Management of Meloidogyne incognita in nematodesusceptible watermelon cultivars using nematoderesistant Cucumis africanus and Cucumis myriocarpus rootstocks

Watermelon (Citrullus lanatus) cultivars are highly susceptible to the southern root-knot nematode (Meloidogyne incognita), with considerable yield losses when this nematode is not managed. Empirical evidence suggested that wild watermelon (Cucumis africanus) and wild cucumber (Cucumis myriocarpus) were highly resistant to M. incognita race 2. The objective of this study was two-fold; viz. to determine whether (1) C. africanus and C. myriocarpus seedling rootstocks would be compatible with watermelon cv. ‘Congo’ and ‘Charleston Gray’ and (2) the two Cucumis spp. rootstocks would retain their nematode-resistance capabilities when grafted with the two highly nematode-susceptible watermelon cultivars. The eight treatment combinations were arranged in a randomised complete block design, with six replications. At harvest, 56 days after transplanting the grafted seedlings, with highly susceptible watermelon cultivars had no effect on nematode-resistance capabilities of C. africanus and C. myriocarpus. Also, the two Cucumis spp. were compatible with the two watermelon cultivars. Consequently, C. africanus and C. myriocarpus rootstocks have the potential for use as resistant rootstocks in the management of M. incognita race 2 in watermelon production.Key words: Cucumis spp., root galls, resistant rootstocks, reproductive factor, watermelon cultivars

Baseline information on using fermented crude extracts from Cucumis africanus fruit for suppression of Meloidogyne incognita and improving growth of tomato plants

Bio-pesticides, when used as a post-planting pesticide, are limited by their potential ability to suppress the pest and their degree of phytotoxicity. Baseline information on the suitability of fermented crude extracts (FCE) of Cucumis africanus fruit as a post-planting bio-nematicide was determined on Meloidogyne incognita and growth of tomato in pot trials. Seedlings were inoculated with 1,130 eggs and juveniles/pot, while FCE  were applied weekly at 0, 10, 20, 30, 40, 50 and 60% dilutions. At harvest, nematode and plant data were  subjected to analysis of variance and the curve-fitting allelochemical response data (CARD) computer-based  model, respectively. Relative to inoculation level, final nematode population density (Pf) at the same level of  inoculation was reduced, while increasing dosages had no effect on Pf and reproductive factor values. Since  increasing dosages had no effect on Pf, the material could possibly still reduce this variable when applied below  10% dilutions. Dosages used were phytotoxic to tomato plants, but CARD model demonstrated that the material stimulated plant growth at dosages below 10%. In conclusion, baseline information from CARD  model suggested that FCE from C. africanus fruit have the potential to serve as a bio-nematicide and  bio-fertiliser on tomato provided the material was applied below 10% dilutions.Key words: Cucumis africanus, bionemagation, effective microbe organisms, ground leaching technology, root-knot nematode