Shaukat Hussain

Characterization of Slow Rusting Resistance against Puccinia striiformis f. sp. tritici in Candidate and Released Bread Wheat Cultivars of Pakistan

A set of 50 candidate and released bread wheat cultivars of Pakistan were studied to identify slow rusting resistance against yellow rust caused by Puccinia striiformis f. sp. tritici (PST). Seedling tests were done under glasshouse conditions at Thiverval-Grignon, INRA, France while slow rusting resistance was evaluated during 2005-07 in field plots using epidemiological variables at Peshawar, Pakistan. Twenty nine cultivars (58%) displayed susceptibility against the two PST races used in the seedling tests. Epidemiological parameters of resistance at the adult-plant stage were significantly (P<0.01) different for years, cultivars and cultivar x year interactions over three years. Analyses were done for sequence tagged site (STS) marker, csLV34 at INRA and revealed that 40% of the tested cultivars possessed adult plant resistance gene Yr18 linked allele of 150 bp. Of the 50 cultivars evaluated under field trials, 11 were highly resistant to both PST races as in the seedling tests and 39 showed different levels of slow rusting. Cultivars Bakhtawar-93, Punjab-96, Bahawalpur-95, V-00183 and V-00125 were relatively more stable over 3-years as Final Rust Severity (FRS), Area Under Disease Progress Curve (AUDPC) and Infection Rate (r) values were 74, 81, and 63% less of the susceptible control, Morocco, respectively. These cultivars also possessed the marker linked to Yr18 and could be exploited for the deployment of Yr18 in breeding for slow rusting in wheat. Both FRS and ACI are suitable parameters and can be used for phenotypic selection in a wheat breeding program for slow rusting resistance.

Pathogenicity variations of Puccinia striiformis f. sp. tritici westend in wheat growing areas of Nepal.

Y ellow rust, caused by Puccinia striiformis f. sp. tritici (PST), is one of the most important diseases threatening wheat productions around the world. Yellow rust population from Nepal was characterized for its frequency and combination of virulences using world, European and s upplemental differential sets under standard glasshouse conditions at Institut e National de la Recherche Agronomique (INRA), France. A total of 62 revived isolates which were collected during 2008 were analyzed. Isolates were differentiated into six pathot ypes (N1 to N6). Two pathotypes N1 and N2 represented 88% of the Nepalese population and shared virulences v1 (virulent to resistance gene Yr1 ) , v2 , v6 , v7 , v27 and vSU . None of the isolates was virulent to resistance genes Yr5, Yr10, Yr15, Yr24, Yr26 and YrEp . The virulence frequencies of v1, v6 , v8 , v9 and vA ranged between 26 - 95% in all samples analyzed while v2, v7, v27 and vSu were fixed in all pathotypes. Results revealed that out of six pathotypes, five were never reported from Nepal and suggested a possibility of spore migration in the region.