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  • Author or Editor: Nicholas S. Dufault x
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Fusarium wilt of watermelon can be effectively managed by grafting with resistant rootstocks. Excision and regeneration of grafted seedling roots is a common practice among cucurbit-grafting nurseries that has not been thoroughly examined. The objectives of this study were to compare the performance of grafted and nongrafted watermelon plants under both greenhouse and field conditions when inoculated with Fusarium oxysporum f. sp. niveum (FON) race 2, and assess the effect of root excision on growth of grafted plants with Cucurbita moschata and Cucurbita maxima × C. moschata rootstocks. Two greenhouse experiments (Fall 2015 and Spring 2016) and one field trial (Spring 2016) of seedless watermelon ‘Melody’ were conducted in this study. In both greenhouse experiments, inoculated, nongrafted watermelon plants showed a significantly higher percentage of recovered Fusarium spp. colonies (70% to 75%) compared with grafted treatments (0% to 7.5%). Some plant growth measurements, including the longest vine length and aboveground fresh and dry weight, indicated less vigorous growth for nongrafted plants compared with the grafted treatments. Significantly higher percent recovery of Fusarium spp. below the graft union was observed in the grafted plants with root excision and regeneration treatment (3.7%) in contrast to the intact root treatment (0.5%), suggesting that the root excision method may possibly create entry points for FON infections. Overall, the root excision treatment showed little influence on aboveground growth and root characteristics of grafted plants. Yield of grafted watermelon with FON inoculation in the fumigated field trial was significantly higher than that of noninoculated, nongrafted ‘Melody’ (NGM) control as reflected by the increase of fruit number and size. Averaged over all the grafted treatments, the increase in marketable fruit number and weight reached 108.3% and 240.9%, respectively, and the total fruit number and weight increase was at 80.0% and 237.2%, respectively. However, grafted plants also exhibited greater levels of root-knot nematode infestation as indicated by the significantly higher root galling ratings. Results from this study demonstrated that grafting with squash rootstocks can effectively limit FON colonization in seedless watermelon plants, although more research in rootstock selection and testing is needed to optimize the use of grafted plants for improving plant growth and fruit yield.

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Interest in producing specialty melons (Cucumis melo) is increasing in Florida, but information on yield performance, fruit quality, and disease resistance of specialty melon cultivars grown in Florida conditions is limited. In this study conducted at Citra, FL, during the 2011 Spring season, 10 specialty melon cultivars were evaluated, in both certified organic and conventionally managed fields, including: Creme de la Creme and San Juan ananas melon (C. melo var. reticulatus), Brilliant and Camposol canary melon (C. melo var. inodorus), Ginkaku and Sun Jewel asian melon (C. melo var. makuwa), Arava and Diplomat galia melon (C. melo var. reticulatus), and Honey Pearl and Honey Yellow honeydew melon (C. melo var. inodorus). ‘Athena’ cantaloupe (C. melo var. reticulatus) was included as a control. ‘Sun Jewel’, ‘Diplomat’, ‘Honey Yellow’, and ‘Honey Pearl’ were early maturing cultivars that were harvested 10 days earlier than ‘Athena’. ‘Athena’ had the highest marketable yield in the conventional field (10.7 kg/plant), but the yield of ‘Camposol’, ‘Ginkaku’, ‘Honey Yellow’, and ‘Honey Pearl’ did not differ significantly from ‘Athena’. Under organic production, ‘Camposol’ showed a significantly higher marketable yield (8.3 kg/plant) than ‘Athena’ (6.8 kg/plant). ‘Ginkaku’ produced the largest fruit number per plant in both organic (10 fruit/plant) and conventional fields (12 fruit/plant) with smaller fruit size compared with other melon cultivars. Overall, the specialty melon cultivars, except for asian melon, did not differ significantly from ‘Athena’ in terms of marketable fruit number per plant. ‘Sun Jewel’, ‘Diplomat’, and ‘San Juan’ showed relatively high percentages of cull fruit. ‘Honey Yellow’, ‘Honey Pearl’, and ‘Sun Jewel’ exhibited higher soluble solids concentration (SSC) than ‘Athena’ in both organic and conventional fields, while ‘Brilliant’, ‘San Juan’, and ‘Ginkaku’ also had higher SSC than ‘Athena’ under organic production. ‘Honey Yellow’, ‘Sun Jewel’, ‘Brilliant’, and ‘Camposol’ were less affected by powdery mildew (caused by Podosphaera xanthii) and downy mildew (caused by Pseudoperonospora cubensis) in the conventional field. ‘Honey Yellow’ and ‘Camposol’ also had significantly lower aboveground disease severity ratings in the organic field compared with ‘Athena’, although the root-knot nematode (RKN) (Meloidogyne sp.) gall rating was higher in ‘Honey Yellow’ than ‘Athena’.

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