Chulze S N, Ramirez M L, Torres A, Leslie J F
Departamento de Microbiología e Inmunologia, Facultad de Ciencias Exactas Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, 5800 Río Cuarto, Córdoba, Argentina.
Appl Environ Microbiol. 2000 Dec;66(12):5312-5. doi: 10.1128/AEM.66.12.5312-5315.2000.
Strains of Fusarium species belonging to section Liseola cause stalk and ear rot of maize and produce important mycotoxins, such as fumonisins. We isolated two species, Fusarium verticillioides (Gibberella fujikuroi mating population A) and Fusarium proliferatum (G. fujikuroi mating population D) from maize cultivated under no-till conditions at five locations in the Córdoba province of Argentina. We determined the effective population number for mating population A (N(e)) and found that the N(e) for mating type was 89% of the count (total population) and that the N(e) for male or hermaphrodite status was 36%. Thus, the number of strains that can function as the female parent limits N(e), and sexual reproduction needs to occur only once every 54 to 220 asexual generations to maintain this level of sexual fertility. Our results indicate that the fungal populations isolated from no-till maize are similar to those recovered from maize managed with conventional tillage. We placed 36 strains from mating population A into 28 vegetative compatibility groups (VCGs). Of the 13 strains belonging to five multimember VCGs, only 2 isolates belonging to one VCG were clones based on amplified fragment length polymorphism (AFLP) fingerprints. Members of the other four multimember VCGs had an average similarity index of 0.89, and members of one VCG were no more closely related to other members of the same VCG than they were to other members of the population as a whole. This finding suggests that the common assumption that strains in the same VCG are either clonal or very closely related needs to be examined in more detail. The variability observed with AFLPs and VCGs suggests that sexual reproduction may occur more frequently than estimated by N(e).
镰孢菌属里氏组的菌株会引发玉米的茎腐病和穗腐病，并产生重要的霉菌毒素，如伏马毒素。我们从阿根廷科尔多瓦省五个地点免耕种植的玉米中分离出了两种镰刀菌，即轮枝镰孢菌（藤仓赤霉菌交配群体A）和层出镰孢菌（藤仓赤霉菌交配群体D）。我们确定了交配群体A的有效种群数量（N(e)），发现交配型的N(e)是计数（总种群）的89%，而雄性或雌雄同体状态的N(e)为36%。因此，能够作为母本发挥作用的菌株数量限制了N(e)，并且有性繁殖仅需每54至220个无性世代发生一次，就能维持这种有性繁殖能力水平。我们的结果表明，从免耕玉米中分离出的真菌种群与从传统耕作管理的玉米中回收的种群相似。我们将来自交配群体A的36个菌株归入28个营养体亲和群（VCG）。在属于五个多成员VCG的13个菌株中，基于扩增片段长度多态性（AFLP）指纹图谱，只有属于一个VCG的2个分离株是克隆体。其他四个多成员VCG的成员平均相似性指数为0.89，并且一个VCG的成员与同一VCG的其他成员之间的亲缘关系并不比它们与整个种群的其他成员之间的亲缘关系更密切。这一发现表明，关于同一VCG中的菌株要么是克隆体要么是密切相关的这一普遍假设需要更详细地研究。AFLP和VCG观察到的变异性表明，有性繁殖可能比N(e)估计的更频繁发生。
