Date of Award

5-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science

Advisor

Hassell, Richard L

Committee Member

Wechter , William P

Committee Member

Adelberg , Jeffrey

Abstract

High, year-round demand, increased production intensity without crop rotation, and the loss of Methyl Bromide as a soil fumigant, results in unfavorable soil conditions with increased soil pathogen populations for growing watermelon [Citrullus lanatus (Thunb) Matsum and Nakai]. Grafting watermelon onto resistant rootstocks provides successful control of soil-borne pathogens, and could increase yield and fruit quality; however, the high production costs, especially from labor, involved in grafted transplant production, has prevented the adoption of grafted watermelon use in the United States. Much of the labor is required for meristematic regrowth control, which can cause abortion of the scion and competition in the field if not removed. Treating rootstock meristems with fatty alcohol has been shown to plasmolyze the meristem and prevent regrowth, while leaving the rootstock seedling intact for grafting. A rate trial experiment was conducted to determine the optimal application concentration of fatty alcohol compound, and determined that a rate between 5.00% and 6.25% fatty alcohol best controlled regrowth without causing damage that prevented rootstocks from being grafted successfully. A second experiment was designed to determine the effects of the fatty alcohol treatment on rootstock size and carbohydrate storage. On 1, 7, 14, and 21 days after fatty alcohol treatment, rootstocks were observed to increase in size and carbohydrate content, with starch being the most notable increase. Starch content of interspecific hybrid squash (Cucurbita maxima × C. moxchata) rootstock hypocotyls increased 193-fold, and 109-fold in cotyledons of bottle gourd (Lagenaria siceraria) rootstocks. This increase in stored carbohydrate energy can be harnessed by the plant to provide energy. Seven days after treatment, we observed a 6% and 10% increase in graft success in interspecific hybrid squash and bottle gourd rootstocks, respectively, that were grafted using the industry-standard, one-cotyledon method. The increased starch content also provided sufficient energy to successfully graft using a new, more efficient grafting method without the rootstock cotyledons. A final experiment was conducted to determine whether increased carbohydrate content resulting from rootstock fatty alcohol treatment conferred an advantage to grafted watermelon transplants in the field. No significant advantages in plant growth or fruit yield were observed. Rootstock fatty alcohol treatment effectively controls regrowth and increases watermelon grafting effectiveness and efficiency by causing the rootstocks to store carbohydrates which provide energy for graft healing and new grafting methods; however, the rootstock treatment does not confer an advantage in field conditions.

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