Field validation of biocontrol strategies to control brown rot on stone fruit in several European countries

Fundamentals of Edible Coatings and Combination with Biocontrol Agents: A Strategy to Improve Postharvest Fruit Preservation

Challenges in global food supply chains include preserving postharvest quality and extending the shelf life of fruits and vegetables. The utilization of edible coatings (ECs) combined with biocontrol agents (BCAs) represents a promising strategy to enhance the postharvest quality and shelf life of these commodities. This review analyzes the most recent developments in EC technologies and their combination with BCAs, highlighting their synergistic effects on postharvest pathogen control and quality maintenance. Various types of ECs, including polysaccharides, proteins, and lipids, are discussed alongside coating fundamentals and the mechanisms through which BCAs contribute to pathogen suppression. The review also highlights the efficacy of these combined approaches in maintaining the physicochemical properties, sensory attributes, and nutritional value of fruits. Key challenges such as regulatory requirements, consumer acceptance, and the scalability of these technologies are addressed. Future research directions are proposed to optimize formulations, improve application techniques, and enhance the overall efficacy of these biocomposite coatings and multifunctional coatings. By synthesizing current knowledge and identifying gaps, this review provides a comprehensive understanding of the potential and limitations of using ECs and BCAs for sustainable postharvest management.

Inhibition of Monilinia fructicola sporulation and pathogenicity through eucalyptol-mediated targeting of MfCat2 by Streptomyces lincolnensis strain JCP1-7

Peach brown rot, attributed to Monilinia fructicola, presents a significant threat to postharvest peach cultivation, causing losses of up to 80%. With an increasing number of countries, spearheaded by the European Union, imposing bans on chemical agents in fruit production, there is a growing interest in mining highly active antibacterial compounds from biological control strains for postharvest disease management. In this study, we highlight the unique ability of Streptomyces lincolnensis strain JCP1-7 to inhibit M. fructicola sporulation, despite its limited antimicrobial efficacy. Through GC-MS analysis, eucalyptol was identified as the key compound. Fumigation of diseased fruits with eucalyptol at a concentration of 0.0335 μg cm-3 demonstrated an in vivo inhibition rate against M. fructicola of 93.13%, completely suppressing spore formation. Transcriptome analysis revealed the impact of eucalyptol on multiple pathogenesis-related pathways, particularly through the inhibition of catalase 2 (Cat2) expression. Experiments with a MfCat2 knockout strain (ΔMfCat2) showed reduced pathogenicity and sensitivity to JCP1-7 and eucalyptol, suggesting MfCat2 as a potential target of JCP1-7 and eucalyptol against M. fructicola. Our findings elucidate that eucalyptol produced by S. lincolnensis JCP1-7 inhibits M. fructicola sporulation by regulating MfCat2, thereby effectively reducing postharvest peach brown rot occurrence. The use of fumigation of eucalyptol offers insights into peach brown rot management on a large scale, thus making a significant contribution to agricultural research.

Field and postharvest application of microencapsulated Yamadazyma mexicana LPa14: anthracnose control and effect on postharvest quality in avocado (Persea americana Mill. cv. Hass)

BACKGROUND

Anthracnose caused by species of Colletotrichum is the most important disease of avocado fruit. The quiescent infection develops in the field, hence, its control from the preharvest stage is necessary. The field application of microencapsulated Yamadazyma mexicana LPa14 could prevent the establishment of Colletotrichum gloeosporioides and reduce the losses in avocado production. This study aimed to evaluate the effectiveness of microencapsulated Y. mexicana applied in the field and postharvest for the anthracnose control in avocado, to evaluate the population dynamics of Y. mexicana in flowers and fruits and the effect of the yeast on the avocado quality.

RESULTS

The concentrations of microencapsulated Y. mexicana after field application ranged from 4.58 to 6.35 log CFU g-1. The population of microencapsulated yeast in flowers and fruits was always higher than treatments with fresh cells. Preharvest application of fresh and microencapsulated Y. mexicana significantly reduced the severity of anthracnose by 71-80% and 84-96%, respectively, in avocado fruits stored at 25 °C. Moreover, at 6 °C and ripening at 25 °C, the fresh yeast reduced the severity by 87-90% and the microencapsulated yeast by 91-93%. However, yeast treatments applied in the field + postharvest under cool conditions were more effective in reducing 100% of anthracnose. Treatments did not negatively affect the quality parameters of the avocado fruits.

