Phenotyping Drought Tolerance in Cotton (Gossypium hirsutum, L.)
Terhune, Austin Cates
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Cotton plant breeders need well-defined phenotypic parameters by which they can select drought tolerant lines as well as correlate phenotypes to allelic polymorphisms in the cotton genome. Soil-moisture availability is usually the most limiting factor for cotton crop productivity, especially in Texas. Characteristics of roots logically play an important role in determining the response of plants to limited soil moisture. The objectives of this study were to develop and refine techniques that could be used by plant breeders to phenotype plants? drought tolerance. Approaches include using a Trimble GreenSeeker?, to identify individual and progeny rows with enhanced photosynthetic capabilities in the presence of drought, leaf canopy temperatures under drought conditions, and measurement of root parameters in growth tubes in a greenhouse. Results from these experiments were related to yield performance in field trials at three locations in 2013. Several conclusions can be drawn from this study. First, Normalized Difference Vegetative Index and leaf temperature are rapid and reliable tools to evaluate plant health. The utility of these tools hinges upon timing of data collection, but they clearly demonstrated the propensity to differentiate phenotypic differences. Secondly, evaluation of root systems in growing tubes in a greenhouse is probably an ineffective method of characterizing drought tolerance potential since the growing conditions are radically different from what a plant would encounter in a field environment. Examining roots with this system would likely yield significant differences among plant species, but within upland cotton, it would be difficult to determine differences among genotypes. Ultimately the best determinant of drought tolerance is performance testing in droughty conditions because it encompasses most of the contributing factors that induce drought stress and measures the cotton plant?s inherent ability to recover and compensate in response to rainfall through the course of a growing season.