Host status of melon genotypes Rotylenchus reniformis and its biocontrol by fungal agents.

Melon (Cucumis melo L. ) is one of the most widely consumed and exported fresh fruits of Brazil. Production is ~257 thousand tonnes annually, mainly exported to Europe, the USA and China, representing an income of US 165 million. This production is, however, limited by several factors, notably plant-parasitic nematodes. Although it is accepted that Meloidogyne spp. (especially M. incognita and M. javanica) are the main species of plantparasitic nematodes associated with melon in Brazil, Rotylenchulus reniformis may be underestimated, as root symptoms are unclear or not readily observable, and infestation often proceeds unnoticed, impairing field diagnostics and reporting. No genotypes of C. melo resistant to R. reniformis are known, and, to our knowledge, many bionematicides have yet to be tested for control of R. reniformis on melon. Our work aimed i) to evaluate the host status of seven genotypes of C. melo to R. reniformis; ii) to evaluate the effect of two doses (recommended and ×5) of Pochonia chlamydosporia (Rizotec®), Purpureocillium lilacinum (Nemat®) and Trichoderma harzianum (Ecotrich®) on the penetration of R. reniformis and its reproduction. All cultivars were ranked as susceptible to R. reniformis. Trichoderma harzianum decreased the number of nematodes per root in one experiment, whereas other fungi did not change it in either experiment. However, in reproduction assays, P. chlamydosporia at higher dosage consistently decreased nematode final population and nematodes per g root in both experiments. In conclusion, P. chlamydosporia can be used for the management of R. reniformis in melon. Other tools, such as crop rotation with non-hosts, should be combined to increase the efficiency of P. chlamydosporia.