Yeasts volatile organic compounds (VOCs) as potential growth enhancers and molds biocontrol agents of mushrooms mycelia.

Volatile organic compounds (VOCs) produced by yeasts can positively affect crops, acting as antifungals or biostimulants. In this study, Aureobasidium pullulans and Metschnikowia pulcherrima were evaluated as potential antagonists of Trichoderma spp., common fungal pathogen in mushroom cultivation. To assess the biocontrol ability and biostimulant properties of the selected yeast species, in vitro co-culture and VOCs exposure assays were conducted. In both assays, VOCs produced by Aureobasidium spp. showed the stronger antifungal activity with a growth inhibition up to 30 %. This result was further confirmed by the higher volatilome alcohol content revealed by solid phase microextraction-gas chromatography mass spectrometry (SPME/GC-MS). Overall, Aureobasidium strains can be potentially used as biocontrol agent in Pleorotus ostreatus and Cyclocybe cylindracea mycelial growth, without affecting their development as demonstrated by VOCs exposure assay and Fourier-transform infrared spectroscopy (FT-IR). Conversely, M. pulcherrima was characterized by a lower or absent antifungal properties and by a volatilome composition rich in isobutyl acetate, an ester often recognized as plant growth promoter. As confirmed by FT-IR, Lentinula mycelia exposed to M. pulcherrima VOCs showed a higher content of proteins and lipids, suggesting an improvement of some biochemical properties. Our study emphasizes that VOCs produced by specific yeast strains are potentially powerful alternative to synthetic fungicide in the vegetative growth of mushroom-forming fungi and also able to modify their biochemical composition.

Pseudomonas synxantha volatile organic compounds: efficacy against Cadophora luteo-olivacea and Botrytis cinerea of kiwifruit.

Volatile organic compounds (VOCs) are responsible for the antagonistic activity exerted by different biological control agents (BCAs). In this study, VOCs produced by Pseudomonas synxantha strain 117-2b were tested against two kiwifruit fungal postharvest pathogens: Cadophora luteo-olivacea and Botrytis cinerea, through in vitro and in vivo assays. In vitro results demonstrated that P. synxantha 117-2b VOCs inhibit mycelial growth of C. luteo-olivacea and B. cinerea by 56% and 42.8% after 14 and 5 days of exposition, respectively. In vivo assay demonstrated significant inhibitory effects. VOCs used as a biofumigant treatment reduced skin-pitting symptoms disease severity by 28.5% and gray mold incidence by 66.6%, with respect to the untreated control. BCA volatiles were analyzed by solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC/MS), and among the detected compounds, 1-butanol, 3-methyl and 1-nonene resulted as the most produced. Their efficacy as pure synthetic compounds was assayed against mycelial growth of fungal pathogens by different concentrations (0.34, 0.56, and 1.12 µL mL-1 headspace). The effect of the application of VOCs as a biofumigant was also investigated as the expression level of seven defense-related genes of kiwifruit at different exposition times. The results indicated an enhancement of the expression of almost all the genes starting from 3 h of treatment. These results described P. synxantha VOCs characteristics and their potential as a promising method to adopt for protecting kiwifruit from postharvest diseases caused by C. luteo-olivacea and B. cinerea.

Acute graft versus host disease 1976-2020: reduced incidence and predictive factors.

We studied the incidence of acute graft versus host disease (GvHD) and its outcome in three consecutive time frames (year <2000; 2000-2010; >2010), in 3,120 patients allografted in two transplant Centers between 1976 and 2020. The median age increased over the three periods from 32 to 42 to 54 years (p < 0.00001). The median day of onset of GvHD in the three periods was day +14, day +16, and day +30, respectively (p < 0.0001). The cumulative incidence (CI) of GvHD grades II-IV in the three periods was 47, 24, and 16%, respectively (p < 0.00001). The CI of GvHD grades III-IV was 13, 5, and 4% (p < 0.001). In multivariate analysis, significant predictive factors for GvHD II-IV, on top of year of transplant, were anti-thymocyte globulin (ATG) (RR 0.67, p > 0.001); post-transplant cyclophosphamide (PTCY) (RR 0.41, p < 0.001), a family mismatched donor (RR 1.31, p = 0.03) a matched unrelated donor (RR 2.1, p < 0.001), an unrelated mismatched donor (RR1.8, p = 0.001), donor age above 40 years (RR 1.27, p < 0.001), hematological malignancy-as compared to aplastic anemia (RR 2.3, p < 0.001). When selecting only GvHD grade II, in a multivariate analysis, there was a significant reduction of transplant-related mortality (TRM) for patients grafted in 2001-2010 (RR 0.62, p < 0.0001) and for patients grafted in 2011-2020 (RR 0.35, p < 0.0001) as compared to grafts before the year 2000. A similar reduction in time was seen for patients with GvHD grades III-IV. The overall TRM in the three periods was 30, 22, and 16% (p < 0.0001) and survival was 47, 51, and 58% (p < 0.0001). Relapse risk was unchanged. In conclusion, we showed improved prevention of acute GvHD with time, together with a significant delay in the onset of the disease. Treatment of GvHD has also improved over time, as suggested by both reduced TRM and improved survival in more recent transplant periods.