黄龙病菌在4个品种柑橘果枝内的时空分布

    Distribution of ‘Candidatus Liberibacter asiaticus’ in the fruit branches of four citrus cultivars

    • 摘要:
      目的  亚洲种韧皮部杆菌(‘Candidatus Liberibacter asiaticus’, CLas)是引起柑橘黄龙病(Citrus Huanglongbing, HLB)的优势种,也是引发我国柑橘HLB的唯一病原菌。探索CLas在柑橘果枝内的时空分布规律,有利于及时准确地对其进行检测,对HLB的防控具有重要意义。
      方法  以砂糖橘、W−默科特、红心蜜柚和沙田柚不同生长期的果枝为材料,利用实时荧光定量PCR检测果枝CLas含量,研究其时空分布规律。
      结果  CLas在病枝中分布不均匀,在果实处(橘络、果中轴或种皮)富集。对于宽皮柑橘的砂糖橘和杂柑的W−默科特,成熟期果实橘络中的CLas含量最高;而对于柚类的红心蜜柚和沙田柚,成熟期果轴中的CLas含量最高。砂糖橘果实膨大与成熟过程中,CLas随着营养物质的流动从源器官(叶片)向库器官(果实)分流并聚集;果轴和橘络中的CLas含量不断增加,且橘络中的CLas含量显著上升。
      结论  CLas随着柑橘果实生长和成熟而汇集,结合源库理论可解析CLas在果枝上的运转和分布规律。

       

      Abstract:
      Objective  ‘Candidatus Liberibacter asiaticus’ (CLas), the main species causing Citrus Huanglongbing (HLB), is also the sole pathogen causing agent of HLB in China. Exploring the temporal and spatial distribution of CLas in citrus fruit branch would help timely and accurate detection of CLas, and is of great significance to the prevention and control of HLB.
      Method  The titers of CLas were measured in HLB-affected fruit branches of four traditional citrus cultivars namely Citrus reticulata Blanco cv. Shatangju, (C. reticulata × C. sinensis) cv. W-Murcott, C. maxima cv. Hongxinmi Yu and C. maxima cv. Shatian Yu using real time PCR method. The temporal and spatial distribution of CLas in citrus fruit branches were studied.
      Result  CLas was unevenly distributed in fruit branches with enrichment in the fruits (Fruit pith, centrol axis or seed coat). For the mandarin of Shatangju and W-Murcott, CLas titers were the highest in the piths at the fruit mature stage. For the pomelos of Hongxinmi Yu and Shatian Yu, CLas titers were the highest in the fruit central axes at ripe stage. CLas transferred from the source organs (leaves) to the sink organs (fruits) along with the flow of nutrients in the processes of fruit swelling and ripening. CLas titers kept increasing in central axes and fruit pith, especially significantly increased in fruit pith.
      Conclusion  CLas is enriched with the fruit developmental stages, and such transfer and distribution pattern of CLas in fruit branches can be explained by the theory of plant source-sink relationship.

       

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