Genetics and drought reaction of epicuticular wax mutants in Sorghum bicolor
Abstract
Epicuticular wax has long been associated with drought tolerance in sorghum. Chemical mutagenesis of two drought resistant sorghum cultivars was used to develop sets of isogenic epicuticular wax lines. These include bloomless mutants with no visible wax, sparse-bloom mutants with reduced visible wax, and sib-derived normal isolines with abundant visible wax. The primary objectives were to determine the number of epicuticular wax production loci and to determine the relationship of epicuticular wax to drought tolerance. Allelism tests distinguished twenty epicuticular wax loci. These loci correspond to mutant groups with specific epicuticular wax biochemistry and ultrastructure. Linkage analysis shows that the $bm\sb2$ epicuticular wax locus is linked to the wx waxy endosperm locus with a recombination value of 16.2 $\pm$ 3.0%, while loci $bm\sb3$ and $h\sb5$ are not linked to wx. Yield trials of the epicuticular wax isolines were conducted in a variety of drought environments. Drought is the primary component of effects that significantly reduced yield. Normal isolines produced significantly greater yields than mutants in all environments. Significant differences in yield of normals indicate background mutations of non-epicuticular wax genes. Regression analyses show a strong highly significant correlation of increased yield with increased wax load. In addition, mutation specific effects of epicuticular wax on yield are associated with differences in epicuticular wax biochemistry. Hopefully, in the future an epicuticular wax gene and the associated drought tolerance will be transferred to other crops such as maize.
Degree
Ph.D.
Advisors
Axtell, Purdue University.
Subject Area
Agronomy|Genetics
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