VARIABILITY IN VIRULENCE OF WHEAT LEAF RUST ( PUCCINIA TRITICINA ) IN THE SINDH PROVINCE, PAKISTAN

Leaf rust of wheat caused by an obligate biotrophic fungus (Puccinia triticina), is one of the widespread diseases of wheat. The emergence of new virulent races of fungal pathogens threatens wheat cultivars' resistance, leading to outbreaks that can cause substantial damage to crops and result in economic losses to farmers. Developing wheat cultivars that have resistance to virulent races is an effective means of reducing the frequency and impact of these outbreaks. An experiment was conducted at 5 locations (a trap nursery consisting of 37 lines of wheat leaf rust differentials and 115 commercial wheat cultivars was established against leaf rust pathogen), for evaluating the virulence pattern of leaf rust under natural field environments across wheat-producing regions of Sindh, Pakistan. Results revealed that Lr9, Lr19 and Lr28 genes were found effective under field environments. The moderate resistance was recorded for Lr18, Lr23 and Lr34 genes at two locations while Lr36 & Lr37 genes had moderate resistance at most of the locations. Results also revealed that Rawal-87, Marvi-2000, Bhittai, Pirsabak-08, Faisalabad-08, Benazir-13 and Shalakot-13 were the commercial wheat varieties having resistance at all locations of Sindh during (year 1 and year 2) years while most of the cultivars showed susceptibility. The scenario clue to a dire necessity to widen the genetic base of Pakistani cultivars by incorporating genes for the resistance against disease. Furthermore, strong monitoring and regular surveys should be conducted for determining current virulence status and resistance genes.