A strong antibiotic producer, Bacillus subtilis strain Bbv 57 (KF718836), has been utilized for the management of wiltnematode complex (Fusarium oxysporum f. sp. gerberae, Meloidogyne incognita) in gerbera under greenhouse conditions in the Department of Floriculture, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India. The strain strongly inhibited F. oxysporum f. sp. gerberae (KM523669) mycelial growth to an extent of 44.33 and 63.33%, at 10 and 100 μl, of culture filtrate, respectively. Further, the culture filtrate at 100% concentration exerted lethal effect on nematode eggs (7.00 hatched) and juveniles (87% mortality) compared to control. The analysis of TLC revealed that Bbv 57 showed the cyclic antimicrobial peptides surfactin and iturin that were confirmed by PCR. Strain Bbv 57 was able to produce antifungal and anti-nematicidal activity with reduced wilt incidence (15.33%) and thus holds a great potential for use in the biocontrol of Fusarium wilt-root-knot nematode disease complex in gerbera under greenhouse conditions.
Two pot culture experiments were carried out in carnation var. redking in two different seasons to study the interactive effect of Fusarium oxysporum and Meloidogyne incognita on the growth, yield and changes in physiological parameters of the plant. Highest reduction of growth and yield parameters were observed in the plants that received sequential inoculation of the nematode followed by fungus. Significant reduction in the nematode population was observed in the sequential inoculation of the fungus followed by nematodes and combined inoculation of the two pathogens. Reduced chlorophyll content and increased protein and sugar content were observed in the plants due to the interaction of nematode and fungus.
Entomopathogenic nematodes (EPNs) parasitize the insect host by entering into the host body, and they lead an endoparasitic mode of life. The symbiotic bacteria associated with them play an important role in the suppression of insect pests. Approximately 30-500 symbiotic bacteria (including Xenorhabdus and Photorhabdus spp.) are reported to be associated with the two nematodes, Steinernema and Heterorhabditis. EPNs and the symbiotic bacteria control a wide range of insect pests living in the soil and in cryptic habits. This chapter focuses on the general biology of EPNs. The symbiotic relationships of nematodes and bacteria, and the survival biology (including cold, heat and desiccation tolerance) and foraging behaviour of nematodes are discussed in detail.
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