Plant Growth and Fruit Quality Response of Strawberry is Improved After Exogenous Application of 24-Epibrassinolide

Xanthan gum-based edible coating effectively preserve postharvest quality of 'Gola' guava fruits by regulating physiological and biochemical processes

BACKGROUND

Guava is a fruit prone to rapid spoilage following harvest, attributed to continuous and swift physicochemical transformations, leading to substantial postharvest losses. This study explored the efficacy of xanthan gum (XG) coatings applied at various concentrations (0.25, 0.5, and 0.75%) on guava fruits (Gola cultivar) over a 15-day storage period.

RESULTS

The results indicated that XG coatings, particularly at 0.75%, substantially mitigated moisture loss and decay, presenting an optimal concentration. The coated fruits exhibited a modified total soluble soluble solids, an increased total titratable acidity, and an enhanced sugar-acid ratio, collectively enhancing overall quality. Furthermore, the XG coatings demonstrated the remarkable ability to preserve bioactive compounds, such as total phenolics, flavonoids, and antioxidants, while minimizing the levels of oxidative stress markers, such as electrolyte leakage, malondialdehyde, and H2O2. The coatings also influenced cell wall components, maintaining levels of hemicellulose, cellulose, and protopectin while reducing water-soluble pectin. Quantitative analysis of ROS-scavenging enzymes, including superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase, revealed significant increases in their activities in the XG-coated fruits compared to those in the control fruits. Specifically, on day 15, the 0.75% XG coating demonstrated the highest SOD and CAT activities while minimizing the reduction in APX activity. Moreover, XG coatings mitigated the activities of fruit-softening enzymes, including pectin methylesterase, polygalacturonase, and cellulase.

CONCLUSIONS

This study concludes that XG coatings play a crucial role in preserving postharvest quality of guava fruits by regulating various physiological and biochemical processes. These findings offer valuable insights into the potential application of XG as a natural coating to extend the shelf life and maintain the quality of guava fruits during storage.

RNAi-Mediated Suppression of OsBBTI5 Promotes Salt Stress Tolerance in Rice

This study explores the impact of RNAi in terms of selectively inhibiting the expression of the OsBBTI5 gene, with the primary objective of uncovering its involvement in the molecular mechanisms associated with salt tolerance in rice. OsBBTI5, belonging to the Bowman-Birk inhibitor (BBI) family gene, is known for its involvement in plant stress responses. The gene was successfully cloned from rice, exhibiting transcriptional self-activation in yeast. A yeast two-hybrid assay confirmed its specific binding to OsAPX2 (an ascorbate peroxidase gene). Transgenic OsBBTI5-RNAi plants displayed insensitivity to varying concentrations of 24-epibrassinolide in the brassinosteroid sensitivity assay. However, they showed reduced root and plant height at high concentrations (10 and 100 µM) of GA3 immersion. Enzyme activity assays revealed increased peroxidase (POD) and superoxide dismutase (SOD) activities and decreased malondialdehyde (MDA) content under 40-60 mM NaCl. Transcriptomic analysis indicated a significant upregulation of photosynthesis-related genes in transgenic plants under salt stress compared to the wild type. Notably, this study provides novel insights, suggesting that the BBI gene is part of the BR signaling pathway, and that OsBBTI5 potentially enhances stress tolerance in transgenic plants through interaction with the salt stress-related gene OsAPX2.

From plant survival to thriving: exploring the miracle of brassinosteroids for boosting abiotic stress resilience in horticultural crops

