The stem rust resistance gene Sr24 is effective against most races of Puccinia graminis f. sp. tritici, including race TTKS (syn. Ug99), and is used widely in commercial wheat cultivars worldwide. In 2006, susceptible infection responses were observed on wheat lines and cultivars carrying Sr24 in a field stem rust screening nursery at Njoro, Kenya. We derived 28 single-pustule isolates from stem rust samples collected from the 2006 Njoro nursery. The isolates were evaluated for virulence on 16 North American stem rust differential lines; on wheat lines carrying Sr24, Sr31, Sr38, and SrMcN; and on a wheat cultivar with a combination of Sr24 and Sr31. All isolates were identified as race TTKS with additional virulence on Sr31 and Sr38. These isolates were divided into two groups: group A (seven isolates and the two control isolates), producing a low infection type, and group B (21 isolates), producing a high infection type on Sr24, respectively. Isolates of group B represented a new v...

During the periodic purity checks of pathotypes 107-1(45R35=JCGPL) and 20(5R27=SGQPL) of Puccinia triticina in national repository at Shimla, India, mixtures of infection types were observed on the differential Lr3 and Lr15 , respectively. Single pustule isolations and further pure cultures in both the cases yielded new pathotypes designated as 57(45R39= KGTPL) and 20-2(57R27= SHKPL). Pathotype 57 was one step gain in virulence on Lr3 in 107-1 whereas 20-2 on Lr15 in mother culture of pathotype 20. The difference of virulence on one gene to each mother culture and their non occurrence in the field samples is indicative of mutation for virulence in situ . To ascertain the novelty of new pathotypes, detailed study on differentials, avirulence/virulence structure, DNA polymorphism using SSR markers, and other related information is presented in this publication. The new cultures are being maintained as PrtI 57 and PrtI 20-2 in the repository.

Wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), has re-emerged as one of the major concerns for global wheat production since the evolution of Ug99 and other virulent pathotypes of Pgt from East Africa, Europe, Central Asia, and other regions. Host resistance is the most effective, economic, and eco-friendly approach for managing stem rust. Understanding the virulence nature, genetic diversity, origin, distribution, and evolutionary pattern of Pgt pathotypes over time and space is a prerequisite for effectively managing newly emerging Pgt isolates through host resistance. In the present study, we monitored the occurrence of stem rust of wheat in India and neighboring countries from 2016 to 2022, collected 620 single-pustule isolates of Pgt from six states of India and Nepal, analyzed them on Indian stem rust differentials, and determined their virulence phenotypes and molecular genotypes. The Ug99 type of pathotypes did not occur in India. Pathotypes 11 and 40A we...

The adaptation of fungal pathogen to its hosts and to the climate variation, in particular to the temperature, was investigated on wheat stripe (yellow) rust, caused by the biotroph fungus Puccinia striiformis f. sp. tritici (Pst) in the Middle East, focusing on Lebanon and Syria. This disease is a major problem for the crop in the region. Specific resistance genes were postulated in 138 wheat genotypes including elite lines, grown varieties and local landraces, using an array of 11 French pathotypes. Resistance gene diversity for yellow rust in wheat elite lines was higher than in current, commercial varieties grown in Lebanon, with nine Yr genes detected singly or in combination. Some varieties were resistant to all tested pathotypes and might provide interesting sources of resistance. Most of the Lebanese landraces were susceptible but also heterogeneous by their number of plants susceptible and resistant to a specific pathotype in a same landrace.A field survey was conducted in ...

Stem rust has become a major cause for concern with the emergence of race Ug99 in Eastern Africa. The potential impact of the disease is particularly serious in Iraq. The current study was conducted to identify the physiological races of Puccinia graminis f.sp.tritici (Pgt), the causal agent of stem rust. Single pustules of stem rust samples collected from different wheat fields from Sulaimani, Erbil, Diala, Nineveh and Babylon were separately multiplied on the susceptible cultivar cv Morocco. Seven-day-old seedlings of the North American stem rust differential set inoculated with urediniospores of each pathogen isolate; the inoculated plants were scored two weeks after inoculation using the infection type scale described by Stakman. Race analysis indicated prevalence of five races of the pathogen. Race TKTRC was prevalent in Sulaimani; RKJTF in Erbil; TKTTC in Nineveh; PRJSC in Diala and KRKSCin Dheqar.The resistance genes Sr24 and Sr31 were effective against all Pgt isolates, while resistance genes Sr7b, Sr9g, Sr9b, Sr30, Sr9a, Sr9d, SrMcN were ineffective against all the isolates. None of the identified races of Pgt belonged to race Ug99 or members of this race group. Real-time PCR analysis of DNA extracted from dead spores, representing each of the Pgt races, at USDA-ARS cereal disease Lab, St Paul, Minnesota confirmed these results.