Influence of grafted watermelon plant density on yield and quality in soil infested with Melon Necrotic Spot Virus

Abstract

The decrease in fruit yield and quality caused by soil diseases is one of the major problems of watermelon production. Soil disinfection with methyl bromide (MB) has been used to prevent fungus attacks; however, its use is being restricted because this substance damages the ozone layer. Field experiments were carried out in open field in soils infested with Olpidium bornovanus and Melon necrotic spot virus (MNSV) in Colima, Mexico, where watermelons had only been grown previously using soil fumigation with MB. Yield and quality of the watermelon cultivar 'Triploid Tri-X 313' grafted on two rootstocks of Cucurbita maxima × Cucurbita moschata ('RS841' and 'Shintosa Camelforce') were evaluated during 2007-2008. Each experiment had five treatments, two of them with non-grafted plants at a density of 3472 plants/ha, with and without MB fumigation. The remaining three treatments had grafted plants in non-fumigated soil with plant densities of 2778, 2083, and 1736 plants/ha. The use of watermelon grafted on 'RS841' and 'Shintosa Camelforce' rootstocks significantly increased the average fruit weight and the total yield of watermelon. Grafting may be considered as an alternative to MB fumigation. With the use of grafted watermelon plants, planting density may be reduced by 50%, obtaining higher yields than those obtained from non-grafted plants grown in fumigated soil. Fruits harvested from grafted plants had higher firmness than those harvested from non-grafted plants, without affecting the content of soluble solids.