种间竞争梯度对白车轴草与其病原菌白车轴草单孢锈菌相互作用的影响(英文)

EFFECTS OF AN INTERSPECIFIC COMPETITION GRADIENT ON THE INTERACTIONS BETWEEN TRIFOLIUM REPENS AND ITS PATHOGENIC RUST FUNGUS UROMYCES TRIFOLII-REPENTIS

白车轴草 (Trifolium repens)在与其病原菌白车轴草单孢锈菌 (Uromyces trifolii- repentis)的长期相互作用中分化形成了抗病型 (Resistance)无性系和易感型 (Susceptibility)无性系。该研究工作旨在了解 :1)在种间竞争不断增强的环境梯度中 ,抗病型无性系和易感型无性系的生长表现有何区别 ?2 )在同样的实验条件下 ,分别对抗病型无性系和易感型无性系进行接种感染后 ,两者的生长表现又有何区别 ?在一严重感病的白车轴草自然种群中 ,分别标定 17个抗病型无性系和 14个易感型无性系 ,从各无性系的匍匐茎上分别剪取长 5 cm ,具两个叶两个腋芽的小段作实验材料。接种孢子采自同一植物种群植株的病叶。实验在一个处在次生演替阶段的草本植物群落上进行 ,在该群落的种间竞争梯度上选定 3个分别具有弱、中等和强种间竞争的生境 (Habitat)建立实验站 ,每站设置等量的实验组和对照组。结果显示 :1)随着环境中种间竞争强度的增加 ,无论接种与否 ,抗病型和易感型白车轴草的叶生长量均递减 ;2 )在弱或强种间竞争环境条件下 ,无论接种与否 ,易感型无性系的生长均好于抗病型无性系 ;但在中等种间竞争强度的环境条件下 ,对照实验中易感型无性系的生长显著好于抗病型无性系 ,而接种实验中的结果相反。

In the long term interactions with its pathogenic rust fungus Uromyces trifolii repentis, Trifolium repens has evolved two genotypes of clones: resistant and susceptible clones. Two questions were addressed in this study. Firstly, whether the susceptible and resistant Trifolium repens clones differed in growth over an environmental gradient of increasing interspecific competition. Secondly, whether the susceptible and resistant T. repens clones differed in their response in the presence of the macrocyclic rust fungus Uromyces trifolii repentis. In a natural, heavily rusted population of T. repens , 17 of the resistant clones and 14 of the susceptible ones were identified; stolon cuttings, 5 cm in length, each with 2 leaves and 2 axillary buds, were taken for the experiments. The spores for inoculation experiment were collected in the same host population as above. The experiments were conducted in a meadow in secondary succession. The cuttings were planted in three habitats in a gradient of increasing interspecific competition, representing low, intermediate and high interspecific competition, respectively. In each of these three habitats, half of the experimental stations were inoculated with the rust spore, the remaining as controls. The experiments exhibit that T. repens had showed decreased leaf production with increasing interspecific competition, for both resistant and susceptible plants, independent of the rust. Susceptible clones produced more leaves than resistant ones, both in the controls and in the inoculation treatments, and both under low and high competition. However, in the habitat with intermediate competition, the susceptible clones showed a drastic decline in the presence of the rust and produced fewer leaves than did the resistant ones. The results show that interspecific competition may be one important factor contributing to influence the proportion of susceptible and resistant genotypes in a given habitat. This proportion is likely to change depending upon whether the pathogen is present or not.