FUTURE CLIMATE RISKS TO COTTON PRODUCTION IN BRAZIL: EVIDENCE FROM EC-EARTH3 PROJECTIONS AND FROM THE SENSITIVITY OF GENETIC PARAMETERS
This study used the DSSAT/CROPGRO-Cotton model and climate projections from EC-Earth3 (SSP2-4.5 and SSP5-8.5 scenarios) up to 2059 to assess the response of cotton yield components to climate change and the sensitivity of the crop genetic parameters in three municipalities representative of Brazilian producing regions: Sapezal (MT), Coromandel (MG) and Luiz Eduardo Magalhães (BA). In order to isolate the climate effect, soil, cultivar and management were kept constant across municipalities; simulations were run under rainfed conditions and without nitrogen limitation. Projections indicate progressive warming and increased interannual variability of maximum temperature and rainfall under SSP5-8.5, with median maximum temperatures approaching 40 °C in Luiz Eduardo Magalhães (BA). The yield response was regionally heterogeneous: Coromandel (MG) showed an increase in productivity up to the 2050s under SSP5-8.5, whereas Luiz Eduardo Magalhães (BA) exhibited a decline after the initial decade and Sapezal (MT) remained relatively stable. The Morris sensitivity analysis identified the maximum leaf photosynthesis rate (LFMAX) as the dominant parameter for total above-ground biomass (CWAD). For lint yield (LIWAM), threshing percentage (THRSH) became the main limiting factor, indicating that the bottleneck under future stress lies in reproductive allocation rather than in maximum carbon assimilation. The duration of the seed-filling phase to physiological maturity (SD-PM) showed increased sensitivity in Coromandel, associated with heat-induced cycle shortening. The σ/μ* ratio revealed a predominantly linear behaviour for LFMAX and THRSH and a non-linear or interaction-dominated response for SFDUR and PODUR. The results, which are comparative in nature across scenarios, support breeding strategies focused on THRSH and on reproductive thermal tolerance for the resilience of Brazilian cotton production.