Colonization of tree xylem by Phytophthora ramorum, P-kernoviae and other Phytophthora species
Colonization of tree xylem by Phytophthora ramorum, P-kernoviae and other Phytophthora species
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DOI：
10.1111/j.1365-3059.2006.01511.x
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发表时间：
2007-04-01
期刊：
影响因子：
2.7
通讯作者：
Brasier, C. M.
中科院分区：
文献类型：
--
作者：
Brown, A. V.;Brasier, C. M.
疫霉属的病原学和频率。在一系列感染 P. ramorum、P. kernoviae、P. cambivora、P. citricola 和其他物种的阔叶树中，研究了韧皮部病变下方变色木质部组织中的细菌。尝试从 53 棵树的 81 块经过消毒的变色木板（6 x 4 厘米）的内表面进行隔离。变色大多延伸至木质部 1-5 毫米 (75%)，但侵入 6-10 毫米 (10%) 和 10-25 毫米 (15%) 的情况也很常见。在木板中，81% 产生疫霉属 (Phytophthora spp)。在 66 个案例中，对木板和覆盖的韧皮部板进行了采样。其中 56% 是疫霉属 (Phytophthora sp.)。与木材和韧皮部板分离。 23% 是疫霉属 (Phytophthora sp.)。仅从木板中分离出来，并且仅从韧皮部板中分离出 8%。小的“岛状”韧皮部病变，通常以与主要病变相邻的线性阵列形式出现，是水青冈和栎属的共同特征。感染 P. ramorum 或 P. kernoviae 的树木。岛状病变通常由与木纹一致的变色木质部的底层条带或间歇性凹坑连接。 ramorum Phytophthora、P. kernoviae 和其他 Phytophthora spp.成功地从这些连接木质部特征中分离出 P. ramorum 和 P. kernoviae，在去除覆盖的韧皮部后 24-27 个月，也从暴露木质部表面下方 5-25 毫米的变色组织中回收。这些结果表明这些病原体通常占据韧皮部病变下方的木质部；它们可以在木质部组织中多年生；它们可以在韧皮部病变之前在木质部组织中传播；并表明它们可能以这种方式引发新的韧皮部病变。这种定植必然导致至少局部木质部功能障碍。如果存在木质部变色，建议隔离疫霉菌。应从木质部和树皮尝试；此外，在切除出血病灶以控制疾病时，以及在旨在防止这些树干病原体在国内或国际传播的方案中，应去除受感染的外部边材。
The aetiology and frequency of Phytophthora spp. in discoloured xylem tissue beneath phloem lesions was investigated in a range of broadleaved trees infected with P. ramorum, P. kernoviae, P. cambivora, P. citricola and other species. Isolation was attempted from the inner surface of 81 sterilized discoloured wood panels (6 x 4 cm) from 53 trees. Discolouration mostly extended 1-5 mm into the xylem (75%), but incursions of 6-10 mm (10%) and 10-25 mm (15%) were frequent. Of the wood panels, 81% yielded Phytophthora spp. In 66 cases, both a wood panel and an overlying phloem panel were sampled. In 56% of these, a Phytophthora sp. was isolated from both the wood and the phloem panel. In 23% the Phytophthora sp. was isolated from the wood panel only and in 8% from the phloem panel only. Small 'island' phloem lesions, often in linear arrays adjacent to main lesions, were a common feature of Fagus sylvatica and Quercus spp. trees infected with P. ramorum or P. kernoviae. Island lesions were often connected by underlying strips or intermittent pits of discoloured xylem in line with the wood grain. Phytophthora ramorum, P. kernoviae and other Phytophthora spp. were successfully isolated from these connecting xylem features with P. ramorum and P. kernoviae also recovered from discoloured tissue 5-25 mm below exposed xylem surfaces 24-27 months after the overlying phloem was removed. These results show that these pathogens commonly occupy xylem beneath phloem lesions; that they can perennate in xylem tissue; that they can spread in xylem tissue ahead of phloem lesions; and indicate that they may initiate new phloem lesions in this way. Such colonization must lead to at least local xylem dysfunction. It is recommended that, if xylem discoloration is present, isolation of the Phytophthora sp. should be attempted from the xylem as well as the bark; also, that removal of infected outer sapwood should be undertaken during excision of bleeding lesions for disease control and in protocols aimed at preventing national or international spread of these tree stem pathogens.