Development of a male sterile eggplant by utilizing the cytoplasm of Solanum virginianum and a biparental transmission of chloroplast DNA in backcrossing

To develop a male sterile line of eggplant (Solanum melongena L.) utilizing the cytoplasm of S. virginianum, an interspecific F1 hybrid between S. virginianum and S. melongena ‘Senryo Nigou’ was continuously backcrossed to S. melongena ‘Uttara’ using ‘Uttara’ as a recurrent pollen parent and four backcross generations, BC1, BC2, BC3 and BC4 were produced. All the plants in backcross generations were anther indehiscent although the F1 hybrid, S. virginianum and S. melongena were dehiscent. Pollen stainability with acetic carmine and in vitro germination ability of pollen in all the backcross progenies were quite lower than those of the parental species. Fruit set percentage, number of seeds per fruit and seed germination rate were high in all the backcross progenies. The present results indicate that anther indehiscent type of functional male sterile line of eggplant could be developed by utilizing the cytoplasm of S. virginianum. PCR-RFLP analysis of chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) were performed to identify the organelle inheritance. The F1 hybrid and all the backcross progenies displayed maternal inheritance of mtDNA. The cpDNA of the examined single BC1 plant exhibited the recombinant cpDNA pattern of the parental F1 hybrid and ‘Uttara’, indicating occurrence of the biparental inheritance of cpDNA. As all the BC2, BC3 and BC4 progenies showed the same recombinant cpDNA patterns of the BC1 plant, the recombinant cpDNA might be stable and harmonize with the nuclear genome of S. melongena. The present male sterile line can contribute to expand the male sterility source of eggplant.