Biological Control of Root-Knot Nematodes, Meloidogyne javanica by Antagonistic Fungus Cladosporium sphaerospermum.

Abstract

Root-knot nematodes (RKNs, Meloidogyne spp.) are significant threats to global agriculture because their host range is broad, and therefore, their adverse effects on crop productivity are substantial. Cladosporium sphaerospermum PQ394940 was isolated from egg masses of RKNs infecting eggplant and examined for its ability as a bioagent against the M. javanica. In an in vitro assay, the fungus effectively inhibited egg hatch (95.3%) and increased the mortality percent of secondstage juveniles (J2s, 73.3%) through direct parasitism. Moreover, after observation, the fungus showed a capacity for paralyzing eggs and juveniles under a compound microscope. Fungal culture filtrate (CF) has been examined against egg hatch and J2s mortality. Data revealed that CF can increase J2s mortality percent and suppress egg hatching. In the seed germination test, C. sphaerospermum PQ394940 significantly increased eggplant seed germination compared with control treatment. Fungus has been identified by amplifying ribosomal internal transcribed spacer (ITS-rDNA) using ITS4 and ITS5 primer pairs. A fragment with 570-580 bp was amplified and the result of rDNA sequencing was recorded in GenBank (PQ394940). Under greenhouse conditions, C. sphaerospermum PQ394940 significantly promoted eggplant growth. Moreover, fungus significantly reduced M. javanica reproduction and root galling. Additionally, fungus significantly reduced the root gall index, egg mass index, and reproductive factor. Thus, C. sphaerospermum PQ394940 is considered larvicidal and ovicidal, can also be added to the soil as a bio-fertilizer. As highlighted in this study, C. sphaerospermum PQ394940 will be useful in integrated pest management, improving crop productivity, and decreasing environmental impact.