Molecular and quantitative genetic analysis of seed size in Faba Bean (Vicia faba L.)

在谷类豆类中，种子大小是一个主要的产量相关性状，在物种之间和物种内部变化很大，在蚕豆中发现了一个极端的情况，其中小类群和大类群之间的种子大小可以变化约15倍。在蚕豆中，种子的大小是由种皮的大小控制的，种皮是一种母体器官。为了阐明种子大小的遗传控制，将在种子大小差异较大的两个近等基因蚕豆系的种皮生长期间的不同阶段确定转录组谱。这将通过在来自两个品系杂交的RIL群体中对种子大小进行QTL定位来补充。通过分析转录组谱，将鉴定作为两个等基因系之间种子大小差异的基础的差异表达基因网络。为了鉴定导致种子大小差异的因果因素，将转录组谱分析的结果与QTL作图结果相结合。为此，将首先将转录本映射到截形苜蓿的基因组序列和M. truncatula和V.faba的QTL将用于鉴定落在作图QTL的置信区间内的差异表达基因。基于基因本体分析和文献中的信息，将选择一组用于定位QTL的候选基因，并通过qPCR验证其表达谱。最后，所选候选基因相对于种子大小的表型效应将在分离该性状的三个F2群体中的至少两个中进行验证，所述F2群体将从与等基因系无关的次要和主要基因型之间的杂交中开发。

In grain legumes seed size, a major yield related trait, varies considerably between species but also within species, with an extreme case found in Vicia faba, where seed size between the minor and major groups can vary by a factor of about 15. In faba bean, seed size is controlled by the size of the seed coat, a maternal organ. To elucidate the genetic control of seed size, transcriptome profiles will be determined at different stages during the growth of the seed coat in two near isogenic lines of faba bean distinguished by a large difference in seed size. This will be complemented by a QTL mapping for seed size in a RIL population derived from a cross of the two lines. By analysing the transcriptome profiles, the differentially expressed gene networks, underlying the difference in seed size between the two isogenic lines, will be identified. To identify the causal factors responsible for the seed size difference, the results from the transcriptome profiling will be combined with the QTL mapping results. For this, the transcripts will first be mapped on the genome sequence of Medicago truncatula and the known synteny between M. truncatula and V. faba will be used to identify differentially expressed genes which fall within the confidence intervals of mapped QTL. Based on gene ontology analyses and information available from the literature, a set of candidate genes for the mapped QTL will be selected and their expression profiles will be verified by qPCR. Finally, the phenotypic effects of the selected candidate genes with respect to seed size will be verified in at least two of three F2 populations segregating for this trait, which will be developed from crosses between minor and major genotypes unrelated to the isogenic lines.