Screening Of Potato Gemplasm With Late Blight Resistance And Dissection Of R Gene Combination

Potato is the third largest food crop in the world,and it plays an important role in people's lives as staple food and vegetables.Late blight is considered to be the most serious disease of potatoes.The main method for the control of potato late blight in the world is using chemical agents.Chemical control not only increases the cost of planting,but also damages the environment and human health.Even worse,Phytophthora infestans can gradually develop resistance to chemical agents.Breeding varieties containing multiple broad-spectrum,long-lasting resistant R genes is the most cost-effective method for controlling late blight.However,lack of disease resistance breeding resources and the unclear genetic background of the resistant breeding parents seriously restricts the efficiency of potato late blight resistant breeding.This study aimed to obtain a number of materials with excellent resistance to late blight through evaluate the domestic and foreign potato resources,at the same time to clarify the resistance genes of these materials and explore the unknown disease resistance genes of late blight.The main results are as follows:1.Three P.infestans virulent strains HB0914-2,UK3928A and NL11564 were used to inoculate more than 300 potato materials combined with local varieties and International Potato Center resources by means of detached leaf assay.Totally 50 potato materials with medium to high level late blight resistance were identified.2.Four R genes(R1,R3a,R3b,R8)specific primers were designed to test 362 potato materials.The R8 gene was detected in 37 of the 68 domestic resistant materials(more than 55%),and the detection rates of R1,R3a and R3b were 29%,44%and 38%,respectively.Many materials contain 3 or more R genes,indicating that some of the most resistant materials from China also stacked other late blight resistance genes beside R8.R8 was detected in 82 materials from the International Potato Center(over 31%),and the detection rates of RI,R3a and R3b were 30%,28%and 14%,respectively.Above results indicate that the R8 gene is prevalent in potato breeding materials with outstanding resistance.3.To further clarify the R gene conbination(including other disease resistance genes)of 50 selected late blight resistant materials,the R genes in these materials were diagnosed using the R gene enrichment and sequencing platform(dRenSeq).A total of 12 known disease resistance genes were detected in these materials,10 of which were late blight resistance genes,including R1,R2-like,R3a,R3b,R8,Rpi-blbl(RB),Rpi-pall,R9a,Rpi-vnt1 and Rpi-abpt.Another two are viral resistance gene Rx and nematode resistance gene Gpa.Sequencing results confirmed that R8 was present in more than 90%of the resistant materials.The P.infestans strain NL11564 was able to overcome R8,but some materials containing only R8 are resistant to NL11564,indicating that these materials contain other unknown R genes.4.Based on the sequencing results of a large number of R8 and its homologous analogs(RGAs),the R8 and its RGA sequences were analyzed to find their accurate different regions,and a highly specific R8 gene diagnostic primer was designed.The PCR detection results using diagnostic primers were highly consistent with the dRenSeq diagnosis results(99%matching).This specific primer can be used for molecular marker assistant selection in potato late blight resistance breeding.This study provides original and diversity materials for breeding broad-spectrum and long-lasting resistant varieties,and provides clear genetic backgroud and technical support for stacking resistance genes.