Assessing agronomic and physiological traits during reproductive developmental stages for breeding upland drought tolerant cotton

Authors: Witt, Travis; Habimana, Aimable; Sanchez, Jacobo; Ulloa, Mauricio

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2024
Publication Date: 11/29/2024
Citation: Witt, T.W., Habimana, A., Sanchez, J., Ulloa, M. 2024. Assessing agronomic and physiological traits during reproductive developmental stages for breeding upland drought tolerant cotton. Agrosystems, Geosciences & Environment. 7(4). Article e70010. https://doi.org/10.1002/agg2.70010.
DOI: https://doi.org/10.1002/agg2.70010

Interpretive Summary: Cotton producers in the United States face many challenges like declining land and water resources. Cotton breeding programs are trying to develop new cultivars that can withstand these challenges. Two cultivars from different production regions [far west and midsouth] were evaluated for their response to limited water. Differences between the cultivars response to limited water were observed. The recommendation from this study is to target the traits of leaf temperature, chlorophyll fluorescence yield, number of leaves, flowers, and bolls and plant height for future cotton breeding for water limited environments.

Technical Abstract: Increasing crop production in an unstable climate is one of the many challenges facing the agricultural research community because of diminishing land and water resources. Different cotton production regions of the United States have distinct growing conditions. Breeding programs around the world are trying to develop cotton cultivars/germplasm under rainfed and/or limited irrigation with improved yield and fiber quality The goal of this study was to identify and evaluate specific determinant traits for improving drought resilience of cultivated Upland cotton (Gossypium hirsutum L.). Two cultivars/genotypes representing different production regions [far west – ‘PhytoGen 72’ (PHY72) and midsouth – ‘Stoneville 474’ (STV474)] of the US were evaluated for drought tolerance under semi environmental control (greenhouse). From plant emergence to open bolls and under two irrigation rates [regular water (RW) – no stress and limited water (LW) – stress), more than 20 vegetative and reproductive traits were evaluated through six physiological reproductive stages. Significant differences (p=0.05) were observed between irrigation levels for all traits within each genotype, except for PHY72 during the 3rd stage 50 % flower and STV474 during the 6th stage boll opening. During the first three physiological reproductive stages, PHY72 had rapid increases in plant height under RW and LW. However, by the 4th stage, peak blooming, the two genotypes were the same height, indicating that early and rapid vegetative plant growth from emergence to 1st reproductive stage was not necessarily a good indicator of improved growth and boll production/retention under diverse irrigation rates. When traits were further examined and compared between genotypes within each irrigation and/or reproductive stage, differences were observed between PHY72 and STV474. Some traits such as leaf temperature, chlorophyll fluorescence yield (CFY), leaf and boll number, and leaf and reproductive fresh weight showed clear differences between the two genotypes in one or both (RW and LW) irrigations. Currently, cotton breeders/geneticists cannot predict end of season productivity based on early season evaluations under drought conditions. An alternative early controlled environment screening before field testing may reveal the genetic potential of breeding lines for drought resilience. In this study, determinant traits such as leaf temperature (4th stage), CFY (1st stage), number of leaves (4th stage), flowers (3rd stage) and bolls (4th and 6th stages), and plant height (1st and 4th stages) if single targeted or in combination, can provide selection strategies for breeding and genetically improving the drought resiliency of cotton.