THE EFFECT OF WATERMELON (CITRULLUS AEDULIS) GRAFTING METHODS ON SEEDLING'S GROWTH RATE AND PLANT STAND ESTABLISHMENT RATE UNDER SALINE CONDITIONS

Abstract

Two different commercial rootstocks were grafted with each of two commercial watermelon cultivars. For each combination, splice grafting (SG) and root pruning splice grafting (RPSG) were simultaneously applied. At the end of the nursery period, 40 plants of 14 days old seedlings for each grafting combinations were transplanted in larger pots filled with vermiculite and divided in two equal groups. In the following 10 days all plants were periodically irrigated with equal amounts of the same nutrient solution, but differing from each other by the quantity of NaCl added in the nutrient solution. Two weeks after grafting, and 10 days after transplanting, 10 plants of each experimental plot were randomly selected. Growth rate during the nursery stage and stand establishment rate after transplanting, defined as the relative growth rate (RGR) and its components, net assimilation rate (NAR) and leaf area ratio (LAR), were computed for each experimental plot. Compared to RPSG seedlings, a higher plant dry matter and larger leaf area per plant were recorded for SG seedlings at the end of nursery stage. Despite that, a significantly higher relative growth rate was found for RPSG seedlings, mostly due to higher net assimilation rate. The same advantage of RPSG was kept during the stand establishment period. As a result, at the end of transplanting period, no significant differences were found between SG and RPSG watermelon seedlings regarding to plant dry matter and leaf area per plant. Generally speaking, the stand establishment rate of transplanted seedlings was drastically reduced due to the increase of nutrient solution salinity, but still significantly higher values were recorded in case of RPSG seedlings.