Formation of 6npentyl2Hpyran2one 6PAP and

Authors: Henryk Jeleń Lidia Błaszczyk Jerzy Chełkowski Katarzyna Rogowicz Judyta Strakowska

Publish Date: 2013/11/12

Volume: 13, Issue: 3, Pages: 589-600

PDF Link

Abstract

Seventyseven headspaceTrichoderma isolates belonging to eight species—T atroviride T citrinoviride T hamatum T harzianum T koningii T viride T viridescens and T virens—were screened for their ability to produce 6npentyl2Hpyran2one 6PAP and other volatiles using solid phase microextraction SPME coupled to gas chromatography–mass spectrometry GCMS Intra and interspecies variability was demonstrated in the 6PAP synthesis The most efficient producer of 6PAP on potato dextrose agar PDA was T atroviride However the variation in 6PAP synthesis differed significantly among strains of this species the lowest value being 334 μg strain AN212 whereas the highest reached 1426 μg per culture for strain AN35 Also T viridescens produced significant amounts of 6PAP 2001–5263 μg for 11 out of 12 strains Moderate producers were isolates belonging to T hamatum up to 155 μg and T citrinoviride up to 200 μg Trichoderma viride isolates showed very little production of 6PP on PDA No 6PAP formation was detected in cultures of 25 isolates belonging to three species T koningii T harzianum and T virens Trichoderma atroviride AN35 as the most efficient producer of 6PAP was selected to observe the dynamics of 6PAP formation during growth on PDA at 20 °C for 6 days A radical increase in 6PAP production started after the fourth day of incubation and the maximum expression was achieved in the final phase of the experiments 6 days after inoculation Apart from 6PAP over 40 other volatile compounds were detected in the survey of Trichoderma species Among them the most commonly produced substrates were 1octene3ol isoamyl alcohol 3octanone cyclohept3en1one 2pentylfuran linalol isobutyrate toluene Dlimonene and αbergamotene Seventeen of the detected compounds have never previously been reported as a secondary metabolite of TrichodermaSpecies of the fungal genus Trichoderma teleomorph in Hypocrea are frequently encountered fungi especially in soil and decaying wood Klein and Eveleigh 1998 Kubicek et al 2008 Jaklitsch 2009 Druzhinina et al 2011 Friedl and Druzhinina 2012 Some of these species are known for their antagonistic activities towards plant pathogens eg Botritis cinerea Fusarium spp Pythium spp Rhizoctonia solani Verticillium dahilae and Sclerotinia spp Harman et al 2004 Verma et al 2007 Druzhinina et al 2011 which makes them highly suitable for use in biological control Mechanisms that have been described as the basis for biocontrol activity include competition for nutrients and space antibiosis and mycoparasitism stimulation of plant growth and elicitation of plant defense reactions against pathogens Papavizas 1985 Howell 1998 Benítez et al 2004 Harman et al 2004 Harman and Kubicek 1998 It has been shown that the ability of Trichoderma species to antagonize is reflected in their capacity to secrete a spectrum of biochemicals such as cell walldegrading enzymes siderophores chelating iron and volatile and nonvolatile metabolites Harman et al 2004 Reino et al 2008 Vinale et al 2008 Stoppacher et al 2010 Druzhinina et al 2011Among the volatile antifungal compounds produced by Trichoderma strains the most important and welldocumented is 6npentyl2Hpyran2one 6PAP a polyketide with a characteristic sweet coconutlike aroma 6PAP and other αpyrone analogs have been detected in cultures of several Trichoderma strains such as T viride Collins and Halim 1972 T harzianum Claydon et al 1987 Bonnarme et al 1997 T koningii Simon et al 1988 and T atroviride Reithner et al 2005 2007 However it should be noted that the identification of most of these strains was based only on morphological characters which are known to be prone to misidentification As the Trichoderma species names reported prior to the introduction of advanced molecular and bioinformatics methods have been found to be questionable it has been suggested to interpret rather cautiously the results of previous studies Samuels 2006 Kubicek et al 20086PAP and its analogs have been demonstrated to inhibit growth of several plantpathogenic fungi Botrytis cinerea Fusarium oxysporum f sp lycopersici Fusarium verticilioides moniliforme Phytophthora megasperma Rhizoctonia solani and Armillaria mellea AlHeeti and Sinclair 1988 Scarselletti and Faull 1994 Worasatit et al 1994 Poole et al 1998 Tarus et al 2003 In addition it has been shown that 6npentyl2Hpyran2one can reduce the production of deoxynivalenol by Fusarium graminearum on agar medium Cooney et al 2001 Recent work has been undertaken to disclose the role of 6PAP in plant growth regulation and activation of plant defense responses Vinale et al 2008 ElHassan and Buchennauer 2009Other volatile metabolites derived from Trichoderma spp which are involved in complex Trichoderma–plant pathogen interactions have been mainly assigned to alcohols ketones alkanes furans and mono and sesquiterpenes Ghisalberti et al 1992 Mannina et al 1997 Wheatley et al 1997 Fiedler et al 2001 Tarus et al 2003 Lloyd et al 2005 Nemčovič et al 2008 Stoppacher et al 2010 Polizzi et al 2011 These volatiles have been described for T atroviride T aureoviride T harzianum T longibrachiatum T pseudokoningii and T viride and their spectrum is characteristic for each strain as well as dependent on growth phase and nutritional biological and environmental conditions Wheatley et al 1997 Bruce et al 2000 Tarus et al 2003 Nemčovič et al 2008 Stoppacher et al 2010 Polizzi et al 2011It is noteworthy that studies on the identification and profiling of volatile metabolites of Trichoderma included only a few species individual strains of this genus—T atroviride T harzianum T longibrachiatum T pseudokoningii and T viride—which are well known for their potential in biological control Furthermore there is only limited information on inter and intraspecific variability in the production of 6PAP and other volatile compounds by strains of various Trichoderma speciesTherefore the aim of this paper was to examine the ability of 77 isolates belonging to eight different Trichoderma species including species that are not yet fully recognized as important biological control agents BCA to form 6npentyl2Hpyran2one and other volatiles In addition an evaluation was conducted on the dynamics of 6PAP production by T atroviride AN35 Furthermore the inhibitory effect of this metabolite on six toxigenic Fusarium species considered to be the most important plant pathogens worldwide was studied

Keywords: