Phytopathology. 2001 May;91(5):449-56. doi: 10.1094/PHYTO.2001.91.5.449.
ABSTRACT Histochemical staining, beta-glucuronidase (GUS) activity, or placing roots on agar were methods used to characterize interactions between the pathogenic fungus, Fusarium oxysporum f. sp. lycopersici, and the nonpathogenic biocontrol F. oxysporum strain 70T01 with respect to colonization behaviors, interaction sites, and population densities on tomato roots. Mycelia of strain 70T01, a genetic transformant expressing stable GUS activity, hygromycin B resistance, and effective disease control, were localized in epidermal and cortex cell layers of tomato roots in a discontinuous and uneven pattern. In contrast, mycelia of F. oxysporum f. sp. lycopersici were found in the vascular bundles. Thus, direct interactions between the two fungi likely happen in the root surface cell layers. Colonization density of strain 70T01 was related to the inoculation density but decreased with distance from the inoculation site. Host defense reactions, including increased cell wall thickness or papilla deposits, were adjacent to 70T01 hyphae. Experiments done in soil showed that strain 70T01 densities in roots were highest at inoculation zones and barely detectable for root segments more than 2 cm away from the inoculation sites. F. oxysporum f. sp. lycopersici densities were lowest at 70T01 inoculation zones and highest (>10 times) where strain 70T01 was not directly applied. Newly elongating roots where strain 70T01 did not reach were available for infection by the pathogen. The higher strain 70T01 density was always found when the plants were simultaneously infected by F. oxysporum f. sp. lycopersici, suggesting that F. oxysporum f. sp. lycopersici has as much influence in predisposing the plant to colonization by strain 70T01 as strain 70T01 has on providing disease protection against the pathogen.
摘要 组织化学染色、β-葡萄糖醛酸酶（GUS）活性或根在琼脂上的放置是用于描述致病真菌尖孢镰刀菌番茄专化型（Fusarium oxysporum f. sp. lycopersici）与非致病性生物防治菌株 F. oxysporum 70T01 之间相互作用的方法，这些相互作用涉及定殖行为、相互作用位点和番茄根上的种群密度。遗传转化体 70T01 表达稳定的 GUS 活性、潮霉素 B 抗性和有效的疾病控制，其菌丝体在番茄根的表皮和皮层细胞层中呈现不连续和不均匀的模式定位。相比之下，尖孢镰刀菌番茄专化型的菌丝体存在于维管束中。因此，两种真菌之间的直接相互作用可能发生在根表面细胞层。70T01 菌株的定殖密度与接种密度有关，但随着与接种点距离的增加而降低。宿主防御反应，包括细胞壁厚度增加或乳突沉积物，与 70T01 菌丝体相邻。在土壤中进行的实验表明，70T01 菌株在根中的密度在接种区最高，在距接种点 2 厘米以上的根段几乎检测不到。尖孢镰刀菌番茄专化型的密度在 70T01 接种区最低，在 70T01 未直接应用的地方最高（超过 10 倍）。新伸长的根为病原体提供了感染的机会，而 70T01 菌株尚未到达这些根。当植物同时受到尖孢镰刀菌番茄专化型和 70T01 菌株感染时，总是发现 70T01 菌株的密度更高，这表明尖孢镰刀菌番茄专化型对植物易受 70T01 菌株定殖的影响与 70T01 菌株对病原体提供疾病保护的影响一样大。
