Development of flue-cured tobacco hybrids in Vietnam
During the last decade, The National Tobacco Corporation of Vietnam has introduced a large number of flue-cured tobacco varieties from different regions over the world in the effort to identify varieties, suitable for commercial production in the country. The results are very limited: only several varieties showed good adaptability to the climatic conditions in Vietnam such as C.176 and K.326 and up to now only these varieties have been used in tobacco leaf production so growers had no chance to select a good variety for their production.In recent years, The National Tobacco Corporation of Vietnam has setting up research program on tobacco hybrid breeding. Besides development of single hybrids we tried to create three-way hybrids because it saves time obtaining new hybrid varieties. In our reseach, we used five male sterile hybrid varieties as female parents and ten elite pure lines as polinators and used line-tester scheme for identifying GCA and SCA for some yield components and yield. Results of experiments showed that, the female parent RGH4 has highest GCA for dry leaf yield and thirteen out of fifty cross combinations give standard heterosis for yield. There is positive correlation between leaf yield and number of "economic leaves" (r = 0,63) and the same tend of correlation between leaf yield and weight of the biggest leaf (r = 0,67). In the preliminary trials we identified four cross combinations (A4, A5, A6, A7), which give highest leaf yield. These combinations are included into the 2000 regional variety test. Results of above mentioned test indicated that A5 and A7 combinations expressed stable standard heterosis for yield at the level of more than 10% and resistant to TMV. The chemical analysis and sensory testing of dry leaf also to be done at our laboratory and indicated the quality of A5 and A7 combinations satisfied the requirement of cigarette production in Vietnam.