FvMYB79 Positively Regulates Strawberry Fruit Softening via Transcriptional Activation of FvPME38

Strawberry is a soft fruit with short postharvest life, due to a rapid loss of firmness. Pectin methylesterase (PME)-mediated cell wall remodeling is important to determine fruit firmness and softening. Previously, we have verified the essential role of FvPME38 in regulation of PME-mediated strawberry fruit softening. However, the regulatory network involved in PME-mediated fruit softening is still largely unknown. Here, we identified an R2R3-type MYB transcription factor FvMYB79, which activates the expression level of FvPME38, thereby accelerating fruit softening. During fruit development, FvMYB79 co-expressed with FvPME38, and this co-expression pattern was opposite to the change of fruit firmness in the fruit of ‘Ruegen’ which significantly decreased during fruit developmental stages and suddenly became very low after the color turning stage. Via transient transformation, FvMYB79 could significantly increase the transcriptional level of FvPME38, leading to a decrease of firmness and acceleration of fruit ripening. In addition, silencing of FvMYB79 showed an insensitivity to ABA-induced fruit ripening, suggesting a possible involvement of FvMYB79 in the ABA-dependent fruit softening process. Our findings suggest FvMYB79 acts as a novel regulator during strawberry ripening via transcriptional activation of FvPME38, which provides a novel mechanism for improvement of strawberry fruit firmness.

Evaluation of Picker Discomfort and Its Impact on Maintaining Strawberry Picking Quality

In this paper, the authors present the relationship between the assumptions of ergonomics in the work of a strawberry picker and quality of picked fruit. The body posture that a person adopts while working has a significant impact on their health, working comfort, and productivity, but also on the quality of the fruit that is harvested. This paper identifies three characteristic picker positions during strawberry harvesting. A synchronized surface electromyography (sEMG) instrument together with the Tekscan® surface pressure measurement system allowed for the determination of the influence of working position on changes in the load of the picker’s musculoskeletal system and the surface pressure exerted on the fruit during manual strawberry picking, which are decisive factors for maintaining fruit quality. In addition, compression tests on whole strawberry fruit were carried out as a benchmark to evaluate and compare the maximum forces as well as the destructive pressures on the fruit. From the tests, we found that the most comfortable position of the worker’s body was determined along with the harvesting technique (position during work) that has the least negative effect on the quality of the harvested fruit. Consequently, the level of dynamic load on the worker was determined.

Biosafe Management of Botrytis Grey Mold of Strawberry Fruit by Novel Bioagents

Recently, there have been urgent economic and scientific demands to decrease the use of chemical fungicides during the treatment of phytopathogens, due to their human health and environmental impacts. This study explored the biocontrol efficacy of novel and eco-friendly preen (uropygial) oil and endophytic Bacillus safensis in managing postharvest Botrytis grey mold in strawberry fruit. The preen oil (25 μL/mL) showed high antifungal activity against B. cinerea Str5 in terms of the reduction in the fungal radial growth (41.3%) and the fungal colony-forming units (28.6%) compared to the control. A new strain of Bacillus safensis B3 had a good potential to produce chitinase enzymes (3.69 ± 0.31 U/mL), hydrolytic lipase (10.65 ± 0.51 U/mL), and protease enzymes (13.28 ± 0.65 U/mL), which are responsible for the hydrolysis of the B. cinerea Str5 cell wall and, consequently, restrict fungal growth. The in vivo experiment on strawberry fruit showed that preen (uropygial) oil reduced the disease severity by 87.25%, while the endophytic bacteria B. safensis B3 reduced it by 86.52%. This study reports the efficiency of individually applied bioagents in the control of phytopathogenic fungi for the first time and, consequently, encourages their application as a new and innovative strategy for prospective agricultural technology and food safety.

Pre-Harvest Application of Salicylic Acid, Abscisic Acid, and Methyl Jasmonate Conserve Bioactive Compounds of Strawberry Fruits during Refrigerated Storage

The short shelf-life and loss of bioactive compounds of strawberry fruit are the most important problems during strawberry refrigerated storage. This study was carried out to evaluate the effect of the pre-harvest foliar application of salicylic acid (SA) (2 and 4 mM), abscisic acid (ABA) (0.25 and 0.50 mM), and methyl jasmonate (MeJA) (0.25 and 0.50 mM) three times, 10 d apart, at fruit development and ripening stages on storage ability and bioactive compounds of strawberry fruit (cv. Festival) stored at 4 °C for 12 d. Our results showed that fruit obtained from both concentrations of ABA and 0.25 mM MeJA was firmer and had higher total soluble solids (TSS) than fruit from non-treated plants. However, all previous applications had no significant effect on weight loss, pH, or color. Applications of 4 mM SA and 0.25 mM MeJA conserved fruit from ascorbic acid (AsA) loss compared to control at the end of the storage period. In addition, all pre-harvest applications remained higher in total phenolic compounds (TPC) and anthocyanin contents compared to controls at the last storage period. Hence, the pre-harvest application of SA, ABA, and MeJA could be used to conserve TPC and anthocyanin as well as the quality of strawberry fruits during refrigerated storage.

Strawberry WRKY Transcription Factor WRKY50 Is Required for Resistance to Necrotrophic Fungal Pathogen Botrytis cinerea

WRKY protein is one of the largest plant-specific transcription factors that plays critical roles in plant stress responses, but few WRKY transcription factors have been functionally analyzed in strawberry. In this study, a Botrytis cinerea response WRKY gene, FvWRKY50, was isolated from the woodland strawberry. Expression analysis indicated that the transcript of FvWRKY50 was gradually decreased with fruit ripening, but was significantly induced by B. cinerea infection in mature strawberry fruit. Subcellular localization assay revealed that FvWRKY50 was localized in the nucleus. Several cis-elements related to pathogen responses were observed in the promoter region of FvWRKY50. Pathogen infection assay indicated that overexpression of FvWRKY50 in strawberry fruit significantly enhanced their resistance against B. cinerea, while the silencing of FvWRKY50 dramatically compromised their disease-resistant ability. The expression levels of several genes involved in jasmonic acid (JA) biosynthesis, signaling transduction, and antimicrobial protein biosynthesis were regulated to diverse extents in FvWRKY50 overexpressed and silenced fruit. Collectively, our study inferred that FvWRKY50 is a positive regulator that mediates resistance against B. cinerea through regulating some JA pathway and defense-related genes.