Distribution, physiologic races and reaction of wheat cultivars to virulent races of leaf rust (Puccinia triticina Eriks and Henn.) in south eastern zone of Tigray, Ethiopia
Journal Title: International Journal of Life Science - Year 2016, Vol 4, Issue 1
Abstract
Leaf rust (Puccinia triticina Eriks and Henn.) is one of the most important foliar diseases of wheat (Triticum aestivum L.) in South eastern zone of Tigray in Ethiopia. Regular surveying, race identification and searching for resistant genes plays significant role to develop resistant varieties against leaf rust. Hence, this study was carried out to determine the distribution and intensity of wheat leaf rust to identify physiologic races of P. triticina and also to evaluate the seedling reaction of commonly grown wheat varieties to virulent races of leaf rust. The results of this study were based on leaf rust survey to compute the prevalence and intensity of the disease; race identification through inoculation of leaf rust populations, isolation, multiplication of mono pustules of the pathogen and determination of races by inoculating on leaf rust differential hosts; and evaluating ten wheat varieties to virulent and dominant races (TKTT, THTT and PHTT) at seedling stage in greenhouse. During the survey, a total of 108 farmers’ wheat fields and experimental plots were assessed in five districts of South Eastern Tigray, of which 95 of the fields (88%) were affected with leaf rust. The overall mean incidence and severity of the disease were 48.4 and 18.2%, respectively. The highest intensity of leaf rust was recorded in Wukro wheat fields with incidence of 63.2% and severity of 37.3%. In contrast, the lowest incidence and severity of the disease were recorded in D/ Temben district with mean values of 7.4 and 4.1%, respectively. The characterization of 40 mono pustules of P. triticina was resulted for the identification of 22 races. Races PHTT and PHRT were predominant with frequencies of 20 and 15%, respectively, followed by THTT and FHRT with a frequency of 10% each. The remaining 18 races were confined to specific locations and detected once with a frequency of 2.5% each. The broadest virulence spectrum was recorded from TKTT race, making all Lr genes except Lr 9 was ineffective. About 81% of the Lr genes were ineffective to more than 55% of P. triticina isolates. High virulence was observed on Lr3, Lr10, Lr B and Lr18 with frequencies of 90, 95, 97.5 and 100%, respectively. However, Lr genes 9, 24 and 2a were found effective to 100, 95 and 82.5 of the tested isolates, respectively. The variety evaluation revealed that, Mekelle-3, Mekelle-4, Picaflor, Dashin and local showed susceptible reactions to TKTT, THTT and PHTT races. Mekelle-1 and Mekelle-2 were susceptible to races TKTT and THTT, but resistant to PHTT. Digalu was only susceptible to TKTT race. Unlike bread wheat varieties, the durum varieties, Ude and Dembi were resistant to these races. The results of this study showed that most bread wheat varieties did not have adequate resistance for leaf rust. Hence, the gene pyramiding of Lr9, Lr24 and Lr2a has paramount importance as the additive effects of several genes offer the variety a wider base for leaf rust resistance. Keywords:
Authors and Affiliations
Tesfay Gebrekirstos Gebremariam, Getaneh Woldeab, Thangavel Selvaraj
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