In vitro effects of cuticular lipids of the aphids Sitobion avenae, Hyalopterus pruni and Brevicoryne brassicae on growth and sporulation of the Paecilomyces fumosoroseus and Beauveria bassiana

Abstract

The exoskeleton lipids of three dangerous pests, Sitobion avenae, Hyalopterus pruni and Brevicoryne brassicae were identified by GC/MS studies. The main components found were triacylglycerols with one hexanoyl group. Fatty acid composition and position of triacylglycerols were determined from mass spectra. There was a trace of triacylglycerol with the E,E-2,4-hexadienoyl group in the extract of Brevicoryne brassicae. A series of hydrocarbons and free fatty acids were identified. Single components of straight chain aldehyde (C 30 ) and alcohol (C 32 ) were detected in the lipids of H. pruni, B. brassicae. Free fatty acids, including these found in the aphid lipids, were subjected to fungi-insect ecological studies. A homologous series of acids were added individually into media used to evaluate the mycelia growth and sporulation tests of the fungi, Beauveria bassiana and Paecilomyces fumosoroseus. The tests were performed in vitro and linear mycelial growth and sporulation of fungi after 14 days were measured. For both fungi, complete inhibition was observed with pentanoic and sorbic (E,E-2,4-hexadienoic) acids at a concentration as low as 0.02% w/v in both tests. Growth stimulation effects were only observed for B. bassiana with tetradecanoic and eicosanoic acid. Inhibitions were noticed for both fungi and the strongest effects were for dodecanoic (B. b.) and eicosanoic acid (P. f.). Beside free fatty acids, no other group of chemical compounds was found in the lipids which could be involved in aphids resistance to entomopathogenic fungi.

Rapid Identification of Aphid Species by Headspace GC-MS and Discriminant Analysis

“…It was apparent that hydrocarbons that were detected in the headspace profile (Table S2) likely originate from symbionts associated with the aphids [49], plants [50] and aphid cuticular hydrocarbons [51]. Saturated alkanes (C13-C28) were also reported in previous studies as aphid cuticular hydrocarbons) from A. craccivora [52], Brevicoryne brassicae, Hyalopterus pruni [53], and Aphis fabae [54]). Decane (detected in E. lanigerum and A. punicae), 9-eicosene, and 8-heptadecene (detected in E. lanigerum) were detected in the headspace hydrocarbons (Figure 2, Table S2) and were also found by Muñoz, Argandoña [55], Ahmed, Agarwal [56], by Pokharel, Zhong [57] in aphid-infested plants, and by Ali, Morgan [58] in Leptothorax ants.…”

Growth Inhibition ofBeauveria bassianaby Bacteria Isolated from the Cuticular Surface of the Corn Leafhopper,Dalbulus maidisand the Planthopper,Delphacodes kuscheli,Two Important Vectors of Maize Pathogens

“…These fungi infect a great number of arthropods and hence can be used as pest control agents in an Integrated Pest Management approach ( Lecuona 1996 ). Fungi, particularly some members of Ascomycota, are attractive candidates as biocontrol agents against leafhoppers and planthoppers ( Rice and Choo 2000 ; Toledo et al 2007 ), but several studies revealed its failure to invade the insect cuticle, possibly due to the presence of inhibitory compounds such as phenols, quinones, and lipids ( Smith and Grula 1981 ; Szafranek et al 2001 ; Howard and Lord 2003 ; James et al 2003 ; Lord and Howard 2004 ) and also by antibiotic effect of the microbiota living on the cuticular surface of the host ( Hubner 1958 ; Walstad et al 1970 ; Schabel 1978 ). Several works reported antagonistic interactions among microorganisms, such as fungi and bacteria ( Currie et al 1999 ; Ansari et al 2005 ; Alippi and Reynaldi 2006 ), but there are no studies about the interactions between the microbiota found on the cuticle of hemipterous species and entomopathogenic fungi.…”

Parasitoid venom alters the lipid composition and development of microorganisms on the wax moth cuticle

“…However, the change in fungal development was unlikely to be solely determined by the lipid composition and N amount. Supplementation of nutrient media with lipids usually does not lead to a substantial increase in mycelia and conidia biomasses and can even lead to a decrease in these parameters (Napolitano & Juárez, 1997; Szafranek et al, 2001; Bogus et al, 2010). An increase in the bacterial load might only inhibit and not stimulate fungal growth.…”

“…The amounts of hydrocarbons, sterols, and fatty acids in the extracts were analyzed. We estimated the total amount of fatty acids (free + bound) because both forms may exhibit antimicrobial properties (Szafranek et al, 2001). Total epicuticular lipids were derivatized with 1% H 2 SO 4 in MeOH at 80 °C for 3 h (Koukos et al, 2015; He et al, 2019).…”

“…Fatty acids may inhibit germination and mycelial growth or change the enzymatic activities of EPF, as observed in studies of Conidiobolus coronatus (Costantin) A. Batko (Bogus et al, 2010, Wrońska et al, 2018), Beauveria bassiana sensu lato (Bals.‐Criv.) Vuill., Cordyceps fumosorosea (Wize) Kepler, B. Shrestha & Spatafora (Saito & Aoki, 1983; Szafranek et al, 2001), Metarhizium brunneum Petch (Ment et al, 2013), and Metarhizium robertsii J.F. Bisch., S.A. Rehner & Humber (Hypocreales: Clavicipitaceae) (Kryukov et al, 2018c).…”