Author(s):

P Kishore Varma, Vijay Krishna Kumar K, Suresh M, V Chandrasekhar, M Bharathalakshmi and P Jamuna

Abstract: Sugarcane is an important cash crop of India grown in an area of 3.93 million hectares with a production of 167 million tonnes. Most of the popular cultivars of sugarcane were withdrawn from cultivation due to their susceptibility to red rot disease incited by Colletotrichum falcatum Went. In Andhra Pradesh, yield losses to a tune of 50% are reported on susceptible cultivars. In the present study an attempt was made to reduce the losses due to red rot disease using PGPR. Different isolates of rhizoplane bacteria were collected from various locations in Visakhapatnam district of Andhra Pradesh, India and cultured by standard protocols. These isolates were tested for their growth promoting traits and antagonistic activity against C. falcatum under in vitro and in vivo conditions. Among the rhizoplane bacteria tested, rhizobacteria 7 and 19 were found promising under in vitro conditions and were selected for sett treatment of single noded setts and evaluated for sett germination and seedling growth. Sett treatment with rhizobacteria resulted in increased sett germination and seedling vigour when compared to control. Further, these isolates were tested for red rot management under field conditions by inoculating red rot susceptible genotype, Co 997 pre-treated with PGPR, by plug and cotton swab methods. All the canes in various treatments inoculated with C. falcatum pathotype Cf 05 by plug method produced highly susceptible reaction. However, differential reaction was observed in cotton swab method of inoculation. Disease severity was found to be less in treatments where the single noded setts and seedlings were treated with Rhizobacteria 19. The prominent isolate, rhizobacteria 19, was characterized as Bacillus amyloliquefaciens using 16S rRNA sequence based homology. Overall, our results suggested the scope and potentiality of PGPR isolated from sugarcane rhizoplane in suppressing the field infection of red rot besides promoting seedling vigour.

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