Isolation and characterization of Pasteuria parasitizing root-knot nematode, Meloidogyne incognita from black pepper fields in India.

Abstract

Root-knot nematode (RKN), Meloidogyne incognita, is one of the most lingering and difficult to manage pest of black pepper in India. The options for controlling RKN are becoming increasingly limited due to the potential risk involved in environmental and health hazards. Biological control using Pasteuria is one of the most effective and efficient ways of nematode management. Pasteuria spp. are obligate parasites of plant-parasitic nematodes and completely inhibit their fecundity. There is also a tremendous opportunity for the discovery of native strains adapted to local environmental conditions and nematode species. Therefore, in the present study, efforts were made to isolate the native strain of Pasteuria from the fields of black pepper. Random sampling was done from black pepper-growing areas of Kerala and Karnataka states of India. Out of 39 samples, Pasteuria was found in 8 samples from the fields of ICAR-IISR, Kozhikode, Kerala, India. The host range study revealed that the identified Pasteuria strain was very specific to M. incognita and completed its life cycle in RKN. Infected females laid no eggs or egg masses; thus, Pasteuria prohibited the total fecundity of the nematodes. The Pasteuria strain was named as IISR-MiP for it was found in the fields of ICAR-IISR and its specificity towards M. incognita. The average size of the identified Pasteuria strain IISR-MiP endospore was 2.75 μm. Light as well as scanning electron micrographs revealed 3 types of endospore attachments viz., conventional, inverted, and sideways. Further, it was found that endospores attached to the nematode cuticle in the maximum number in a conventional type of attachment (87.62%), followed by inverted (6.55%) and sideways attachments (5.82%). The inverted and sideways attachments were unique to the biology of Meloidogyne-Pasteuria interactions, indicating the presence of collagenlike fibres on the entire surface of Pasteuria endospores. Pasteuria strain IISR-MiP had the potential biocontrol capabilities and provided an opportunity for its evaluation against M. incognita on black pepper under field conditions.