Formation of 6-n-pentyl-2H-pyran-2-one (6-PAP) and other volatiles by different Trichoderma species

Seventy-seven 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 6-n-pentyl-2H-pyran-2-one (6-PAP) and other volatiles using solid phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS). Intra- and interspecies variability was demonstrated in the 6-PAP synthesis. The most efficient producer of 6-PAP on potato dextrose agar (PDA) was T. atroviride. However, the variation in 6-PAP synthesis differed significantly among strains of this species, the lowest value being 33.4 mu g (strain AN212), whereas the highest reached 1,426 mu g per culture for strain AN35. Also, T. viridescens produced significant amounts of 6-PAP (200.1-526.3 mu g for 11 out of 12 strains). Moderate producers were isolates belonging to T. hamatum (up to 155 mu g) and T. citrinoviride (up to 200 mu g). Trichoderma viride isolates showed very little production of 6-PP on PDA. No 6-PAP 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 6-PAP, was selected to observe the dynamics of 6-PAP formation during growth on PDA at 20 A degrees C for 6 days. A radical increase in 6-PAP 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 6-PAP, over 40 other volatile compounds were detected in the survey of Trichoderma species. Among them, the most commonly produced substrates were 1-octene-3-ol, isoamyl alcohol, 3-octanone, cyclohept-3-en-1-one, 2-pentylfuran, linalol isobutyrate, toluene, D-limonene, and alpha-bergamotene. Seventeen of the detected compounds have never previously been reported as a secondary metabolite of Trichoderma.