Ching'anda Connel, Atehnkeng Joseph, Bandyopadhyay Ranajit, Callicott Kenneth A, Orbach Marc J, Mehl Hillary L, Cotty Peter J
School of Plant Sciences, University of Arizona, Tucson, AZ, United States.
International Institute of Tropical Agriculture (IITA), Lilongwe, Malawi.
Front Fungal Biol. 2021 Aug 26;2:720276. doi: 10.3389/ffunb.2021.720276. eCollection 2021.
Fungal species within section contaminate food and feed with aflatoxins. These toxic fungal metabolites compromise human and animal health and disrupt trade. Genotypically and phenotypically diverse species co-infect crops, but temporal and spatial variation in frequencies of different lineages suggests that environmental factors such as temperature may influence structure of aflatoxin-producing fungal communities. Furthermore, though most species within section produce sclerotia, divergent sclerotial morphologies (small or S-type sclerotia vs. large or L-type sclerotia) and differences in types and quantities of aflatoxins produced suggest lineages are adapted to different life strategies. Temperature is a key parameter influencing pre- and post-harvest aflatoxin contamination of crops. We tested the hypothesis that species of aflatoxin-producing fungi that differ in sclerotial morphology will vary in competitive ability and that outcomes of competition and aflatoxin production will be modulated by temperature. Paired competition experiments between highly aflatoxigenic S-type species ( and Lethal Aflatoxicosis Fungus) and L-type species ( L morphotype and ) were conducted on maize kernels at 25 and 30°C. Proportions of each isolate growing within and sporulating on kernels were measured using quantitative pyrosequencing. At 30°C, S-type fungi were more effective at host colonization compared to L-type isolates. Total aflatoxins and the proportion of B vs. G aflatoxins were greater at 30°C compared to 25°C. Sporulation by L-type isolates was reduced during competition with S-type fungi at 30°C, while relative quantities of conidia produced by S-type species either increased or did not change during competition. Results indicate that both species interactions and temperature can shape population structure of section , with warmer temperatures favoring growth and dispersal of highly toxigenic species with S-type sclerotia.
该部分的真菌物种会用黄曲霉毒素污染食物和饲料。这些有毒的真菌代谢产物会损害人类和动物健康并扰乱贸易。在基因型和表型上具有多样性的物种会共同感染作物，但不同谱系频率的时空变化表明，诸如温度等环境因素可能会影响产黄曲霉毒素真菌群落的结构。此外，尽管该部分的大多数物种都会产生菌核，但不同的菌核形态（小型或S型菌核与大型或L型菌核）以及所产黄曲霉毒素的类型和数量差异表明，各谱系适应不同的生活策略。温度是影响作物收获前和收获后黄曲霉毒素污染的关键参数。我们测试了这样一个假设：菌核形态不同的产黄曲霉毒素真菌物种在竞争能力上会有所不同，并且竞争结果和黄曲霉毒素产生会受到温度的调节。在25℃和30℃下，对高黄曲霉毒素产毒S型物种（和致死性黄曲霉毒素中毒真菌）与L型物种（L形态型和）进行了配对竞争实验，实验对象为玉米粒。使用定量焦磷酸测序法测量了每个分离株在玉米粒内生长和产孢的比例。在30℃时，与L型分离株相比，S型真菌在宿主定殖方面更有效。与25℃相比，30℃时总黄曲霉毒素以及B型与G型黄曲霉毒素的比例更高。在30℃与S型真菌竞争期间，L型分离株的产孢减少，而S型物种产生的分生孢子相对数量在竞争期间要么增加要么不变。结果表明，物种相互作用和温度都可以塑造该部分的种群结构，温度升高有利于具有S型菌核的高毒性物种的生长和扩散。
