Genetic regulation of maize and sorghum under abiotic stress
Climate extremes of temperature, drought and flooding continue to challenge global agricultural production and food security. If modeling studies are accurate, climate variability and drought will be a more prevalent occurrence in the future, not only inhibiting grain yield but also stressing water resources. Thus, it is critical to breed for improved climate resilience in agronomic crops and understand the genetic mechanisms conferring adaptation to water-limited environments. Sorghum is an important crop grown in drought prone locations around the world and serves as a model crop for studying plant adaptation to water-limited environments. Sorghum breeders have been successful in developing drought-tolerant sorghum hybrids using stay-green as a phenotype. The ability of annual crop species to delay senescence or "stay-green" throughout the grain filling period has been associated with increased yield, decreased lodging, and stalk rot resistance. Genetic analyses of stay-green in sorghum suggest the trait is controlled by four to six loci that have been integrated into commercial programs by marker-assisted breeding. The goal of my research is to characterize the genetic architecture of stay-green in maize. Maize exhibits substantial genetic variation for stay-green. We evaluated the Nested Association Mapping (NAM) populations of maize and testcross hybrids with PHZ51 for variation in stay-green in multi-location trials. Joint linkage mapping was used to identify multiple QTL for stay-green across several linkage groups with sources of stay-green alleles coming from diverse genetic backgrounds. Association mapping was conducted using maize stay-green data to characterize gene families potentially associated with these phenotypes. Genetic associations from these studies were validated in the Ames Diversity Panel. Advancements in comparative genomics and statistics provide powerful tools for examining the biological relationships between maize and sorghum. Comparisons between maize and sorghum indicate that several genomic regions associated with stay-green are similar including major sorghum QTL Stg1, Stg2, Stg3, and Stg4. Identification and integration of stay-green genes into commercial programs may provide the opportunity to sustainably enhance the productivity of maize and sorghum in drought environments. Additionally, our research examined the genetic regulation of premature senescence associated with sink-inhibition and hyper-senescence. When the ear of B73 is covered or removed to eliminate the sink, the plant prematurely and rapidly senesces around 800 growing degree days (GDD) post anthesis. The NAM populations of maize were used to identify candidate genes associated with this premature senescence trait and develop a potential model for the expression and regulation of the phenotype.
Tuinstra, Purdue University.
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