Pathogenic Behaviour Pattern of Colletotrichum falcatum Isolates of Sugarcane in Sub-tropical India

Pathogenic Behaviour Pattern of Colletotrichum falcatum Isolates of Sugarcane in Sub-tropical India

Red rot caused by Colletotrichum falcatum is the most serious disease of sugarcane affecting cane production in different states in India. Since the pathogenic variants very frequently emerge in the field we have assessed pathogenic variation in 12 C. falcatum isolates collected from subtropical India along with previously designated pathotypes on a set of 16 host differentials for the eight seasons. By and large, a variable virulence pattern in C. falcatum isolates was recorded on most of the host differentials. The results showed that the predominant sub-tropical pathotypes (CF09 and CF08) isolated from then the ruling cultivars CoS 767 and CoJ 64, respectively showed less virulence and the pathotype CF02 isolated from Co 7717 showed higher virulence over the period of time on the host differentials. The higher aggressiveness exhibited by CF02 over on the differentials such as Co1148, Co 975 and Khakai and known susceptible differentials Co 997, Co 62399, CoC 671, CoJ 64 and another variety Co 89003 clearly revealed higher virulence of CF11 pathotype. Even though the pathotype CF08 remained virulent on its host cultivar CoJ 64, it could not cause same type of virulence on the recently developed cultivars and it suggests that the pathotype no longer maintains its virulence once a popular cultivar CoJ 64 removed from the cultivation. Among the 11 new C. falcatum isolates evaluated, the isolate Cf8436 Karnal was found to be virulent and the differential CoS 8436 succumbed to this isolate only. Of the different CoJ 64 pathotypes, Cf64-I exhibited higher virulence and showed susceptible to intermediate reaction on different host differentials. This study suggests continuous evolution of red rot pathogen and its adaptation to the new host cultivars in subtropical India....