STUDIES ON BOTRYODIPLODIA THEOBROMAE CAUSING DIEBACK AND GUMMOSIS IN MANGO

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Date
2019-11
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UHF,NAUNI
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ABSTRACT Mango (Mangifera indica L.) is one of the most important and esteemed fruit of the tropical and subtropical world and cultivated extensively as a commercial fruit crop in India. Mango is subjected to a number of diseases at all stages of its development from nursery to the consumption of fruits. Among all diseases infecting mango, the mango die back and gummosis is the most severe threat for the mango industry and also for foreign exchange earnings. This disease is incited by number of pathogens but the major causal organism is Botryodiplodia theobromae (Pat.) Griffon and Maube with its teleomorphic state Botryosphaeria rhodina. It is a cosmopolitan and diverse species. The micro-organism associated with dieback and gummosis was morphologically and molecularly confirmed as B. theobromae. The pathogenicity test proved Koch’s postulates, showed incubation period of 48 hours and dieback occurred within 10 to 14 days of inoculation. Potato dextrose agar and Czapek’s dox agar media recorded maximum mean diametric growth, maximum mean growth rate, sporulation and pycnidial production. Potato dextrose broth showed maximum mean dry mycelial weight, and good sporulation and pycnidial production. Sucrose and mannitol, recorded best source of carbon while ammonium oxalate was found to be the best source of nitrogen for the growth of B. theobromae. B. theobromae grew between 10 to 40oC, with maximum mean mycelial growth at 40oC, maximum mean growth rate at 15oC and 20oC, and good sporulation and pycnidial production at 30oC. pH 7.0 showed maximum mean diametric growth, pH 7.0 and 7.5 showed maximum mean growth rate, and pH 6.5 showed good pycnidial production. There was no significant effect found of duration of light periods on the fungus growth, sporulation and pycnidial production. At 30oC and 35oC, shortest incubation period (48 hours) was recorded whereas maximum mean rate of lesion development was observed at temperature of 30oC and 25oC. Shortest incubation (29 hours) was observed at 100 per cent relative humidity, while maximum mean rate of lesion development (0.53mm/h) was observed at 98.5 per cent relative humidity. Cannabis leaf extract was found to be most effective giving 20.49 per cent inhibition in the mycelial growth. Carbendazim was found to be most effective, giving 98.75 per cent inhibition of mycelial growth followed by chlorothalonil (95.74 %) and carbendazim + mancozeb (95.37%).
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