2018 ASHS Annual Conference

While interspecific hybrid squash rootstocks are effective in managing soil-borne diseases in grafted melon production, their adverse impacts on fruit quality remains a major concern. This study was conducted to examine the influence of grafting with an interspecific hybrid squash rootstock on fruit quality modification, including volatile compounds, in muskmelon (Cucumis melo) under different field management systems. A specialty muskmelon ‘Tasty Bites’, developed from a cross between Charentais and Ananas melons, was grafted onto a Cucurbita maxima × C. moschata rootstock ‘Super Shintosa’ with organic or conventional fertilization, with or without application of plant-growth-promoting rhizobacteria (PGPR). The field trial was carried out during the 2016 spring season in Citra, FL. A split-plot design with four replications was used with the fertilization system and PGPR treatment combinations in the whole plots and grafted vs. non-grafted plants in the subplots. Fully ripe fruit were sampled for quality assessment. Glucose content was significantly higher for organic than conventional fertilization, whereas conventional fertilization resulted in a significantly higher fructose content. The PGPR decreased fruit glucose content, but led to higher sucrose. Fertilization and PGPR showed significant interaction effects on the sugar profile of melon fruit. Flesh firmness of melons decreased under PGPR application or organic fertilization and it was also affected by the interactions among grafting, fertilization, and PGPR. Treatment effects were not observed in fruit soluble solids content, pH, or titratable acidity. Fifty-six volatile compounds were detected, including mainly esters, alcohols, and aldehydes. Non-grafted melons with organic fertilization plus PGPR had the lowest levels of total volatile compounds and esters. Although grafting did not show a significant main effect on total volatile and ester contents, it significantly increased the levels of certain ester compounds such as ethyl propionate, butyl acetate, amyl acetate, prenyl acetate, furfuryl acetate, hexyl acetate, isoamyl butyrate, and benzyl formate. Melons from grafted plants had higher contents of total aldehydes and alcohols than non-grafted melons. In contrast, other volatile compounds such as allyl methyl sulfide were lower in the grafted melons. Overall, grafting appeared to exhibit greater impacts on melon volatile compounds compared with fertilization and PGPR treatments. Future research is warranted to determine the influence of melon volatile profile modification by the C. maxima × C. moschata rootstock on fruit flavor and other sensory properties perceived by consumers.