Evaluation Of Canker Disease Resistance Of Kiwifruit ’Golden Fruit’ × ’Xiong No.22’ Hybrid Seedlings

Kiwifruit bacterial canker is caused by the infection of Pseudomonas syringae pv.Actinidiae(Psa),which is known as the ’ cancer ’ disease of Chinese kiwifruit.After infection,it can cause serious economic losses such as dead trees and garden destruction in a short period of time.Canker disease is the main factor limiting the cultivation of Actinidia chinensis in the northern foot of Qinling Mountains in Shaanxi Province,and the incidence is related to the cold resistance of the tree.Low temperature and freezing injury can aggravate the occurrence of canker disease.Cultivating high-quality germplasm resistant to canker disease is the fundamental guarantee for the extensive cultivation of Actinidia chinensis.Based on the previous investigation of kiwifruit germplasm materials,the research group obtained the male plant ’ Xiong No.22 ’ with canker resistance.In order to strengthen the utilization of’ Xiong No.22 ’ and the innovation of resistant germplasm,this paper evaluated the resistance of 1107 hybrid populations and cultivars of kiwifruit(’ Huangjinguo ’ × ’ Xiong No.22 ’)to canker disease and evaluated the cold resistance and sex identification of the selected resistant hybrid lines.The main results are as follows:1.Resistance screening of hybrid population to strain Psa.The resistance of five kiwifruit cultivars and three Chinese kiwifruit hybrid lines(HX-)to canker disease was compared and analyzed by quantitative inoculation of detached branches and leaves.The results showed that the disease resistance of each material was significantly different,and the disease resistance was as follows: ’ Xuxiang ’ > ’ Cuixiang ’ > ’ HX-38 ’ > ’ HX-37 ’ > ’ Huangjinguo ’ > ’Nongdayuxiang ’ > ’ Hongyang ’ > ’ HX-68 ’.The order of disease resistance of the cultivars was consistent with previous studies.At the same time,it was found that the average lesion length of branches and the relative lesion area of leaves had the same trend,and the disease resistance of kiwifruit could be accurately evaluated by co-inoculation verification of branches and leaves.According to the average lesion length of branches and the relative lesion area of leaves,the disease resistance of 500 kiwifruit hybrid seedlings was divided into four grades:high sensitivity,susceptibility,disease resistance and high resistance,among which the proportion of disease resistance was 40 %.The proportion of susceptible strains was 27 %,the proportion of highly susceptible strains was 21 %,and the proportion of highly resistant strains was 12 %.In this study,a total of 1107 Actinidia chinensis hybrid seedlings were identified and evaluated,and 129 hybrid seedlings with high resistance to canker disease were screened.25 strains were selected and grafted onto kiwifruit orchards with canker pathogens.2.Evaluation of cold resistance of canker resistance hybrid lines.In this experiment,the relative conductivity at-15 °C treatment temperature was used as the evaluation index of cold resistance.Firstly,the cold resistance of six kiwifruit cultivars was evaluated.According to their relative conductivity,the cold resistance was ranked as follows: ’ Nongda Yuxiang ’ > ’Hayward ’ > ’ Xuxiang ’ > ’ Cuixiang ’ > ’ Huangjinguo ’ > ’ Hongyang ’,which was consistent with the order of cold resistance of kiwifruit cultivars obtained by predecessors.In this study,40 Actinidia chinensis hybrid strains with high resistance to Psa were selected,and their cold resistance was evaluated by relative conductivity and cluster analysis.The cold resistance of40 hybrid strains was divided into three categories: high cold resistance,medium cold resistance,low cold resistance.Among them,high cold resistance strains accounted for 12%,medium cold resistance strains accounted for 33%,and low cold resistance strains accounted for 55%.Five Actinidia chinensis hybrid strains with high resistance to canker and low temperature resistance were screened.3.Sex identification of hybrid lines resistant to canker disease.The universality of S1032850,SmX,SmY1,L11 and L51 gender molecular markers was verified in 8 cultivated kiwifruit germplasms with known genders.It was found that the bands amplified by S1032850 and SmX markers in male and female plant materials did not show gender specificity,and the accuracy was low.No stable and clear bands were amplified by L11 and L51 markers.The SmY1 marker has good gender specificity,and the accuracy of gender identification in male kiwifruit is 100%,and 75% in female.The similarity between SmY1 marker product sequence and kiwifruit sex related PAPD marker fragment sequence was as high as 81.43%.SmY1 may be located in the male-specific region of kiwifruit Y chromosome.Therefore,SmY1 markers can be used to identify male plants in 129 hybrid lines with high resistance to canker disease,and 44 male plants were identified.