Changes in the Fungal Community Assembly of Apple Fruit Following Postharvest Application of the Yeast Biocontrol Agent Metschnikowia fructicola

Recently, increasing focus has been placed on exploring fruit microbiomes and their association with their hosts. Investigation of the fruit surface microbiome of apple has revealed variations in the composition and structure depending on management practices, phenological stages, and spatial distribution on the fruit itself. However, the fate of the fruit surface microbiome assembly and dynamics in apple following interventions such as the application of biocontrol agents remains unknown. The objective of the study was to explore the effect of a postharvest application of a yeast biocontrol agent, Metschnikowia fructicola, on the composition of the epiphytic fungal microbiota on apples during cold storage. Our results demonstrated that the applied biocontrol agent, M. fructicola, persisted in high abundance (>28% relative abundance) on the fruit surface throughout the storage period. The biocontrol application significantly decreased the richness and caused a significant shift in the overall composition and structure of the fungal microbiome relative to untreated or water-treated controls. The yeast application reduced the abundance of several apple fungal pathogens, namely, Alternaria, Aspergillus, Comoclatris, Stemphylium, Nigrospora, Penicillium, and Podosphaera, throughout the cold storage period.

Investigating the Effect of Fruit Size on Ripening Recovery of Banana Treated with 1-Methylcyclopropene

Postharvest application of 1-methylcycloprepene (1-MCP) on banana fruit to extend shelf-life and maintain quality is inconsistent as treated fruit do not ripen uniformly. Banana response to 1-MCP treatment can be variable due to within-bunch variation in fruit size, composition, and maturity. Therefore, the present study investigated whether fruit size variation explains variability in ripening recovery. To investigate this relationship, large, medium, and small fruit were treated with 0 nL L−1 1-MCP (control), 400 nL L−1 1-MCP and 50 µL L−1 ethephon + 400 nL L−1 1-MCP. Fruit were then ripened using 800 µL L−1 ethephon and stored at 23 °C for 30 d. Irrespective of fruit size, treating banana with 1-MCP and ethephon + 1-MCP prolonged shelf-life by 30 d compared to control, which were fully ripe at 15 d for medium and large fruit, and 20 d for small fruit. 1-MCP significantly delayed yellow colour development (colour stage 4), chlorophyll degradation (97.4 µg/g), and sucrose (2.57 mg/g) and glucose (0.86 mg/g) accumulation in small compared to medium and large fruit. However, firmness (56.13 N) and starch (0.68 mg/g) were significantly lower in 1-MCP-treated small-sized fruit compared to medium and large fruit. Moisture loss was also significantly higher (19.49%) in 1-MCP-treated small fruit compared to medium (14.89%) and large (18.11%). Combined ethephon and 1-MCP allowed for an increase in ripening in small, medium, and large fruit. Overall, medium and large fruit treated with 1-MCP and ethephon + 1-MCP recovered their ripening capacity better compared to small fruit. The results demonstrate that 1-MCP efficacy is influenced by fruit size, whereas ethephon + 1-MCP treatment was consistent across small, medium, and large fruit. The effect of fruit size on 1-MCP efficacy might explain the inconsistency of the treatment in the banana fruit. Therefore, it is important to apply 1-MCP on fruit of approximately the same size to achieve the full benefit of the treatment. Moreover, fruit treated with 1-MCP + ethephon recovered their ripening capacity, irrespective of size, suggesting that it is a beneficial treatment.

Differential effects of postharvest application of ethylene inhibitors on guava stored under ambient conditions

Aim: To assess the efficiency of ethylene synthesis and action inhibitors on postharvest shelf life of guava fruits under ambient conditions. Methodology: Mature green guava fruits (P. guajava L. cv. Arka Mridula) were harvested and treated with ethylene inhibitors. Various physiological, physical and nutritional changes of the treated fruits in comparison with untreated ones were monitored during ambient temperature storage. Multivariate analysis approach was used for interpreting the data on quality changes during storage. Results: Significant positive correlation (p<0.01) was observed among rates of ethylene production, respiration, ripening and Hunter’s a* value. Biplot from principal component analysis of eleven parameters showed that 1-MCP (500 ppb) treated fruits were grouped together with freshly harvested fruits throughout storage period, and proved superior over other treatments in delaying ripening and quality maintenance. Seven days stored 3.0 mM Salicylic acid and 1.5 mM Sodium nitroprusside treated fruits were grouped together with 5 days stored control fruits, suggesting their effectiveness in extending the shelf life by additional two days. Interpretation: Postharvest application of 1-MCP on guava fruits can extend the shelf life by four days when compared with control. Even PCA indicated that the study of major ripening attributes (L*, a*, b*, Hue, texture, acidity, ethylene rate and respiration rate) was quite sufficient to know the ripening status of the fruits.