Investigation of Methods to Evaluate Drought Tolerance among Selected Cotton Lines

Abstract

Currently there are agricultural companies developing plant-based biotechnology solutions for addressing drought and other abiotic stresses. Within the near future these technologies will be entering the marketplace, and in order for the cotton industry to make informed decisions a standard evaluation method is needed. Therefore, it is critical that an effective, efficient protocol to evaluate drought tolerance in cotton be developed. Thus the primary objective of this study is to develop methods and protocols for evaluating drought tolerance among bio-engineered and conventional cotton lines. In order to achieve the objective there are three components that are being analyzed to develop an effective protocol. Each of the three components is based on a set of cotton lines that includes twelve lines selected from preliminary testing in 2004, three conventional lines previously identified as having evidence of drought tolerance, and seven transgenic lines from Texas Tech University transformed for drought tolerance. The first component is a field test method comprised of three randomized complete block tests planted on drip irrigation, each watered at a different rate in order to establish a baseline for yield and fiber quality across irrigation regimes. The three irrigation rates are based upon replacement of evapotranspiration (ET) with the high rate being 75% replacement of ET, the mid rate being 50% replacement, and the low rate being 25% replacement. The second component is an investigation of fluorescence yield as related to stress tolerance. One plant from each plot of the above mentioned test was selected for this test. Fluorescence yield was taken from each sample at hourly intervals each week to determine the stress level of that particular plant. The final component is a salt tolerance test which was run on each line. Seedlings of each line were grown hydroponically in a system in which salt was added weekly at a rate of 3000ppm. At present, the field trial has not been harvested, but visual ratings show promising results. The fluorescence yield data also has not been analyzed, however, when completed will be compared to field data to find possible correlations. The salt tolerance test data showed five lines having greater than 80% tolerance to salt concentrations greater than 18,000ppm. These results will simultaneously be compared to field and fluorescence yield data for more possible correlations, and for the ultimate development of a protocol for evaluating drought tolerance.