离体砂糖橘黄龙病病果中病菌浓度变化规律的探究

Quantitative analysis of “Candidatus Liberibacter asiaticus” in the excised citrus fruits

柑橘黄龙病(Citrus Huanglongbing,HLB)是柑橘生产上最具毁灭性的病害,对我国乃至世界的柑橘产业造成了巨大的经济损失[1]。由于CLas还无法进行分离培养[2],导致对CLas的研究(如病原学、基因组学等)主要依赖于含有CLas的寄主材料,如染病柑橘和带菌柑橘木虱(Diaphorina citri)[3]。因此,获取含有高浓度CLas寄主材料成为了当前CLas研究的前提。

Early studies have revealed the uneven distribution of Candidatus Liberibacter asiaticus(CLas) in Huanglongbing(HLB)-affected citrus trees. Bacteria of CLas were found to be enriched in the fruit, especially in the pith. In this study, we further investigated the dynamics of CLas population in excised citrus fruits. The CLas-infected Shatangju fruits were collected and kept for 4 weeks under constant temperature and moisture. The concentrations of CLas in the pith of fruits were detected weekly, and the fruits on trees were detected at the same time as the control. Our results showed that the total DNA, citrus DNA and CLas DNA from the excised fruits all decreased during the storage, but the CLas concentration in the pith of excised fruit increased firstly, and then decreased with time. The CLas concentrations in the pith of diseased fruit at 14 d and 28 d after picking were higher than that of the first day and reached the highest at 14 d. Comparing with the fruits on the tree, CLas concentrations in the pith of excised fruits were also significantly higher at the 14 d and 28 d. With the degrading of total DNA in fruit pith, the proportion of CLas DNA was increased, which could be served as a suitable material for the DNA extraction and CLas genome sequencing.