Biocontrol of Aspergillus root rot by tripartite symbiosis in groundnut

Aspergillus niger is responsible for causing root rot of groundnut. Ten A. niger isolates were isolated and studied in the groundnut cultivated area of Madurai. Groundnut was challenged with Aspergillus, and the production of pectinase and cellulase enzymes was investigated to assess the virulence of the fungal isolates. Among the ten isolates A. niger CLR10 produced highest percentage (40%) of diseased plants. Based on the production of these enzymes in groundnut plants challenged with the pathogen A. niger CLR10 produced highest level of these enzymes so it was used for further studies. The treatment AT13 recorded minimum percentage mortality (15.9%) and the pathogen only inoculated control recorded 100% mortality. Application of AMF with rhizobial isolates decreased the mortality in groundnut. The biocontrol studies revealed that the combined inoculation of AMF and Rhizobium sp. reduced the pathogenesis of A. niger CLR10. However, the treatment AT13 recorded significantly (p<0.05 and 0.01) higher growth parameters than other treatments. The investigation suggested that inoculation of Glomus mosseae and Gigaspora albida along with Rhizobium sp.GPMK1 and GMDU1 can improve not only the growth but also render disease resistance to groundnut. It can be summarized that the practice of multiple inoculation is found more effective as compared to the traditional practice of single inoculation of inoculums.