Creation Of New Germplasms Resistant To Late Blight By Potato Mesophyll Protoplast Fusion

Potato (Solanum tuberosum L.) is the world’s4th largest food crop. Potato late blight is themost devastating disease in potato production,which is caused by Phytophthora infestans. Theworldwide control stategy is breeding of new cultivars for disease resistance. Many wild species,which have resistance or tolerance to late blight, cannot be hybridized with the tetraploidcultivated species. The somatic cell hybridization technique is a new method that can use thesewild resistance genes. This study is on the creation of new germplasms resistant to late blight, andthe establishment of high efficient fusing system of potato mesophyll protoplasts. The majorresults were as follows:1.The number④media（MS+0.5mg/L NAA+1mg/L AgNO3）was the most suitable to theCulture of parents plantlets in vitro; The Leaf area was increased significantly in the mediumcontaining AgNO3,the maximum leaf area was got in the medium added2mg/L AgNO3and2%sucrose; The medium added1mg/L AgNO3and2%sucrose is the most suitable to the culture ofpotato plantlets in vitro which were used to the isolation of protoplasts.2. The results showed that the optimal parameters for electrofusion was: alternating current(AC)1.0×104V/m, AC duration30s, direct current (DC)1.0×105V/m, pulse width60μs. Underthese conditions, the effective fusion rate reached29.7%, and the breakage rate was13.86%.3.The35plants were regenerated，and the regenerate frequency is13.3%. The35regenerantswere identified by RAPD markers, the results showed that28were true somatic hybrids.The other7regenerants were not somatic hybrids, but self-fusion plants. The4regenerants of them werecontain the characteristic band of parental S.chacoense, the other3regenerants were contain thecharacteristic bands of parental DY4-5-10.4. The ploidy identification showed that16of the28somatic hybrids were hexaploids, its ratewas57.1%;3somatic hybrids were Octoploid, its rate was10.7%;5somatic hybrids wereaneuploidy, its rate was17.9%;4somatic hybrids were Mixoploid, its rate was14.3%.5.Proving by the isolate09-13of the late blight, the18somatic hybrids were significantlyhigher resitance than the high susceptible parent DY4-5-10.3of them accounting for16.7%,whose lesion area percentages were2.0,2.7and2.8, had significantly stronger resistance than theresistance parent S.chacoense,which is5.7.11of them accounting for61.1%had no significantdifference than the resistance parent S.chacoense, and the other4of them accounting for22.2%had resistance between their parents.