Abiotic stresses pose significant threat to horticultural crop production worldwide. These stresses adversely affect plant growth, development, and ultimately declined crop growth, yield and quality. In recent years, plant scientists have been actively investigating innovative strategies to enhance abiotic stress resilience in crops, and one promising avenue of research focuses on the use of brassinosteroids (BRs). BRs are a class of plant hormones that play crucial roles in various physiological processes, including cell elongation, differentiation, and stress responses. They have emerged as potent regulators of plant growth and development, and their role in improving abiotic stress tolerance is gaining considerable attention. BRs have been shown to mitigate the negative effects of abiotic stresses by modulating key physiological and biochemical processes, including stomatal regulation, antioxidant defense, osmotic adjustment, and nutrient uptake. Abiotic stresses disrupt numerous physiological functions and lead to undesirable phenotypic traits in plants. The use of BRs as a tool to improve crop resilience offers significant promise for sustainable agriculture in the face of increasing abiotic stresses caused by climate change. By unraveling the phenomenon of BRs, this review emphasizes the potential of BRs as an innovative approach for boosting abiotic stress tolerance and improving the overall productivity and quality of horticultural crops. Further research and field trials are necessary to fully harness the benefits of BRs and translate these findings into practical applications for crop production systems.

Exogenous brassinosteroids alleviate calcium deficiency-induced tip-burn by maintaining cell wall structural stability and higher photosynthesis in mini Chinese Cabbage

Tip-burn has seriously affected the yield, quality and commodity value of mini Chinese cabbage. Calcium (Ca²⁺) deficiency is the main cause of tip-burn. In order to investigate whether exogenous brassinosteroids (BRs) can alleviate tip-burn induced by calcium (Ca²⁺) deficiency and its mechanism, in this study, Ca²⁺ deficiency in nutrient solution was used to induced tip-burn, and then distilled water and BRs were sprayed on leaves to observe the tip-burn incidence of mini Chinese cabbage. The tip-burn incidence and disease index, leaf area, fluorescence parameters (Fv/Fm, NPQ, qP andφPSII) and gas exchange parameters (Tr, Pn, Gs and Ci), pigment contents, cell wall components, mesophyll cell ultrastructure and the expression of genes related to chlorophyll degradation were measured. The results showed that exogenous BRs reduced the tip-burn incidence rate and disease index of mini Chinese cabbage, and the tip-burn incidence rate reached the highest on the ninth day after treatment. Exogenous BRs increased the contents of cellulose, hemifiber, water-soluble pectin in Ca²⁺ deficiency treated leaves, maintaining the stability of cell wall structure. In addition, BRs increased photosynthetic rate by increasing the activities of Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and fructose 1,6-bisphosphatase (FBPase) related to Calvin cycle, maintaining relatively complete chloroplast structure and higher chlorophyll content via down-regulating the expression of BrPPH1 and BrPAO1 genes related to chlorophyll degradation. In conclusion, exogenous BRs alleviated calcium deficiency-induced tip-burn by maintaining cell wall structural stability and higher photosynthesis.

Enhancement of photosynthesis efficiency and yield of strawberry (Fragaria ananassa Duch.) plants via LED systems

Due to advances in the industrial development of light-emitting diodes (LEDs), much research has been conducted in recent years to get a better understanding of how plants respond to these light sources. This study investigated the effects of different LED-based light regimes on strawberry plant development and performance. The photosynthetic pigment content, biochemical constituents, and growth characteristics of strawberry plants were investigated using a combination of different light intensities (150, 200, and 250 μmol m^-2 s^-1), qualities (red, green, and blue LEDs), and photoperiods (14/10 h, 16/8 h, and 12/12 h light/dark cycles) compared to the same treatment with white fluorescent light. Plant height, root length, shoot fresh and dry weight, chlorophyll a, total chlorophyll/carotenoid content, and most plant yield parameters were highest when illuminated with LM7 [intensity (250 μmol m^-2 s^-1) + quality (70% red/30% blue LED light combination) + photoperiod (16/8 h light/dark cycles)]. The best results for the effective quantum yield of PSII photochemistry Y(II), photochemical quenching coefficient (qP), and electron transport ratio (ETR) were obtained with LM8 illumination [intensity (250 μmol m^-2 s^-1) + quality (50% red/20% green/30% blue LED light combination) + photoperiod (12 h/12 h light/dark cycles)]. We conclude that strawberry plants require prolonged and high light intensities with a high red-light component for maximum performance and biomass production.

