Foliar Application of Salicylic Acid at Different Phenological Stages of Peach Fruit CV. 'Flordaking' Improves Harvest Quality and Reduces Chilling Injury during Low Temperature Storage

PhWRKY30 activates salicylic acid biosynthesis to positively regulate antiviral defense response in petunia

Petunia (Petunia hybrida) plants are highly threatened by a diversity of viruses, causing substantial damage to ornamental quality and seed yield. However, the regulatory mechanism of virus resistance in petunia is largely unknown. Here, we revealed that a member of petunia WRKY transcription factors, PhWRKY30, was dramatically up-regulated following Tobacco rattle virus (TRV) infection. Down-regulation of PhWRKY30 through TRV-based virus-induced gene silencing increased green fluorescent protein (GFP)-marked TRV RNA accumulation and exacerbated the symptomatic severity. In comparison with wild-type (WT) plants, PhWRKY30-RNAi transgenic petunia plants exhibited a compromised resistance to TRV infection, whereas an enhanced resistance was observed in PhWRKY30-overexpressing (OE) transgenic plants. PhWRKY30 affected salicylic acid (SA) production and expression of arogenate dehydratase 1 (PhADT1), phenylalanine ammonia-lyase 1 (PhPAL1), PhPAL2b, nonexpressor of pathogenesis-related proteins 1 (PhNPR1), and PhPR1 in SA biosynthesis and signaling pathway. SA treatment restored the reduced TRV resistance to WT levels in PhWRKY30-RNAi plants, and application of SA biosynthesis inhibitor 2-aminoindan-2-phosphonic acid inhibited promoted resistance in PhWRKY30-OE plants. The protein-DNA binding assays showed that PhWRKY30 specifically bound to the promoter of PhPAL2b. RNAi silencing and overexpression of PhPAL2b led to decreased and increased TRV resistance, respectively. The transcription of a number of reactive oxygen species- and RNA silencing-associated genes was changed in PhWRKY30 and PhPAL2b transgenic lines. PhWRKY30 and PhPAL2b were further characterized to be involved in the resistance to Tobacco mosaic virus (TMV) invasion. Our findings demonstrate that PhWRKY30 positively regulates antiviral defense against TRV and TMV infections by modulating SA content.

Enhancing soybean germination and vigor under water stress: the efficacy of bio-priming with sodium carboxymethyl cellulose and gum arabic

Seed priming can significantly enhance the tolerance of soybean against different environmental stresses by improving seed water uptake and modulating stress-response mechanisms. In particular, seed priming with sodium carboxymethylcellulose (SCMC) and gum Arabic (GA) can support seeds to withstand extreme conditions better, promoting more consistent germination and robust seedling establishment, which is crucial for achieving stable agricultural yields. The present study investigated the effects of seed priming using a combination of SCMC and GA (10% CG) on the germination, growth, and biochemical responses of six soybean varieties under drought and flooding stress conditions. The results revealed significant differences among varieties and applied treatments on germination, vigor, and physiological traits. Under drought stress, seed priming with 10% CG significantly improved germination percentage, germination rate, shoot length, root length, and biomass compared to unprimed seeds. Notable reductions in malondialdehyde (MDA) content and enhanced antioxidant enzyme activities, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), suggest that 10% CG priming mitigates oxidative damage through enhanced antioxidant defense mechanisms. Moreover, 10% CG seed priming improved germination and growth parameters under flooding stress, but the advantages were less significant. In addition, the priming treatment significantly reduced electrolyte conductivity (EC) across all varieties compared to unprimed seeds, indicating improved membrane stability. Overall, 10% CG seed priming was more effective under drought and flooding conditions, demonstrating a potential strategy for enhancing stress tolerance in soybean varieties.

Preharvest Elicitors as a Tool to Enhance Bioactive Compounds and Quality of Both Peel and Pulp of Yellow Pitahaya (Selenicereus megalanthus Haw.) at Harvest and during Postharvest Storage

Yellow pitahaya is a tropical fruit that has gained popularity in recent years. Natural elicitors are compounds that can stimulate the resistance and quality of fruits. The objective of this study was to evaluate the effects of natural elicitors, methyl salicylate (MeSa), methyl jasmonate (JaMe), salicylic acid (SA) and oxalic acid (OA) at concentrations of 0.1 mM (MeSa and JaMe) and 5 mM (SA and OA), applied to the yellow pitahaya fruits under greenhouse conditions. After full blossom, four applications were made with a frequency of 15 days. At the time of harvest and after storage, the following variables were evaluated: firmness (whole fruit), total soluble solids (TSS), total acidity (TA), phenolics and carotenoids (in the pulp), while phenolics, carotenoids, macronutrients and micronutrients were determined in the peel. The results showed MeSa advanced the fruit maturation, according to higher TSS, lower TA and firmness than MeJa-treated fruits, for which a delayed ripening process was shown. All treatments induced a higher polyphenolic concentration during storage. Regarding the alternative use of the peel as a by-product, the application of natural elicitors significantly increased the content of polyphenols, carotenoids, macronutrients and micronutrients in the peel, especially MeSa, which can be used as a bioactive compound in the food industry. In conclusion, the results indicate that natural elicitors can be an alternative to improve the quality and shelf life of yellow pitahaya fruits.

