Status of nematode resistance of in vitro propagated Cucumis africanus plantlets to Meloidogyne incognita race 2
Wild watermelon (Cucumis africanus) seedlings are highly resistant to Meloidogyne incognita race 2 and 4, along with M. javanica. This plant species has the potential for use in inter-generic grafting with watermelon (Citrullus lanatus) cultivars, which are susceptible to Meloidogyne species. In order to ensure the availability of uniform C. africanus plantlets for inter-generic grafting, an in vitro propagation procedure using terminal buds was researched and developed. However, it was not known whether the plantlets would retain their resistance to Meloidogyne species. A study was conducted to determine whether in vitro-propagated plantlets of C. africanus could retain their resistance to M. incognita race 2. Rooted plantlets at five leaf-stage, were transplanted into 15 cm-pots containing steam-pasteurised sand and Hygromix at 3:1 ratio (v/v) and placed in the greenhouse. Plantlets were inoculated with M. incognita race 2 eggs and J2 inocula at 0, 200, 600, 1000, 1400, 1800 and 2200 plantlet-1, arranged in a randomised complete block design, with 10 replicates. Fifty-six days after inoculation the vine length, stem diameter, chlorophyll content, dry shoot and root mass were measured. The roots were scored for root galls and the nematode density in total root system and total soil pot-1 were also measured. The reproductive factor (RF = final population (Pf)/initial population (Pi)) values were computed for each inoculum level. The treatments had no significant (p≤0.05) effects in all plant variables and population densities of M. incognita in roots and soil. The RF values at all levels of inoculation were less than 1, suggesting that plantlets retained their nematode resistance. Results of this study conclude that in vitro-propagated C. africanus plantlets can serve as nematode-resistant rootstocks in watermelon production.
Maila, M.Y., Mashela, P.W. and Nzanza, B. (2018). Status of nematode resistance of in vitro propagated Cucumis africanus plantlets to Meloidogyne incognita race 2. Acta Hortic. 1204, 187-194
Cucumis africanus, cucurbitacin, indigenous plants, plant-parasitic nematodes, nematicides