| Kiwifruit is one of the most popular fruit in the world,and Kiwifruit also has high edible and economic value.Kiwifruit bacterial canker is a common and serious disease in the production of kiwifruit and it cannot be cured totally.Breeding resistant materials is one of the effective ways to control the kiwifruit bacterial canker.The basis of the breeding work is to screen and analysis the resistance materials.China is the origin and distribution center of kiwifruit.There are many wild kiwifruit resource in China.These features provide good conditions for screening the resistance materials.However,there are few resistance materials reported so far and there is a lack of research on the relationship between resistance materials and major cultivated varieties.In this study,we evaluated the resistance of kiwifruit bacterial canker by in-vitro inoculation of bacillus kiwifruit pathogen P.yringae pv.Actinidae(Psa-2)firstly.Then we combined the cytogenetics and molecular biology to analyze the relationship between the major kiwifruit species,especially the relationship between resistance materials and major cultivated varieties.We infected the branches of 9 kiwifruits,totally 28 kiwifruit materials,by in-vitro inoculation of bacillus kiwifruit pathogen P.yringae pv.Actinidae.We selected 3 kinds of high-resistance materials(A.eriantha-1、A.eriantha-3 and A.arguta-“Kuilv”)and 6 kinds of resistance materials(A.eriantha-4、A.henryi-2、A.polygama、Unknown-1、A.eriantha-2 and A.arguta-“Haijia”).For the high-resistance materials,they all come from A.eriantha and A.arguta.We used 6 kinds of materials from Sect.Stellatae、Sect.Maculatae and Sect.Leiocarpae to count their chromosomes and do the FISH based on the sites of 45 S rDNA and 5S rDNA.The results revealed that they are 2n=2x=58,2n=2x=58,2n=2x=58,2n=4x=116,2n=4x=116,2n=6x=174.The number of 45 S rDNA and 5S rDNA sites is 2,2,2,4,4,6 respectively,which are the same as their ploidy.This result indicated that the genus Kiwifruit had a variety of ploidy,and the number of 45 S rDNA and 5S rDNA sites was stable,which were the same as their ploidy.The ITS1-5.8S-ITS2 and 5S-NTS sequences analysis revealed that ITS1 and ITS2 have the same nucleobase length,and the variation of their sequence bases mainly comes from reversal and conversion.According to ITS to construct a phylogenetic tree,six kiwifruits can be divided into three groups: the first group is A.chinensis(Hongyang)and A.deliciosa;the second group is A.eriantha and Sect.Maculatae(Lvsexiaojindian);the third group is A.arguta(Hongse1hao 、Hongse2hao),wherein the first group and the second group have a larger similarity coefficient.However,there are a large of base differences in the NTS sequence,and the clustering result is similar to those of the ITS1-5.8S-ITS2 sequences.However,The A.eriantha is different from the former,and its similarity with A.chinensis(Hongyang)and A.deliciosa was higher.In other words,the relationship between A.eriantha and A.chinensis(Hongyang)is close,and A.arguta(Hongse1hao、Hongse2hao)are farther away from A.chinensis,but Sect.Maculatae(Lvsexiaojindian)is in the middle of them.The results of SSR molecular markers showed that Hongse1hao、Hongse2hao were first grouped into the first class,and then A.chinensis(Hongyang)and A.deliciosa were clustered into the second category.Finally,Sect.Maculatae(Lvsexiaojindian)and A.eriantha were clustered into the third class.And the first and third class have higher similarity coefficients.The similarity coefficients between the first and second class was lower than the similarity coefficients between the third and second class.The result based on the genetic distiance 0.49.In brief,A.eriantha、A.arguta have strong tolerance to kiwifruit bacterial canker.The number of 5S rDNA and 45 S rDNA sites of Actinidia species is stable,which is the same as their ploidy.Based on the results of ITS1-5.8S-ITS2,5S-NTS sequences and SSR,the A.deliciosa classes to A.chinensis.A.eriantha may be closer to the Sect.Maculatae,and A.arguta is far from the A.chinensis.Furthermore,A.eriantha may be also close to Sect.Maculatae,and Sect.Maculatae may belong to the intermediate type.Thus,we speculate that the cross-compatibility between A.eriantha and the major cultivated species is higher than A.arguta when it crosses with the major cultivated species.This study also laid a foundation for the utilization and creation of germplasm resources which are resistant to kiwifruit bacterial canker. |
