EPIDEMIOLOGY, SYMPTOMATOLOGY AND MANAGEMENT OF THE FRUIT ROT OF BOTTLE GOURD (LAGENARIA SICERARIA STANDL.) CAUSED BY ALTERNARIA ALTERNATA (FR.) KEISSLER

Abstract

The disease epidemiology and symptomatology of black fruit rot of bottle gourd caused by Alternaria alternata (Fr.) Keissler was studied under both in vitro and in vivo conditions. The results revealed that, A. alternata can grow at wide range of temperatures between 15-30ºC; with 26-28ºC as the most favoured temperature range. The pathogen required high relative humidity (> 90 %) for optimum growth and sporulation. Microscopic observations revealed that the pathogen bear hyaline, septate and irregularly branched mycelia, hyphae of an average width 3.50 μm (range 1.50-7.30 μm), short or long conidiophores arising singly or in groups of 2-6 from host tissue, and 48 x 14 μm sized conidia borne in long chains of 10 or more bearing 2-10 septa. Artificially inoculated healthy fruits of bottle gourd expressed the typical symptoms of water soaked lesions which turned brown within 2-3 days. The fungicide mancozeb (0.25 %) was found most effective with 100 % inhibition of pathogen, in vitro. Among the two antagonistic fungi, Trichoderma hamatum with 87.77 % inhibition of pathogen growth under in vitro was more promising than Trichoderma harzianum (77.77 %). The findings of the present study are crucial in understanding the field epidemiology and severity of A. alternata incidence. The knowledge on efficacy of fungicides and antagonistic fungal bioagents in suppressing the pathogen growth will aid in implementing effective management strategy for A. alternata.