Study On Identification Method Of Tomato Chlorosis Virus Disease And Preliminary Mapping Of Resistance Genes

Tomato(Solanum lycopersicum)is one of the most important vegetable crops.It has been cultivated for only 90 years in China,but it has become an important vegetable crop.Tomato chlorosis virus(ToCV)was first reported in Florida in 1998.It has spread to all over the world.The outbreak of ToCV has caused serious impact on Tomato Yield and quality.Because there is no systematic identification method of ToCV,the pathogenesis,pathological characteristics,resistance gene identification and resistance mechanism of ToCV are less understood.It is of great significance to establish a ToCV identification method for the control of ToCV and the location of resistance gene.In this study,three ToCV resistant tomato LA2157(S.peruvianum),LA0444(S.peruvianum),LA1028(S.chmielewskii),two ToCV susceptible tomato 172-ToCV15(S.peruvianum)and Shouguang 11 were used as main materials.A ToCV identification method was established by phenotypic identification,RT-qPCR,RNA-seq,expression profile analysis and QTL-seq.The pathogenesis,resistance mechanism and resistance gene location of ToCV were studied.The main results are as follows:1.This study established a ToCV identification method: Transplanting tomato infected with ToCV into insect cage,releasing non-toxic Bemisia tabaci,making Bemisia tabaci feed on the infected tomato to cultivate the infected Bemisia tabaci,transplanting multiple susceptible tomatoes into insect cage to expand the population of Bemisia tabaci.Tomato seeds were seeded in the non-toxic environment to the plug.After 40 days,the tomato reached the four leaf growth stage.The tomato was planted in the greenhouse,and the greenhouse was isolated from the external environment by using 60 mesh gauze net.The tomato carrying Bemisia tabaci in the insect cage was transplanted into the greenhouse for ToCV inoculation.About 15 days after inoculating ToCV,the leaves of two susceptible materials appeared chlorotic spots and entered the stage of ToCV chlorotic spot(Stage 1,S1).About 30 days after inoculating ToCV,the chlorotic spots were contiguous,the veins were chlorotic,the leaves were yellowing and entered the stage of ToCV chlorosis stage(Stage 2,S2).There were no corresponding pathological characteristics in these two stages.The results showed that the titer of ToCV in Stage 1 was much higher than that in Stage 2.Virus quantification based on RT-qPCR can be used as one of the criteria for phenotype identification.2.The whole gene expression profiles of Shouguang 11,172-ToCV15,LA2157,LA0444 and LA1028 were obtained by RNA-seq.Through the analysis of gene expression profiles,it was clear that the expression of mictube system related genes in susceptible materials decreased during the Stage 1,and a large number of differential genes obtained in Stage 2 were enriched in the pathway of photosynthetic antenna protein,plant pathogen interaction,hormone signal transduction and brassinolide synthesis.The expression levels of mictube system related genes in LA2157 and LA0444 were lower than those in the susceptible materials in the Stage 1.The expression of peptidase inhibitor related genes of LA2157 and LA1028 was higher than that of susceptible materials in Stage 2.3.The F2 population of 199 individuals was constructed using la0444 and 172-ToCV15 as parents.The disease progression of F2 population was continuous normal distribution.Combined with ToCV identification and QTL-seq results,QTL loci for resistance were detected on chromosome 7 and 9 of S.peruvianum.