Characterization and etiolgy of pathogen (S) associated with wilt complex disease of Lagenaria siceraria in Himachal Pradesh

The microscopic examination of the diseased plant parts of bottle gourd revealed the association of three pathogens of the wilt complex namely, Colletotrichum orbiculare, Fusarium oxysporum and Didymella bryoniae. Pathogenicity test with each of the three isolated pathogens was conducted on the highly susceptible bottlegourd variety MHBG 8 and the Koch's postulates were proved by Didymella bryoniae thereby, confirming the pathogenicity of the test pathogen. D. bryoniaee xhibited white cottony aerial mycelium and olive green to dark green or black substrate mycelium. Pycnidia were brown coloured and contained hyaline, cylindrical conidia having rounded ends with two guttules, non or mono septate, measuring 3-5 x 2-3 μm. Pseudothecia expressed as dark brown with hyaline pseudoparaphyses protruding from ostiole and contained numerous asci with 8 ascospores each. Ascospores were hyaline, oval, monoseptate and measured 5-8 x 3-5 μm in size. Blast results of the ITS sequences obtained through PCR amplification of the fungal DNA using ITS1 and ITS4 primers were 99 per cent coinciding with that of Stagnosporopsis cucurbitcearum. Thus, on the basis of, morpho-cultural characteristics and molecular characterization, the test pathogen is identified and confirmed as Didymella bryoniae (Stagnosporopsis cucurbitcearum) to be the cause of wilt disease of bottle gourd.