Sánchez M E, Andicoberry S, Trapero A
Departamento Agronomía, Universidad de Córdoba, Apdo. 3048, 14080, Córdoba, Spain.
Plant Dis. 2002 May;86(5):563. doi: 10.1094/PDIS.2002.86.5.563C.
Since 1993, more than 120,000 ha of former agricultural lands has been forested in southern Spain. However, there is a lack of information about the etiology of the diseases affecting nursery seedlings in the region. During 1998 and 1999, death of Aleppo pine (Pinus halepensis) seedlings was associated with episodes of excess water. The plants were grown in containers in fertilized peat under shade cloth and remained waterlogged for long periods. A few weeks before their scheduled planting in the field, the plants exhibited needle wilting, extensive root necrosis, and root death. Phytophthora species were suspected as the cause of the mortality, and several species of the genus Phytophthora have been reported to cause damping-off of seedlings of Pinus spp. Only P. citrophthora, however, has been associated with Aleppo pine (1). In a nursery in southern Spain, P. drechsleri mating type A2 was isolated consistently from rotted roots of Pinus halepensis seedlings. Fungal identification was based on temperature-growth relationships and sporangial and gametangial characteristics (1). The optimum growth temperature was 24°C, with a rapid decline in growth rate above 30°C. Sporangia were persistent, terminal, nonpapillate, ovoid, and averaged 41 ± 4 × 29 ± 3 μm. The isolates were self-sterile, and antheridia and oogonia were only observed in pairings with A1 testers of P. drechsleri. Oogonia appeared smooth, spherical, and 33 ± 2 μm in diameter, with amphigynous antheridia that were 14 ± 1 μm long. Pathogenicity tests were conducted on 1-year-old seedlings of Pinus halepensis inoculated with two isolates of P. drechsleri collected from Aleppo pine and Quercus ilex seedlings, respectively, and two isolates of P. cinnamomi from Q. ilex. Inoculated and noninoculated control plants were waterlogged 2 days per week. After 18 weeks, both species of Phytophthora produced extensive root necrosis that resulted in needle wilting. Control plants did not develop needle symptoms and only had a low level of root necrosis. No difference in pathogenicity was observed between the isolates of either species. However, disease severity was less with isolates of P. drechsleri from Q. ilex than with those from Aleppo pine. To our knowledge, this is the first report of P. drechsleri causing root rot of Aleppo pine seedlings in forest tree nurseries in Spain and also demonstrates the potential for P. cinnamomi to cause damping-off on this pine species. Reference: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996.
自1993年以来，西班牙南部超过12万公顷的 former agricultural lands 已被造林。然而，关于该地区影响苗圃幼苗的疾病病因的信息却很缺乏。在1998年和1999年期间，阿勒颇松（Pinus halepensis）幼苗的死亡与积水事件有关。这些植物种植在装有施肥泥炭的容器中，置于遮阳网下，长期处于积水状态。在预定移栽到田间前几周，这些植物出现针叶枯萎、广泛的根坏死和根部死亡。疫霉属物种被怀疑是致死原因，据报道疫霉属的几个物种会导致松属植物幼苗猝倒。然而，只有柑桔疫霉（P. citrophthora）与阿勒颇松有关（1）。在西班牙南部的一个苗圃中，从阿勒颇松幼苗的腐烂根部持续分离出A2交配型的德氏疫霉（P. drechsleri）。真菌鉴定基于温度与生长关系以及孢子囊和配子囊特征（1）。最适生长温度为24°C，高于30°C时生长速率迅速下降。孢子囊持久、顶生、无乳突、卵形，平均大小为41 ± 4 × 29 ± 3 μm。这些分离株是自交不育的，仅在与德氏疫霉的A1测试菌株配对时观察到雄器和藏卵器。藏卵器表面光滑、球形，直径为33 ± 2 μm，有侧生雄器，长14 ± 1 μm。对1年生的阿勒颇松幼苗进行了致病性测试，分别接种从阿勒颇松和冬青栎（Quercus ilex）幼苗上分离得到的两株德氏疫霉以及从冬青栎上分离得到的两株肉桂疫霉（P. cinnamomi）。接种和未接种的对照植株每周积水2天。18周后，两种疫霉都导致了广泛的根坏死，进而引起针叶枯萎。对照植株未出现针叶症状，仅根部有少量坏死。两种疫霉的分离株之间未观察到致病性差异。然而，来自冬青栎的德氏疫霉分离株引起的病害严重程度低于来自阿勒颇松的分离株。据我们所知，这是德氏疫霉在西班牙林木苗圃中导致阿勒颇松幼苗根腐病的首次报道，同时也证明了肉桂疫霉对该松树品种有导致猝倒病的可能性。参考文献：（1）D. C. Erwin和O. K. Ribeiro。《全球疫霉病》。美国植物病理学会，明尼苏达州圣保罗，1996年。
