Bacterial wilt resistance in the progenies of the fusion hybrids between haploid of potato andSolanum commersonii

Bacterial wilt of potatoes, which used to be a widespread disease in tropics and subtropics, has become a threat to potato production in temperate region. The diploid species Solanum commersonii has several desirable characteristics including cold tolerance and resistance to several diseases. Selected somatic hybrids between S. tuberosum dihaploid and bacterial-wilt-resistant S. commersonii clones were cross pollinated with S. tuberosum cultivars for further selection of bacterial wilt resistance. The chromosome numbers of the fusion parents were confirmed as 24, and the three fusion hybrids crossed were all tetraploids. The chromosome number of 11 backcross 1 progenies (BC1) was 48 and that of the other six was close to the tetraploid number. Backcross 2 progenies (BC2) were obtained from only three of the 44 BC1 clones crossed. The S. commersonii parent clone, LZ3.2, was the most resistant to bacterial wilt among wild species clones tested. The first sexual progenies segregated for resistance, with one clone highly susceptible and four clones highly resistant. Three highly resistant BC1 clones, CT02-4, CT08-4, and CT10b-4, were backcrossed to cultivars. Two cross combinations produced mostly susceptible BC2 progenies; however seven clones were resistant or highly resistant for both race 1 and race 3. The highly resistant three clones, CT204-3, CT206-9 and CT206-10, were selected for the further testing as cultivars or breeding materials.