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Progress ofMai-:.e Breeding in Vietnam 525Tolerance of inbred lines and hybrids to some stresses such as drought, saline acid tolerance, andlodging resistance are a concern.Developing early hybrids with short plant height, good grain quality and high yield are the mainobjectives.In addition, we have done some study on cytoplasmic male sterility and maize pollen culture.After 25 years of research in very difficult conditions with lack of equipment and funds, we havemade encouraging progress.Early hybrids (LS-3, LS-4, LS-5) with yield potential of 4-6 Tlha, intermediate hybrid (LS-6)with yield potential of 5-6 Tlha, and late hybrids (LS-7, LS-8) with yield potential of 5-7 Tlha havebeen released in the period of 1991-1993.In 1991-1997, 12 conventional hybrids had been released and widely used. They are:• LVN-I (SC), LVN-5 (DC), LVN-20 (SC), LVN-26 (SC), LVN-32 (TC) are early hybridswith yield potential of 5-9 Tlha• LVN-4 (SC), LVN-I J(TC), LVN-12 (DC), LVN-17 (TC), LVN-I 8 (DC) are intermediatehybrids.• LVN-IO (SC), LVNI 6 (SC), LVN- I 9 (SC) are late hybrids.• LVN-4, LVN-18, LVN-26 have just been released since 1997.5. Research on Agronomic TechniquesHundreds of OPVs, and hybrids of NMRL and other hybrids from foreign seed companies havebeen tested in 8 ecological zones of Vietnam. Twenty good varieties have been identified for thistesting program.In maize nutrient study has shown that producing one ton of dry grain need 39.9 kg of N, 14.5 kg.of PzOs, and 17.2 kg of KzO, the ratio of N, P, K is I : 0.35 : 0.45. Also determined were theappropriate doses of fertilizer in Central Coastal, Southern East areas, and Mekong River Delta.Research on intercropping systems had a conclusion that intercropping has given better resultsthan mono-cropping.The effect of climate factors to growing stages and maize yield had been carried out. Theintegrated pest and insect management for maize has been studied.• Intensive hybrid maize models, and model of transplanting maize on wet land after two ricecrops have been set up.ConclusionIn last years, the Maize Breeding Program and research on agronomy techniques of Vietnam havemade considerable progress, but we always supposed that a part of success is the result of greatassistance of FAO, CIMMYT and it is also due to the success of cooperation of other Maize Programsin Asian region. Let me express my sincere thanks to all of you for that valuable cooperation.