Soil salinity is one of the major factors that affect plant growth and decrease agricultural productivity worldwide. Chitosan (CTS) has been shown to promote plant growth and increase the abiotic stress tolerance of plants. However, it still remains unknown whether the application of exogenous CTS can mitigate the deleterious effects of salt stress on lettuce plants. Therefore, the current study investigated the effect of foliar application of exogenous CTS to lettuce plants grown under 100 mM NaCl saline conditions. The results showed that exogenous CTS increased the lettuce total leaf area, shoot fresh weight, and shoot and root dry weight, increased leaf chlorophyll a, proline, and soluble sugar contents, enhanced peroxidase and catalase activities, and alleviated membrane lipid peroxidation, in comparison with untreated plants, in response to salt stress. Furthermore, the application of exogenous CTS increased the accumulation of K⁺ in lettuce but showed no significant effect on the K⁺/Na⁺ ratio, as compared with that of plants treated with NaCl alone. These results suggested that exogenous CTS might mitigate the adverse effects of salt stress on plant growth and biomass by modulating the intracellular ion concentration, controlling osmotic adjustment, and increasing antioxidant enzymatic activity in lettuce leaves.

The WRKY transcription factors play important roles in plant growth and resistance, but only a few members have been identified in strawberry. Here we identified a WRKY transcription factor, FvWRKY50, in diploid strawberry which played essential roles in strawberry vegetative growth, and reproductive growth. Knocking out FvWRKY50 by genome editing accelerated flowering time and leaf senescence but delayed anthocyanin accumulation in fruit. Further analysis showed that FvWRKY50 acted as a transcriptional repressor to negatively regulate the expression of flowering- and leaf senescence-related genes, including FvFT2, FvCO, FvFT3, and FvSAUR36. Notably, FvWRKY50 directly upregulated the expression of FvCHI and FvDFR by binding their promoter under normal conditions, but at low temperature FvWRKY50 was phosphorylated by FvMAPK3 and then induced protein degradation by ubiquitination, delaying anthocyanin accumulation. In addition, the homozygous mutant of FvWRKY50 was smaller while the biallelic mutant showed normal size. These new findings provide important clues for us to further reveal the regulatory mechanisms of strawberry growth and fruit ripening

Strawberry is one of the most highly consumed fruits worldwide, but is extremely perishable. This study systematically compared the effects of chitosan, sucrose, glucose, and fructose immersion on the physiology and disease development in harvested strawberries. After storage at 15 °C for 9 days, all sugar treatment groups had significantly higher total soluble solids and total anthocyanin content than those of the control group. All sugar treatment groups inhibited malondialdehyde accumulation. At the end of the storage, chitosan, glucose, and fructose maintained higher superoxide dismutase activity and chitosan maintained higher catalase activity. The chitosan and glucose groups had lowest fruit decay index, followed by sucrose and fructose groups. The fruit firmness and luster were better maintained in the glucose group. Furthermore, genes related to sucrose metabolism (e.g., FaSUS1 and FaSUS2), titratable acidity accumulation (e.g., FaMDH1, FaMDH2, FaCS1, and FaCS2), disease resistance (e.g., FaPGIP1, FaWRKY1, and FaWRKY33) and to anabolic jasmonic acid and abscisic acid pathways (e.g., FaJAZ1, FaJAZ2, FaOPR3, FaNCED1, and FaNCED2) were regulated to varying degrees, suggesting that chitosan and glucose participate in plants’ immune signaling networks and regulate disease resistance in fruit through hormone pathways. The findings provide new insights into the physiological regulation of harvested strawberries.

Enzymatic browning is a major issue that reduces the commercial value of Luffa cylindrica during storage, processing, and transportation. Our results showed that 1% CaCl₂ treatment was optimal for reducing the surface browning of fresh-cut luffa. After storage at 25 °C for four days, the treated luffa had a significantly higher total phenolic (TP) content than the untreated luffa. At the end of the storage period, the calcium treatment showed low malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) accumulation in the luffa. The treated luffa maintained higher superoxide dismutase (SOD), catalase (CAT), and phenylalanine ammonia lyase (PAL) activities and lower polyphenol oxidase (PPO) activity as compared to the untreated luffa. Furthermore, the genes regulating SOD (e.g., SOD1, SOD2, and SOD3), CAT (e.g., LcCAT1 and CAT2), and PAL (e.g., PAL1 and PAL2) in calcium-treated luffa were upregulated to varying degrees, suggesting that Ca²⁺ inhibited the browning of fresh-cut tissue by regulating the activities of those enzymes. Ultrastructure images showed that the treated luffa could maintain the relative integrity of the cell membrane and organelles. Therefore, Ca²⁺ might act as a second messenger to reduce ROS oxidative damage and maintain the cell membrane integrity. This study provides new insights into the breeding of new luffa varieties that are resistant to browning and post-harvest treatments to reduce the browning of luffa tissue.

The ABA receptor pyrabactin resistance 1-like (PYR/PYL) protein family is among the key regulators of plant growth and development, participating in ABA signaling. However, information on this family in strawberry (Fragaria × ananassa), an important fleshy fruit crop worldwide, is limited. In the present work, seven homologs of Arabidopsis PYL were first identified and characterized from Fragaria × ananassa. Furthermore, a comprehensive analysis of the FaPYLs was performed, including their phylogenetic relationships, gene structures, chromosomal locations, and conserved domains. The qRT–PCR analysis showed that FaPYL genes had differential expression patterns between fruit ripening stages, and most of them were transcribed in the SG (small green fruits,) and Wh (white fruits) stages of fruit ripening. Treatment of strawberry fruits with ABA and JA changed the expression of all FaPYLs in a gene-specific manner, depending on the berry ripening stage; at the turning stage, only the expression levels of FaPYL3 and FaPYL4 increased in response to ABA. Promoter analysis showed that most FaPYL genes contain cis-acting elements that respond to stress, light, and phytohormones and are associated with tissue-specific expression. Additionally, FaPYL3 and FaPYL4 were further functionally characterized using transient expression technology. Overexpression of FaPYL3 and FaPYL4 promoted strawberry fruit ripening, which positively regulated FaSnRK2.2 and FaNCED1 transcripts. Our results highlight the great potential of FaPYL genes in breeding genetically modified strawberry varieties with accelerated fruit ripening.

Plant-endophytic microbes affect plant growth, development, nutrition, and resistance to pathogens. However, how endophytic microbial communities change in different strawberry plant compartments after Fusarium pathogen infection has remained elusive. In this study, 16S and internal transcribed spacer rRNA amplicon sequencing were used to systematically investigate changes in the bacterial and fungal diversity and composition in the endophytic compartments (roots, stems, and leaves) of healthy strawberries and strawberries with Fusarium wilt, respectively. The analysis of the diversity, structure, and composition of the bacterial and fungal communities revealed a strong effect of pathogen invasion on the endophytic communities. The bacterial and fungal community diversity was lower in the Fusarium-infected endophytic compartments than in the healthy samples. The relative abundance of certain bacterial and fungal genera also changed after Fusarium wilt infection. The relative abundance of the beneficial bacterial genera Bacillus, Bradyrhizobium, Methylophilus, Sphingobium, Lactobacillus, and Streptomyces, as well as fungal genera Acremonium, Penicillium, Talaromyces, and Trichoderma, were higher in the healthy samples than in the Fusarium wilt samples. The relative abundance of Fusarium in the infected samples was significantly higher than that in the healthy samples, consistent with the field observations and culture isolation results for strawberry wilt. Our findings provide a theoretical basis for the isolation, identification, and control of strawberry wilt disease.