DISEASE DEVELOPMENT AND MANAGEMENT OF LEAF BLIGHT [Stemphylium vesicarium (Wallr.) E. Simmons] OF GARLIC {Allium sativum L.) 1974
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2015-01
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JAU, JUNAGADH
Abstract
Garlic {Allium sativum L.) belonging to the family Alliaceae is the second most important bulb crop grown throughout the plains of India for spices and condiments. Though, garlic is seriously affected by many diseases, leaf blight caused by Stemphylium vesicarium (Wallr.) E. Simmons is an important destructive disease. It appears every year in a moderate to severe form in garlic growing areas of Saurashtra region of Gujarat.
The causative organism isolated from the infected leaves of the diseased plants of garlic grew in the form as dark green to blackish mycelium, which later turned olivaceous brown to black and finally velvety on PDA. Conidia were light brown or golden brown to olive brown, oblong or broadly oval, producing on straight to variously curved cylindrical and septate conidiophores. Based on the morphological characters viz., mycelium, conidiophores, conidia and growth patterns, the causative fungus isolated from the leaves of infected garlic plant was identified as Stemphylium vesicarium (Wallr.) E. Simmons.
Garlic plants were susceptible to leaf blight from 30 to 35 days of growth, but it was more prominent at 50 days onwards. Initially the infected plants exhibited characteristic symptoms of white flecks that enlarged and produced sunken purple lesions which were surrounded by a yellow to pale brown border. Later, small light yellow to brown, water soaked and non-delineated lesions developed on older leaves. Finally, these lesions grew into elongated spots that frequently coalesced resulting in blighting of leaves.
The pathogenicity of S. vesicarium was confirmed by reproducing the same field symptoms like discolouration and withering of the leaves. Re-isolations confirmed the pathogenicity of S. vesicarium as the infected tissues produced the same type of mycelial growth, conidiophores and conidia of the original fungus.
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PLANT PATHOLOGY