Selection and application of antifungal VOCs-producing yeasts as biocontrol agents of grey mould in fruits.

Rotting caused by grey mould (Botrytis cinerea) is a concerning disease for numerous crops both pre- and postharvest stages. Application of antagonistic yeasts is a promising strategy for controlling grey mould incidence which could mitigate undesirable consequences of using synthetic fungicides. In this work, a screening for detection of yeasts isolated from figs producers of antifungal volatile organic compounds (VOCs) were performed by confrontation in double dishes systems. Eleven out of 34 yeasts confronted reduced B. cinerea growth parameter in vitro. This reduction was correlated (p ≤ 0.050) with the production of 10 volatile compounds: two acids (acetic acid and octanoic acid), 7 esters (Ethyl propionate, n-Propyl acetate, Isobutyl acetate, 2-methylbutyl acetate, furfuryl acetate, phenylmethyl acetate, 2-phenylethyl acetate) and one ketone (Heptan-2-one). In bases on in vitro assay, Hanseniaspora uvarum 793 was applied to in vivo assays with strawberries and cherries. The reduction of incidence of B. cinerea in strawberries at 7 °C and 25 °C was 54.9 and 72.1% after 6 and 3 days, respectively. The reduction of incidence of B. cinerea in cherries at 7 °C and 25 °C was 48.9 and 45.6% after 5 and 4 days, respectively. These results showed that VOCs produced by Hanseniaspora uvarum 793 are effective in the control of incidence of Botrytis cinerea in fruits, being a potential alternative to chemical fungicide.

Lactobacillus delbrueckii subsp. bulgaricus F17 and Leuconostoc lactis H52 supernatants delay the decay of strawberry fruits: a microbiome perspective.

Strawberries are vulnerable to physical injuries and microbial invasion. To explore if beneficial lactic acid bacteria can improve the shelf life and edible quality of postharvest strawberry fruits, the effects of Lactobacillus delbrueckii subsp. bulgaricus (ital.) F17 (F17) and Leuconostoc lactis (ital.) H52 (H52) inoculation on the strawberry microbial community structure and saleable characteristics were examined by bacterial 16S rRNA and fungal ITS sequencing techniques. Lactobacillus (ital.) F17 and Leuconostoc lactis (ital.) H52 isolated from the traditional fermented yak milk in the Qinghai-Tibetan Plateau were used as the potential probiotic inocula. Samples from treated strawberries stored at 25 °C for 0, 12, 24, 48, and 72 hours were analyzed for their pH, weight loss percentage, decay percentage, total soluble solid content (SSC) and microbial counts, and for microbiome community diversity and canonical correspondence analysis. The results showed that F17 and H52 did not only significantly reduce the weight loss and decay percentage of strawberry fruits, but also delayed the decrease of the total SSC and pH (P < 0.05). In addition, F17 and H52 significantly inhibited the growth and colonization of aerobic mesophilic bacteria, yeast, mold and coliform bacteria. In particular, by comparing the microbiota composition of the samples, F17 significantly inhibited Pantoea, Mycospherella, unclassified_Pleosporales, Aureobasidium and Phoma at the genus level, whereas H52 inhibited Bacillus, Streptophyta, Mycospherella, Aureobasidium and Phoma. Moreover, analysis of alpha and beta diversity revealed that F17 and H52 had a significantly greater inhibitory effect on bacterial species compared to fungi. The results of canonical correspondence analysis revealed that the total SSC and pH were positively correlated with bacteria, whereas the decay percentage, weight loss percentage and total SSC were positively associated with fungi. Additionally, Podosphaera, Hanseniaspora, Botrytis and unclassified_Pleosporales were positively correlated with strawberry fruit decay and weight loss percentage. As a general result, Lactobacillus F17 and Leuconostoc lactis H52 have the potential to promote biological preservation, which is economically important to reduce the loss due to strawberry spoilage.

Hanseniaspora uvarum prolongs shelf life of strawberry via volatile production.

Gray mold caused by Botrytis cinerea led to severe postharvest losses for strawberry industry. In recent years, some studies have shown that postharvest diseases of strawberry can be controlled by using bacterial, fungal and yeast strains. The yeast strain Hanseniaspora uvarum was shown as an effective antagonist against B. cinerea growth. Here, we further investigated the volatile organic compounds (VOCs) production of H. uvarum and how this could impact on postharvest gray mold control of strawberry. A total of 28 VOCs were detected by GC-MS in the headspace of H. uvarum and strawberry with/without B. cinerea (SI and RSI ≥800). Among these VOCs, 15 VOCs were detected in both conditions, 4 VOCs were H. uvarum and strawberry without B. cinerea and the other 9 VOCs were only detected when B. cinerea was inoculated. Two VOCs, ethyl acetate and 1,3,5,7-cyclooctatetraene, enhanced by inoculation of B. cinerea. In in vitro assay, H. uvarum significantly inhibited mycelial growth and spore germination of B. cinerea via VOCs production. Moreover, in vivo assay showed that H. uvarum reduced B. cinerea infection of strawberry and maintained fruit appearance, firmness and total soluble solids via VOCs production. Collectively, our results showed that H. uvarum VOCs significantly controlled postharvest gray mold of strawberry and prolonged the storage time and shelf life.