Summary: Drought tolerance is an important trait being pursued by the agbiotech industry. Abscisic acid (ABA) is a stress hormone that mediates a multitude of processes in growth and development, water use efficiency (WUE) and gene expression during seed development and in response to environmental stresses. Arabidopsis B3‐domain transcription factor Related to ABA‐Insensitive3 (ABI3)/Viviparous1 (namely AtRAV2) and basic leucine zipper (bZIPs) AtABI5 or AtABF3 transactivated ABA‐inducible promoter:GUS reporter expression in a maize mesophyll protoplast transient assay and showed synergies in reporter transactivation when coexpressed. Transgenic cotton (Gossypium hirsutum) expressing AtRAV1/2 and/or AtABI5 showed resistance to imposed drought stress under field and greenhouse conditions and exhibited improved photosynthesis and WUEs associated with absorption through larger root system and greater leaf area. We observed synergy for root biomass accumulation in the greenhouse, intrinsic WUE in the field and drought tolerance in stacked AtRAV and AtABI5 double‐transgenic cotton. We assessed AtABI5 and AtRAV1/2 involvement in drought stress adaptations through reactive oxygen species scavenging and osmotic adjustment by marker gene expression in cotton. Deficit irrigation‐grown AtRAV1/2 and AtABI5 transgenics had ‘less‐stressed’ molecular and physiological phenotypes under drought, likely due to improved photoassimilation and root and shoot sink strengths and enhanced expression of endogenous GhRAV and genes for antioxidant and osmolyte biosynthesis. Overexpression of bZIP and RAV TFs could impact sustainable cotton agriculture and potentially other crops under limited irrigation conditions.

Core Ideas: Timing of water deficit stress affects boll production. Stress timing influences fiber quality. Multiple timings of water deficit stress interact. Decreased aquifer water in the Texas High Plains has increased the risks associated with irrigation, including lower irrigation volume and the need to balance seasonal water demands among crops, requiring management of both irrigation rate and timing. Boll distribution measurements in cotton (Gossypium hirsutum L.) can be used to quantify the effects of irrigation on productivity and were used in a study of irrigation rate × timing from 2011 to 2013 in Halfway, TX. Field experiments quantified cotton boll distribution using three in‐season irrigation levels (maximums of 0_, 3.2_, and 6.4 mm d⁻¹) during three different irrigation periods determined by accumulated growing degree days (GDD) based on the threshold of 15.6°C: period 1 (P1, 750 GDD). Combinations of these factors resulted in 27 irrigation treatments, applied with a low energy precision application (LEPA) pivot. Heavy irrigation early in the growing season used more water, did not increase boll number, and was often detrimental to yield. Mid‐ and late‐season irrigation improved yield and fiber quality, with P2 irrigation influencing yield in the middle of the plant and P3 irrigation controlling yield at the top of the plant. Moderate irrigation later in the season minimized effects of short‐term water deficit observed in other similar studies. These results provide insight into optimizing cotton water use in a region with declining crop water availability, increased pumping restrictions, and a challenging climate.

Modern cotton (Gossypium hirsutum L.) cultivars are more productive and have unique growth and fruiting characteristics due to optimization of genetics and management practices in the past 30 yr. The most recent work evaluating nutrient uptake and partitioning by cotton was conducted in the early 1990s, necessitating a re‐evaluation of nutrient accumulation and requirements in modern high productivity cultivars. Modern cultivar (FiberMax [FM] 958 and Deltapine [DP] 1646) resource allocation, including dry matter production, yields, and accumulation and partitioning of N, P, K, Ca, Mg, and S to different organs, was compared with that of a 1990s cultivar (Paymaster [PM] HS26) in 2018 and 2019. The modern cultivars tested in this study partitioned a greater percentage of dry matter, N, P, K, and S into the fruit than the older cultivar, highlighting the importance of partitioning for increased production potential of these cultivars from the 1990s to the 2010s. Greater efficiencies in partitioning and remobilization of N, P, K, and S resulted in 66, 88, 64, and 30% increase in the amount of lint yield produced for every unit of uptake, respectively, under favorable growing conditions. These findings suggest that existing fertility paradigm in cotton may underestimate the accumulation expectations during the middle and latter part of the growing season. These results can be a basis for optimizing nutrient application to address partitioning changes. Adjusting nutrient recommendations to the shift in cultivar growth characteristics may improve both yield and application efficiency of fertilizers.