CONCLUSION

Yamadazyma mexicana microencapsulated by electrospraying is a promising bioformulation for the management of anthracnose in avocados at preharvest and postharvest levels. Yamadazyma mexicana offers a new biological control solution for growers in avocado orchards. © 2024 Society of Chemical Industry.

Colonization and population dynamics of total, viable, and culturable cells of two biological control strains applied to apricot, peach, and grapevine crops

The ecological fitness of the biological control strains Bacillus velezensis A17 and Lactiplantibacillus plantarum PM411 was evaluated in different crops, geographical zones, and growing seasons. Both strains (2 g L-1 of dried formulation) were spray-inoculated on apricot trees, peach trees, and grapevines. Depending on the crop, flowers, fruits, and leaves were picked at several sampling time points. The population dynamics of viable, viable but non-culturable, and dead cells were studied by comparing viability qPCR (v-qPCR), qPCR, and plate counting estimations. A17 showed high survival rates in apricot, peach, and grapevine organs. The A17 viability was confirmed since qPCR and v-qPCR estimations did not significantly differ and were rather constant after field applications. However, higher population levels were estimated by plate counting due to the non-selective characteristics of the medium used. The viability of PM411 was constrained by plant organ, crop, and climate conditions, being higher in apricot than in grapevine. PM411 survival declined after field application, indicating difficulties in its establishment. The PM411 population level was made up of dead, culturable, and viable but non-culturable cells since significant differences between the three methods were observed. In conclusion, A17 and PM411 differ strongly in their survival in grapevine, peach, and apricot.

Monilinia fructigena Suppressing and Plant Growth Promoting Endophytic Pseudomonas spp. Bacteria Isolated from Plum

Brown rot caused by Monilinia spp. fungi causes substantial losses in stone and pome fruit production. Reports suggest that up to 90% of the harvest could be lost. This constitutes an important worldwide issue in the food chain that cannot be solved by the use of chemical fungicides alone. Biocontrol agents (BCAs) based on microorganisms are considered a potential alternative to chemical fungicides. We hypothesized that endophytic bacteria from Prunus domestica could exhibit antagonistic properties towards Monilinia fructigena, one of the main causative agents of brown rot. Among the bacteria isolated from vegetative buds, eight isolates showed antagonistic activity against M. fructigena, including three Pseudomonas spp. isolates that demonstrated 34% to 90% inhibition of the pathogen's growth when cultivated on two different media in vitro. As the stimulation of plant growth could contribute to the disease-suppressing activity of the potential BCAs, plant growth promoting traits (PGPTs) were assessed for bacterial isolates with M. fructigena-suppressing activity. While all isolates were capable of producing siderophores and indole-3-acetic acid (IAA), fixating nitrogen, mineralizing organic phosphate, and solubilizing inorganic phosphate and potassium, only the Pseudomonas spp. isolates showed 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. Overall, our study paves the way for the development of an eco-friendly strategy for managing M. fructigena pathogens by using BCAs including Pseudomonas spp. bacteria, which could also serve as growth stimulators.

Microbial Biocontrol as an Alternative to Synthetic Fungicides: Boundaries between Pre- and Postharvest Applications on Vegetables and Fruits

From a ‘farm to fork’ perspective, there are several phases in the production chain of fruits and vegetables in which undesired microbial contaminations can attack foodstuff. In managing these diseases, harvest is a crucial point for shifting the intervention criteria. While in preharvest, pest management consists of tailored agricultural practices, in postharvest, the contaminations are treated using specific (bio)technological approaches (physical, chemical, biological). Some issues connect the ‘pre’ and ‘post’, aligning some problems and possible solution. The colonisation of undesired microorganisms in preharvest can affect the postharvest quality, influencing crop production, yield and storage. Postharvest practices can ‘amplify’ the contamination, favouring microbial spread and provoking injures of the product, which can sustain microbial growth. In this context, microbial biocontrol is a biological strategy receiving increasing interest as sustainable innovation. Microbial-based biotools can find application both to control plant diseases and to reduce contaminations on the product, and therefore, can be considered biocontrol solutions in preharvest or in postharvest. Numerous microbial antagonists (fungi, yeasts and bacteria) can be used in the field and during storage, as reported by laboratory and industrial-scale studies. This review aims to examine the main microbial-based tools potentially representing sustainable bioprotective biotechnologies, focusing on the biotools that overtake the boundaries between pre- and postharvest applications protecting quality against microbial decay.