STUDIES ON Helminthosporium LEAF BLIGHT OF BROWNTOP MILLET [Brachiaria ramosa (L.) Stapf]
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Date
2020-12-31
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University of Agricultural Sciences, Bangalore
Abstract
Browntop millet was recently introduced into millet system in India for domestic purpose. In Kharif 2018, leaf blight was observed at Bangalore, India. Spots were brownin colour with small yellow halo eventually enlarged with light brown centre. Spots coalesce causing blight. Maximum disease severity was recorded in Bengaluru (8.46 G) and minimum in Mandya (4.80 G). Morphologically the pathogen was identified as Bipolaris sp. by comparing with standard descriptions of Helminthosporium species.
BTMH5 isolate was identified as more virulent. Pathogen was able to infect only browntop millet. Czapek Dox agar (CDA) and host leaf decoction agar with 2 per cent sucrose and pH 6.0 to pH 7.0 were found to be ideal for radial mycelial growth and sporulation. In vegetative compatibility, BTMH2 × BTMH6 showed compatibile reaction where H-shaped hyphal anastomosis was observed. Barren pseudothecia are produced on Sach’s agar medium. BLAST results of GPDH sequences confirmed that Bipolaris setariae as the causal organism of browntop millet leaf blight in India. Specific primers
were designed and validated. Among the botanicals, maximum per cent inhibition was noticed in agave with no inhibition in calotropis. Trichoderma viride along with T.harzianum strain 14 among the fungal bio agents and P42 strain of Bacillus velezensis among the bacterial bio agents accounted maximum per cent inhibition. Mancozeb (96.54 %) among the contact fungicides, propiconazole (100.00 %) among the systemic fungicides and cymoxanil + mancozeb among the combi-product fungicides exhibited maximum inhibition of mycelial growth. Amongst the 40 germplasm screened, none of the germplasm showed resistant reaction.