Phytopathology. 2001 Feb;91(2):120-6. doi: 10.1094/PHYTO.2001.91.2.120.
ABSTRACT To investigate host specialization in Macrophomina phaseolina, the fungus was isolated from soybean, corn, sorghum, and cotton root tissue and soil from fields cropped continuously to these species for 15 years in St. Joseph, LA. Chlorate phenotype of each isolate was determined after growing on a minimal medium containing 120 mM potassium chlorate. Consistent differences in chlorate sensitivity were detected among isolates from different hosts and from soil versus root. To further explore genetic differentiation among fungal isolates from each host, these isolates were examined by restriction fragment length polymorphism and random amplified polymorphic DNA (RAPD) analysis. No variations were observed among isolates in restriction patterns of DNA fragments amplified by polymerase chain reaction covering the internal transcribed spacer region, 5.8S rRNA and part of 25S rRNA, suggesting that M. phaseolina constitutes a single species. Ten random primers were used to amplify the total DNA of 45 isolates, and banding patterns resulting from RAPD analysis were compared with the neighbor-joining method. Isolates from a given host were genetically similar to each other but distinctly different from those from other hosts. Chlorate-sensitive isolates were distinct from chlorate-resistant isolates within a given host. In greenhouse tests, soybean, sorghum, corn, and cotton were grown separately in soil infested with individual isolates of M. phaseolina that were chosen based on their host of origin and chlorate phenotype. Root colonization and plant weight were measured after harvesting. More colonization of corn roots occurred when corn was grown in soil containing corn isolates compared with isolates from other hosts. However, there was no host specialization in isolates from soybean, sorghum, or cotton. More root colonization in soybean occurred with chlorate-sensitive than with chlorate-resistant isolates.
为了研究 Macrophomina phaseolina 的宿主专化性，从路易斯安那州圣约瑟夫市连续种植大豆、玉米、高粱和棉花 15 年的田间采集大豆、玉米、高粱和棉花根组织和土壤，从中分离出该真菌。将每种分离株在含有 120mM 氯酸钾的最小培养基上生长后，确定其氯酸盐表型。从不同宿主和土壤与根分离出的分离株之间检测到氯酸盐敏感性的一致差异。为了进一步探索来自每个宿主的真菌分离株之间的遗传分化，用限制性片段长度多态性和随机扩增多态性 DNA（RAPD）分析对这些分离株进行了检查。用聚合酶链反应（PCR）扩增的 DNA 片段的限制图谱在覆盖内部转录间隔区、5.8S rRNA 和部分 25S rRNA 的区域内没有观察到不同分离株之间的变化，这表明 M. phaseolina 构成一个单一的物种。用 10 个随机引物扩增了来自 45 个分离株的总 DNA，并用 RAPD 分析比较了产生的带型与邻接法。来自给定宿主的分离株彼此之间在遗传上相似，但与其他宿主的分离株明显不同。在给定宿主内，氯酸盐敏感的分离株与氯酸盐抗性的分离株明显不同。在温室试验中，将单独生长在含有根据其来源宿主和氯酸盐表型选择的单个 M. phaseolina 分离株的土壤中的大豆、高粱、玉米和棉花种植在土壤中。收获后测量根的定殖和植物重量。与来自其他宿主的分离株相比，当玉米在含有玉米分离株的土壤中生长时，玉米根的定殖更多。然而，在来自大豆、高粱或棉花的分离株中没有宿主专化性。与氯酸盐抗性分离株相比，氯酸盐敏感的分离株在大豆中具有更多的根定殖。
