Characterization of Powdery Mildew of Snake Melon (Cucumis melo var. Flexuosus L.) And Evaluation of Some Inbred Lines of Snake Melon for Powdery Mildew Resistance

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Author(s) Mohamed. T. Y. | Muna. E. S. | Amira N. O.
Pages 597-605
Volume 5
Issue 12
Date December, 2016
Keywords Incidence; Severity; Podosphaera xanthii; Powdery mildew; Physiological races.
Abstract

Snake melon (Cucumis melovar. flexuosus L.) is among the desirable melon groups in the Sudan, it is consumed locally as green salad or pickles. The crop is being affected by major biotic and abiotic stresses which have laid to drastic reduction in yield. One of the major biotic stress is powdery mildew. The disease can reduce yield by decreasing fruit size, number of fruits. Cucurbit powdery mildew is most frequently caused by two obligate fungal pathogens, Podosphaera xanthii and Golovinomyces cichoracearum. The most commonly identified pathogen; particularly in warmer production regions has been P. xanthii, therefore the study was carried out to identify the causal agent of the disease, to screen some inbred lines of snake melon (Cucumis melo var. flexuosus) for resistance to powdery mildew and to determine the physiological races under local field. Nine landraces of snake melon were used, they were sampled for incidence and severity of the disease under studied area. Disease incidence was determined by using rate and severity of the disease by using severity scale of 1- 5. A Complete Randomized Block Design (CRBD), with three replications was used. Although determination of the physiological races by the used differential melon cultivars growing in the field was carried out. Pathogen identification was done microscopy according to morphological characters of conidia, conidiophores, conidia germination, presence or absence of fibrosin bodies and the perfect stage (chasmothecia) of the fungus. Field trial revealed that, incidence ranged from (50.0–80.0%) on leaves. The severity was (2.0–4.8) moderate–very severe infection (40.0–96.0%) on leaves. Significant differences (P= 0.05) were observed in disease severity. The causal agent of powdery mildew disease of snake melon (Cucumis melo var. flexuosus) was conclusively identified as Podosphaera xanthii, microscopic observations of all tested samples revealed hyaline conidia, ellipsoid to ovoid in shape, with fibrosin bodies, also the chasmothecia were exist in a high number, which contained only one ascus with 3-8 ascospores, hayline appendages and globose. At least, the 9 local cultigenes tested they are susceptible to races 1 and 2US of Px under field conditions

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