Major biotic and abiotic stresses limit the productivity of vegetables in the humid tropics and sub-tropics. Prominent biotic factors include major pests and diseases which drastically reduce yield and quality. Abiotic stresses are high temperature, high rainfall, drought, and poor tropical soils. Researdh at the Asian Vegetable Research and Development Center (AVRDC) addresses the above constrains from two general perspective - genetic manipulation to enhance crop adaptation (crop improvemnet) and reduction for production stresses through improved management (production systems). The crop improvement component is reviewed herwith from the context of enhancing the tropical adaptation of three selected vegetables - Chinese cabbage, tomato and sweet potato. The goal of AVRDC's crop improvement research is tropical adaptation. General strategies that were adopted in quest of this goal are as follows : massive germplansm assembly, evaluation and utilization; interdisciplinary research; stepwise genetic improvement; and, an adequate blend of strategic and applied research. National programs worldwide have relaeased a total of 84 improved AVRDC germplasm. The most advanced breeding lines combine desirable features such as heat tolerance, resistance to one or more major diseases and acceptable quality. Given these genetic gains, the prospects of further improvemnet of AVRDC's crop for the benefit of tropical vegetable farmer are discussed. [AS]
