Genetic Variation and QTL Mapping of Drought Tolerance in Cotton Under PEG Conditions

Cotton is the most important fiber crop and the second most important oilseed crop in the United States. However, drought remains one of the major abiotic stresses lowering cotton yield in the United States and worldwide. The main objective of the current study was to, first evaluate the performance of a backcross inbred line (BIL) population under well-watered and stress treatments using polyethylene glycol (PEG 8000) in the greenhouse. The second objective was to detect quantitative trait loci (QTLs) for drought tolerance. The BIL population was derived from a cross between an upland cotton Sure-Grow747 (Gossypium hirsutum) and Pima S-7 (G. barbadense). One hundred forty-two BIL lines plus two parents were evaluated for plant height (cm), shoot weight (g), and root weight (g) under well-watered and drought stress (5% PEG 8000) in a hydroponic system. These lines were arranged using a randomized complete block design (RCBD) with three replications under well-watered and PEG stress each. After two true leaves the lines were transferred to the hydroponic system for treatments for three weeks. The same test was conducted twice. Four statistical methods were used to analyse the data: (1) analysis of variance (ANOVA) using PROC GLM; (2) correlation coefficients; (3) genetic variation and heritability; and (4) QTL analysis.