Rangel Drauzio E N, Braga Gilberto U L, Fernandes Éverton K K, Keyser Chad A, Hallsworth John E, Roberts Donald W
Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraíba, São José dos Campos, SP, 12244-000, Brazil,
Curr Genet. 2015 Aug;61(3):383-404. doi: 10.1007/s00294-015-0477-y. Epub 2015 Mar 20.
The virulence to insects and tolerance to heat and UV-B radiation of conidia of entomopathogenic fungi are greatly influenced by physical, chemical, and nutritional conditions during mycelial growth. This is evidenced, for example, by the stress phenotypes of Metarhizium robertsii produced on various substrates. Conidia from minimal medium (Czapek's medium without sucrose), complex medium, and insect (Lepidoptera and Coleoptera) cadavers had high, moderate, and poor tolerance to UV-B radiation, respectively. Furthermore, conidia from minimal medium germinated faster and had increased heat tolerance and were more virulent to insects than those from complex medium. Low water-activity or alkaline culture conditions also resulted in production of conidia with high tolerance to heat or UV-B radiation. Conidia produced on complex media exhibited lower stress tolerance, whereas those from complex media supplemented with NaCl or KCl (to reduce water activity) were more tolerant to heat and UV-B than those from the unmodified complex medium. Osmotic and nutritive stresses resulted in production of conidia with a robust stress phenotype, but also were associated with low conidial yield. Physical conditions such as growth under illumination, hypoxic conditions, and heat shock before conidial production also induced both higher UV-B and heat tolerance; but conidial production was not decreased. In conclusion, physical and chemical parameters, as well as nutrition source, can induce great variability in conidial tolerance to stress for entomopathogenic fungi. Implications are discussed in relation to the ecology of entomopathogenic fungi in the field, and to their use for biological control. This review will cover recent technologies on improving stress tolerance of entomopathogenic fungi for biological control of insects.
昆虫病原真菌分生孢子对昆虫的毒力以及对热和UV-B辐射的耐受性在菌丝体生长期间受到物理、化学和营养条件的极大影响。例如，在各种基质上产生的罗伯茨绿僵菌的应激表型就证明了这一点。来自基本培养基（不含蔗糖的察氏培养基）、复合培养基和昆虫（鳞翅目和鞘翅目）尸体的分生孢子分别对UV-B辐射具有高、中、低耐受性。此外，来自基本培养基的分生孢子萌发更快，耐热性增强，对昆虫的毒力也比来自复合培养基的分生孢子更强。低水分活度或碱性培养条件也导致产生对热或UV-B辐射具有高耐受性的分生孢子。在复合培养基上产生的分生孢子表现出较低的应激耐受性，而添加了NaCl或KCl（以降低水分活度）的复合培养基产生的分生孢子比未改良的复合培养基产生的分生孢子对热和UV-B更具耐受性。渗透和营养胁迫导致产生具有强大应激表型的分生孢子，但也与分生孢子产量低有关。诸如在光照下生长、低氧条件以及分生孢子产生前的热激等物理条件也诱导了更高的UV-B和耐热性；但分生孢子产量并未降低。总之，物理和化学参数以及营养来源可导致昆虫病原真菌分生孢子对胁迫的耐受性产生很大差异。文中讨论了这对于昆虫病原真菌在田间的生态学及其用于生物防治的意义。本综述将涵盖用于提高昆虫病原真菌对昆虫进行生物防治的胁迫耐受性的最新技术。
