A meta-analysis on rootstock-induced effects in grafted watermelon (Citrullus lanatus var. lanatus)

Abstract

Sweet watermelon (Citrullus lanatus var. lanatus) grafting with complementary rootstocks is necessary for new variety design and to enhance product profiles, including fruit yield and quality and tolerance to biotic and abiotic stresses.. Integrated selection of successful watermelon grafts using multiple traits ensures breeding and economic gains. Therefore, the objective of this study was to undertake a meta-analysis on the responses of watermelon when grafted with contrasting rootstocks involving cucurbit species or interspecific hybrids using agronomic, physiological and quality traits, and insect pest and disease reactions for rootstock selection, variety development and deployment. A meta-analysis was conducted involving 65 studies, and data were analysed using various statistical methods. Results indicated significant (p < 0.05) variations among watermelon varieties for economic traits when grafted onto different cucurbit rootstock species. Interspecific hybrid [Cucurbita maxima × C. moschata] and Lagenaria siceraria (Molina) Standl rootstocks induced high and variable effects on fruit yield and related traits of grafted watermelon.. Watermelon/L. siceraria graft combinations showed high phenotypic variation on sugar profiles. Lycopene content of grafted watermelon was highly variable when grafted onto C. lanatus var. citroides and C. maxima × C. moschata rootstocks. Graft combinations involving L. siceraria and C. maxima × C. moschata were significantly (p < 0.05) differentiated for fruit flesh firmness and color. C. lanatus var. citroides rootstock enhanced low and variable infections for root-knot nematodes, whereas C. maxima × C. moschata rootstock induced high and variable resistance to Fusarium and Verticillium wilt in grafted watermelon. Fruit yield and quality traits of grafted watermelon positively and significantly (p <0.05; p <0.001) correlated with root and photosynthetic parameters useful in selection programs. Overall, the meta-analysis revealed the need to integrate root traits (e.g., increased root weight and total root length, higher root surface area and average root diameter), high photosynthetic efficiency, fruit yield and quality in selecting desirable rootstock in the development of market preferred watermelon varieties.