Molecular identification characterization and biological control of sugarcane red rot pathogen Colletotrichum falcatum Went

Abstract

Red rot of sugarcane caused by the fungus Colletotrichum falcatum Went is the most destructive and severe disease. South Gujarat is prominent sugarcane growing region and as the genetic make-up of its pathogen C. falcatum changes continuously, prompt characterization and its biological control is essential to prevent the spread and effective control of the disease. Sample collection and isolation was carried out from South Gujarat region. Nine strains of C. falcatum from different cultivar were isolated and identified at molecular level using the sequencing of conserved ITS rDNA gene. The phylogeny of ITS1 sequence reveals the genetic divergence among the nine C. falcatum isolates. The morphological characters such as conidia and setae of all isolates were studied on PDA. The size of conidia (length x width) varied from 20.0 X3.89 to 25.52 X5.34µm and size of setae (length x width) varied from 112.37X2.78 to 167.66 X6.73µm. Growth of fungi C. falcatum to different ranges of temperature and pH were studied. Results indicated that C. falcatum isolates had variations in their tolerance to different abiotic stress conditions, they were exposed. Though more alkaline and acidic liquid media have shown mycelial growth to certain extent, pH 6.0 was optimum for pathogen growth. Highest dry mycelial weight was recorded for isolate cfGAN (662.3mg) on Czapek dox broth. Among the temperature range studied, 28 - 32°C supported the maximum growth of all the isolates. Out of nine isolates, cfKAM reached its best up to 8.5cm mean mycelial diameter on Oat meal agar after seven days of incubation at 30±1°C. newlinePathogenicity tests validated on nine different sugarcane cultivars showed that strain cfCHA has infected maximum seven cultivars (virulence frequency 77.9 %). The study on pathogenicity clearly points out that once the pathogen gets access into the host, it causes severe damage to the sugarcane crop. Interestingly, none of the C. falcatum isolates were able to infect the Co 94004 cultivars, whereas Co 671 cultivars infected...