Molecular and quantitative genetic analysis of seed size in Faba Bean (Vicia faba L.)
Plant Genetics and Genomics
Final Report Abstract
In many crop plants, seed size is one of the major yield related traits and may vary considerably between varieties. An extreme variation is found in Vicia faba, where seed size between the minor and major groups can vary by a factor of about 15. To analyze the molecular and quantitative genetics of seed size in Vicia faba, two near isogenic lines (NILs) for seed size had been created from a cross between inbred lines of large seeded ‘Pietranera’ and small seeded ‘HediLin’. QTL mapping in a RIL population of 184 lines derived from a cross between the two NILs resulted in the identification of 10 QTL and two epistatic interactions for seed size, whose additive respectively additive x additive interaction effects ranged from 10.6 – 72.6 mg. Taken together in a multiple-QTL model, the QTL and interactions explained 87.4% of the phenotypic variation observed in the RIL population. With one exception, the QTL alleles increasing seed size came from ‘Pietranera’. Seven of the 10 QTL could be detected again in 3 F2 populations derived from crosses between unrelated genotypes. To identify possible candidate genes for the mapped QTL, the parents of the RIL population were subjected to a differential expression analysis using mRNA isolated from immature seeds/seed coats harvested at 10, 14, 18, and 22 days after pollination. After a de novo assembly of the RNAseq reads, the resulting transcripts were mapped to the reference sequence of the Vicia faba genome. Differentially expressed transcripts that fell into the confidence intervals for the positions of the mapped QTL were compared to 73 genes implicated in the literature to be involved in the control of seed size. Two possible candidate genes were found. One transcript showed significant sequence identity to CYP78A13 and KLU/CYP78A5 from O. sativa and A. thaliana, respectively, both of which encode proteins of the cytochrome P450 family. Another transcript showed significant sequence identity to the SLG gene from O. sativa, which encodes a BAHD acyltransferase-like protein. Both, the cytochrome P450 proteins and the BAHD acyltransferases are large gene families whose members cover a range of functions. At the moment it is not possible to decide whether the V. faba transcripts encode true homologs to the O. sativa and A. thaliana proteins or unrelated members of the two gene families that may have other functions.
Publications
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Current faba bean research at Göttingen, Germany. Legume Perspectives 24:18-20
Brünjes L., Ecke W., Windhorst A., Laugel H. & Link W.
