Abstract

Prema Ranjitham Thangamani, Raguchander Thiruvengadam and KalaimaniThillaigovindan

Sugarcane is an important cash crop and used as the chief source of sugar in India. Sugarcane production is challenged by various biotic and abiotic stress among the biotic factors, red rot disease caused by Colletotrichum falcatum is a major disease leading to severe reduction in sugarcane production. Morphological studies conducted under in vitro in Potato Dextrose Agar (PDA) showed characteristic variation in their cultural and colony characters which were collected from different places. Based on pathogenicity test the variety Coc671 showed more susceptiblilty to all the isolate. The variety Co 86249 resistant to all the isolates except Cf3 which showed intermediate reaction. Toxins from various isolates was extracted from culture filtrate grown in Czapek-Dox yeast (CDY) broth and extracted using ethyl acetate. The ethyl acetate fraction was injected to two different varieties. Among the crude toxins extracted from different isolates, the ethyl acetate fraction from Cf3 showed maximum reddening symptoms on 6th day with 92.3 (% infected area on cane stem) in 200 µl injected samples. Cf3 partially purified toxins when treated in leaves showed maximum reddening area of 70.20 % infected area on leaf in Coc671. Serial dilution of toxin to 10-5 showed symptoms in susceptible cultivar whereas no reaction was noticed below 10-1 dilution in resistant variety. Thus present study brings the morphological variations and virulence characters of C. falcatum.