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Subject: Plant Breeding and Genetics × End date: 2009 × Start date: 2009 ×
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    EPIDEMIOLOGY AND MANAGEMENT OF ALTERNARIA LEAF SPOT OF Aloe barbadensis
    (2009) Pawan Kumar Amrate; J. R. Sharma
    Surveys conducted during 2008 revealed that Alternaria leaf spot disease of Aloe barbadensis was prevalent at all the locations viz. Ludhiana, Malerkotla, Nawanshahar (Ballowal Saunkhri) and Bathinda. Disease incidence and severity was highest at P.A.U. Regional Research Station, Bathinda which recorded 90.0 and 34.0 per cent respectively. Alternaria alternata (Fr.) Keissler was isolated from diseased leaves and pathogenicity was proved on healthy leaves. Disease development and progression were correlated with prevailing environmental factors at Ludhiana during the year 2008. Highest disease incidence and intensity was recorded during August. However correlation study showed that all the factors (atmospheric temperature, relative humidity and cumulative rainfall) were positively correlated with disease development. This investigation revealed that the atmospheric temperature between 23 to 300C, relative humidity between 65 to 95 per cent and higher rainfall were conducive for development and progression of the disease. To find out effective strategies for the management of the disease various fungicides, plant oils and plant extracts were evaluated in vitro as well as in vivo for their efficacy against the pathogen A. alternata. Among these Amistar, garlic oil and turmeric extract were found to be most effective in inhibiting the spore germination of A. alternata and recorded ED50 values of 5.5 g/ml, 155 g/ml and <10000 g/ml respectively whereas Score was found to most effective in checking the mycelial growth of the pathogen as it completely inhibited the growth even at 25 g/ml and recorded ED50 value of 1.7 g/ml. Garlic oil and turmeric extract were also found to be effective in inhibiting the mycelial growth of the pathogen. In the field experiment, all the tested fungicides reduced disease intensity significantly. Among these Score 25 EC was found to be highly effective as it reduced 80.6 per cent disease at 0.1 per cent concentration whereas garlic oil and turmeric extract also showed promising result. In vitro screening of genotypes for their resistance/susceptibility response revealed that Aloe barbadensis contracted maximum disease and showed 100 per cent disease incidence.