Diversity of opportunistic fungi colonizing egg and femaleroot-knot nematodes of tobacco

Suppression of plant parasitic nematodes with nematode predators, parasites or antagonists is a more eco-friendly approach than using nematicides. Opportunistic fungi have been investigated as potential biological control agents for root-knot nematodes. In this study, sequence data for the 18S rDNA-ITS region were used in conjunction with morphological observations to resolve opportunistic fungi taxonomy associated with eggs and female root-knot nematodes of tobacco. Fungal colonization was determined for eggs, egg masses and females of 156 specimens of tobacco root-knot nematodes from 7 provinces in China during 2010-2011. A total of 9 839 eggs, 408 egg masses and 284 females of Meloidogyne incognita and M. hapla were examined. Also 13 species, belonging to 9 genera of fungi, were isolated and identified. The common fungi associated with eggs, egg masses and females were Purpureocillium lilacinum, Fusarium oxysporum, F. solani, Penicillium purpurogenum, Alternaria alternata, Aspergillus unguis, A. niger and Acremonium strictum. The new strains of root-knot nematodes were Isaria farinose, Trichoderma longibrachiatum, Lecanicillium attenuatum, F. redolens and A. implicatum. P. lilacinum was the dominant species, which predominated in egg, egg masses and female root-knot nematodes with average frequencies of 0.49%, 24.00% and 16.90%, respectively. It occupied a wide range of niches in the study area, isolated from Yunnan, Anhui, Hubei, Guizhou, Shandong Provinces. Significant differences existed among fungal species communities isolated from eggs and females from various locations. As there hardly existed any information on the potential importance of I. farinose and L. attenuatum as nematode pathogens, pathogenicity tests were recommended in future studies.