Virulence of the insect-pathogenic fungi Metarhizium spp. to Mormon crickets, Anabrus simplex (Orthoptera: Tettigoniidae)

Abstract The Mormon cricket (MC), Anabrus simplex Haldeman, 1852 (Orthoptera: Tettigoniidae), has a long and negative history with agriculture in Utah and other western states of the USA. Most A. simplex populations migrate in large groups, and their feeding can cause significant damage to forage plants and cultivated crops. Chemical pesticides are often applied, but some settings (e.g. habitats of threatened and endangered species) call for non-chemical control measures. Studies in Africa, South America, and Australia have assessed certain isolates of Metarhizium acridum as very promising pathogens for Orthoptera: Acrididae (locust) biocontrol. In the current study, two isolates of Metarhizium robertsii, one isolate of Metarhizium brunneum, one isolate of Metarhizium guizhouense, and three isolates of M. acridum were tested for infectivity to MC nymphs and adults of either sex. Based on the speed of mortality, M. robertsii (ARSEF 23 and ARSEF 2575) and M. brunneum (ARSEF 7711) were the most virulent to instars 2 to 5 MC nymphs. M. guizhouense (ARSEF 7847) from Arizona was intermediate and the M. acridum isolates (ARSEF 324, 3341, and 3609) were the slowest killers. ARSEF 2575 was also the most virulent to instar 6 and 7 nymphs and adults of MC. All of the isolates at the conidial concentration of 1 × 107 conidia ml−1 induced approximately 100% mortality by 6 days post application of fungal conidia. In conclusion, isolates ARSEF 23, ARSEF 2575, and ARSEF 7711 acted most rapidly to kill MC under laboratory conditions. The M. acridum isolates, however, have much higher tolerance to heat and UV-B radiation, which may be critical to their successful use in field application.

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Ubiquity of Insect-Derived Nitrogen Transfer to Plants by Endophytic Insect-Pathogenic Fungi: an Additional Branch of the Soil Nitrogen Cycle

Applied and Environmental Microbiology ◽

10.1128/aem.03338-13 ◽

2013 ◽

Vol 80 (5) ◽

pp. 1553-1560 ◽

Cited By ~ 88

Author(s):

Scott W. Behie ◽

Michael J. Bidochka

Keyword(s):

Panicum Virgatum ◽

Pathogenic Fungus ◽

Insect Herbivory ◽

Pathogenic Fungi ◽

Nitrogen Transfer ◽

Metarhizium Robertsii ◽

Content Type ◽

Lecanicillium Lecanii ◽

Worldwide Distribution ◽

Insect Pathogenic Fungi

ABSTRACTThe study of symbiotic nitrogen transfer in soil has largely focused on nitrogen-fixing bacteria. Vascular plants can lose a substantial amount of their nitrogen through insect herbivory. Previously, we showed that plants were able to reacquire nitrogen from insects through a partnership with the endophytic, insect-pathogenic fungusMetarhizium robertsii. That is, the endophytic capability and insect pathogenicity ofM. robertsiiare coupled so that the fungus acts as a conduit to provide insect-derived nitrogen to plant hosts. Here, we assess the ubiquity of this nitrogen transfer in fiveMetarhiziumspecies representing those with broad (M. robertsii,M. brunneum, andM. guizhouense) and narrower insect host ranges (M. acridumandM. flavoviride), as well as the insect-pathogenic fungiBeauveria bassianaandLecanicillium lecanii. Insects were injected with15N-labeled nitrogen, and we tracked the incorporation of15N into two dicots, haricot bean (Phaseolus vulgaris) and soybean (Glycine max), and two monocots, switchgrass (Panicum virgatum) and wheat (Triticum aestivum), in the presence of these fungi in soil microcosms. AllMetarhiziumspecies andB. bassianabut notL. lecaniishowed the capacity to transfer nitrogen to plants, although to various degrees. Endophytic association by these fungi increased overall plant productivity. We also showed that in the field, where microbial competition is potentially high,M. robertsiiwas able to transfer insect-derived nitrogen to plants.Metarhiziumspp. andB. bassianahave a worldwide distribution with high soil abundance and may play an important role in the ecological cycling of insect nitrogen back to plant communities.

