Study Of Molecular Markers Linked To Resistance Locus Of Scab In Pear

Pear (Pyrus spp.) is an important pome fruits in temperate regions, since their extensive cultivation. Pear scab is one of the most harmful diseases of pear, it is most prevalent in mild, damp seasons. The fungus can infect leaves, fruit, blossom, young shoots as well as other parts of the tree. The most serious consequence of scab is weakening vigour of the trees caused by early leaf fall. And this may limit the crop of fruit.With the development of molecular markers technique, the markers closely linked to genes will be greatly useful for improving breeding by marker-assisted selection.In this study, a F1 population of 139 individuals from the cross'Huangguan'(Resistable) and'Yali'(Susceptible) was analyzed. Markers linked to this resistance gene have been identified using bulked segregant analysis coupled with the fluorescen AFLP techniques and SRAP techniques .The results are as follow:1 The resistance of pear scab was studied by manual infection in field conditions with F1 progenies. The results indicated all of cross, 71 plants were resistant to scab and 68 plants were susceptible to scab in 139 plants of cross F1. A 1:1 segregation ratio was observed between resistant and susceptible plants which based on the Chi-square test (χ2 (1) (0.05) = 3.814), indicating a monogenic inheritance.2 The orthogonal design was used to optimize the SRAP reaction system in pear. The optimum system was as follows: Mg2+ 2.4 mmol/L, dNTPs 200μmol/L, Taq DNA polymerase 1U, template DNA 80ng, primer 0.2μmol/L, and the total volume of reaction was 25μl. At the same time, the stability and polymorphism of different species in pear were tested under the optimal system.3 Out of 64 fluorescen AFLP primers, D3-365 were found linked to the resistance locus. By using selective genotype linkage analysis, the genetic distances between the marker and the resistable locus were 14.9cM.4 Out of 120 SRAP primers,a marker was found linked to the resistable locus.