Genetic analysis of roots, shoots, and several morphologic traits in soybean [Glycine max (L.) Merr.]

Crop productivity is severely reduced by root diseases, water deficit and soil derived nutrients in many plant species including soybean. The objectives of the current study were to (1) identify QTL that underlie several root, shoot, and morphologic traits using a recombinant inbred line (RIL) population derived from a cross between two elite soybean cultivars \u27Essex\u27 and \u27Forrest\u27 (ExF RILs, n=100) provided by SIUC. Plants were grown in the greenhouse at Fayetteville State University and in the field in Harnett County, NC. Simple sequence repeat (SSR) markers and a genetic linkage map was compared to phenotypic data, from field and greenhouse trials, of basal root thickness (BRT), lateral root number (LRN), maximum root length (MRL), root fresh weight (RFW), root dry weight (RDW), shoot fresh weight (SFW), shoot dry weight (SDW), RFW/SFW, and RDW/SDW by composite interval mapping (CIM) with QTL Cartographer. A total of 87 QTL for these traits were identified on different linkage groups (LGs). Sixty eight QTL were identified using field data and 19 QTL using greenhouse data. Out of 68 QTL, three QTL for each of BRT and MRL, one QTL for each of LRN, RDW, and SFW/SDW, 13 QTL for RFW, 16 QTL for SFW, 25 QTL for SDW, and 5 QTL for RFW/RDW. Nineteen greenhouse identified QTL included six QTL were found for LRN, 7 QTL for MRL, one QTL for RDW, 2 QTL for SFW/SDW, and 3 QTL for RFW/RDW. Five QTL were identified for plant height and mapped on LGs A2 (3 QTL – qph-1-3) and G (2 QTL – qph-4-5), one QTL was identified for days to germination and mapped on LG M ( qdg-1), and one QTL was identified for days to flowering and mapped on LG D1a+Q. The root, shoot, yield, and morphologic traits QTL found here may be of interest in breeding programs to produce cultivars with extensive root systems, tolerant to water deficit and high yielding