Development of an in vitro Grafting Method for the Enhancement of Growth of Isolated Shoots and Buds in Soybean (Glycine max L.)

In most Agro bacterium-mediated soybean transformation systems antibiotics are used for suppressing the growth of the bacteria. However, these antibiotics could also hinder largely the transformed cells, caused the further growth of the resulted buds very difficult. To tackle this problem, grafting methods were tested by using soybean buds and shoots isolated from seedlings as scions and the lower part of soybean seedlings as stocks. It was found that the most suitable stocks were those prepared from five days old seedlings grown in hormone free MB medium and had the intact radical. Hormone free MS medium was found to be the most suitable medium for the growth of the grafted seedlings. 100% survival rate in almost all the experiments demonstrated that in vitro grafting of soybean was highly efficient. In later experiments, significant inhibitory effects of cefolexin, a popular antibiotic used in Agro bacterium-mediated soybean transformation system on the growth of buds in culture was confirmed, and with the above established grafting methods by grafting the buds to the stocks could effectively enhance the growth of the grafted buds. Because the stocks had fully developed root system, the grafted seedlings could be transplanted to soil with quite high survival rate.