Influence of drought stress on the root system of the `Maryland 96-5722 by `Spencer\u27 recombinant inbred line (RIL) population of soybean (Glycine max. (L.) Merrill)

The important crop soybean [Glycine max (L.) Merr.] is cultivated worldwide and the US is, its number one exporter. However, farmers face many challenges in cultivating soybeans, including drought and diseases that drastically reduces yield. The objectives of this study were to (1) grow the `MD 96-5722\u27 by `Spencer\u27 recombinant inbred line (RIL) population (n=82) in the greenhouse under normal (Group I) and water stress (Group II) conditions, and (2) compare the root length (RL), root surface area (RSA), average root diameter (ARD), and average root volume (ARV) in the groups of plants using the WinRhizo software. The results showed that there is a huge variation in these traits among the parents `MD 96-5722\u27 and `Spencer\u27, and among their RILs. For Group I plants, the RL of parents and RILs ranged from (20.67 cm to 2,327.88 cm); the RSA ranged from (4.57 cm2 to 1,176.79 cm2); the ARD ranged from (0.38 mm to 4.04 mm); and the ARV ranged from (0.08 cm3 to 47.34 cm3). For Group II plants, the RL of parents and RILs ranged from (15.70 cm to 3,562.42 cm); the RSA ranged from (4.15 cm2 to 829.72 cm2); the ARD ranged from (0.24 mm to 5.74 mm); and the ARV ranged from (0.03 cm 3 to 23.67 cm3). It is clear from the results that Group I plants have higher means of RL (572.58 cm vs. 537.33 cm), RSA (201.20 cm2 vs. 165.50 cm2), ARD (3.96 mm vs. 1.45 mm), and ARV (6.31 cm3 vs. 5.61 cm3) compared to Group II plants which demonstrates that drought-stressed plants have reduced overall plant growth and development. However, statistically, these differences were not significant; therefore, further studies with several replicates should be conducted both in the greenhouse and the field in order to determine the effects of drought stress on the `MD 96-5722\u27 by `Spencer\u27 RILs Moreover, studies of quantitative trait loci (QTL) mapping of the root traits studied here are underway to genetically map QTL for these root traits in this soybean RIL population