Effect of Hypocotyl Morphology on Survival Rate and Growth of Watermelon Seedlings Grafted on Rootstocks with Different Emergence Performance at Various Temperatures

Authors: HALİT YETİŞİR, NEBAHAT SARI

Abstract: The emergence performance of different rootstocks and watermelon cultivars at different temperatures, and the effect of hypocotyl structure on grafting success and survival rate were investigated. Evaluated rootstocks were Cucurbita moschata (landrace), C. maxima (Arıcan local cultivar), Strong Tosa (C. maxima x C. moschata), P360 (C. maxima x C. moschata), Luffa cylindrica, Benincasa hispida, Lagenaria siceraria (landrace), Skopje (Landrace), and 2 Lagenaria hybrids, 216 and FR Gold. The Crimson Tide watermelon cultivar was used as scion. Emergence tests at 14 ºC, 18 ºC and 25 ºC were carried out for all rootstocks and scion seeds in a growth chamber. Cucurbita type rootstocks showed better emergence performance at low temperatures than did other rootstocks and scion. However, B. hispida, L. cylindrica, Lagenaria type rootstocks and scion did not emerge at 14 ºC and they were rotten. At 18 ºC, the earliest emergence was recorded in Cucurbita type rootstocks while the latest emergence was observed in B. hispida and L. cylindrica. Rootstocks and scion did not show any difference in emergence rate at 25 ºC. B. hispida and L. cylindrica had the thinnest and shortest hypocotyls which made grafting difficult. The survival rate of grafted plants was inversely correlated with the difference in diameters of scion and rootstock. At the same time survival rate was significantly affected by the rootstocks genotype. Rootstocks had different numbers of vascular bundles but the survival rate was not affected by the number of vascular bundles whereas the plant growth rate was positively affected. In general, Lagenaria type rootstocks had a higher survival rate than did other rootstocks. The hole insertion grafting technique had a significantly lower survival rate than did the approaching technique in Cucurbita type rootstocks. All graft combinations produced higher plant biomass than did the control plant, except for the L. cylindrica. The study showed that rootstock influences survival rates and plant growth in the use of grafting applications in watermelon.

Keywords: Citrullus lanatus, emergence rate, grafting, rootstocks, scion, hypocotyl

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