Heat stress mitigation in tomato (Solanum lycopersicum L.) through foliar application of gibberellic acid

Phytohormones mediate physiological, morphological, and enzymatic responses and are important regulators of plant growth and development at different stages. Even though temperature is one of the most important abiotic stressors for plant development and production, a spike in the temperature may have disastrous repercussions for crop performance. Physiology and growth of two tomato genotypes ('Ahmar' and 'Roma') were studied in two growth chambers (25 and 45 °C) when gibberellic acid (GA₃) was applied exogenously. After the 45 days of planting, tomato plants were sprayed with GA₃ at concentrations of 25, 50, 75, and 100 mg L⁻¹, whereas untreated plants were kept as control. Under both temperature conditions, shoot and root biomass was greatest in 'Roma' plants receiving 75 mg L⁻¹ GA₃, followed by 50 mg L⁻¹ GA₃. Maximum CO₂ index, photosynthetic rate, transpiration rate, and greenness index were recorded in 'Roma' plants cultivated at 25 °C, demonstrating good effects of GA₃ on tomato physiology. Likewise, GA₃ enhanced the proline, nitrogen, phosphorus, and potassium levels in the leaves of both genotypes at both temperatures. Foliar-sprayed GA₃ up to 100 mg L⁻¹ alleviated the oxidative stress, as inferred from the lower concentrations of MDA and H₂O_2, and boosted the activities of superoxide dismutase, peroxidase, catalase. The difference between control and GA₃-treated heat-stressed plants suggests that GA₃ may have a function in mitigating heat stress. Overall, our findings indicate that 75 mg L⁻¹ of GA₃ is the optimal dosage to reduce heat stress in tomatoes and improve their morphological, physiological, and biochemical characteristics.

Preharvest Foliar Applications of Citric Acid, Gibberellic Acid and Humic Acid Improve Growth and Fruit Quality of ‘Le Conte’ Pear (Pyrus communis L.)

A two-year (2020-21) study was conducted to investigate the possibility of relying of ten-years old pear trees grown on sandy loam soil irrigated by drip on citric acid (CA), gibberellic acid (GA3) and humic acid (HA). The CA was applied at the concentrations of 500, 1000 and 1500 ppm, GA3 at 50, 100 and 150 ppm and HA at 3, 4 and 5%, whereas water spray was used as the control. The results of our study proved that CA, GA3 and HA improved the shoot length, shoot thickness, leaf area and leaf chlorophyll of pear as compared with the control. Moreover, they also positively increased the fruit set percentage and final yield of ‘Le Conte’ pear. The fruit weight, size and firmness were also improved under the influence of aforementioned treatments. The fruit soluble solids, total sugars, leaf nitrogen, leaf phosphorus and leaf potassium of pear were also enhanced as compared with the control. Additionally, spraying of GA3 at 150 ppm, as well as, HA at 5 and 4% were the superior treatments and showed the most significant impact on plant growth, yield, fruit quality and leaf mineral content of pear. This study provides a basis for the future elucidation of HA-, GA3- and CA-modulated molecular mechanisms in pear, which can make a significant contribution in the scientific community.

Effect of Paper and Aluminum Bagging on Fruit Quality of Loquat (Eriobotrya japonica Lindl.)

Bagging regulates the fruit microenvironment and improves the quality and market value of fruits. It is a safe and ecofriendly technique to protect fruits from insect/pest infestation and multiple biotic and abiotic stresses. In the current study, the influence of fruit bagging was evaluated on the development and quality of loquat fruits. Fruits from a healthy loquat orchard (Cv. Zaozhong No.6), located in Fujian, China, were enveloped in paper (T1), aluminum (T2), and aluminum-polyethylene bags (T3), while unbagged fruits were maintained as control (T0). In general, fruit bagging improved fruit quality in terms of fruit physiological and biochemical attributes and protected fruits from physical damage. In particular, aluminum-polyethylene bagging enhanced fruit weight, length, and width by 1.37-, 1.18-, and 1.13-fold, respectively. Loquat fruits bagged with paper bags exhibited the maximum soluble sugar and lowest titratable acid content. Fruits treated with paper and aluminum-ethylene bags showed twofold higher sugar-acid ratio as compared to control. Aluminum-polyethylene bagging caused 66.67%, 55.56%, and 33.33% reductions in skin burn, fruit rotting, and black spot of loquat. The fruits bagged in aluminum and aluminum-polyethylene did not show insect or bird damage, while unbagged fruits had 14.70% and 17.65% insect and bird damage, respectively. Overall, the results suggest that paper, aluminum, and aluminum-polyethylene bagging improved fruit health by 75%, 131%, and 144%, respectively, as compared to control. To delineate bagging type-dependent effects, principal component analysis was performed. Paper bagging was positively correlated with fruit firmness, rotting, soluble sugars, sugar-acid ratio, and proline content. Aluminum bagging was highly associated with improvements in titratable acids, cystine, and methionine. Aluminum-polyethylene bags were correlated with fruit weight, size, peel thickness, edible rate, and certain amino acids.

