Frozen section and electron microscopy studies of the infection of the red palm weevil, Rhynchophorus ferrugineus (coleoptera:curculionidae) by the entomopathogenic fungus Metarhizium anisopliae
Sun et al. SpringerPlus
Frozen section and electron microscopy studies of the infection of the red palm weevil, Rhynchophorus ferrugineus (coleoptera:curculionidae) by the entomopathogenic fungus Metarhizium anisopliae
Xiaodong Sun 0 2 3
Wei Yan 0 3
Jing Zhang 0 3
Xiaoqing Niu 0 3
Fuheng Li 2
Weiquan Qin 0 3
Guangchang Ma 1
0 Hainan Key Laboratory of Tropical Oil Crops Biology/Coconuts Research Institute, Chinese Academy of Tropical Agricultural Sciences , Wenchang 571339, Hainan , People's Republic of China
1 Environment and Plant protection Research Institute, Chinese Academy of Tropical Agricultural Sciences , Haikou 571101, Hainan , People's Republic of China
2 College of Science, Northeast Agricultural University , Harbin 150030, Heilongjiang Province , People's Republic of China
3 Hainan Key Laboratory of Tropical Oil Crops Biology/Coconuts Research Insti- tute, Chinese Academy of Tropical Agricultural Sciences , Wenchang 571339, Hainan , People's Republic of China
This study determined the pathogenicity of Metarhizium anisopliae strain SD-3 against invasive red palm weevil (RPW), Rhynchophorus ferrugineus Olivier (coleoptera:curculionidae) larvae in Hainan Province, China. Inoculation of 1 × 108 conidia/mL caused 100 % mortality of R. ferrugineus, indicating that the conidia of strain SD-3 were highly virulent. The process of invasion mechanism was showed by scanning electron microscopy (SEM) and frozen section as follows. Once R. ferrugineus was infected by strain SD-3, M. anisopliae hyphae first invaded the cuticular and body cavity of R. ferrugineus. Secondly, well-developed muscles, fat, tracheaes and digestive tube tissues in the abdomen of R. ferrugineus were then decomposed and absorbed by M. anisopliae hyphae, leading to the total destruction of the larvae. Finally, M. anisopliae hyphae reproduced, resulting in a large number of conidia in the body of RPW. The SEM and frozen section are convenient tools to observe the mode of action of entomopathogenic fungi and to observe how M. anisopliae is able to colonize and infect the host.
Metarhizium anisopliae; Rhynchophorus ferrugineus; Frozen section; Electron microscopy studies
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Invasive red palm weevil (RPW), Rhynchophorus
ferrugineus Olivier (coleoptera:curculionidae), is an important
pests of a world range of palms of economic importance
(Faleiro 2006). R. ferrugineus was originally reported in
India, while now has been widely distributed in Asia,
Africa, Australian (Fiaboe 2012; Kehat 1999; Mankin
2009). In China, R. ferrugineus is considered as a
quarantine pest, and it has been found in 19 species of 15 palm
genera (Dembilio et al. 2009). According to international
standards for pest measurements (ISPM). This indicates
R. ferrugineus can easily settle down in China, where it
potentially poses a great threat to palm trees (Wu et al.
2007).
According to IPM strategy, several control methods
have been used to R. ferrugineus invasion of palms, These
methods include, cutting down and burning infected
palms, trapping adult R. ferrugineus, chemical control,
host plant resistance, bacteria control, viruses control,
nematodes mites control, parasitoid and predator insects,
male sterile techniques and so on (Faleiro 2006; Francardi
et al. 2013). Beside these, a number of
entomopathogenic fungi (Metarhizium anisopliae, Beauveri bassiana,
Aspergillus sp., Trichothecium sp., Penicillium sp.,
Fusarium sp.) isolated from naturally infected R. ferrugineus
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as a biological control agent against this weevil (Ghazavi
and Avand-Faghih 2002; Gindin et al. 2006; Dembilio
et al. 2010; Güerri-Agulló et al. 2011; Francardi et al.
2013), Metarhizium anisopliae is one of the most
commonly studied species of entomopathogenic fungi, it is
environmentally-friendly and harmless to human.
However, M. anisopliae was discovered in naturally infected
R. ferrugineus in Egypt and this strain caused a high
mortality rate for larval and adult stages only under
laboratory conditions (Merghem 2011; Cito et al. 2014).
Despite investigations of infection patterns and
histopathology of M. anisopliae in selected insects is of
economic importance, less study has documented the
histopathology of M. anisopliae in R. ferrugineus (Toledo
et al. 2010). Moreover, as the R. ferrugineus is highly
promiscuous and adults live in aggregation, the fungi could
spread in the population, infecting healthy insects by
horizontal transmission, as suggested also by Llácer et al.
(2013) and Francardi et al. (2013).
Scanning electron microscopy (SEM) has
frequently been used to evaluat (...truncated)