Doctoral Degrees (Genetics)

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Marker assisted breeding in sugarcane : a complex polyploid
(Stellenbosch : University of Stellenbosch, 2007-03) Butterfield, Michael Keith; Botha, F. C.; Warnich, L.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics.
Association analysis was used to improve the efficiency of breeding sugarcane varieties for the negatively correlated traits of resistance to sugarcane smut and the eldana stalk borer. 275 RFLP and 1056 AFLP markers were scored across a population of 77 genotypes representing the genetic variation present within the SASRI breeding programme. Genetic diversity analysis did not detect significant structure within the population. Regression analysis identified 64 markers significantly associated with smut rating and 115 markers associated with eldana rating at r2 > 6.25%. Individual markers with the largest effects explained 15.9% of the phenotypic variation in smut rating and 20.2% of the variation in eldana. Five markers were significantly associated with both smut and eldana. In each case the marker effect was negatively correlated between the two traits, suggesting that they are genetically as well as phenotypically negatively correlated.