Nematode egg parasitic fungus, Purpureocillium lilacinum: efficacy of indigenous strains for the management of Meloidogyne incognita in chickpea

Abstract

BackgroundNematode egg parasitic fungus, Purpureocillium lilacinum is the most effective biocontrol agent and has been widely used commercially in many countries for the management of root-knot nematode, Meloidogyne incognita. Availability of indigenous potential strains specific to an agro ecosystem is very crucial for their successful commercial exploitation for suppression of nematode population. Hence, an attempt was made to isolate, characterize, evaluate and identify potential indigenous strains of P. lilacinum from pulse ecosystem for root-knot nematode management in chickpea.ResultsThe fungal colony was initially white and when spore was formed it turned into pink colour in 72 to 96 h. Hyphae was hyaline and septate, conidiophore was blunt, and phialides were with wide base and long neck bearing round to oval conidia in chains. Molecular identification of the species, P. lilacinum was carried out based on ITS1-5.8S-ITS2 region of the genomic DNA. In vitro bioassay of cultural filtrates on juvenile mortality revealed that maximum percentage of mortality was observed in IIPR-Pl-11 (88.36%). Spectrophotometric assay on chitinolytic activity showed that the strain IIPR-Pl-11 produced significantly high chitinolytic activity, chitinase enzyme and total protein content (0.139, 51.1 and173.75 µg/ml at 5days); (0.245, 90.1 and 272.67 µg/ml at 10 days) and (0.273, 100.4 and 306.25 µg/ml), respectively, at 15 days of culturing in colloidal chitin-enriched medium C. 2D gel electrophoresis of the crude chitinase suspension showed the presence of chitinase (32, 46 kDa size) in the sample from chitinase-induced medium C. In vitro bioassay of the cultural filtrates of the fungus grown in chitin-enriched medium C on inhibition on egg hatching revealed that the highest percent inhibition on egg hatching showed by IIPR-Pl-8 strain at 5 days of inoculation (42.6%) and IIPR-Pl-11 at 10 and 20 days of inoculation (62.80 and 93.50%), respectively. In vivo pot experiment revealed that among all strains, IIPR-Pl-11 was efficient in promoting plant growth very effectively by reducing gall number (41.3 per plant), egg mass (28.3 per plant) and soil population (284.3 per 200cc of soil) compared to control.ConclusionP. lilacinum strain IIPR-Pl-11 was the highest potential strain from pulse rhizosphere for the management of root-knot nematode, M. incognita in chickpea.