Curso de Pós Graduação em Ciências Veterinárias, Universidade Federal Rural do Rio de Janeiro, Seropédica, RJ 23890-000, Brazil.
Vet Parasitol. 2011 Dec 15;182(2-4):307-18. doi: 10.1016/j.vetpar.2011.05.046. Epub 2011 Jun 1.
Entomopathogenic fungi have been investigated worldwide as promising biological control agents of the cattle tick Rhipicephalus microplus. The current study evaluates the virulence of several fungal isolates to R. microplus larva in the laboratory as part of an effort to identify isolates with promise for effective biocontrol of R. microplus in the field. Sixty fungal isolates, encompassing 5 Beauveria spp. and 1 Engyodontium albus (=Beauveria alba), were included in this study. In addition to bioassays, the isolates were characterized morphologically and investigated as to their potential for conidial mass production. These findings were correlated with previous reports on the same fungal isolates of their natural UV-B tolerance (Fernandes et al., 2007), thermotolerance and cold activity (Fernandes et al., 2008), and genotypes (Fernandes et al., 2009). R. microplus larvae obtained from artificially infested calves were less susceptible to Beauveria bassiana infection than ticks acquired from naturally infested cattle from a different location. Isolates CG 464, CG 500 and CG 206 were among the most virulent Beauveria isolates tested in this study. All fungal isolates presented morphological features consistent with their species descriptions. Of the 53 B. bassiana isolates, five (CG 481, CG 484, CG 206, CG 235 and CG 487) had characteristics that qualified them as promising candidates for biological control agents of R. microplus, viz., mean LC(50) between 10(7) and 10(8)conidiaml(-1); produced 5000 conidia or more on 60mm(2) surface area of PDAY medium; and, in comparison to untreated (control) conidia, had the best conidial tolerances to UV-B (7.04 kJ m(-2)) and heat (45°C, 2h) of 50% or higher, and conidial cold (5°C, 15d) activity (mycelial growth) higher than 60%. The current study of 60 Beauveria spp. isolates, therefore, singles out a few (five) with high potential for controlling ticks under field conditions.
已在全球范围内研究了昆虫病原真菌，将其作为防治 cattle tick Rhipicephalus microplus 的有前途的生物防治剂。本研究评估了几种真菌分离物对 R. microplus 幼虫的毒力，作为鉴定对田间 R. microplus 具有有效生物防治潜力的分离物的一部分。本研究包括 60 种真菌分离物，包括 5 种 Beauveria spp. 和 1 种 Engyodontium albus (=Beauveria alba)。除了生物测定外，还对分离物进行了形态学特征描述，并研究了它们产生大量分生孢子的潜力。这些发现与之前关于同一真菌分离物的自然 UV-B 耐受性（Fernandes 等人，2007 年）、耐热性和耐寒性（Fernandes 等人，2008 年）以及基因型（Fernandes 等人，2009 年）的报告相关。从人工感染的小牛中获得的 R. microplus 幼虫比从不同地点自然感染的牛中获得的蜱虫更容易感染 Beauveria bassiana。在本研究中测试的最毒 Beauveria 分离物中，有 CG 464、CG 500 和 CG 206 等分离物。所有真菌分离物均具有与其种描述一致的形态特征。在 53 个 B. bassiana 分离物中，有 5 个（CG 481、CG 484、CG 206、CG 235 和 CG 487）具有作为 R. microplus 生物防治剂的有前途的候选物的特征，即 LC(50)均值在 10(7)和 10(8)conidiaml(-1)之间；在 PDAY 培养基 60mm(2)表面积上产生 5000 个分生孢子或更多；与未处理（对照）分生孢子相比，对 UV-B（7.04 kJ m(-2))和热（45°C，2h)的分生孢子耐受性为 50%或更高，对分生孢子耐寒性（5°C，15d)的活性（菌丝生长）高于 60%。因此，本研究对 60 个 Beauveria spp. 分离物进行了研究，从中挑选出了一些（5 个）具有在田间条件下控制蜱虫的高潜力的分离物。
