Assessing the molecular variability in Ustilaginoidea virens, the rice false smut pathogen with ISSR markers

Rice false smut disease is gaining importance because of its impact on the grain yield and its toxin production ability. Fifty-eight isolates of Ustilaginoidea virens were collected from different rice-growing regions of India. DNA of U. virens was isolated by the CTAB method and fifty ISSR primers were screened for molecular variability studies. Twelve primers viz., UBC series 807, 808, 809, 810, 811, 812, 834, 835, 836, 840, 841, and 842 were selected to study the genetic variability. Different parameters of tested primers viz., heterozygosity (Hn), polymorphism information content (PIC), effective multiplex ratio (EMR), marker Index (MI), and resolving power (RP) were calculated. Primers UBC 812 and UBC 809 recorded maximum heterozygosity (Hn). The PIC values ranged from 0.10 to 0.27 and UBC 807 recorded the maximum value of 0.27. The EMR value varied from 6.75 to 24.0, Similarly, UBC 807 recorded the highest value of MI (24) and RP (8.55). A dendrogram was generated using the DARwin software (version 6.0.21A) based on the unweighted neighbor-joining cluster method. All the fifty-eight U. virens isolates were grouped into three major clusters. Clusters I and II had 21 and 35 U. virens isolates respectively. Cluster III had only two isolates. The isolates showed genetic variations and there was no specific grouping based on the geographical distance.