Environmental, Developmental and Physiological Determinants of Curcurbit Seed Quality

Environmental, developmental, physiological and biochemical determinants of cucurbit seed quality were investigated in field and laboratory experiments. The major factor influencing seed quality is seed maturity at harvest, with both immature and overmature seeds exhibiting reduced quality. Planting density and fruit load per plant can be manipulated to maximize seed yield per unit area without adversely affecting seed quality. Seeds harvested at optimal maturity will have the greatest germination vigor and will maintain quality longer during storage. Seed priming can improve germination rates and uniformity, but can reduce storage life. Tissues enclosing the embryo (the endosperm envelope and seed coat) are involved in regulating germination. The seed coat (testa) may restrict oxygen diffusion to the embryo in some muskmelon genotypes. Weakening of the endosperm envelope is associated with radicle emergence. Callose deposition in the endosperm envelope results in semipermeability. Defense proteins such as chitinase are also present in the endosperm. Numerous genes were identified that are expressed specifically in association with germination, but their functions are yet to be elucidated. These studies have provided guidelines for producing and harvesting cucurbit seeds for maximum yield and quality and have identified physiological and biochemical processes contributing to seed germination vigor.