Genetic Contributions to Drought Response Mechanisms in Temperate and Tropical Maize Hybrids.

Drought tolerance is becoming an increasingly high-value trait in maize.  Due to the difficulty of performing controlled drought field trials, our current understanding the genetics of drought responses is limited.  This is particularly true in the context of testcross hybrids representing the diversity of elite temperate and tropical germplasm.  Here, recently expired Plant Variety Protection (ex-PVP) inbred lines and Drought Tolerant Maize for Africa (DTMA) inbred lines were crossed to a common tester, PHP02, and grown over two years in controlled-irrigation drought trials in Arizona.  Relevant phenotypes (flowering time, plant and ear height, stay-green, yield, and test weight) were collected under both well-watered and drought conditions.  Statistical analyses quantified i) the extent of variation present in temperate vs. tropical material, ii) the heritability of traits observed under these treatments, and iii) the phenotypic and genetic correlations between treatments.  Traits were then linked to genetic variation via a Genome-Wide Association Study (GWAS) to investigate the basis of drought-affected phenotypes in the temperate and tropical gene pools.  GWAS hits were subjected to network analysis to identify biological pathways responding to drought and/or corresponding to hybrid performance.  Characterization of temperate and tropical germplasm using genome-wide marker effects revealed untapped genetic potential and target haplotype regions for improving drought tolerance in maize.