Infectivity and reproduction of Scutellonema bradys on weeds and cultivated plant species

Abstract

The nematode Scutellonema bradys is the main phytosanitary problem of yam (Dioscorea rotundata) in the Brazilian State of Bahia. Little is known about the host range of this nematode in Brazil, especially on weeds and plant species cultivated together with yam. This study aimed at evaluating different plant species to determine their host status to S. bradys and to study the relative infectivity of different stages of the nematode on selected host plants. Among the 48 evaluated plant species, 12 were infected by S. bradys. Yam was considered to be the only good host of the nematode, while Luffa algyptiaca, Momordica charantia, Heliotropium indicum, Vigna unguiculata. Cucúrbita pepo, Abelmoschus esculentus, Sicana odorifera, Solanum lycopersicum and Ipomoea batatas were classified as bad hosts because of the relatively low reproduction factor as compared to yam. Crotalaria júncea and Cajanus cajan behaved as trap plants because large numbers of S. bradys penetrated their roots but populations decreased over time. Our results showed that juveniles are more infective than females and these are more infective than males on roots of five host plants. We also demonstrated that S. bradys prefers certain host plants as inferred by their lower reproduction on roots of these hosts. Penetration of juveniles tended to be spread over 16 days after inoculation, whereas for adults it was more concentrated at 8 days after inoculation. These results may be important to plan crop rotation schemes to control the yam nematode.

Host status of weeds for Pratylenchus coffeae

“…Other issue related to the dry rot disease which interferes directly in the disease intensity are weeds, which can act as alternative hosts, supporting the survival of nematode in the fields (Lordello et al, 1988). In Brazil, there is little information on the host range of weeds for the yam dry rot nematodes, for instance the studies of Carmo et al (2014) with S. bradys and Almeida et al (2019), which included S. bradys and Pratylenchus spp. Considering weeds can represent sources of nematode inoculum, new studies will allow for an understanding of the reaction of these plant species to the causal agents of the disease, and additionally, to recommend management practices aiming to control these host plants and consequently to reduce nematode populations for the next cropping season.…”