Phytopathology. 1998 Sep;88(9):930-8. doi: 10.1094/PHYTO.1998.88.9.930.
ABSTRACT Systematic studies were conducted to elucidate the role of different soil microbial groups in the development of apple replant disease. Populations of targeted microorganisms were reduced by the application of semiselective biocides and soil pasteurization. Bacteria were not implicated in the disease, because application of the antibiotic chloramphenicol reduced soil populations of bacteria but failed to improve growth of apple transplants, while enhanced growth was achieved at pasteurization temperatures that did not alter attributes of the bacterial community recovered from apple roots. Populations of Pratylenchus penetrans were below the damage threshold level in eight of nine orchards surveyed, and nematicide applications failed to enhance apple growth in four of five replant soils tested, indicating that plant parasitic nematodes have a minor role or no role in disease development. Application of the fungicide difenconazole or metalaxyl enhanced growth of apple in all five replant soils, as did fludioxinil in the two soils tested. Soil pasteurization enhanced growth of apple and resulted in specific changes in the composition of the fungal community isolated from the roots of apple seedlings grown in these treated soils. Cylindrocarpon destructans, Phytophthora cactorum, Pythium spp., and Rhizoctonia solani were consistently isolated from symptomatic trees in the field and were pathogenic to apple. However, the composition of the Pythium and Rhizoctonia component and the relative contribution of any one component of this fungal complex to disease development varied among the study orchards. These findings clearly demonstrate that fungi are the dominant causal agents of apple replant disease in Washington state.
为了阐明不同土壤微生物群体在苹果再植病发展中的作用，进行了系统研究。通过应用半选择性杀菌剂和土壤巴氏灭菌来减少目标微生物的种群。细菌与疾病无关，因为应用抗生素氯霉素减少了土壤中细菌的数量，但未能改善苹果移植的生长，而在巴氏灭菌温度下，细菌群落的属性不会改变，从苹果根系中恢复的细菌群落增强了生长。在所调查的 9 个果园中的 8 个中，Pratylenchus penetrans 的种群数量低于损害阈值水平，杀线虫剂的应用未能在 5 个再植土壤中的 4 个中增强苹果的生长，这表明植物寄生线虫在疾病发展中作用较小或没有作用。杀菌剂二苯醚菌酯或甲霜灵在所有 5 个再植土壤中增强了苹果的生长，氟啶菌胺在测试的 2 个土壤中也增强了苹果的生长。土壤巴氏灭菌增强了苹果的生长，并导致从在这些处理土壤中生长的苹果幼苗根部分离的真菌群落的组成发生特定变化。旋孢腔菌（Cylindrocarpon destructans）、番茄溃疡病菌（Phytophthora cactorum）、腐霉属（Pythium spp.）和立枯丝核菌（Rhizoctonia solani）从田间感病的树上一致分离出来，并对苹果具有致病性。然而，腐霉属和立枯丝核菌的组成以及该真菌复合体的任何一个组成部分对疾病发展的相对贡献在研究果园中各不相同。这些发现清楚地表明，真菌是华盛顿州苹果再植病的主要致病因子。
