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In the progenies from the radish plants (Raphanus sativus L.) transformed by the microinjection of Altari DNA into the ovary of Kungzung radish. The genetic stability of the expression of the transformed character, hypocotyl color, was examined up to the third generation. All the progenies of one transformant, T3, had red hypocotyls, indicating the stable expression of the transformed character one generation after another. It was concluded that the foreign gene had been stably incorporated into the recipient genome, resulting in a consistent expression of the transferred gene in all the progenies. This conclusion was supported further by the consistent banding patterns of total seed proteins as well as the isozymes of malate dehydrogenase in all three generations. Co-transformed characters such as the morphology and the size of the roots were also stably inherited in these progenies. The hypocotyl color of the progenies from three other transformants was segregated. However, the expression of the color in a population of progenies was determined largely by the color of a plant at the previous generation. Much more progenies had red hypocotyls when they were derived from a plant having a red hypocotyl. Although difficult to explain, the segregation of the color in the progenies from these transformants suggests that the gene controlling the expression of red color was not stably introduced to the recipient genome. Unstability of the expression of the transferred gene was also reflected by the reappearance of DNA recipient-type banding patterns of total proteins and the isozymes at later generations. The importance of selecting an appropriate genetic marker in transformation studies and the potential of the microinjection technique in crop breeding programs are discussed.
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