Pathogen Effector Recognition-Based Evaluation For Late Blight Resistance In Potato Varieties Longshu10 And Longshu12

Potato is the fourth main food crop in China.Late blight caused by Phytophthora infestans is the most serious disease and is main constraint for sustainable potato production.Employment of resistance（R）genes is the most efficient strategy for disease control.According to the principle of gene-for-gene interaction between host plants and pathogens,pathogen effectors can be used for identifying R genes and understanding genetic resistance in host plant materials,thereby accelerating breeding for disease resistance.In this research,we focus on dissection of genetic resistance in potato varieties Longshu10 and Longshu12that showed excellent field performance in late blight resistance in northwestern China.The achieved main results are summarized as follows:1.By using different Agrobacterium tumefaciens strains,optimized concentration of bacterial suspensions and cultural conditions for potato seedlings,and five potato differential lines（R1,R2,R3a,R4 and R8）,an efficient A.tumefaciens-mediated transient gene expression assay was established on potato.A high-efficiency transient gene expression was achieved with minor background reactions with A.tumefaciens strain AGL1 at a concentration of OD₆₀₀value 0.4 on 3-4 week-old cultured potato seedlings.2.Following the principle of effector recognition-based resistance,we employed A.tumefaciens-mediated transient gene expression assay understand genetic resistance in Longshu10 and Longshu12,by examining their recognition of 10 known avirulence genes(Avr1,Avr2,Avr3a ^KI,Avr3b,Avr4,Avrblb2,Avr Smira1,Avr Smira2/Avr8,Avrvnt1)and 16candidate core RXLR effector genes of P.infestans.The results showed that Longshu10 was capable of recognizing two avirulence genes（Avrsmira2 and Avrvnt1）and four candidate core effector genes（E05,E08,E10,E16）,while Longshu12 was capable of recognizing four avirulence genes(Avr2,Avr3a ^KI,Avr4,Avrblb2)and three candidate core RXLR effector genes（E03,E07,E14）,indicating their highly differential composition of resistance genes.3.Assessment of late blight resistance by inoculating detached potato leaves of zoospores of 6 P.infestans strains（Pj Y061,Pa21106,Pd21410,88069,88029）that are diverse in genetic background（isolated from different regions in different years）indicated that Longshu10 and Longshu12 were highly resistant to 5 of them except Pj Y061,to which both were susceptible.