Development of the Functional Male Sterile Line of Eggplant Utilizing the Cytoplasm of Solanum kurzii by Way of the Amphidiploid

Eggplant (Solanum melongena L.) is an important and popular vegetable crop, especially in Asia (Yamaguchi, 1983). Most commercial cultivars of eggplant are F1 hybrids, as inter-breed hybrids of eggplant develop considerable heterosis, especially in yield (Kakizaki, 1931; Sambandum, 1962). Seed production in eggplant hybrid cultivars is cumbersome, as it requires manual emasculation, pollination, bagging, etc. If it is possible to establish a superior male sterility system in eggplant, it can reduce the labor required to produce F1 hybrid seeds. In our laboratory, we have developed the cytoplasm substitution lines of eggplant by continuous backcrossing between S. kurzii Brace & Prain and eggplant using S. kurzii as cytoplasm donor and eggplant as nucleus one (Khan and Isshiki, 2009). The lines showed the anther indehiscent type (i.e., pollen non-release type) of functional male sterility in the BC1, BC2, and BC3 plants, however, the genetic segregation of anther dehiscent and indehiscent types occurred in each of the generation (Khan and Isshiki, 2009). Cytoplasmic substitution lines of eggplant could be obtained in another method through the amphidiploid. This method restores the fertility of the F1 by chromosome doubling with colchicine consequently the backcrossing is often successful. It is a common practice in Brassica vegetables (Kanada and Kato, 1997). In the present study, therefore, we performed cytoplasmic substitution by the way of amphidiploid because this method might be able to accelerate genetic fixation of the anther indehiscent type. Each of the backcross generations was investigated for the fertility traits and the data were compared with the previous ones (Khan and Isshiki, 2009).