PJB-2023-502
CHARACTERIZATION AND MANAGEMENT OF LASIODIPLODIA THEOBROMAE CAUSING COCONUT LEAF BLIGHT DISEASE
RAJENDRAN RAMJEGATHESH
Abstract
Leaf blight disease caused by Lasiodiplodia theobromae (Pat.) Griffon & Maubl is an important disease of coconut in the southern parts of India. Significant differences on colony morphology, colour, spore characters and production of fruiting bodies were observed among the twelve isolates from various parts of Tamil Nadu, Southern India. Majority of the isolates produced pycnidia only after 21-24 days of incubation at 27°C and 85 % RH and the conidia were released through the ostiole which was ranged between the length of 23.358 to 27.634 and 12.462 to 14.354 mm in size. The immature conidia were hyaline, aseptate while, the matured one were dark brown, septate with longitudinal striations, oval in shape. ITS primers were used for molecular characterization and an amplicon of ~550 bp was partially sequenced, confirmed as L. theobromae (MG685854). Analysis of the genetic coefficient matrix derived from the scores of RAPD profile showed 28 to 85 per cent similarities among the L. theobromae isolates. In order to manage the disease, complete inhibition of mycelial growth was observed with carbendazim, tebuconazole + trifloxystrobin, tebuconazole and propiconazole at 100 ppm, 250 ppm, 100 ppm and 500 ppm concentrations, respectively. Based on the in vitro screening results, the effective fungicides were tested in farmer’s holdings. This experiment revealed that, the root feeding of tebuconazole @ 2 ml in 100 ml of water /palm for thrice along with along with recommended integrated nutrient management practices was highly effective and recommended for the management of coconut leaf blight disease.
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