The Relationships between Waxes and Storage Quality Indexes of Fruits of Three Plum Cultivars

In the present study, the cuticular wax morphology, composition and the relationship with storage quality in three plum cultivars of Prunus salicina 'Kongxin' (KXL), Prunus salicina 'Fengtang' (FTL) and Prunus salicina 'Cuihong' (CHL) were investigated during storage at room temperature of 25 ± 1 °C. The results illustrated that the highest cuticular wax concentration was discovered in KXL, followed by FTL and the lowest in CHL. The fruit wax composition of the three plum cultivars was similar and principally composed of alkanes, alcohols, fatty acids, ketones, aldehydes, esters, triterpenes and olefins. Alcohols, alkanes and triterpenes were the dominant fruit wax compounds of the three plum cultivars. After storage for 20 d at room temperature, the variation of cuticular wax crystal structure and composition showed significant cultivar-associated differences. The total wax content decreased for FTL and CHL and increased for KXL, and the wax crystal degraded and melted together over time. The higher contents of the main components in the three plum cultivars were nonacosane, 1-triacontanol, 1-heneicosanol, nonacosan-10-one, octacosanal, ursolic aldehyde and oleic acid. Alcohols, triterpenes, fatty acids and aldehydes were most dramatically correlated with the softening of fruit and storage quality, and alkanes, esters and olefins were most significantly correlated with the water loss. Nonacosane and ursolic aldehyde can enhance the water retention of fruit. Overall, this study will provide a theoretical reference for the further precise development of edible plum fruit wax.

Evaluation of Preharvest Melatonin on Soft Rot and Quality of Kiwifruit Based on Principal Component Analysis

Botryosphaeria dothidea is the source of the deadly kiwifruit disease known as soft rot. In order to explore the role of melatonin in regulating the postharvest quality and disease resistance of kiwifruit at different growth and development stages, in this study, we applied melatonin at different concentrations to kiwifruit at the young fruit, expansion, and late expansion stages to assess its effect on fruit resistance to B. dothidea, minimize soft rot, and maintain postharvest fruit quality. The results showed that melatonin significantly suppressed the mycelial growth of B. dothidea, with 1.0 mmol/L melatonin inhibiting it by up to 50%. However, 0.1–0.3 mmol/L melatonin had the best control over soft rot. Furthermore, spraying MT during kiwifruit growth can successfully increase fruit weight; preserve postharvest fruit firmness; reduce respiration intensity in the early stages of storage; delay the rise in soluble solids, while maintaining a high titratable acid content to ensure suitable solid acid ratio; increase total phenol, flavonoid, chlorophyll, carotenoid, and ascorbic acid contents; and delay the rise in soluble sugar contents in the late stages of storage. These results have a positive effect on maintaining the nutritional composition of kiwifruit. However, the effects on weight loss, dry matter content, and soluble protein content were not significant. In addition, the results of the principal component analysis demonstrated that 0.3 mmol/L MT increased kiwifruit’s resistance to soft rot while preserving postharvest fruit quality.

Quality Responses of Table Grapes ‘Flame Seedless’ as Effected by Foliarly Applied Micronutrients

Micronutrient (iron, zinc and boron) deficiencies are a basic and prominent factor affecting grape quality and yield in the Pothwar region. To overcome these deficiencies, different levels of micronutrients were applied foliarly on grapevines at five different berry developmental stages during two consecutive growing seasons (2018 and 2019). The data suggested that foliar treatment of micronutrients significantly increased the yield, number of bunches per vine, bunch weight, yield per vines, bunch length, berry number per cluster, berry diameter, berry weight and cluster compactness. The biochemical quality attributes of berries, including sugars (reducing, non-reducing as well as total sugars), ascorbic acid content, pH and TSS values, were at their highest levels in grapevines supplemented with Fe, Zn and B treatment at 200 ppm, respectively, i.e., the highest concentrations used. Biochemical leaf values, including chlorophyll a and b and leaf micronutrient content (Fe, Zn and B), were also highest in grapevines that were sprayed with Fe, Zn and B at 200 ppm. Overall, the results revealed that the performance of grapevine cv. ‘Flame Seedless’ growing in agroclimatic conditions of the Pothwar region was improved as a result of the foliar application of Fe, Zn and B at 200 ppm. The results also suggested that a further increase in the concentration of each nutrient might be helpful to obtain berries of improved quantity and quality.