Vettraino A M, Flamini L, Pizzichini L, Prodi A, Nipoti P, Vannini A, Lagnese R
Dipartimento di Protezione delle Piante, Università degli Studi della Tuscia, Viterbo, Italy.
ASSAM, Servizio Fitosanitario Regionale, Ancona, Italy.
Plant Dis. 2008 Jan;92(1):177. doi: 10.1094/PDIS-92-1-0177A.
Sweet cherry (Prunus avium L.) cultivation has increased in Italy and ≈30,000 ha are now in production. In the spring of 2006, a disease survey was conducted in orchards of central Italy. Decline symptoms of Prunus avium 'Durone' grafted on wild rootstocks of Prunus avium consisted of reduced tree vigor, yellowing of leaves, and development of root and collar rot. A reddish brown discoloration of the inner bark and wood was observed on symptomatic trees. Symptoms were recorded in three cherry orchards seasonally submitted to soil saturation conditions. In one orchard, symptoms were observed on approximately 30% of 170 surveyed trees. A Phytophthora species was consistently isolated on PARPH-V8 medium (2) from collar lesions of five cherry trees over nine trees randomly chosen among symptomatic trees in the three orchards. Colonies (20) were isolated and all appeared fluffy on potato dextrose agar and did not grow at 35°C. The morphological characteristics fit the descriptions of Phytophthora cryptogea Pethybr. & Lafferty (1). Sequence analysis of the internal transcribed spacers region of isolates shared 100% homology with P. cryptogea (GenBank Accession Nos. EF418948.1, EF418943.1, and EF153671.1). Pathogenicity of two P. cryptogea isolates (AN1 and AN2, Accession Nos. EF661576 and EF661577, respectively) was tested by soil infestation in a growth chamber at 22°C using 15 1-year-old rooted seedlings of wild rootstock of Prunus avium for each isolate. Noninoculated seedlings (15) were used as negative controls. The inoculum was produced by growing isolates on autoclaved millet grains moistened with V8 juice for 4 weeks. Each plant was inoculated with 30 cm of inoculum per liter of soil. Each seedling was randomly assigned to isolates AN1, AN2, or the noninoculated control and arranged in a complete random design. All plants were flooded for 24 h every 2 weeks for 8 weeks. At the end of the experiment, all inoculated seedlings showed crown wilting and root rot. Control plants showed no symptoms. Percentage of necrotic lateral roots expressed as dry weight (±SE) was 19.9 ± 0.6, 17.5 ± 0.2, and 4.4 ± 0.5, respectively, for seedlings inoculated with isolates AN1, AN2, and controls (analysis of variance F = 7.48, P < 0.01). Values of inoculated seedlings were significantly different from the control plants with the Tukey Post-Hoc test. No difference in virulence was observed between the two isolates. P. cryptogea was always reisolated from the roots of inoculated plants. Although pathogenicity of P. cryptogea on sweet cherry has been reported in the United States and other European countries (3,4), to our knowledge, this is the first record of P. cryptogea on sweet cherry orchards in Italy. The presence of P. cryptogea in cherry orchards is of significant concern because of its aggressiveness to this host and woody hosts such as apple, apricot, peach, walnut, and kiwi. References: (1) D. C Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (2) A. J. Ferguson and S. N. Jeffers. Plant Dis. 83:1129, 1999. (3) T. Tomidis and T. Sotiropoulos. N. Z. J. Crop Hortic. Sci. 31:355, 2003. (4) W. F. Wilcox and S. M. Mircetich. Phytopathology 75:1451, 1985.
意大利甜樱桃（Prunus avium L.）的种植面积有所增加，目前约有30000公顷投入生产。2006年春季，在意大利中部的果园进行了一项病害调查。嫁接在野生甜樱桃砧木上的甜樱桃品种“Durone”出现衰退症状，表现为树势减弱、叶片发黄以及根腐和根颈腐烂。在有症状的树上观察到内树皮和木质部呈红棕色变色。在三个季节性遭受土壤饱和条件的樱桃园中记录到了症状。在一个果园中，在170棵被调查的树中约30%观察到了症状。从三个果园中有症状树木中随机选取的9棵樱桃树中的5棵的根颈病斑上，在PARPH - V8培养基（2）上始终分离出一种疫霉属真菌。分离出了20个菌落，在马铃薯葡萄糖琼脂上均呈绒毛状，且在35°C下不生长。其形态特征符合隐地疫霉（Phytophthora cryptogea Pethybr. & Lafferty）（1）的描述。分离株内部转录间隔区的序列分析与隐地疫霉（GenBank登录号EF418948.1、EF418943.1和EF153671.1）具有100%的同源性。通过在22°C的生长室中进行土壤接种，对两个隐地疫霉分离株（分别为AN1和AN2，登录号分别为EF661576和EF66157）进行致病性测试，每个分离株使用15株1年生的野生甜樱桃砧木生根苗。15株未接种的幼苗用作阴性对照。接种物是通过将分离株在经高压灭菌并用V8汁浸湿的小米粒上培养4周产生的。每升土壤中用30厘米接种物接种每株植物。每株幼苗随机分配到分离株AN1、AN2或未接种对照，并按完全随机设计排列。所有植物每2周淹水24小时，持续8周。在实验结束时，所有接种的幼苗均表现出树冠萎蔫和根腐。对照植物未出现症状。接种分离株AN1、AN2的幼苗和对照幼苗的坏死侧根干重百分比（±标准误）分别为19.9±0.6、17.5±0.2和4.4±0.5（方差分析F = 7.48，P < 0.01）。经Tukey事后检验，接种幼苗的值与对照植物有显著差异。两个分离株之间未观察到毒力差异。总是能从接种植物的根部重新分离出隐地疫霉。尽管在美国和其他欧洲国家（3,4）已报道隐地疫霉对甜樱桃的致病性，但据我们所知，这是意大利甜樱桃果园中首次记录到隐地疫霉。由于隐地疫霉对甜樱桃以及苹果、杏、桃、核桃和猕猴桃等木本寄主具有侵袭性，其在樱桃果园中的存在令人高度关注。参考文献：（1）D. C Erwin和O. K. Ribeiro所著的《全球疫霉病害》。美国植物病理学会，明尼苏达州圣保罗，1996年。（2）A. J. Ferguson和S. N. Jeffers所著的《植物病害》83:1129，1999年。（3）T. Tomidis和T. Sotiropoulos所著的《新西兰作物与园艺科学杂志》31:355，2003年。（4）W. F. Wilcox和S. M. Mircetich所著的《植物病理学》75:1451，1985年。
