The Relationship Between Resistance To Ralstonia Solanacearum And Cytoplasmic Components Of The Potato Somatic Hybrids

The wild diploid potato species contain genes encoding numerous traits not found in cultivars and represent an especially rich source of disease resistance, environmental tolerance and other agronomic traits of interest. The application of these desirable genes is confined, however, as differences in ploidy level or endosperm balance numbers that cause sexual incompatibility or low fertility of the progenies. Somatic hybridization can integrate desirable genes across species to bypass the sexual incompatibilities, male and female gametes infertility and other biological obstacles in potato conventional breeding and to obtain hybrids with nuclear and cytoplasmic DNAs recombinations. For investigating the relationship between the resistance to Ralstonia solanacearum and the cytoplasmic genome of the somatic hybrids,107 somatic hybrids were used to characterize the compositions of mitochondria and chloroplast genomes by molecule marker technology, and the disease resistance of the somatic hybrids was tested by using the in vitro method. The major results are as following:1. Four out of 17 pairs of mitochondrial primers were found polymorphic between the fusion parents. One hundred and seven somatic hybrids were subjected to the mitochondria components analysis. The results revealed that 85.0% of the hybrids combined the two parental mitochondria components, while 10.3% hybrids showed a mitochondria type of the cultivated parent and 4.7% had a mitochondria type of the wild parent. So it can be presumed that the recombination of mitochondrial genomes may occur in most of the somatic hybrids.2. The chloroplast components of the somatic hybrids were clarified with the chloroplast SSR primer NTCP-9. The results showed that only 6.5% of the hybrids combined the two parental chloroplasts while the majority contained the chloroplast from either of the fusion parents,43.0% showing chloroplast type of the cultivated parent and 50.5% showing the wild parent.3. Ninety somatic hybrids were inoculated with R. solanacearum in vitro. The results indicated that 20% somatic hybrids were highly resistant to R. solanacearum,22.2% were moderately resistant and 55.5% were susceptible. Further analysis of the relationship between somatic hybrids resistance to R. solanacearum and cytoplasmic components revealed that there was no significant correlation between the resistance and the cytoplasmic components under experimental condition, indicating that potato resistance to R. solanacearum could be mainly controled by the nuclear genes.