QTL Analysis Of Resistance To Late Blight In Tomato

Late blight of tomato is a cosmopolitan disease. It causes a significant yield losses and quality,degradation especially in spring tomato area. Development of varieties or hybrids resistant to this disease is one of the effective approaches to control the disease. Molecular marker technology will contribute to explore the useful information in efforts to develop resistant germplasm efficiently through locating the QTL relevant to diseases resistance. In this study,we mapped and characterized quantitative trait Loci (QTL) conferring resistance to late blight.The F2 population ( 195 individuals) from the cross of 04968(sensitive)×L3708(resistant) were used as testing material.The study use tomato late blight strains T1,2 in main tomato growth area of harbin ,Hei Longjian province. The objectives of this work were to identify and map QTLs for resistance to Late blight in tomato with the aid of Composite Interval Mapping method (CIM).The results are summarized as follows:1. Appling to the software of Microsoft Excel 2000,the verification of normal distribution was carried out for late blight charactor in tomato of F2 population .The value of deviation and peak is–0.78 and 0.86 respectively. The detection of the figure of frequence distribution skew degree and peak degree, accord the demand of QTL.range of disease was 0-6,the average was 3.55±1.13; the individual of the most resistant and sensitive was fewer. Most of resistant individual was 3-4 and sensitive individual was 4-5 in F2 population.2. Use the 195 individuals of F2 population from the cross 04968(sensitive)×L3708(resistant) were used as testing material.Genetic linkage map witch called A with 3 locus 25.5 cM in chromosome length were constructed by S71,S12 and S22, The distance of S71 and S12 is 10.9cM, another distance is 14.6 cM between S12 and S22.3. There are two QTLs, which map 2.89 cM from S12 marker and 4.61 cM from s22 marker on linkage group A, they are named as Ph-3a1 and Ph-3a2 that explains 8.92%and 25.69% of the total phenotypic variation respectively, and the additive effect of two QTL are 0.1003 and 0.1697 respectively. The sum of variation of two QTLs is 34.61%.