Entomopathogenic fungi in Portuguese vineyards soils: suggesting a 'Galleria-Tenebrio-bait method' as bait-insects Galleria and Tenebrio significantly underestimate the respective recoveries of Metarhizium (robertsii) and Beauveria (bassiana).

Lav Sharma,Irene Oliveira,Guilhermina Marques,Laura Torres

doi:10.3897/mycokeys.38.26790

Abstract

Entomopathogenic fungi (EPF) are the natural enemies of insect-pests. However, EPF recoveries can be influenced by the soil habitat-type(s) incorporated and/or the bait-insect(s) used. Galleriamellonella (GM) as bait-insect, i.e. ‘Galleria-bait’, is arguably the most common methodology, which is sometimes used solely, to isolate EPF from soils. Insect baiting using Tenebriomolitor (TM) has also been employed occasionally. Here 183 soils were used to estimate the functional diversity of EPF in Portuguese Douro vineyards (cultivated habitat) and adjacent hedgerows (semi-natural habitat), using the TM bait method. Moreover, to study the effect of insect baiting on EPF recovery, 81 of these 183 soil samples were also tested for EPF occurrences using the GM bait method. Twelve species were found in 44.26% ± 3.67% of the total of 183 soils. Clonostachysroseaf.rosea was found in maximum soils (30.05% ± 3.38%), followed by Beauveriabassiana (12.57% ± 2.37%), Purpureocilliumlilacinum (9.29% ± 2.14%) and Metarhiziumrobertsii (6.01% ± 1.75%). Beauveriapseudobassiana (P < 0.001), C.roseaf.rosea (P = 0.006) and Cordycepscicadae (P=0.023) were isolated significantly more from hedgerows, highlighting their sensitivities towards agricultural disturbances. Beauveriabassiana (P = 0.038) and M.robertsii (P = 0.003) were isolated significantly more using GM and TM, respectively. Principal component analysis revealed that M.robertsii was associated both with TM baiting and cultivated habitats, however, B.bassiana was slightly linked with GM baiting only. Ecological profiles of B.bassiana and P.lilacinum were quite similar while M.robertsii and C.roseaf.rosea were relatively distant and distinct. To us, this is the first report on (a) C.cicadae isolation from Mediterranean soils, (b) Purpureocilliumlavendulum as an EPF worldwide; and (c) significant recoveries of M.robertsii using TM over GM. Overall, a ‘Galleria-Tenebrio-bait method’ is advocated to study the functional diversity of EPF in agroecosystems.

Highlights

Grape production and winemaking contribute significantly in many economies worldwide
Clonostachys rosea f. rosea (Link) Schroers, Samuels, Seifert & Gams was found in the maximum number of soil samples i.e. 30.05% ± 3.38% (N = 55), followed by B. bassiana (12.57% ± 2.37% (N = 23)), Purpureocillium lilacinum (Thom) Luangsa-ard, Houbraken, Hywel-Jones & Samson (9.29% ± 2.14% (N = 17)) and Metarhizium robertsii Bischoff, Rehner & Humber (6.01% ± 1.75% (N = 11))
Entomopathogenic fungi have been known for their potential as insect biocontrol agents and recent studies focus on their use for conservation biological control

Summary

Introduction

Grape production and winemaking contribute significantly in many economies worldwide. Vineyards attract many primary, secondary or tertiary insect pests (Gonçalves et al 2017, Sharma et al 2018). One of the key insect-pest in vineyards is the European Grapevine Moth, Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae). It exhibits polyphagy and is distributed across Asia, Central Europe and the Mediterranean basin, USA, Chile and Argentina. Finding strategies to control vineyards’ pests is of utmost importance especially from an economic point of view (Sharma et al 2018)

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