Abstract
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 twoCucumis 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.
Highlights
Watermelon (Citrullus lanatus) cultivars suffer considerable yield losses due to infection by the southern rootknot nematode (Meloidogyne incognita) in tropical areas with sand (Davis, 2007; Sumner and Johnson, 1973; Thies, 1996)
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
Widespread screening in wild watermelons (Citrullus lanatus var. citroides) for nematode resistance resulted in the identification of moderate resistance to M. incognita (Thies and Levi, 2007)
Summary
Watermelon (Citrullus lanatus) cultivars suffer considerable yield losses due to infection by the southern rootknot nematode (Meloidogyne incognita) in tropical areas with sand (Davis, 2007; Sumner and Johnson, 1973; Thies, 1996). The suspension of methyl bromide due to its environment-unfriendliness resulted in the management focus shifting towards alternatives that included the use of nematode-resistant rootstocks. In Asia, Europe and the Middle East, bottle gourd (Lagenaria siceraria) and hybrid squash (Cucurbita moschata x C. maxima) were widely used as rootstocks in watermelon production due to their resistance to fusarium wilt (Cohen et al, 2007). The fusarium-wilt resistant rootstocks were highly susceptible to M. incognita (Thies et al, 2008). The availability of nematode resistant germplasm from wild watermelons would provide an alternative to methyl bromide for managing the root-knot nematodes in watermelon production
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