Fungal leaf spot of greengram [Vigna radiata (L.) R. Wilczek] in Kashmir: Etiology and management

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Fungal leaf spot of greengram [Vigna radiata (L.) R. Wilczek] in Kashmir: Etiology and management

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Title: Fungal leaf spot of greengram [Vigna radiata (L.) R. Wilczek] in Kashmir: Etiology and management
Author: Bhat, Farooq Ahmad; Bhat, G. N. (Guide)
Abstract: Cercospora leaf spot is the predominant foliar fungal disease of greengram in Kashmir and affected 5.87-28.43 per cent leaf area in crop stands at pod development stage during kharif 2008. Cercospora canescens an imperfect fungus belonging to class Hyphomycetes was found associated with the manifestation. The diagnostic symptoms comprised of roughly circular to irregular, white centered reddish brown to brown leaf spots measuring 2-12 mm in diameter. Potato and carrot-oatmeal based agar media supported equall growth of the pathogen. The survival of test pathogen in infected leaves, pods and seeds was influenced by surrounding environment. While the leaves and pods supported viable pathogen only upto March under open field conditions, the pathogen was recovered from same kind of debris during May when exposed to only post winter open field conditions. The seed and other infected material also supported survival of pathogen beyond March when kept inside room during winter and spring months. Cercospora canescens from Shalimar was host specific and host range was confined to blackgram and cowpea. Shalimar Mung-1 was invariably susceptible to C. canescens at all growth stages for having high sugar (124.03-134.89 mg/g dry weight) to support pathogenisis besides lacking in sufficient phenol (20.73-26.53 mg/g dry weight) to contain the invasion. Under natural epiphytotic conditions, sharp increase in Cercospora leaf spot intensity was recorded during August which witnessed maximum and minimum temperatures of about 30 and 17 oC, respectively, besides experiencing high RH (over 80 %). Higher values of periodic disease (>6%) coincided with average maximum temperature 27.16-30.23 oC, minimum temperature 10.07-16.5 oC, RH 81.65-84.50 per cent and periodic rainfall of 2.3-33.6 mm. The disease intensity was, however, less influenced by most of the weather factors, though minimum temperature was significantly correlated with disease for the period between July-25 and September-13. Most of the available germplasm of greengram including Shalimar Mung-1 showed susceptible response to the test fungus under field conditions with only four genotypes viz., ML-935, PDM-54, SM-710 and SM-366 suffering less leaf spot intensity (26.77-29.47 %). The terminal disease intensity manifested by May sown crop (23.34-27.21 %) was significantly low when compared to late sowings which suffered maximum disease attack and experienced proportionate decrease in seed yield with lowest (7.33-7.42 q/ha) obtained in July sown crop. Foliar application of carbendazim 50WP (0.05 %) at first appearance of disease followed by another spray with hexaconazole 5EC (0.02 %) or mancozeb 75WP (0.25 %) ensured significant control of disease incidence (47.13-77.26 %) and intensity (48.44-68.71 %) besides supporting proportionately attractive seed yield (8.62-8.95 q/ha) at an acceptable B:C ratio of 3.05-6.38:1.
URI: http://dspaces.uok.edu.in/jspui//handle/1/1081
Date: 2011


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