黄龙病菌在柑橘果实橘络中的分布

The Distribution Pattern of Candidatus Liberibacter asiaticus in Fruit Pith

黄龙病菌(Candidatus Liberibacter asiaticus,CLas)可在柑橘果实橘络中大量增殖。为探究其在染病柑橘果实橘络内的增殖与分布规律,以感染黄龙病的沃柑、脐橙、琯溪蜜柚和沙田柚果实为材料,利用RT-qPCR对果实橘络单位片段(每1.5cm长片段)组织中的CLas含量进行定量分析,同时对感染黄龙病的沃柑和脐橙同一果实橘络不同位置片段中的CLas含量进行定量分析。结果表明,4个品种橘络中的CLas数量存在差异,其中沃柑和琯溪蜜柚橘络平均每1.5 cm片段中的CLas数量显著高于脐橙和沙田柚(P<0.05)。沃柑和脐橙果实同一橘络位于中端或中后端片段组织中的平均CLas显著高于前端(P<0.05),而琯溪蜜柚和沙田柚各部位无差异。CLas在不同品种果实橘络中的丰度差异可能与不同品种橘络中的物质组成有关,而CLas更倾向于在果实橘络中端或中后端组织中增殖的原因可能与营养物质在橘络中的分布有关。

The pathogen of citrus Huanglongbing,Candidatus Liberibacter asiaticus(CLas)was able to multiply in fruit pith.To analyze the proliferation regularity and the distribution pattern of CLas within fruit pith tissue of infected citrus fruit,CLas-infected Wokan(Citrus reticulata Blanco‘Wokan'),Navel orange(C.sinensis),Guanxi pomelo(C.maxima‘Guanxi Miyou')and Shatian pomelo(C.maxima‘Shatianyou')were collected for sampling of fruit pith.RT-qPCR was applied to quantify the CLas population in different segments(1.5 cm segment)from the individual fruit pith.The CLas population in different fruit pith from individual fruit of Wokan and Navel orange was also analyzed.The abundance of CLas in different segment of the individual fruit pith and different fruit pith from the individual fruit was statistically compared.Quantitative analyses revealed that CLas population in each of the 1.5 cm segment varied among fruit pith of four citrus varieties.The CLas population in 1.5 cm segments of fruit pith from Wokan and Shatian pomelo fruit was significantly higher than those from Navel orange and Guanxi pomelo fruit.The variable abundance of CLas in four citrus cultivars could be associated with the different substance composition in fruit pith of four citrus cultivars.The reason of CLas tended to multiply in the middle region or stylar region of the individual fruit pith was mainly due to the distribution of nutrients in fruit pith.