Isolation of Pasteuria penetrans, an obligate hyper-parasite, infecting root knot nematode, Meloidogyne spp. from the rhizosphere of pulses in India

Abstract Background Pasteuria penetrans is a mycelial, endospore forming, obligate, bacterial parasite that has shown enormous potential for biological control of root-knot nematode, Meloidogyne spp. In the present study, the effort has been made to isolate effective and high temperature tolerant indigenous strains from pulse rhizosphere in India. Results Surveys were carried out in four different agro-climatic zones and collected 106 root-knot nematode infected soil and plant samples from pulses rhizosphere. Of these, we observed Pasteuria spore attachment on root knot nematode juveniles from seven samples: three from Varanasi, two from Salem and one each from Deoria and Kushinagar. The pure cultures of these seven isolates (named as IIPR-Pp-1 to IIPR-Pp-7 from single infected female, respectively) were developed in 7 cm pot and soil-less CYG medium. The nematode host species was identified as Meloidogyne incognita by perineal pattern and confirmed by sequencing of ITS region. The host range study with M. incognita and Heterodera cajani showed the spore attachment was specific to M. incognita revealed that the species of the parasite was Pasteuria penetrans. SEM study on morphometrics of Pasteuria spores belong to two groups. In vitro assay on endospore attachment assay with pre-treated endospores at 20, 30, 40, 50, 60 and 70 °C revealed that maximum number of endospore attachment of all isolates was observed at 30 °C followed by 40 °C, and the least number of them was observed at 60 °C and above. The isolate Pp3 exhibited maximum number of spore attachments among all isolates at 30 °C treatment (14) and 40 °C treatment (10.67). Endospore attachment assay with pre-treated J2 at 20, 25, 30, 35, 40 and 45 °C revealed that maximum number of attachment of all isolates was observed at 30 °C treatment, and no attachment was observed at 40 °C and above. Conclusion Pasteuria penetrans isolate IIPR-Pp3 exhibited high temperature tolerance and can be used further to develop Pasteuria-based biopesticide for management of root-knot nematode, M. incognita in pulses.