Monday, November 5, 2007 - 10:00 AM
78-3
Genetic Mapping and Characterization of an Epicuticular Wax (Bloom) Gene, Sb Bl, in Sorghum bicolor L. (Moench).
Genes involved in wax production can have significant potential in enhancing drought tolerance in many crop species. Here, we describe the genetic mapping and characterization of the gene, bloom (Sb Bl), involved in the expression of profuse white fluffy epicuticular wax in sorghum. Genetic mapping was accomplished by crossing BTx 623, a well studied inbred line that exhibit profuse deposition of white epicuticular wax, to KFS2021, a mutant line characterized by absence of wax in its aerial organs. Phenotypic segregation for the bloom/bloomless trait in an F2 and F2:3 populations from the cross between BTx623 and KFS 2021 suggest that bloom is controlled by a single nuclear dominant gene. Genetic mapping studies using 126 microsattelite or simple sequence repeat (SSR) markers indicate that the bloom gene is localized in sorghum chromosome 10. Characterization of the gene based on physiological features showed that bloomless parent (KFS2021) and F2 individuals had lower frequency of guttation, leakier cuticular layer (based on chlorophyll leaching in 80% ethanol) and higher rate of seedling water loss than BTx623 and F2 bloom individuals. Bloomless F2 individuals consistently showed three to six- fold higher nighttime transpiration rates relative to F2 individuals with bloom. Correlation analysis showed significant negative associations between leaf epicuticular wax load with cuticular permeability and nighttime conductance which indicate the important role of epicuticular wax in these physiological traits. These results suggest that bloom gene could have significant contribution in the overall drought tolerance of sorghum. Mapping and cloning of sorghum bloom gene could open up untapped avenues for manipulation of wax production in cereal crops and related species.
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