Assessment of cotton leaf and yield responses to water-deficit stress during flowering and boll development

Authors: Burke, John; Ulloa, Mauricio

Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2019
Publication Date: 3/10/2019
Citation: Burke, J.J., Ulloa, M. 2019. Assessment of cotton leaf and yield responses to water-deficit stress during flowering and boll development. Journal of Cotton Science. 23:109-117.

Interpretive Summary: The combination of reduced well capacities and predicted declines in rainfall across the Texas High Plains in the years to come will significantly impact future cotton yields. It is essential that cotton with improved drought tolerance be identified. This study imposed water-stress during boll development on 13 commercial cotton cultivars and evaluated their responses using a water-stress bioassay. In twelve of the cultivars, harvested yields were reduced as the stress levels in the leaves increased in the plants. One cultivar, Phytogen 72, had very good stress tolerance in the leaves, but did not yield as expected. ARS scientists from Lubbock, TX investigated the reason for this and found a defect in the protective coating on the pollen grains of Phytogen 72. The protective coating protects the pollen from drying out and scientists at the USDA-ARS, Lubbock, TX found that the Phytogen 72 pollen dried out more rapidly that those of the other commercial lines. With the predictions of climate unrest, less rainfall and high temperatures in the future, approaches to improve not only vegetative structures but also reproductive structures will be important for breeding the new generation of crops.

Technical Abstract: Rainfall future events are predicted to decline to 30 to 127 mm in the majority of counties of the Texas High Plains and Rolling Plains because of climate change. Cotton (Gossypium hirsutum L.) is the major crop grown on the High Plains of Texas, and the lower humidity associated with the predicted reduction in rain raises the possibility of increased vegetative water-deficit stress and reproductive dehydration stress. This study assesses the vegetative and reproductive developmental processes of commercial cotton cultivar-response following water-deficit stress, specifically during flowering and boll development. Cultivars showed a significant relationship between the vegetative water-deficit stress levels and final seed cotton yields. However, cultivar Phytogen 72 (PHY72) was an exception to this observation. PHY72 exhibited excellent leaf water-deficit stress tolerance yet had reduced seed cotton yields compared with the other cultivars evaluated. Genetic analysis of the sensitivity of the PHY 72 pollen suggested a maternal deficiency in the tapetum development of the PHY 72 pollen coat resulting in increased dehydration sensitivity. Structural differences in pollen coat development in two cultivars (PHY 72 and NM67) were observed under both scanning electron and transmission electron microscopy. Predicted reduced rainfall and high temperatures in the future, may necessitate approaches to improve not only vegetative tolerance but also reproductive tolerance both of which may be important for breeding the new generation of crops.