Analysis of QTLs for the Trichome Density on the Upper and Downer Surface of Leaf Blade in Soybean [Glycine max (L.) Merr.]

Trichomes (plant hairs) are present on nearly all land plants and are known to play important roles in plant protection, specifically against insect herbivory, drought, and UV radiation. The identification of quantitative trait loci (QTL) associated with trichome density should help to interpret the molecular genetic mechanism of soybean trichome density. 184 recombinant inbred lines (RILs), derived from a cross between soybean cultivars Kefeng 1 and Nannong 1138-2 were used as segregating population for evaluation of TDU (trichome density on the upper surface of leaf blade) and TDD (trichome density on the downer surface of leaf blade). A total of 15 QTL were detected on molecular linkage groups (MLG) A2, D1a, D1b, E and H by composite interval mapping (CIM) and among all the QTL, qtuA2-1, qtuD1a-1, qtuD1b-2, qtuH-2 qtuE-1, qtdD1b-2, and qtdH-2 were affirmed by multiple interval mapping (MIM). The contribution of phenotypic variance of qtuH-2 was 31.81 and 29.4% by CIM and MIM, respectively, suggesting it might be major gene Ps loci. Only 10 pairs of main QTL interactions for TDU were detected, explained a range of 0.2-5.1% of phenotypic variations for each pair for a total of 22.8%. The QTL on MLG D1b affecting trichome density were mapped near to Rsc-7 conditioning resistance to SMV (soybean mosaic virus). This study showed that the genetic mechanism of trichome density was the mixed major gene and polygene inheritance, and also suggested that the causal nature between trichome density and other agronomic traits.