Antitranspirant Application Increases Grafting Success of Watermelon

摘要

The one-cotyledon splice grafting method is commonly used for watermelon (Citrullus lanatus) because it is relatively rapid and there is less rootstock regrowth than with other grafting methods. However, plants must rely on moisture in the air for survival during at least the first 4 days after grafting. In 2015 and 2016, greenhouse experiments were conducted to investigate if application of commercial stomata-coating and stomata-closing antitranspirant products, applied 1 day before grafting to both scion and rootstock seedlings, could increase the survival of watermelon transplants grafted using the one-cotyledon method. 'TriX Palomar' watermelon was grafted onto rootstock 'Tetsukabuto' (Cucurbita maxima x C. moschata) in Expt. 1, and onto rootstock 'Emphasis' (Lagenaria siceraria) in Expt. 2. The survival of grafted watermelon differed because of experiment (P = 0.0003), antitranspirant treatment (P < 0.0001), and experimental repeat (P < 0.0001). The survival of 'TriX Palomar' grafted onto 'Tetsukabuto' was greatest for plants treated with the stomata-coating + stomata-closing antitranspirants (92% to 100%), followed by the stomata-closing antitranspirant (79% to 97%), water (72%), and the stomata-coating antitranspirant (50% to 60%). For 'TriX Palomar' grafted onto 'Emphasis', plants treated with the stomata-closing antitranspirant had the greatest survival (87% to 97%), followed by stomata-coating + stomata-closing antitranspirants (84% to 94%), the stomata-coating antitranspirant (50% to 67%), and water (53% to 68%). In Expt. 3, stomatal conductance (gS) was similar for both 'TriX Palomar' and 'Emphasis' seedlings before treatment application, but differed because of the treatments 1 and 2 days after application. Stomatal conductance did not change for 'TriX Palomar' seedlings after application of the stomata-coating antitranspirant or water, or for 'Emphasis' seedlings after application of the stomata-coating antitranspirant. Stomatal conductance of 'TriX Palomar' seedlings decreased 57% to 62% after application of the stomata-closing antitranspirant and decreased 48% to 60% after application of the stomata-coatingD stomata-closing antitranspirants. Stomatal conductance for 'Emphasis' seedlings increased 37% after water application, and decreased 58% to 68% after application of the stomata-closing antitranspirant, and decreased 42% to 45% after application of the stomata-coating + stomata-closing antitranspirants. The survival rate of grafted 'TriX Palomar' transplants was increased nearly 30% by application 1 day before grafting of the commercial stomata-closing antitranspirant or stomata-coating + stomata-closing antitranspirants in this study. Increase in grafting success is likely due to a reduction in transpiration that occurs when the stomata-closing antitranspirant is applied to the seedlings before grafting.