| Peanut is an important oil crop in China.Pod abscission and pod size is of great significance to pod numbers and yield in peanut.However,most studies on peanut focused on high yield,high quality and disease resistance,while fewer studies on pod abscission and pod size.With the ongoing refinement of genome sequencing and statistical methods,genome-wide association studies（GWAS）has been successfully used for genetic analysis of complex traits.In this study,GWAS was conducted in a natural population of 390 peanut varieties to analyze genetic basis of pod abscission and pod size.Through GWAS,the markers associated with pod abscission were mined and candidate genes of pod size were predicted,which provide a theoretical basis for the utilization of genetic resources and more efficient breeding of new varieties.The results are shown below:1.Through the correlation analysis of peanut pod-dropping traits,main stem height and fruit number per plant,it was found that the correlation coefficients between the fracture force of fresh peanut pedicel-pod and pedicel-stem,the fracture force of peanut pedicel-pod and pedicel-stem after 2 days of drying,and the fracture force of peanut pedicel-pod and pedicel-stem after 4 days of drying were extremely significant positive correlation,respectively.The correlation coefficients between the main stem height,fruit number per plant and pod-dropping traits were generally low,indicating that there were great differences in the fracture force of pedicel-pod and pedicel-stem of pod-dropping traits whether in peanut or after drying.Genome-wide association analysis of pod-dropping traits in peanut was carried out.A total of 32 significant aboriginal association sites were detected.There were 17 markers associated with peanut stalk-pod traits,2 markers associated with peanut stalk-stem traits,4 markers associated with peanut stalk-pod traits after 2 days of drying,4 markers associated with peanut stalk-stem traits after 2 days of drying,4 markers associated with peanut stalk-pod traits after 4 days of drying,and 1 marker associated with peanut stalk-stem traits after 4 days of drying.2.Genome-wide association analysis was performed on pod size related traits.In natural populations,pod width,pod thickness and hundred pods weight were mapped to a distinct SNP cluster on the same interval of chromosome B06,within candidate interval143340440 bp–146081396 bp.Through analysis,25 candidate genes were found to control pod size probably.By analyzing the expression levels of the candidate genes,it was found that two candidate genes Ahy＿B06g085507 and Ahy＿B06g085516 showed large differences.Ahy＿B06g085507 was highly expressed in seed kernels and increased with pod enlargement,and the average expression level in large pod varieties was higher than small pod varieties during pod swelling.Ahy＿B06g085516 was highly expressed in leaves,flowers and kernels,and increased with pod enlargement,and the expression level in kernels of small pod varieties was extremely high,while there was no significant difference in the expression levels between large and small pod materials.3.The microstructure of seed kernels at different developmental stages of big pod variety（L-A539）and small pod variety（S-A465）was observed,and found that the cross section,seed coat and cotyledon area in big pod variety L-A539 were larger than small pod variety S-A465 at all developmental stages.The cotyledons of L-A539 were tighter than those of S-A465.The intercellular space in cotyledons of L-A539 was tighter than that of S-A465.Exogenous auxin and gibberellin were applied at the gynophore of large and small pod varieties and results showed that when gibberellin concentration was 10-5,the promoting effect of large pod weight was better than that of small pod.When gibberellin concentrations were 10-3,10-5 and 10-7,the promoting effect on small pod length was better than that on large pod length,and the promoting effect on large pod width was better than that on small pod.Auxin concentration of 10-7 can promote small pod weight,but inhibit large pod weight increase;the promoting effect of auxin on the length,width and thickness of large pods was better than that of small pods. |
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