Cotton genotypic variability for transpiration decrease with progressive soil drying

Authors: MURA, JYOSTNA - Orise Fellow; Reddy, Vangimalla

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2020
Publication Date: 8/31/2020
Citation: Mura, J., Reddy, V. 2020. Cotton genotypic variability for transpiration decrease with progressive soil drying. Agronomy. 10(9):1290. https://doi.org/10.3390/agronomy10091290.
DOI: https://doi.org/10.3390/agronomy10091290

Interpretive Summary: Cotton is commonly grown under dryland conditions, where soil water deficits limit yields. Yield increase may be possible by selecting genotypes that express traits that are desirable for water-limited conditions. In this study, fifteen cotton cultivars were tested for their transpiration response to progressive drought. A variation in the cotton cultivars for their response to drought was observed, and some varieties showed water conservation by partially closing their stomata. This study is useful in identifying and developing the cotton cultivars suitable for the drought conditions along with understanding the physiological mechanisms involved in the water saving trait.

Technical Abstract: Cotton is grown as a leading commercial crop providing the majority of the fiber used in the textile industry globally. However, the cotton yield is hindered by water stress when the crop is grown in arid and semi-arid areas. Yield increase may be possible by selecting genotypes that express physiological traits that are desirable for water-limited conditions. Water conservation is one possible physiological trait for increasing yield since this trait could increase water availability during critical stages of plant development. Fifteen cotton genotypes were selected for this study based on differences in their sensitivity to drought. The plants were grown in a controlled environmental facility at BARC under well-watered conditions for 30 days. The plants were subjected to dry-down experiments in controlled environmental growth chambers to determine the threshold fraction of transpirable soil water (FTSW) for the decrease in transpiration rate as the soil dried. Significant differences (P<0.001) in the threshold FTSW for transpiration decline were observed ranging from 30 to 60 percent of soil water content. Four genotypes out of fifteen were further selected to study the water potential differences to the soil drying. Genotypes differed between low and high thresholds for transpiration decline also differed significantly (P<0.05) in their water potentials. The genotypes with high FTSW threshold reduced their water potential values (-1.30±0.20 MPa) at a higher fraction of available soil water level compared to low FTSW-threshold genotypes (0.88±0.18 MPa). Water conservation could be achieved by slower transpiration rate with soil drying initiated at a high FTSW so that the use of soil water is extended over a longer period of time. This water conservation strategy may allow the crop to have water available during the critical phase of crop growth. These results demonstrated that among the cotton genotypes there are several alternative traits for enhancing soil water conservation for growth under dryland conditions.