A Stable Simple Sequence Repeat Marker for Resistance to White Mould in Tobacco

Abstract

White mould, caused by Golovinomyces cichoracearum, is a major fungal disease of tobacco. Breeding for resistance to white mould is slow due to the intensive labour needed in artificial screening and the huge effect of the environment. In order to improve selection efficiency, molecular markers need to be identified to help in the rapid selection of germplasm resistant to white mould. The purpose of this study was, therefore, to identify the neutral, simple sequence repeat markers that can assist breeders in selecting for resistant plants. Two resistant parental lines XZ and STNCB, and three susceptible parental lines XSR, K51 and T71, were used in this study. Backcrosses of the hybrid from XZ and XSR were grown in a greenhouse, and DNA was extracted for molecular analysis. Eight simple sequence repeat markers and ten inter-simple sequence repeat markers were used. These markers were screened on the parental lines and the backcross generations for the differences between resistant (score 1) and susceptible (score 5) material. Single marker analysis was done using a t-test and significant (P<0.001) differences were found between the means of resistant and susceptible plants based on the marker PT30021. Marker PT30021 showed linkage to the white mould resistance gene, and thus managed to distinguish between resistant and susceptible materials in parental and advanced generations. Locus PT30021 has the potential of being used to identify white mould resistant germplasm in marker assisted backcrossing.

Keywords: Golovinomyces cichoracearum, Marker-assisted Backcrossing, Molecular Markers, Resistance