2019 ASHS Annual Conference

Natto, a traditional Japanese soyfood, is produced usually using small-seeded soybean (Glycine max L.). Seed coat deficiency (SCD) is an undesirable trait for natto production because they cause an inferior appearance of the products and it clogs the production lines. Development of soybean cultivars with decreased SCD is crucial for maintaining and increasing the natto soybean market. However, the understanding of the genetic control of SCD on soybean seeds was very limited. Thus, the objective of this study was to identify and validate quantitative trait loci (QTL) underlying SCD. V12-1626 (SCD, 6.8%) and V11-0883 (SCD, 37.7%) exhibited significant differences in SCD. One mapping population derived from V11-0883 x V12-1626 were grown in Blacksburg, VA in 2016 (240 F₃), 2017 (240 F₅) and 2018 (222 F₆), respectively. One validation population derived from V11-0883 x V12-1885 were grown in Blacksburg, VA in 2016 (155 F₃), 2017 (153 F₅) and 2018 (153 F₆), respectively. Phenotypic data of SCD of each individuals of all populations were collected after 100 unbroken seeds soaking for 10 min in 1% bleach. Mapping population SCD variated from 0 to 91% with a mean of 21.8%. Broad sense heritability of SCD was estimated to be 0.40. A total of 1,318 single nucleotide polymorphism (SNPs) out of 6,000 SNPs tested were polymorphic between parents in the mapping population. Linkage maps consisted of 1258 SNPs on 20 linkage groups with a total length of 1,826 cM and average marker interval of 1.6 cM. One major QTL across three years (qSCD20_1) was identified near Gm20_34881595_C_T and Gm20_36651429_T_C on chromosome 20 (LG I) with logarithmic odds score of 8.43, 15.15 and 3.08, accounting for 11.3, 24.3 and 5.6% of the variation of the trait in 2016, 2017 and 2018, respectively. The study of QTL confirmation is still on going, but we expect that the high phenotypic variation explained by qSCD20_1 will be able to be confirmed using the validation population. Then, the SNP markers identified will be used for marker assisted selection to accelerate the breeding of this trait in natto lines.