Phytopathology. 2005 Dec;95(12):1381-90. doi: 10.1094/PHYTO-95-1381.
ABSTRACT The fungus Cylindrocarpon destructans (Zins) Scholten is the cause of root rot (disappearing root rot) in many ginseng production areas in Canada. A total of 80 isolates of C. destructans were recovered from diseased roots in a survey of ginseng gardens in British Columbia from 2002-2004. Among these isolates, 49% were classified as highly virulent (causing lesions on unwounded mature roots) and 51% were weakly virulent (causing lesions only on previously wounded roots). Pectinase and polyphenoloxidase enzymes were produced in vitro by C. destructans isolates when they were grown on pectin and phenol as a substrate, respectively. However, highly virulent isolates produced significantly (P < 0.001) higher enzyme levels compared with weakly virulent isolates. Histopathological studies of ginseng roots inoculated with a highly virulent isolate revealed direct hyphal penetration through the epidermis, followed by intracellular hyphal growth in the cortex. Subsequent cell disintegration and accumulation of phenolic compounds was observed. Radial growth of highly and weakly virulent isolates on potato dextrose agar was highest at 18 and 21 degrees C, respectively and there was no growth at 35 degrees C. Mycelial mass production was significantly (P </= 0.01) lower at pH 7.0 compared with pH 5.0. To study the effects of pH (5.0 and 7.0) and wounding on disease development, ginseng roots were grown hydroponically in Hoagland's solution. Lesions were significantly larger (P < 0.001) at pH 5.0 compared with pH 7.0 and wounding enhanced disease by a highly virulent isolate at both pHs. In artificially infested soil, 2-year-old ginseng roots were most susceptible to Cylindrocarpon root rot among all root ages tested (1 to 4 years) when evaluated using a combined scale of disease incidence and severity. Root rot severity was significantly (P < 0.002) enhanced by increasing the inoculum density from 3.45 x 10(2) CFU/g of soil to 1.86 x 10(3) CFU/g of soil. Disease severity was higher at 20 degrees C compared with 15 and 25 degrees C and at -0.02 MPa soil moisture compared with -0.005 and -0.001 MPa. A significant interaction between soil moisture and temperature was observed for root rot severity.
摘要 真菌 Cylindrocarpon destructans (Zins) Scholten 是导致加拿大许多人参生产区发生烂根病（消失根腐病）的原因。2002-2004 年，在不列颠哥伦比亚人参园的调查中，从患病根部共回收了 80 株 C. destructans 分离株。这些分离株中，49%为高毒力（引起未受伤成熟根的病变），51%为弱毒力（仅引起先前受伤根的病变）。当 C. destructans 分离株在果胶和苯酚作为底物上生长时，果胶酶和多酚氧化酶在体外产生。然而，高毒力分离株产生的酶水平明显（P < 0.001）高于弱毒力分离株。用高毒力分离株接种人参根的组织病理学研究表明，菌丝直接穿透表皮，随后在皮层内进行细胞内菌丝生长。随后观察到细胞解体和酚类化合物的积累。高毒力和弱毒力分离株在马铃薯葡萄糖琼脂上的径向生长在 18 和 21°C 时最高，而在 35°C 时则没有生长。在 pH 值为 7.0 时，与 pH 值为 5.0 时相比，菌丝体质量的产生明显（P </= 0.01）较低。为了研究 pH 值（5.0 和 7.0）和创伤对疾病发展的影响，人参根在 Hoagland 溶液中进行水培生长。与 pH 值为 7.0 相比，pH 值为 5.0 时病变明显更大（P < 0.001），在两种 pH 值下，创伤都会增强高毒力分离株的疾病。在人工侵染土壤中，2 年生人参根在所有测试根龄（1 至 4 年）中对 Cylindrocarpon 根腐病最敏感，使用发病率和严重程度的综合量表进行评估。与 15 和 25°C 相比，在 20°C 时，与 -0.005 和 -0.001 MPa 土壤水分相比，在 -0.02 MPa 土壤水分时，根腐病的严重程度更高。在土壤水分和温度之间观察到显著的相互作用，对根腐病的严重程度有影响。
