Hongyan Zhang

Saline–alkali stress significantly affects crop growth and yield, yet research on faba beans across vegetative and reproductive stages remains limited. We used a 124 mM mixed saline–alkali solution (pH 9.25) to test germination tolerance in 912 accessions, then grew 234 faba bean accessions with moderate saline–alkali tolerance at germination under substrate-based saline–alkali stress conditions (140 mM saline–alkali, pH 10.5) during the vegetative and reproductive stages. Under a 124 mM mixed saline–alkali solution, 912 faba bean accessions had an average germination rate (GR) of 49%. Stress significantly decreased the number of healthy seedlings (NHS); the average was only 33%. Accessions that performed relatively better under saline–alkali stress were the least common (18.31%), whereas those that performed relatively worse were the most common (39.58%). Faba bean accessions from China’s Shanxi Province (GR% and NHS% as high as 65.8% and 63.3%, respectively) and Africa showed better germination performance under saline–alkali stress. Autumn-sown accessions performed better than spring-sown accessions under saline–alkali stress (germination potential(GP), germination index (GI), GR and NHS: 44%, 3.22, 53% and 35% vs. 37%, 2.82, 47% and 31%, respectively). Accessions with red–purple and dark-green seed coats generally showed superior germination performance across most germination parameters. Accessions with wrinkled seed coats showed higher germination performance (the GP, GI, GR, and NHS were 47%, 3.08, 59%, and 35%) than those with smooth coats. Small-seeded accessions tended to perform slightly better under saline–alkali stress. Based on germination, seedling, and vegetative and reproductive stages assessments, H0001722 was identified as highly tolerant to saline–alkali stress, with 96.7% for each of GP, GR, and NHS, while Qingcan 19 was classified as extremely sensitive. H0001722’s MFV was twice that of Qingcan 19 through the vegetative and reproductive stages. This study provides valuable resources for identifying genes associated with saline–alkali tolerance and developing stress-resistant varieties.

Candidate genes related to first pod height (FPH) traits in faba bean plants are crucial for mechanised breeding. However, reports on quantitative trait locus (QTL) mapping related to the FPH of faba bean are few, thus limiting the high-quality development of the faba bean industry to a certain extent. The identification and screening of candidate genes related to FPH is extremely urgent for the advancement of mechanised breeding for faba bean. In this study, a high-density genetic linkage map was constructed using genotyping-by-sequencing (GBS) of an F₃ population and QTLs (genes) related to FPH were identified. The genetic linkage map contained seven linkage groups with 3012 SNP markers with an overall length of 4089.13 centimorgan (cM) and an average marker density of 1.36 cM. Thirty-eight QTLs for the first pod node (FPN) and FPH were identified (19 each for FPN and FPH). The 19 QTLs associated with FPN were located on chromosomes 1L, 1S, 2, 3, 4, 5, and 6; the 19 QTLs associated with FPH were located on chromosomes 1L, 1S, 2, 3, 5, and 6. There was a co-localisation interval of qFPN6-1 and qFPH6-1 on chromosome 6. By annotating the QTL qFPH6-1 interval, 36 genes that may be related to FPH were identified, these genes are related to plant growth and development. The results provide a basis for the precise location of QTLs related to FPH and could accelerate the breeding of faba bean varieties adapted to mechanised harvesting.

Novel germplasm resources are the key to crop breeding, with their genetic diversity and population structure analysis being highly significant for future faba bean breeding. We genotyped 410 global faba bean accessions using the 130K targeted next-generation sequencing (TNGS) genotyping platform, resulting in a total of 38,111 high-quality SNP loci by high-standard filtering. We found the polymorphism information content (PIC) and Nei’s gene diversity were 0.0905–0.3750 and 0.0950–0.5000, with averages of 0.2471 and 0.3035, respectively. After evaluating the genetic diversity of 410 accessions using Nei’s gene diversity and PIC, on the basis of their geographical origin (continent) and structure-analysis-inferred subpopulations, we found that the faba bean accessions from Asia (except China) and Europe had rich genetic diversity, while those from the winter sowing area of China were low. The 410 faba bean accessions were divided into four subpopulations according to population structure analysis and clustering analysis based on Nei’s (1972) genetic distance using the neighbor-joining (NJ) method. However, the same subpopulation contained materials from different geographical origins, thereby indicating that the gene flow or introgression occurred among the accessions. Results from NJ clustering based on shared allele genetic distance indicated that the 410 accessions were divided into three groups according to their dissemination routes. The genetic diversity analysis results demonstrated that the genetic relationships among the faba bean groups with similar ecological environments and geographic origins in neighboring regions or countries were closer and frequently found within the same group, while genetic variation among individuals was the main source of their total genetic variation.

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 NextSeq^TM 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.

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.