IITA's research in breeding cassava and sweet potato for resistance to pests and diseases of major economic importance in Africa is discussed under the headings: breeding cassava for resistance to pests (cassava green spider mite (Mononychellus progresivus and M. tanajoa) and cassava mealybug (Phenacoccus manihoti)); breeding cassava for resistance to disease (African cassava mosaic geminivirus, cassava bacterial blight (Xanthomonas campestris pv. manihotis) and cassava anthracnose disease (Colletotrichum gloeosporioides f.sp. manihotis)); and breeding sweet potato for resistance to sweet potato virus, weevils and nematodes and integrated control of nematodes.

Variety-related constraints and varietal characters that deserve priority attention in potato breeding for Bangladesh are discussed. A simple breeding method for developing varieties with good storability and resistance/immunity against important virus disease is proposed.

S. K. Hahn, F. E. Caveness, K. Lema, R. L. Theberge, 'Breeding cassava and sweet potato for pest and disease resistance in Africa', pp.66-72, International Institute of Tropical Agriculture (IITA), 1990

In Japan, sweet potato is grown annually with the acreage of approximately 65,000 ha as of 1989. It is utilized mostly for starch production and table use through the market. Recent cultivars released from the breeding center have a wide range of utilizations not only in conventional use but also in food processing industry for high content of vitamins, low-amylase activity and extremely high starch content. Germplasm collections at the breeding center include Japanese old local cultivars, breeding lines and introductions from China, Fiji, Indonesia, New Zealand, Papua New Guinea, the Philippines, Solomon Islands and U.S.A. Total accessions of 1,200 were characterized and evaluated with their yielding abilities and degrees of resistance against pests and diseases. Wild relatives of sweet potato were also introduced from Latin america. The breeding program generally employs a usual crossing method, including combining ability tests. Biotechnology works have recently been initiated, aiming at improvement of breeding efficacy. Objectives of the breeding program are to raise productivity with a high starch content, pest and disease resistance, high quality for table use with better marketability and to develop new characteristics which facilitate greater utilization in food processing industry with a large scale

This cultivar resulted from a cross made at the Jogeva Plant Breeding Station in 1974 between the cultivars "Commandeur" and "M-987" and was passed over the State Strain Testing Service (SSTS) in 1985 as a medium-late high-yielding table potato variety slightly susceptible to potato wart disease and with relatively good late blight resistance. The both parents have resistance to host specific phenotypes of Phytophthora infestans (Mont.) de Bary. The Dutch variety C. carries R3 and the Siberian irradiation mutant M.-RlR2R4. The late blight seedling screening was made in 1977 with a population in which there were complex virulent strains of Ph. infestans. In field trials, experiments and lab tests the cultivar "Sarme" was compared with the Dutch variety "Eba" and with other Estonian potato varieties. The present paper gives in tables 1-3 data about the experiments of the last six years (1983...1988). In table 2, FGH are comparable average data from SSTS (8 trials) in Estonia in years 1986-1987

Since 1975, the Institute of Plant Breeding has been engaged in developing and utilizing tools of biotechnology for crop improvement. In vitro technique ranging from embryo culture, organ culture-tissue culture, anther culture, callus and cell culture as well as protoplast culture were developed for rapid propagation, disease elimination, germplasm conservation or as tools in breeding for recovering haploids, somaclonal variants with resistance to stresses. The in vitro techniques were applied for food crops such as wheat, corn, white potato, banana, citrus, sugarcane, legumes; fiber crops such as ramie and abaca; industrial crops such as bamboo and rattan; ornamentals such as anthuriums and orchids; and tobacco. Expansion of the program will include other crops such as papaya, sweet potato, onion, garlic as well as ornamentals as the mussaendas and foliage plants. Other tools of biotechnology such as restriction fragment length polymorphism (RFLP) and nucleic acid hybridization will be developed for monitoring of genotype stability of accessions in the in vitro collections, in establishing variety identity; in seed purity testing, and in indexing plants for diseases.

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. Research at the Asian Vegetable Research and Development Center (AVRDC) addresses the above constraints from two general perspectives - genetic manipulation to enhance crop adaptation (crop improvement) and reduction of production stresses through improved management (production systems). The crop improvement component is reviewed herewith 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 germplasm assembly, evaluation and utilization; interdisciplinary research; stepwise genetic improvement; and, an adequate blend of strategic and applied research. National programs worldwide have released 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 disease and acceptable quality