The identity and reproduction potential of South African Meloidogyne species

Root-­-knot nematodes, Meloidogyne spp., generally are the economically most important nematode pests that parasitise agri-­- and horticultural crops in South Africa. The aims of the study were to i) identify Meloidogyne spp. individuals that infect roots/tubers/pods of crop plants received for diagnostic analyses and from research sites across South Africa using molecular and morphological identification techniques and ii) determine the reproductive potential of Meloidogyne species populations identified during the study in a greenhouse experiment (randomised complete block design with six replicates). Deoxyribonucleic acid (DNA) was extracted from mature females obtained from infected, below-­-ground parts of crops and subjected to polymerase chain reaction (PCR) analyses. For the reproduction-­- potential study, 1 000 eggs and second-­-stage juveniles (J2) of the respective Meloidogyne spp. populations identified were inoculated on roots of a susceptible tomato cultivar Floradade. Nematode parameters assessed 56 days later included egg-­-laying female indices, egg and J2 numbers and reproduction factors/root system. Meloidogyne incognita and M. javanica proved to be the predominant species that infected maize, potato and soybean crops, while the emerging M. enterolobii (= M. mayaguensis) have also been identified from pepper and guava roots. Other unknown species have also been detected and are currently being identified. The reproduction potential of the various Meloidogyne spp. populations differed substantially within and among species. Positive identification of M. enterolobii, which is easily confused with M. incognita in terms of its morphological identification will contribute towards research aimed at determining the distribution, life cycle and pathogenicity of this pest. This study is ongoing and knowledge generated will benefit the research fraternity as well as producers and ultimately consumers.