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Genetics and Physiology of Abiotic Stress Tolerance in Crops
Extreme temperatures, drought, and nutrient stresses threaten global food security. Specifically, the response of plants to varying nitrogen (N) and water (W) interactions yields various plant phenotypes. However, molecular mechanisms that sense and respond to such interactions to produce diverse shoot phenotypes are poorly understood. Also, the spatial variation along the leaf axis to varying N-W levels is unknown. Studies indicate that polyploid crops are tolerant to salinity and drought, but their response to high day high night temperature (HDNT; 36/32 ºC) stress is unknown. Thermo-priming is part of stress response, but whether thermo-priming at the vegetative stage triggers seed development thermotolerance during the maturity stages of plant growth is unknown.The overall goal of this research was to determine the responses of the maize shoot to varied N-W interaction levels, and study the systematic response of two autotetraploid rice lines, in comparison to their respective diploids, to HDNT stress at two distinct stages. For N-W interaction, phenomics and transcriptomic approaches were employed to understand the spatiotemporal responses to differential levels of N-W interactions in different leaf sections. Results suggest that lower doses of N (5 and 10mM-N) promote shoot developmental trait and overall biomass under well-watered conditions while 20mM-N reduces these traits. Transcriptome analysis of leaf segments across a development gradient suggests that the N-W combinatory effect yielded different shoot phenotypes possibly due to the crosstalk of N with N-transporters, NIGT, SAURs-like auxin-responsive, aquaporin, and rubisco genes. Under water-limited and N stress conditions, the study revealed 14 inducible drought genes expressed across the leaf gradient that are important in drought tolerance and growth regulation.In the HDNT response study, autotetraploids showed basal sensitivity to HDNT, while their respective diploids exhibited adaptive HDNT stress tolerance mechanisms. Under HDNT, seed morphometrics of the genotypes were reduced partly due to precocious endosperm-cellularization. Thermo-priming did not trigger seed development thermotolerance. This study improves our understanding of how N and W shape plant shoot architecture and autotetraploid rice response to HDNT.
Doku, Henry Akrofi, "Genetics and Physiology of Abiotic Stress Tolerance in Crops" (2021). ETD collection for University of Nebraska-Lincoln. AAI28864633.