Genetic analysis of the hl locus in maize

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Ferreiro, Maria Aurelia
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Lee, Michael
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Several genetic factors determining the phenotype of maize (Zea mays L.) kernels have been identified and characterized through the analysis of mutant genotypes. The h1 locus is defined by a genetic mutation that results in a starchy and opaque endosperm. This study was conducted to determine the genetic location of the h1 locus using DNA polymorphism. The effect of the h1 mutation on the level and composition of storage proteins (zeins) was also examined. Near isogenic lines (NILs) of Oh43 and H95 differing for alleles at the h1 locus were used to develop a mapping population of 50 BC1F1 individuals. The h1 locus was mapped with respect to 8 restriction fragment length polymorphisms (RFLPs) loci from chromosome 3. The closest RFLP loci were asg24 and bnl8.35; located 2 cM proximal and 2 cM distal to h1, respectively. The extent of the donor parent DNA retained in the lines developed by backcross breeding was estimated on the basis of the DNA polymorphism detected between the normal (H1H1) and mutant (h1h1) genotypes of the NILS. The extent of the donor parent DNA segment retained in Oh43 hlhl and H95 hlhl was estimated to be 30 and 40 cM, respectively. The information provided by the genetic analysis of the h1 locus may be of value for marker-assisted backcross breeding and eventually, for gene tagging and cloning. Zeins were characterized in normal (H1H1H1) and mutant (h1h1h1) developing endosperm and in mature endosperm with 0 to 3 doses of the H1 allele, using reverse phase-high performance liquid chromatography (RP-HPLC). The level and composition of zeins were similar in normal and mutant developing endosperm of Oh43 and H95. Similar results were also observed in endosperm with 0 to 3 doses of H1. These observations suggest that the allelic variation at the h1 and the resulting endosperm phenotype are not associated with the accumulation of zeins in those genotypes.