Comparative Study of Selected Cucumber Cultivars Resistant To Powdery Mildew Caused

R.G.A.S. Rajapaksha, Shyamalee Kohombange, H.M.P.S. Kumari

Abstract


Genetic resistance is one of the most suitable strategies to control cucurbit powdery mildew (CPM) on cucumber, incited by Podosphaera xanthii or Golovinomyces orontii. Annual surveys of the screening of germplasm for new sources of genetic resistance provide a vital support to cucumber breeding programs. The objective was to determine whether resistance to powdery mildew which has been bred into most commercial resistant cucumber cultivars, was continuing to provide suppression of the pathogen. In this study eight genotypes in greenhouse condition and six genotypes in open field condition were evaluated for resistance to the pathogen by a visual scale for leaf lesions of disease symptoms. This study was conducted at Horticultural crop research and development Institute, Gannoruwa, Sri Lanka (Agro ecological zone WU1). Powdery mildew species differ in host range, ecological requirements, and geographic distribution. But, in here causal agent of the powdery mildew of cucumber was identified as Podosphaera xanthii based on microscopic observation as oval shape, presence of fibrosin bodies in the conidia and size of conidia. These observations are compatible with published data. There was a considerable variation among cucumber cultivars in terms of resistance to powdery mildew resulting in the identification of five tolerant cultivars (R2 x M2 self, Big white self, White Jade self, Kalpitiya white x G17 and White Jade self long) belonging to greenhouse class and three resistant varieties (Big white self, G17 x Kalpitiya White self and Kalpitiya white x G17) belonging to open field condition. Big White Self variety is suggested to be used in both greenhouse cultures and open field cultures to control powdery mildew caused by Podosphaera xanthii.


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