RAPD and Nuclear rDNA ITS Polymorphism Within Macrophomina phaseolina Isolated from Arid Legumes of Western Rajasthan

Abstract

Concurrent heat and moisture stress often favours root diseases caused by Macrophomina phaseolina in arid legumes. Molecular analysis revealed 92 % variation within M. phaseolina populations as compared to 8 % among populations. The first three principle coordinates of PCA analysis accounted for a 69.61 % of total variance and Eigen vectors revealed 22.89 % of total variability. The mean values of all the four populations together for Nei’s gene diversity (h) was 0.1990 and Shannon’s information index (i) was 0.3113. The result showed that the genetic diversity of M. phaseolina isolates of population 2 (cowpea) was richest among all the four populations. Analysis of molecular variance indicated that main proportion of genetic variation was within the host than among different hosts. Out of 13 representative isolates seven were molecularly identified as Rhizoctonia bataticola and six as M. phaseolina upon sequencing of 5.8S RNA region. Besides length variation in ITS-1, 5.8S rRNA gene, ITS-2 and total length, the authors report insertion/deletions at a number of places in 13 isolates sequenced. This study underlines that M. phaseolina distribution is independent of host and/or geography and validates the utility of ITS rDNA region as a reliable indicator of phylogenetic interrelationships as an additional approach for identification of the genus Macrophomina and assessing its genetic diversity.