Abstract Armillaria root disease causes growth reduction and mortality in forest trees and agricultural plants. Root colonization is poorly documented but important for predicting interactions with environmental factors and disease spread. Nine planted and one older naturally regenerated Douglas fir (Pseudotsuga menziesii) sites were identified for sampling. Tree roots were pulled out of the soil, cleaned, and inspected for lesions arising from Armillaria root disease. A total of 1097 root systems were measured for host reaction, lesion type, age of infection, and size of the roots and stems. Callus tissue indicated successful lesion containment, and most lesions callused within five years. Patch lesions, girdled root lesions, or collar lesions on the lower stem differed in callus rates. In planted sites, girdled roots had the lowest callus rate coinciding with lack of induced bark hypertrophy ahead of lesions. Bark hypertrophy was more prevalent on smaller diameter roots and infection probably induced the phellogen to create more inner and outer bark, while older roots or stems had thicker bark initially. In planted trees, lower callus rate was also associated with longer growing season. In an older natural stand, induced bark hypertrophy was rare and without effect on callus formation. Callus rate was lowered with increasing infection intensity of the root system and with collar lesions. In both stand types, the main effect of tree age was increased callus rate, and for larger tree size it was lower callus rate. The study represents a macro examination of root lesions that affect the ability of trees to survive and grow or die.

中文翻译：

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种植和自然花旗松树根感染蜜环菌根病的反应：病斑类型、愈伤组织时间、感染时间以及部位和环境因素对病斑形成的影响。

摘要 蜜环菌根病导致林木和农业植物生长减慢和死亡。根系定植的记录很少，但对于预测与环境因素和疾病传播的相互作用很重要。确定了 9 个种植的和一个较老的自然再生花旗松 (Pseudotsuga menziesii) 地点进行采样。将树根从土壤中拔出、清洗并检查是否有蜜环菌根病引起的病灶。总共测量了 1097 个根系的宿主反应、病变类型、感染年龄以及根和茎的大小。愈伤组织表明病灶控制成功，大多数病灶在五年内愈合。下部茎上的斑块病灶、带状根病灶或项圈病灶的愈伤组织率不同。在种植地点，带环根的愈伤组织率最低，这与损伤前缺乏诱导的树皮肥大相吻合。树皮肥大在直径较小的根上更为普遍，感染可能会诱导腐生菌产生更多的内部和外部树皮，而较老的根或茎最初具有更厚的树皮。在种植的树木中，较低的愈伤组织率也与较长的生长季节有关。在较老的自然林分中，诱发的树皮肥大很少见，而且对愈伤组织的形成没有影响。愈伤组织率随着根系感染强度的增加和颈圈病变而降低。在两种林分类型中，树龄的主要影响是愈伤组织率增加，而对于较大的树而言，愈伤组织率较低。该研究代表了对影响树木生存和生长或死亡能力的根部病变的宏观检查。