INTERNATIONAL JOURNAL OF AGRICULTURAL TECHNOLOGY

Volume 14, No. 07, Month DECEMBER, Year 2018, Pages 2261 - 2270

Fine mapping of quantitive trait loci for seed-related traits in yardlong bean

Yoshida, A. K. and Tomooka, N.

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Yardlong bean is an important legume of Southeast and East Asia. It is believed to have been domesticated from vegetable (pod) cowpea. Among domestication-related traits, seed size is a distinctly trait that distinguish yardlong bean from its wild ancestor which has resulted in an approximately three-fold increase in seed length. Previously, we identified major QTLs for seed-related traits on linkage group 7, which were located on pleiotropic quantitative loci. Seed-related traits are highly complex quantitative traits that are controlled by multiple quantitative loci (QTLs) with a major and several minor effects and are influenced by multiple genetic and environmental factors. Thus, it is challenging to identify the major genes for controlling seed-related traits in yardlong bean. As the basis for fine mapping, a set of near isogenic lines (NILs) was developed from the cross between yardlong bean (JP81610) and wild cowpea (JP89083) population based on three generations of backcrossing and three generations of selfing. We have been able to narrow down the location of the genes underlying seed-related traits from 4.3 Mbp to 1.65 Mbp region. The locus was associated with transgressive variation for seed-and pod-related traits in this population. The phenotype was difficult to evaluate due to the influence of pod-related traits (pod length, pod width and pod softness) affected to seed size variation, underscoring the value of using multiple approaches to phenotyping, including extreme sampling and NILs group-mean comparisons. The fact that the QTLs controlling podrelated traits have also been detected on this target region, in which the genes for seed-related traits were associated, suggest that this region may generally not randomly distributed across the genome.

Keywords

yardlong bean, QTL, fine mapping

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