RESEARCH-PGR: Developing novel strategies to enhance the tolerance of crops to a combination of drought and heat stress.

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Heat waves occurring during periods of drought stress have a devastating impact on agricultural production and yield. A combination of drought and heat stress occurring during the summers of 1980, 1988, 2000, 2003 and 2008, for example, resulted in yield losses estimated in 33, 44, 7.6, 7 and 8.6 billion dollars, respectively. Because episodes of drought and heat stress are expected to increase in intensity and frequency in the coming years, due to the largely unopposed process of global warming and its consequential impacts on climate change, breeding crops for enhanced tolerance to a combination of drought and heat stress is of the utmost importance for modern agriculture and food sustainability. Crucial for yield loss during episodes of drought and heat stress are processes such as flowering and fertilization that are especially sensitive to these conditions, as well as highly important for yield production in almost all cereals and legumes. In this project the focus is on the impact of heat, drought, and drought and heat combination on flowering, fertilization, and seed production of soybean. Using a combination of experimental tools, genes and proteins that are essential for enhancing the tolerance of soybean to these stressful conditions will be identified. These proteins and genes will enable breeders to develop new genotypes that will resist the harsh conditions of our current and future environment and ensure a secure and sustainable soybean seed production for years to come.A combination of drought and heat stress occurring during the reproductive growth phase of many different crops, such as soybean, corn, rice, and wheat, has a devastating impact on yield. In soybean, a considerable effort has been made to develop genotypes with enhanced yield production under conditions of drought or heat stress. However, how these genotypes perform under conditions of drought and heat stress combination is mostly unknown. Moreover, although past research has focused on the impact of abiotic stress on pollen viability, recent findings reveal that the combination of drought and heat stress has a unique impact on reproductive processes that occur post pollen germination. Here, it is proposed to utilize a unique collection of soybean genotypes with altered seed production under conditions of drought or heat stress conditions to identify genes and gene networks impacting seed production under a combination of drought and heat stress. Using a combination of field and growth chamber studies focused on the effect of drought and heat stress combination on reproductive tissues and yield of different soybean genotypes, coupled with microdissection techniques, RNA sequencing and machine learning-driven network analysis tools, genes and gene networks that impact reproductive processes under conditions of stress combination will be identified. The function of these genes/gene networks will be validated by genetically modifying their expression in transgenic soybean plants with the overall goal of enhancing yield of soybean plants grown under conditions of drought and heat stress combination.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.