| Potato(Solanum tuberosum L.)plays an important role in global food security.China is the largest potato grower and producer in the world,and potato plays an important role in improving agricultural quality and efficiency,increasing farmers’ incomes,alleviating poverty and promoting rural revitalization.Late blight caused by Phytophthora infestans is the most serious disease of potato,which severely restricts the world potato production.Late blight control practice shown that growing broadspectrum and durable resistant varieties is the most economical,effective and green way to control P.infestans,but so far there are few durable and good resistant varieties in China.It is urgent to develop varieties with broad-spectrum and durable resistance.In this study,molecular marker-assisted selection,combined with traditional late blight resistance evaluation,was used to screen a number of potato materials containing R8 and with stable and durable resistance,which will provide excellent resource materials for the selection and breeding of late blight resistant varieties.Aimed to improve the efficiency of R8 molecular markers in selecting resistant plants,the efficiency and reliability of marker selection were also analysed,and the reasons for the low consistency between marker and resistance level were explored.The main findings are as follows:1.The distribution of R8 gene marker in 319 progenies of 4 crosses was examined.The results showed that the percentages of presence of R8 marker in the progenies of crosses 9 and 2(both parents contained R8)was 43.03%(34/79)and 61.40%(70/114)and 39.04%(57/146)and 58.04%(65/112)in the progenies of crosses 10 and 1(one parent contained R8),respectively.2.Resistance of progenies of 4 crosses was evaluated by detached leaf inoculation method.The results showed that the resistance of 19 randomly selected plants without R8 markers in crosses 1 and 2 were all susceptible,while the resistance of progenies with R8 marker was quite different,and the number of different resistance grades(HR,R,MR,MS and S)was nealy normal distribution.Among them,91 progenies containing marker from crosses 9 and 10 were inoculated using HB0914-2,and 45 clones with stable resistance were screened.135 progenies containing markers in crosses 1 and 2 were inoculated by HB0914-2 and 88069 respectively.The results showed that 88069 was weaker in pathogenicity.Based on the resistance evaluation using HB0914-2,68 resistant clones were selected.3.Combined the data of molecular marker analysis and resistance evaluation,it was found that the degree of agreement between marker detection results and resistance evaluation was low in the progenies of crosses 9(47.06%,16 R/34),10(50.88%,29R/57),1(53.85%,35 R/65)and 2(47.14%,33 R/70).To confirm the acurrecy of the results of R8 makers detaction results,full length CDS of R8 was amplified in g DNA from progenies of 9 and 10,the results showed that they agree with each other with little diffrences.To test the expression of R8 gene,CDS of R8 was amplified in c DNA from three clones(HR: 10-20,R: 10-58,S: 10-65)and single clone sequenced.The results showed that intact R8 was normally expressed in both resistant and susceptible clones.This results suggested that the detaction results of the R8 marker are reliable and that the variable resistance levels in clones containg the R8 markers is not due to inaccurate marker detaction,but may be due to more complex reasons.In this study,a number of potato materials contaning durable resistant R8 were screened by molecular markers.It is clear that the available markers are effective in accurately selection clones containing R8 gene and can be used in resistance breeding work.The reasons for the low consistance between R8 marker presence and resistance level were explored.This study provided late blight resistance materials and technical basis for the selection of stable and durable disease resistant potato varieties. |
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