Elmhirst J F, Hudgins E J
Elmhirst Diagnostics and Research, 5727 Riverside Street, Abbotsford, British Columbia, V4X 1T6, Canada.
British Columbia Ministry of Agriculture, Food and Fisheries, 1767 Angus Campbell Road, Abbotsford, British Columbia, V3G 2M3, Canada.
Plant Dis. 2003 Jun;87(6):751. doi: 10.1094/PDIS.2003.87.6.751A.
In 2001, a stem canker and dieback associated with a Colletotrichum sp. was observed on Gaultheria procumbens L. (wintergreen) seedlings grown from seed in soilless potting mix at four commercial nurseries in coastal British Columbia, Canada. Black, water-soaked lesions developed into tan cankers girdling stems and petioles, and a black rot extended into the base of leaves. In 2002, a Colletotrichum sp. was isolated from similar stem cankers from wintergreen plants. One flat of healthy, 13-week-old seedlings of G. procumbens (one- to three-leaf stage; approximately 380 seedlings per flat) was inoculated with a mycelial and spore suspension of one of the Colletotrichum sp. isolates at 10 CFU/ml using a hand atomizer. The flat was covered with black plastic for 24 h after inoculation and maintained in a growth chamber at 22°C with overhead watering. After 7 days, 98% of seedlings in the inoculated flat were necrotic with abundant sporulation of the Colletotrichum fungus on stem and petiole lesions. Plants in noninoculated flats remained healthy. Reisolation of the fungus from symptomatic tissues confirmed the causal agent to be Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz, based on morphology (1,2) and polymerase chain reaction (PCR) using the species-specific primer CgInt (3). Cylindrical, hyaline, aseptate conidia measuring 16 to 20 × 4 to 6 μm were produced in acervuli with setae. Perithecia of the teleomorph, Glomerella cingulata, observed on the plants and in culture, measured 100 to 128 μm in diameter and contained acsi measuring 56 to 60 × 8 to 10 μm. Ascospores were hyaline, unicellular, slightly curved, and measured 18 to 20 × 4 to 6 μm. Subsequently, a single-spore isolate of the fungus was used to inoculate 21-week-old seedlings in the greenhouse as described above. Four inoculated and four noninoculated half-flats containing an average of 160 seedlings each were randomized on the greenhouse bench and maintained at 22°C with daily overhead misting. Stem and petiole cankers appeared on 65.1% of inoculated seedlings at 10 days after inoculation (mean of four inoculated half-flats); increasing to 90.5% at 14 days. At 14 days, 5.9% of seedlings in four noninoculated half-flats were also symptomatic, possibly from spore contamination as a result of overhead watering. To our knowledge, this is the first confirmation of the causal agent of wintergreen seedling death in seed propagation nurseries in British Columbia. References: (1) J. E. M. Mordue. Glomerella cingulata. No. 315 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1971. (2) B. C. Sutton. The Coelomycetes. CAB International Publishing, New York, 1980. (3) P. Talhinhas et al. Phytopathology 92:986, 2002.
2001年，在加拿大不列颠哥伦比亚省沿海地区的四个商业苗圃中，人们在以无土盆栽介质播种培育的平铺白珠树（冬绿树）幼苗上，观察到一种与炭疽菌属真菌有关的茎干溃疡和枯死症状。黑色、水渍状病斑发展成环绕茎干和叶柄的棕褐色溃疡，黑色腐烂蔓延至叶片基部。2002年，从患有类似茎干溃疡的平铺白珠树植株上分离出一种炭疽菌属真菌。选取一平板健康的、13周龄的平铺白珠树幼苗（处于一叶至三叶期；每平板约380株幼苗），使用手动喷雾器，以10 CFU/ml的浓度接种其中一种炭疽菌属真菌分离株的菌丝体和孢子悬浮液。接种后，平板用黑色塑料覆盖24小时，并置于22°C的生长室中，顶部浇水养护。7天后，接种平板中98%的幼苗坏死，茎干和叶柄病斑上有大量炭疽菌真菌孢子形成。未接种平板中的植株保持健康。从有症状组织中再次分离出该真菌，基于形态学（1,2）以及使用物种特异性引物CgInt进行的聚合酶链反应（PCR）（3），确认病原菌为盘长孢炭疽菌（Penz.）Penz. & Sacc. in Penz。在分生孢子盘中产生圆柱形、透明、无隔膜的分生孢子，大小为16至20×4至6μm，伴有刚毛。在植株上和培养物中观察到的有性型围小丛壳菌子囊壳直径为100至128μm，包含大小为56至60×8至10μm的子囊孢子。子囊孢子透明、单细胞、略弯曲，大小为18至20×4至6μm。随后，如上述方法，使用该真菌的单孢分离株对温室中21周龄的幼苗进行接种。四个接种的半平板和四个未接种的半平板，每个半平板平均含有160株幼苗，随机放置在温室苗床上，保持在22°C，每天顶部喷雾。接种后10天，接种幼苗中有65.1%出现茎干和叶柄溃疡（四个接种半平板的平均值）；14天时增至90.5%。14天时，四个未接种半平板中的5.9%的幼苗也出现症状，可能是由于顶部浇水导致的孢子污染。据我们所知，这是不列颠哥伦比亚省种子繁殖苗圃中平铺白珠树幼苗死亡病原菌的首次确认。参考文献：（1）J. E. M. Mordue。围小丛壳菌。载于《病原真菌和细菌描述》第315号。英联邦真菌研究所，英国邱园，萨里，1971年。（2）B. C. Sutton。腔孢纲真菌。CAB国际出版社，纽约，1980年。（3）P. Talhinhas等人。植物病理学92:986，2002年。
