea germplasms tested by InDel111-120, seven were detected containing resistance allele er1-7, which was verified by sequencing their PsMLO1 cDNA. Here, a novel er1 allele was characterized and its an ideal functional marker was validated, providing valuable genetic information and a powerful tool for breeding pea resistance to powdery mildew.

High-Throughput Development of SSR Markers from Pea (Pisum sativum L.) Based on Next Generation Sequencing of a Purified Chinese Commercial Variety.

Pea (Pisum sativum L.) is an important food legume globally, and is the plant species that J.G. Mendel used to lay the foundation of modern genetics. However, genomics resources of pea are limited comparing to other crop species. Application of marker assisted selection (MAS) in pea breeding has lagged behind many other crops. Development of a large number of novel and reliable SSR (simple sequence repeat) or microsatellite markers will help both basic and applied genomics research of this crop. The Illumina HiSeq 2500 System was used to uncover 8,899 putative SSR containing sequences, and 3,275 non-redundant primers were designed to amplify these SSRs. Among the 1,644 SSRs that were randomly selected for primer validation, 841 yielded reliable amplifications of detectable polymorphisms among 24 genotypes of cultivated pea (Pisum sativum L.) and wild relatives (P. fulvum Sm.) originated from diverse geographical locations. The dataset indicated that the allele number per locus ranged from 2 to 10, and that the polymorphism information content (PIC) ranged from 0.08 to 0.82 with an average of 0.38. These 1,644 novel SSR markers were also tested for polymorphism between genotypes G0003973 and G0005527. Finally, 33 polymorphic SSR markers were anchored on the genetic linkage map of G0003973 × G0005527 F2 population.

Genetic diversity of grasspea and its relative species revealed by SSR markers.

The study of genetic diversity between Lathyrus sativus L. and its relative species may yield fundamental insights into evolutionary history and provide options to meet the challenge of climate changes. 30 SSR loci were employed to assess the genetic diversity and population structure of 283 individuals from wild and domesticated populations from Africa, Europe, Asia and ICARDA. The allele number per loci ranged from 3 to 14. The average gene diversity index and average polymorphism information content (PIC) was 0.5340 and 0.4817, respectively. A model based population structure analysis divided the germplasm resources into three subgroups: the relative species, the grasspea from Asia, and the grasspea from Europe and Africa. The UPGMA dendrogram and PCA cluster also demonstrated that Asian group was convincingly separated from the other group. The AMOVA result showed that the cultivated species was quite distinct from its relative species, however a low level of differentiation was revealed among their geographic origins. In all, these results provided a molecular basis for understanding genetic diversity of L. sativus and its relatives.