Evaluation Of Citrus Germplasm Resources In Hunan And Main Diseases Molecular Detection

Hunan located at transitional region between south subtropical and temperate, which exist abundant citrus native citrus resources through long term evolution and cultivation. Collection, conservation, identification, evaluation and utilization on citrus native citrus resources in Hunan is very imperative and important. This project was supported by Hunan Scientific and technological Tepartment and Hunan Agricultural Department and focus on the distribution trait, classification ,genetic diversity and major diseases on citrus native citrus resources in Hunan by means of molecular biological methods. It aimed to provide more convincing evidences for origin and taxonomy of citrus plants and supply theoretical basis for foundation of reasonable position in citrus classification system for wild citrus originated from Nanling mountain and for their conservation and utilization as well as technological foundation for cultivar registration, identification and protection in future.The main results are as follows:1.Through long term natural evolution,hybridization, mutation,selection there are abundant native citrus germplasm resources in hunan,which are classified into Poncirus, Fortunella, Citrus genus with 11 species and distribute in Nanling mountains, Wuling mountains and Xuefeng mountains.2. 38 native citrus germplasm resources have been collected, conserved and evaluated. Mangshanyeju, Daoxianyeju, Jiangyongyeju are relatives of Eucitrus for study of citrus classification; Bingtangchen with red rind, lager Bingtangchen , Bingtangchen with navel, seedless Zhuhongju, Cili- pumelo with green flesh, Cili- pumelo with red flesh, Annong-pumelo are bud mutants and hybids newly selected in the research;Yongshunmiju, Anjiangxiangyou, Dayongjuhuaxinyou, Cilijingxianyou, Hongjiangbi ngtangyou, Poluoxiangyou, Zaotianyou, Nanshangjingan, Cilixianchen are native cultivars with high-quality and special flavor. Yongshunzhichen, Shangjingan, Ichangenes, Juhong are suitable roostocks and resources for hybridization, Dongkoubukuzhi, Xiangci-33 are very unique germplasm resources.3. More than 20 patented varieties are recently introduced. New Newhall, CaraCara, Fukumoto, Nova, Fallglo,HB pumelo, behave characteristics of vigorous growth habit, fair productivity and ability to bear fruit at a young age, rich ahd sweet flavor. The study analyzed and evaluated citrus quality of different varieties and made suggestion out for improving citrus structure and citrus quality regionalization in hunan and provide scientific results for construction of dominated citrus production regions.4. AFLP technique was used to determine DNA polymorphism of the wild Mangshanyeju,Daoxianyeju,Jiangyongyeju,Citus indica and Citrus tachibana and eighteen cultivated germplasm resources of Citrus. Eight AFLP primer pairs was selected out of 64 and 334 PCR bands were obtained. Among which 294 (88%) were polymorphic. The Dice' coefficient of the samples was 0.68-0.91. the results showed Mangshanyeju,Daoxianyeju,Jiangyongyeju are different wild species of Eucitrus in comparison with Citrus indica and Citrus tachibana. Mangshanyeju is more primitive wild species than Daoxianyeju,Jiangyongyeju. The pointed leaf form and round leaf type are found in Mangshan wild mandarins. The small fruit with rough rind and large fruit with smooth rind type are found in Daoxianyeju and Jiangyongyeju. In addition to the existence and the wild distribution of wild Citrus species in Nanling Mountains plus the DNA polymorphic data, pollen morphology and taxonomic characteristics obtained in this study supported that Nanling Mountains is one of the native centers of the subgenus Eucitrus.5. AFLP technique was used to determine DNA polymorphism of citrus mutants originated from 2different parent cultivars in Hunan province. Eight was selected out among 64 pairs of prime combinations and 2099 polymorphism bands were amplified. There are 36 to 92 polymorphism bands between mutants and parent cultivars. Ratio of polymorphism bands of every mutant to total bands of parent cultivars is 0.1721 to 0.4182. The results show that 7different type of citrus mutants are bud mutant, have got genetic basis to be selected as new variety. AFLP is characterized with abundant, clear polymorphism bands and is very effectively analysis method for identification of citrus mutants.6. Through PCR detection, we have collected information of citrus Huanglongbing in Hunan Province. 48 samples were collecting from 22 production districts to detect Citrus huanglongbing, Citrus Huanglongbing have been detected from16 samples. The results showed that trees from eight places were infected. The places lie in Xiangnan Citrus producing district. Comparing with the condition that occurred in 1980's, it shows the tendency to spread to the north. Some orchards have citrus psyllas, which may be the major carrying medium. This research has detected citrus Huanglongbing in some orchards in Yueyang and Changde for the first time. The infected variety is only Guanximiyou pommelo. Others are not infected. There are no psyllas in Xiangbei district. The pathogen in Xiangbei may come from young trees from other provinces, where citrus trees are severely infected by Huanglongbing. Test has successfully cloned a sequence of Citrus Huanglongbing pathogen, cloned DNA was 99.8% homogous to the GenBank(AY342001.1) of Asian citrus candidates Liberibacter asiaticus, a member of L.asiaticum pathogen. CTV, CEV, CTLV have been detected simultaneously,results show 82% citrus trees were infected by CTV RFLP was used to examine the cost protein gene of CTV, and it was found that CP/Hinfl RFLP group 1,3,6 were dominant in Hunan. The results btained by RFLP analysis revealed that mixture of CTV strains often ocoured in field trees. Huanglongbing and CTV are going up as dominating Virus and viruslike diseases in Hunan. Procedure, timeline and virus-free propagation system for the introduction and propagation of new varieties should be found to support citrus industry.2...