Identification Methods Of Resistance In Apple Rootstocks To Ring-rot And Screening Of Rootstocks With Resistance

Apple, one of the first four fruits in the world, was the first fruit which was popular with consumes in China. However, apple was susceptible to ring-rot disease which leaded to numerous rotten fruits after harvest and caused weak trees, which became the serious problem of restriction of apple production. In this research, some apple cultivars and a large number of hybrid rootstocks were used to study resistance index of ring-rot disease. The aim of this study was to screen the apple root stocks which could resist ring-rot disease, thereby laid the foundation of solving the problems of weak trees and rotten fruits resulted from ring-rot disease. The mainly research results were as follows:1. The leaves which were inoculated after wound pringking 1, 5 and 10-times produced different lesion. While leaves wound pringking once on the upper side, diameter of the lesions on Liquan leaves was the biggest and had a significant difference with the moderate resistance material Jonagold and highly resistance material Jiguan.2. Difference of organization structure of lenticel existed in different resistant materials. The lenticel structure of resistant materials owned the characteristic of later opening, more and clearer closed layers, more supplementary tissue, tightly arranged phelloderm cells, which could effectively hinder the infecton of ring rot spores. However, the lenticel structure of susceptible materials was to the contrary.3. Four physiological indexes such as the activities of protective enzyme, contents of total phenolic and NO of branches and leaves of different resistant materials were determined. The results showed that the SOD activity of leaves of high suspitible materials was the lowest and much lower than other resistant grades. The SOD activity showed the highest leave on high resistant materials and lowest leave in the branches of high suspitible materials. But there was no significant difference between them above. The POD activity of branches of high suspitible materials was the lowest and had significant differences with other resistant grades. POD activity of leaves of high resistant materials was the highest and much higher than other resistant grades. There were little obvious differences of total hydroxybenzene contents in leaves of different resistant materials. Contents of total hydroxybenzene in branches of high resistant materials were higher than the suspitible materials. Contents of total phenolic in medium resistant materials were slightly lower than other resistant grades. Contents of NO in leaves of high suspitible materials were the lowest and much lower than other disease resistant grades. There were little obvious differences of NO contents in branches of different resistant materials.4.Identification between 370 materials about ring-rot disease resistance was studied using the method of branches inoculation on the field. The results were showed that 47 of all were high resistant grades which took 12.70% portions of all the materials. There 79 in all were medium resistant grades, which took 21.35% portions of all the materials. Medium and high suspitible grades were 41 and 203, which took 11.08% and 54.86% portions of all the materials, respectively.