The effect of elevated atmospheric [CO2] and increased temperatures on an older and modern cotton cultivar

Impact of elevated CO2 and heat stress on wheat pollen viability and grain production

Periods of high temperature and an expected increase in atmospheric CO2 concentration as a result of global climate change are major threats to wheat (Triticum aestivum L.) production. Developing heat-tolerant wheat cultivars demands improved understanding of the impacts of high temperature and elevated CO2 on plant growth and development. This research investigated the interactive effects of heat stress and CO2 concentration on pollen viability and its relationship to grain formation and yield of wheat in greenhouse conditions. Nineteen wheat genotypes and a current cultivar, Suntop, were heat stressed at either meiosis or anthesis at ambient (400 µL L-1) or elevated (800 µL L-1) CO2. Elevated CO2 and heat stress at meiosis reduced pollen viability, spikelet number and grain yield per spike; however, increased tillering at the elevated CO2 level helped to minimise yield loss. Both heat-tolerant genotypes (e.g. genotype 1, 2, 10 or 12) and heat-sensitive genotypes (e.g. genotype 6 or 9) were identified and response related to pollen sensitivity and subsequent impacts on grain yield and yield components were characterised. A high-throughput protocol for screening wheat for heat stress response at elevated CO2 was established and meiosis was the most sensitive stage, affecting pollen viability, grain formation and yield.

Late planting has great potential to mitigate the effects of future climate change on Australian rain-fed cotton

The rain-fed cotton industry in Australia is vulnerable to climate change due to its high dependence on seasonal climate and summer rainfall. The rain-fed cotton in eastern Australia is increasingly being incorporated into cereal crop rotations due to government regulation of water resources, restricting opportunities for irrigated cotton. The accurate quantification of future climate impacts on exposed cropping systems such as rain-fed cotton is required to identify effective agronomic practices and inform strategic industry planning for the expansion of Australian cotton industry. Our study utilized 32 General Circulation Model (GCMs) for four cotton-growing regions representing the geographic range of cotton production in eastern Australia. We assessed the climate impacts on rain-fed cotton yield for two future periods (2040s and 2080s) under the RCP4.5 (low) and RCP8.5 (high) emissions scenarios employing the processed-based APSIM-Cotton model. Our results showed that current cotton yields varied with planting date, and the magnitude of yield change was consistent with regional climate variations at four locations representing the current geographic distribution of rain-fed cotton production. Means from multi-GCM ensemble showed growth period temperature increased more under RCP8.5 in the longer-term (2080s). Growth period rainfall changes had significantly positive effects on yield at all planting dates over each site. The projected increases in rainfall were more evident at later planting dates for dry sites than early planting dates at wet sites. In addition, we found planting date had the greatest influence on cotton yield at wet sites, while GCMs accounted for a large portion of variation in cotton yield at dry sites. We conclude that later planting has a great potential to increase rain-fed cotton yields. This provides important insights for regional-specific adaptation strategies for the rain-fed cotton industry in eastern Australia.

Coping with drought: stress and adaptive mechanisms, and management through cultural and molecular alternatives in cotton as vital constituents for plant stress resilience and fitness

Increased levels of greenhouse gases in the atmosphere and associated climatic variability is primarily responsible for inducing heat waves, flooding and drought stress. Among these, water scarcity is a major limitation to crop productivity. Water stress can severely reduce crop yield and both the severity and duration of the stress are critical. Water availability is a key driver for sustainable cotton production and its limitations can adversely affect physiological and biochemical processes of plants, leading towards lint yield reduction. Adaptation of crop husbandry techniques suitable for cotton crop requires a sound understanding of environmental factors, influencing cotton lint yield and fiber quality. Various defense mechanisms e.g. maintenance of membrane stability, carbon fixation rate, hormone regulation, generation of antioxidants and induction of stress proteins have been found play a vital role in plant survival under moisture stress. Plant molecular breeding plays a functional role to ascertain superior genes for important traits and can offer breeder ready markers for developing ideotypes. This review highlights drought-induced damage to cotton plants at structural, physiological and molecular levels. It also discusses the opportunities for increasing drought tolerance in cotton either through modern gene editing technology like clustered regularly interspaced short palindromic repeat (CRISPR/Cas9), zinc finger nuclease, molecular breeding as well as through crop management, such as use of appropriate fertilization, growth regulator application and soil amendments.