Rubber Tree (Hevea brasiliensis) Bark Necrosis Syndrome I: Still No Evidence of a Biotic Causal Agent.
Rubber Tree (Hevea brasiliensis) Bark Necrosis Syndrome I: Still No Evidence of a Biotic Causal Agent.
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DOI：
10.1094/pdis.2004.88.9.1046c
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发表时间：
2004-09
期刊：
影响因子：
4.5
通讯作者：
F. Pellegrin;D. Nandris;H. Chrestin;N. Duran‐Vila
中科院分区：
文献类型：
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作者：
F. Pellegrin;D. Nandris;H. Chrestin;N. Duran‐Vila
世界范围内橡胶种植园的主要限制是由于两种综合征而停止胶乳生产：（i）割胶板干燥（TPD），对过度开采的可逆生理反应;和（ii）树皮坏死（BN），从衣领向割胶切口蔓延的不可逆综合征。BN的早期症状发生在韧皮部组织内部，但从不影响形成层。坏死斑块出现在外部韧皮部，诱导树皮开裂和剥落，但这些变化永远不会导致树木死亡。BN逐渐传播到邻近的橡胶树，线性疾病中心的证据表明，可能涉及病原体，可能是通过割胶刀传播的。使用不同的方法（例如，分离、透射、化学处理以及光学和电子显微镜研究）。最近的工作集中在机械传播的病原体，如类病毒（2）或病毒/双链RNA，使用RNA提取（非离子纤维素和适当的乙醇浓度）和用RNase A处理，然后依次进行聚丙烯酰胺凝胶电泳（s-PAGE），逆转录-聚合酶链反应（RT-PCR），简并寡核苷酸引物-PCR（DOP-PCR），克隆和序列分析。虽然观察到许多类病毒（250和400个核苷酸之间）和双链病毒样（1,800 bp）低分子量RNA，但没有发现与树木BN状态的明确相关性。对各种分离的RNA进行测序，仅鉴定出质粒、非致病性细菌和酵母菌，但没有鉴定出可疑的病原体。此外，以前和最近的传播试验（割胶刀消毒、芽接、树皮植入等）未能证实是否涉及生物制剂总之，由于这些病因学研究是不确定的，现在怀疑生理疾病，涉及外源压力，非最佳的血管关系在砧木/接穗连接和受损的氰化物代谢（1，4）。参考文献：（1）H. Chrestin等人，Plant Dis.88：1047，2004. (2)N. Duran-Vila等人，J. Gen. Virol. 69：3069，1988. (3)D. Nandris等人，Eur. J. For. Pathol. 21：340，1991. (4)D. Nandris等人，Plant Dis.88：1047，2004.
The main constraint in rubber plantations worldwide is the cessation of latex production because of two syndromes: (i) tapping panel dryness (TPD), a reversible physiological response to overexploitation; and (ii) bark necrosis (BN), an irreversible syndrome spreading from the collar toward the tapping cut. Early BN symptoms develop in the inner phloem tissues but never affect the cambium. Necrotic patches appear in the outer phloem, inducing bark cracking and peeling, but these alterations never lead to tree death. BN spreads gradually to neighboring rubber trees, and evidence of linear disease centers suggest that a pathogen may be involved, possibly transmitted by the tapping knife. Several previous etiological investigations (fungi, phytoplasma, bacteria, and virus) were performed (3) on leaves, bark, and latex using different methods (e.g., isolation, transmission, chemical treatments, and optic and electron microscope studies). Recent works focused on mechanically transmissible pathogens, such as viroid (2) or virus/double strand RNA, using RNA extraction (nonionic cellulose and appropriate ethanol concentrations) and treatment with RNase A, followed with sequential polyacrylamide gel electrophoresis (s-PAGE), reverse transcription-polymerase chain reaction (RT-PCR), degenerate oligonucleotide primer-PCR (DOP-PCR), and cloning and sequence analysis. While numerous viroid-like (between 250 and 400 nucleotides) and double strand virus-like (1,800 bp) low-molecular-weight RNAs were observed, no definite correlation was found with the BN status of trees. Sequencing of the various isolated RNAs only identified plasmids, nonpathogenic bacteria and yeasts, but none of the suspected pathogens. In addition, previous and recent transmission trials (tapping knife disinfection, bud grafting, bark implantation, and etc.) failed to confirm the involvement of a biotic agent. In conclusion, since these etiological investigations were inconclusive, a physiological disease is now suspected that involves exogenous stresses, nonoptimal vascular relations at the rootstock/scion junction and impaired cyanide metabolism (1,4). References: (1) H. Chrestin et al. Plant Dis. 88:1047, 2004. (2) N. Duran-Vila et al. J. Gen. Virol. 69:3069, 1988. (3) D. Nandris et al. Eur. J. For. Pathol. 21:340, 1991. (4) D. Nandris et al. Plant Dis. 88:1047, 2004.