Microbiome Response to Hot Water Treatment and Potential Synergy With Biological Control on Stored Apples

Abstract

Postharvest food decay is one major issue for today’s food loss along the supply chain. Hot water treatment (HWT), a sustainable method to reduce pathogen-induced postharvest fruit decay, has been proven to be effective on a variety of crops. However, the microbiome response to HWT is still unknown, and the role of postharvest microbiota for fruit quality is largely unexplored. To study both, we applied a combined approach of metabarcoding analysis and real time qPCR for microbiome tracking. Overall, HWT was highly effective in reducing rot symptoms on apples under commercial conditions, and induced only slight changes to the fungal microbiota, and insignificantly affected the bacterial community. Pathogen infection, however, significantly decreased the bacterial and fungal diversity, and especially rare taxa were almost eradicated in diseased apples. Here, about 90% of the total fungal community was composed by co-occurring storage pathogens Neofabraea alba and Penicillium expansum. Additionally, the prokaryote to eukaryote ratio, almost balanced in apples before storage, was shifted to 0.6% bacteria and 99.4% fungi in diseased apples, albeit the total bacterial abundance was stable across all samples. Healthy stored apples shared 18 bacterial and 4 fungal taxa that were not found in diseased apples; therefore, defining a health-related postharvest microbiome. In addition, applying a combined approach of HWT and a biological control consortium consisting of Pantoea vagans 14E4, Bacillus amyloliquefaciens 14C9 and Pseudomonas paralactis 6F3, were proven to be efficient in reducing both postharvest pathogens. Our results provide first insights into the microbiome response to HWT, and suggest a combined treatment with biological control agents.

Effect of Washing, Waxing and Low-Temperature Storage on the Postharvest Microbiome of Apple

“…In contrast, other natural antagonists such as Aureobasidium showed the opposite trend. This is in agreement with a previous study of stored apples [39]. While the specific mechanisms behind these changes are unclear, the compositional changes have pathological significance in relation to the development of decay and natural antagonisms during prolonged storage periods.…”

“…The significant shifts in bacterial community composition suggest that it may have undergone species replacement (turnover) and/or a significant change in the relative abundance of the present taxa. These findings agree with previous studies showing a compositional shift in microorganisms, especially fungi, in stored apples [39,41]. The significant shift that occurred in both fungal and bacterial communities, regardless of treatment or tissue type, between T0 and T2, may have been a direct result of storing the apples at low temperature.…”

“…In contrast, the current study utilized 'Enterprise' apples that were harvested from trees located in an orchard on the grounds of the USDA-ARS in WV, and processed all in a single day. Nevertheless, the microbial community found to be associated with different tissue types in the present study was very similar to what has been described in previous studies [10,14,39]. In the present study, however, we found fewer fungal and bacterial taxa with potential pathogenicity to humans.…”

16S rRNA gene-based microbiome analysis identifies candidate bacterial strains that increase the storage time of potato tubers

“…Much research has been carried out to understand the microbiomes of crop plants during vegetative growth, with the goal of improving agricultural productivity [2][3][4][5] . In contrast, few studies have been published on the postharvest microbiomes of food crops and their role in storage stability [6][7][8][9] , although strategies to reduce food loss are as important in ensuring food supply as an increase in food production.…”

Dynamics of the Apple Fruit Microbiome after Harvest and Implications for Fruit Quality

“…To date, the microbial communities in the apple phyllosphere [ 12 ], the apple flower microbiome [ 13 ], associations with genetic heritage in the apple endosphere [ 14 ] or on different fruit tissue types [ 15 ] have been characterized. Some studies have tried to characterize the effect of different plant protection schemes such as organic farming [ 15 , 16 ], or post-harvest treatments such as hot water treatment [ 17 ] on the microbial communities. However, specific insights into the microbial communities of apple fruits are still missing.…”