亚洲韧皮杆菌在单株脐橙病树的分布情况

Distribution of Candidatus Liberibacter asiaticus in individual navel orange tree

【目的】研究亚洲韧皮杆菌(CLas)在纽荷尔脐橙病树的分布情况,为柑橘黄龙病(HLB)的防控提供参考依据。【方法】以1~3个枝条表现斑驳黄化叶片症状的纽荷尔脐橙病树为研究对象,对主干发出的5个主枝(A、B、C为斑驳黄化枝条,D、E为无症状枝条)的叶片分别取样,运用PCR和实时荧光定量PCR(qPCR)分别检测,用2^(-ΔΔCr)法分析树体各部分黄龙病菌含量。对于果树上表现典型HLB病果但叶片无症状的结果枝,分别检测典型病果和相应叶片的感病情况。【结果】PCR对A、B、C、D、E的阳性检出率分别为88.57%、61.11%、54.17%、6.67%和0,qPCR对A、B、C的阳性检出率均为100.00%,对D、E的阳性检出率分别为40.00%和13.33%;2^(-ΔΔCr)法分析发现,斑驳黄化叶片中病原菌含量更高,病果的阳性检出率高于相应的无症状叶片样品。【结论】CLas在表现典型斑驳黄化症状的叶片和果实中的含量及阳性检出率均较高,病原菌在病树中分布不均匀。在进行HLB检测时,应选取典型或疑似症状样品,并运用qPCR进行检测,一旦发现树体局部发病,应当整株销毁。

[Objective]Distribution of Candidatus Liberibacter asiaticus（CLas） in Newhall navel orange tree was in-vestigeted, in order to provide reference for prevention and control of citrus Huanglongbing（HLB）. [Method]Newhall tree were used as research object, which had 1-3 branches with mottled yellow leaf symptoms. The leaves were collected from five main branches（A, B and C branches with mottled yellow leaves, D and E asymptomatic branches） on the trunk, re-spectively. Then samples were detected and analysed by using PCR and quantitative real-time PCR（qPCR）, and CLas content in different parts of tree was analyzed by using 2^-△△Ct method. For some branches with pathognomonic HLB-infected fruits but without symptomatic leaves, their fruits and leaves were detected, respectively. [Result]The results showed that, using PCR method, the positive rates of A, B, C, D, E were 88.57%, 61.11%, 54.17%, 6.67% and 0, re-spectively, while using qPCR method, the positive rates of A, B, C, D, E were 100.00%, 100.00%, 100.00%, 40.00%, 13.33% , respectively. Furthermore, 2^-△△Ct analysis showed that, CLas content was higher in mottled yellow leaves than asymptomatic leaves, and the positive rate of infected fruits was higher than corresponding asymptomatic leaves. [Conclu-sion]Content and positive rate of CLas are higher in mottle yellow leaves and pathognomonic HLB-infected fruits than asymptomatic leaves, and CLas was distributed unevenly in the whole infected tree. In the detection, the samples with typi-cal symptoms or suspected samples should be selected, and then detected by qPCR method. Furthermore, once partial branchs of tree are found to be infected, the whole tree should be destroyed immediately.