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Buffalograsses: Their organelle DNA, chinch bug resistance variation, and peroxidase enzyme responses to chinch bug injury
Information on genetic diversity and relationship of native buffalograss germplasm is limited and genetic basis of agronomic traits is unknown. The objectives of this research were to determine: (1) the genetic diversity, relationships, and organelle DNA inheritance based on cpDNA and mtDNA, (2) chinch bug resistance variation in natural buffalograss populations characterized for cpDNA and mtDNA; (3) the degree of correlation between total protein content, basal peroxidase level, chinch bug injury, and ploidy level, and (4) total protein content and peroxidase changes of resistant and susceptible germplasm in response to chinch bugs. Fifty-six, 48, 28, and, 6 buffalograsses were evaluated for organelle DNA, chinch bug resistance, correlation analysis, and peroxidase changes, respectively. Six cpDNA and three mtDNA non-coding regions were amplified by polymerase chain reaction, using universal chloroplast and mitochondrial primer pairs. Each amplified fragment was digested with 2 to 6 different restriction enzymes. For the chinch bug study, genotypes were evaluated in replicated trials under greenhouse conditions. Leaf samples were collected for peroxidase changes from infested and control plants at 7, 14, 21, and 28 day after exposure (DAE) to chinch bugs. Peroxidase analyses were carried out using native gels stained for anionic peroxidases and enzyme kinetics were measured with a spectrophotometer. Forty-seven of 56 genotypes had identical cpDNA and mtDNA RFLPs and the rest showed only a few polymorphic markers, which suggests a single maternal origin for the four buffalograss ploidy levels. Based on the use of cpDNA primers amplifying intergenic region between psbC and trnS genes, and restriction enzyme Hae III, cpDNA was determined to be maternally inherited in buffalograss. The germplasm had considerable diversity for chinch bug resistance, with approximately 10% of the germplasm having a high resistance level. There was no significant correlation between chinch bug resistance and ploidy level or chinch bug resistance and pubescence. Of the genotypes studied, 4 were highly resistant, 22 were moderately resistant, 19 were moderately susceptible and three were highly susceptible to chinch bug injury, showing a continuous distribution. Basal peroxidase expression levels measured in the 28 non-infested plants of resistant and susceptible buffalograsses did not correlate with chinch bug injury. All six genoptypes evaluated for chinch bug activity showed an increased level of peroxidase levels in infested plants, suggesting upregulation in response to chinch bug injury. Relatively low levels of peroxidase in a highly chinch bug resistant genotype, PX-3-5-1, infers contribution of other genes to chinch bug resistance. Overall results indicate substantial genetic variation in buffalograss germplasm that can be used to enhance buffalograss breeding programs and increase understanding of the chinch bug resistance mechanism. ^
Gulsen, Osman, "Buffalograsses: Their organelle DNA, chinch bug resistance variation, and peroxidase enzyme responses to chinch bug injury" (2004). ETD collection for University of Nebraska - Lincoln. AAI3152611.