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Scientia Silvae Sinicae ›› 2021, Vol. 57 ›› Issue (11): 49-58.doi: 10.11707/j.1001-7488.20211105

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Detection and Molecular Variation of Jujube Witches' Broom Phytoplasma in Resistant Jujube Scions Grafted on Diseased Root Stocks in Three Jujube Orchards

Wenxin Zhang1,Shaoshuai Yu2,Guozhong Tian1,He Wang3,Zhengguang Ren4,Shengjie Wang1,Dezhi Kong1,Yong Li1,Caili Lin1,*   

  1. 1. Key Laboratory of Forest Protection of National Forestry and Grassland Administration Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry Beijing 100091
    2. Coconut Research Institute, Chinese Academy of Tropical Agricultural Sciences Wenchang 571339
    3. Beijing Forestry Protection Station Beijing 100029
    4. College of Plant Science and Technology, Beijing University of Agriculture Beijing 102206
  • Received:2020-10-19 Online:2021-11-25 Published:2022-01-12
  • Contact: Caili Lin

Abstract:

Objective: This study aimed to detect the jujube witches'-broom(JWB) phytoplasma status of jujubes cultivated in three jujube orchards after inoculating the trees by graft, and to analyze the transmission, epidemic, heritable variation, and phylogeny of different phytoplasma strains; and reveal the relationship between different phytoplasma strains and different resistance jujube cultivars. Method: In April 2017, different resistant jujube scions were collected and grafted on the phytoplasma-infected rootstocks cultivated in three jujube orchards including Yuquanshan and Changping orchards in Beijing and Juncheng orchard in Tang county, Hebei province. The total DNA of scion and rootstock tissue samples were extracted from August to October of that year, to be used as templates for PCR amplification. Specific PCR products of 16S rDNA, 16S-23S intergenic region(SR), secA, tuf, fusA-tuf intergenic region, himA and its downstream putative protein gene were sequenced. Genetic variation and phylogenetic evolution were analyzed with obtained sequence data. Result: The symptom severity of resistant scions was generally lower than that of susceptible rootstocks. No phytoplasma was detected in all of T30 scions without symptoms of witches'-broom by direct and nested PCR and LAMP. The homology of 16S rDNA, SR, tuf and secA gene sequences of JWB phytoplasma isolates from three orchards was 100%. According to the base variation of himA and its downstream putative protein gene at 117, 154 and 190 bp sites in 38 samples, JWB strains from Junchengzhen were clustered in the T-A type, JWB strains from Yuquanshan and Liangjiagou were clustered in the C-A type, while JWB strains from Changping were clustered in the C-C type. According to the insertion or deletion of base A at 39 bp in the sequence of the fusA-tuf intergenic region in 29 samples, JWB strains from Yuquanshan and Juncheng were clustered in the TJ2(A+) type, while others were clustered in the TJ1(A-) type. There were dominant strains in each orchard that cause the sequence types of both regions(himA and its downstream putative protein gene, intergenic region of fusA-tuf genes) were mutually corroborated. Conclusion: In this study 'Junyou No.2' (Z18) jujube is for the first time identified as the high resistant cultivar to JWB. The variations of different JWB strains from two orchards have no significant correlation with the disease resistance of cultivars, while with the regional difference. The gene sequences of JWB strains from the two regions provide the evidence that JWB strains of Yuquanshan are not originated from Sihong County, Jiangsu Province. The results are helpful to reveal the genetic variation characteristics of JWB phytoplasma population and provide a theory basis for rational utilization of resistant cultivars and JWB disease control.

Key words: graft, disease resistance, jujube witches'-broom disease, phytoplasma, 16S rDNA, himA and its downstream hypothetical protein

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