Morphological and pathogenic variability in Macrophomina phaseolina isolates of pigeonpea (Cajanus cajan L.) and their relatedness using principle component analysis

Sixty-one isolates of Macrophomina phaseolina were characterised on the basis of different morphological characters to study the variability in the population. PCA analysis extracted three main components, microsclerotia, texture and colour, from the population that described the variability in the population most appropriately. Colour of the isolates and the presence of the microsclerotia have a significant effect on the area under disease progress curve. Isolates with the production of microsclerotia (M⁺) were more aggressive as compared to isolates with no production of microsclerotia (M^?). The study has brought out pathogenic variation in M. phaseolina, thus better understanding of host pathogen relationship to identify physiologic races in the breeding programme.