Efecto de la densidad de plantación en sandía sin semilla injertada sobre bule (Lagenaria siceraria (Molina) Standl.)

In recent years, there has been an increased interest in watermelon plants grafted onto Fusarium resistant rootstocks. Since the plant density is a factor determining in the degree of competition between plants, and the yield per plant decreases as the density per unit area increases, the objective of this study was to evaluate the effect of three plant densities, in rows 2.0 m apart with plants spaced at 1.25, 1.55, and 2.00 m on yield and quality of seedless watermelon hybrid 'Tri-X 313' grafted onto bottle gourd (Lagenaria siceraria (Molina) Standl.) hybrid 'Emphasis'. The trial was carried out in a randomized complete block design, with four replications. Plant densities evaluated did not had influence on the production in seedless watermelon plants, hybrid 'Tri-X 313', grafted onto L. siceraria; however, grafted plants had lower yield per area than nongrafted ones, wich ranged from 10 to 24%, so their use is restricted to soils with stress problems caused mainly by soilborne diseases. Average fruit weight was increased by 10% with plant spacing at 2.00 m. Also, the number of fruit per plant decreased significantly as density increased. The results in grafted watermelon plants were not positive per unit area; however, more yield was obtained per plant when planting density was decreased (spaced was increased). Given the increase in production costs when grafted plants are used, there is advantage in the use of lower plant density (higher spacing), still possible to use a 50% less plant density than in nongrafted watermelon plants, without significantly affecting the production, and fruit quality, with the same production cost when using Methyl Bromide in watermelon without grafting in soils infested with the Fusarium wilt pathogen. A disadvantage of grafted watermelon plants is the increase in the number of days to harvest, like the higher susceptibility of L. siceraria rootstock to Meloidogyne, so its use is a problem in soils with nematodes.