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Horizontal gene transfer allowed the emergence of broad host range entomopathogens

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1816430116 ◽

2019 ◽

Vol 116 (16) ◽

pp. 7982-7989 ◽

Cited By ~ 18

Author(s):

Qiangqiang Zhang ◽

Xiaoxuan Chen ◽

Chuan Xu ◽

Hong Zhao ◽

Xing Zhang ◽

...

Keyword(s):

Gene Transfer ◽

Horizontal Gene Transfer ◽

Host Range ◽

Range Expansion ◽

Pathogenic Fungi ◽

Broad Host Range ◽

Metarhizium Robertsii ◽

Metarhizium Acridum ◽

Host Range Expansion ◽

Underlying Mechanisms

The emergence of new pathogenic fungi has profoundly impacted global biota, but the underlying mechanisms behind host shifts remain largely unknown. The endophytic insect pathogen Metarhizium robertsii evolved from fungi that were plant associates, and entomopathogenicity is a more recently acquired adaptation. Here we report that the broad host-range entomopathogen M. robertsii has 18 genes that are derived via horizontal gene transfer (HGT). The necessity of degrading insect cuticle served as a major selective pressure to retain these genes, as 12 are up-regulated during penetration; 6 were confirmed to have a role in penetration, and their collective actions are indispensable for infection. Two lipid-carrier genes are involved in utilizing epicuticular lipids, and a third (MrNPC2a) facilitates hemocoel colonization. Three proteases degraded the procuticular protein matrix, which facilitated up-regulation of other cuticle-degrading enzymes. The three lipid carriers and one of the proteases are present in all analyzed Metarhizium species and are essential for entomopathogenicity. Acquisition of another protease (MAA_01413) in an ancestor of broad host-range lineages contributed to their host-range expansion, as heterologous expression in the locust specialist Metarhizium acridum enabled it to kill caterpillars. Our work reveals that HGT was a key mechanism in the emergence of entomopathogenicity in Metarhizium from a plant-associated ancestor and in subsequent host-range expansion by some Metarhizium lineages.

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Using Commercial Compost as Control Measures against Cucumber Root-Rot Disease

Journal of Mycology ◽

10.1155/2013/324570 ◽

2013 ◽

Vol 2013 ◽

pp. 1-13 ◽

Cited By ~ 7

Author(s):

Kamel Kamal Sabet ◽

Magdy Mohamed Saber ◽

Mohamed Adel-Aziz El-Naggar ◽

Nehal Samy El-Mougy ◽

Hatem Mohamed El-Deeb ◽

...

Keyword(s):

Root Rot ◽

Control Measure ◽

Disease Incidence ◽

Pathogenic Fungi ◽

Pythium Ultimum ◽

Control Measures ◽

Infested Soil ◽

Fungal Isolates ◽

Cucumber Root

Five commercial composts were evaluated to suppress the root-rot pathogens (Fusarium solani (Mart.) App. and Wr, Pythium ultimum Trow, Rhizoctonia solani Kuhn, and Sclerotium rolfsii Sacc.) of cucumber plants under in vitro and greenhouse conditions. In vitro tests showed that all tested unautoclaved and unfiltrated composts water extracts (CWEs) had inhibitor effect against pathogenic fungi, compared to autoclaved and filtrated ones. Also, the inhibitor effects of 40 bacteria and 15 fungi isolated from composts were tested against the mycelial growth of cucumber root-rot pathogens. Twenty two bacteria and twelve fungal isolates had antagonistic effect against root-rot pathogens. The antagonistic fungal isolates were identified as 6 isolates belong to the genus Aspergillus spp., 5 isolates belong to the genus Penicillium spp. and one isolate belong to the genus Chaetomium spp. Under greenhouse conditions, the obtained results in pot experiment using artificial infested soil with cucumber root-rot pathogens showed that the compost amended soil reduced the percentage of disease incidence, pathogenic fungi population, and improved the cucumber vegetative parameters as shoot length, root length, fresh weight, and dry weight. These results suggested that composts are consequently considered as control measure against cucumber root-rot pathogens.

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