Abstract

The bread wheat is an important crop of Pakistan. The average yield of wheat in the country is much behind the potential yield of the improved wheat cultivars. The low yield of wheat is the consequence of many factors including rust diseases that cause yield along with quality losses. Most of breeding programs in the country lack facilities for screening against rust diseases. Usually, selection is done with inadequate rust epidemic or improper pathotypes. As a result, only a few of released cultivars exhibit desired resistance against the prevailing rust races/pathotypes. A study was conducted from 2007 to 2011 at National Agricultural Research Center, Islamabad, Pakistan to provide information on the level of resistance in 113 released Pakistani bread wheat cultivars against stripe rust. The results indicated that most of the cultivars exhibited compatible reaction with prevailing pathotypes/races of stripe rust fungus at Islamabad. Only six cultivars including, Tatara, Faisalabad 08, Bahawalpur 94, Sassui, Chakwal 86 and Fakhr-e-Sarhad demonstrated hypersensitive type of resistance against naturally prevailing stripe rust races/pathotypes. However, year x cultivar interaction was observed in many cultivars against stripe rust races. Among the cultivars that showed compatible type of reactions, four were highly partial (non-hypersensitive) resistant (disease severity (DS) < 5% of Morocco), nineteen were partially (non-hypersensitive) resistant (DS < 20% of Morocco), forty-three were moderately partial (non-hypersensitive) resistant (DS < 50% of Morocco) and forty-one were moderately to highly susceptible. Virulence was observed against resistant genes YrA, Yr2, Yr4 Yr6, Yr7, Yr9 and Yr27.

Key words: Puccinia striiformis f. sp. tritici, stripe rust, virulence, wheat, Yr genes.