Source-Sink Relationships and their Effects on Fruit Growth and Quality in Casaba Melon (Cucumis melo L. var. Inodorous)

Two field experiments were conducted in two successive spring-summer seasons at the Newe Ya'ar Research Center (northern Israel) to examine source-sink relationships in ‘Noy Amid’, a Casaba-type melon. The source and sink were artificially manipulated by removing leaves and fruit shortly after fruit-set. Highest fruit yield and fruit quality were obtained in control plants and any reduction in source size (by leaf removal) resulted in yield decline. In ‘Noy Amid’ melon, plants with 4-8 leaves could not support more than one fruit and all other young fruits aborted. The weight of mature fruits was reduced with decreasing source size (leaf number). The sink size (number of young fruits) at the beginning of treatment application had a significant effect on assimilate production and translocation to the fruits. Plants with 2 young fruits as compared to a single fruit, and with 4 young fruits as compared to 2 fruits produced larger mature fruits with the same number of leaves. These data strongly support the idea that sink size affects the photosynthetic activity of the leaves, which is increasing by increased demand of the sink organs. Decreased source size had a negative effect not only on fruit yield but also on fruit quality characters. Fruit shape, flesh perfection and total soluble solid content were all adversely affected by artificially reducing leaf number.