Negative synergistic effects of drought and heat during flowering and seed setting in soybean

Authors: POUDEL, SADIKSHYA - Mississippi State University; VENNAM, RANADHEER REDDY - Mississippi State University; SANKARAPILLAI, LEKSHMY - Mississippi State University; LIU, JINBAO - Mississippi State University; REDDY, K. RAJA - Mississippi State University; WIJEWARDANE, NUWAN - Mississippi State University; MUKHTAR, M. SHAHID - Mississippi State University; BHEEMANAHALLI, RAJU - Mississippi State University

Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2024
Publication Date: 4/7/2024
Citation: Poudel, S., Vennam, R., Sankarapillai, L.V., Liu, J., Reddy, K., Wijewardane, N.K., Mukhtar, M., Bheemanahalli, R. 2024. Negative synergistic effects of drought and heat during flowering and seed setting in soybean. Environmental and Experimental Botany. 222:1005769. https://doi.org/10.1016/j.envexpbot.2024.105769.
DOI: https://doi.org/10.1016/j.envexpbot.2024.105769

Interpretive Summary: The study investigated the genetic variability in physiological, yield, and quality traits of soybean cultivars under individual drought or heat stress and combined stress conditions. The findings revealed that the cultivars were more susceptible to combined drought and heat stress than individual stresses. The performance of ten cultivars under different stress conditions showed a complex interaction between individual and combined stressors. Contrary to previous assumptions, resilience to individual stressors did not consistently translate to performance under combined stress for all measured traits. This indicates that selecting cultivars for multi-stress environments requires a comprehensive approach that considers specific stress combinations and their intricate impact on plant physiology, yield, and quality. The research underscores the importance of understanding cultivar-specific responses to combined stresses during the reproductive stage to develop stress-tolerant cultivars. These findings will be useful for soybean breeders whose programs target stress tolerance.

Technical Abstract: Rising intense heat waves combined with lower precipitations are the new norms of current global scenarios. These altered climatic conditions negatively impact soybean yield potential and quality. Ten soybean cultivars were subjected to four different growing conditions: control, drought, heat, and combined drought and heat to understand the physiological, yield, quality and molecular changes. Stomatal conductance was reduced by 62% and 10% under drought and heat, respectively. This reduction was further exacerbated to 93% when exposed to combined stress. The highest canopy temperature was recorded at +8 .C with combined stress treatment, whereas drought and heat exhibited +2 .C and +5.4 .C, respectively. Furthermore, combined stress displayed a more pronounced negative impact on greenness-associated vegetative index; the gene expression analysis further corroborated these findings. Each degree Celsius increase in temperature during flowering and seed-filling reduced seed weight by approximately 7% and 4% with and without drought, respectively. The seed protein increased under drought, whereas the oil showed a converse trend under drought and combined stresses. Most physiological and yield traits showed no significant correlations between control and individual or combined stress. This suggests that selecting crops for combined stress tolerance may not be appropriate based on nonstress or individual stress performance. Thus, incorporating combined stress-resilient traits into elite soybean cultivars could significantly boost soybean production under hot and dry climatic conditions.