Awika, Henry (2012-07). Determining Genetic Overlap between Staygreen, Leaf Wax and Canopy Temperature Depression in Sorghum RILs. Master's Thesis.
Thesis
Crops adapted to dry conditions are essential to meet future food, feed and energy needs. Knowledge of interaction between drought tolerance traits and their response to varying water supply conditions would improve selection for yield stability traits. This study focused on determining the association between the QTL regulating the staygreen trait in sorghum with improved canopy temperature depression (CTD) as regulated by total and compositional epicuticular wax content in a recombinant inbred line population derived from BTx642 and RTx7000. Phenotypic data were collected in 3 replicated field trials and 1 greenhouse trial. Plants with higher leaf EWL had cooler canopies. Our results also confirmed that staygreen genotypes are able to maintain cooler canopy than the non-stay-green genotypes under drought and hot conditions. We have suggested that wax might offer a more stable indicator for selection of drought tolerance under a variety of weather conditions. Composite interval mapping identified a total of 28 QTL, fifteen of which had significant overlaps. The overlap between QTL for cuticular leaf wax and QTL for staygreen exhibits a departure from the QTL overlaps for other traits with that of cuticular leaf wax. We have also suggested that under drought stress, the QTL for staygreen may be expressed earlier in time (at anthesis) than had been previously believed.
