RAPD-PCR analysis of molecular variability in the red rot pathogen (Colletotrichum falcatum) of sugarcane.
C. falcatum [Glomerella tucumanensis] is the causal organism of sugarcane red rot disease. For rapid identification and characterisation of G. tucumanensis isolates a RAPD technique was developed and optimized. Decanucleotide primers e.g. GGTGCGGGAA, CCAGGTGCAC, GTGACATGCC and TCASGGAGGT were useful in differentiating 5 pathogenic variants, collected in Haryana, India. Of these 5, only 4 had been previously tested, on 13 different sugarcane varieties, for their pathogenicity. Five primers produced 73 DNA fragments from the genomic DNA of 5 different pathogenic variants/isolates of G. tucumanensis, of which 23% were polymorphic. DNA polymorphism in these isolates showed genetic variation in pathogenicity within a common agro-ecosystem. Total RAPD data derived from 5 primers and 5 isolates were used in the unweighted pair group method with arithmetic means analysis (UPGMA) to generate a tree of visual relatedness displaying genetic variations. By this method, the pathogenic potential of these isolates was separated into 2 distinct clusters.