Effect of Foliar Supplied PGRs on Flower Growth and Antioxidant Activity of African Marigold (Tagetes erecta L.)

Marigold is one of the commercially exploited flowering crops that belongs to the family Asteraceae. The production of economical yield and better quality of marigold flowers requires proper crop management techniques. Crop regulation is an important technique to make the marigold production profitable. This can be done by adopting application of plant growth regulators (PGRs). The present study was designed to investigate the effect of PGRs on flowering and antioxidant activity of two cultivars of African marigold (Tagetes erecta L.) viz. “Pusa Narangi Gainda” (hereinafter referred to as Narangi) and “Pusa Basanthi Gainda” (hereafter referred to as Basanthi). Plants were sprayed with abscisic acid (ABA), N-acetyl thiazolidine (NAD), gibberellic acid (GA3), salicylic acid (SA), indole-3-butyric acid (IBA) and oxalic acid (OA) at the concentrations of 100, 150, 250, 300 and 800 mg·L−1, each. Results revealed that the plants treated with 500–600 mg·L−1 IBA exhibited maximum increase in floral diameter (34–51%). The use of 500–550 mg·L−1 IBA exhibited maximal enhancement in flower fresh weight (21–92%). The exogenously applied OA significantly (p ≤ 0.05) improved flower dry weight, total phenolic contents, total flavonoid contents and reducing power ability of marigold plants. Overall, “Narangi” performed better than “Basanthi”, in terms of flowering and antioxidant activity. Conclusively, the results suggest that foliar application of PGRs favors flowering and antioxidant activity of African marigold.

Transcriptome data-based identification of candidate genes involved in metabolism and accumulation of soluble sugars during fruit development in 'Huangguan' plum

Fruit sweetness being an important factor of organoleptic quality directly affects the consumers' preferences for fresh fruit consumption, and is influenced by the composition and quantity of sugars. In this study, four soluble sugars (sucrose, fructose, glucose, and sorbitol) were identified and quantified in plum fruits cv. 'Huangguan' at four different maturity stages (fruitlet, green, veraison, and mature stage). The results revealed that sucrose and glucose are major soluble sugar components at the fruitlet and mature stages, respectively. RNA-Seq analysis was carried out and 6,778 differentially expressed genes (DEGs) were identified, including 121 genes involved in sugar metabolism. Furthermore, a total of 39 transcripts of 8 gene families encoding key enzymes related to the metabolism and accumulation of soluble sugars were separately identified. ERD6L (gene 103322904) was involved in keeping a balance of glucose between the inside and outside of vacuole. SS (gene 103333990) and SDH (gene 103335104) regulated the accumulation of fructose at the green stage. SDH (gene 103335104) controlled the degradation of sorbitol at the green stage. SS (gene 103333990) and PFK (gene 103333391) regulated the degradation of sucrose at the early stages of fruit development. Moreover, NINV (gene 103331108) regulated the accumulation of total sugar in plum. Genes 103321334 and 103335689 were important bZIP transcription factors that regulate the accumulation of glucose and fructose in fruits. Twelve DEGs were selected and validated to observe the relative accuracy of transcriptome sequencing data using qRT-PCR. Gene expression patterns were consistent between qRT-PCR and RNA-Seq data, indicating the reliability of RNA-Seq data. PRACTICAL APPLICATIONS: The results of this study provided new insights into comprehensive understanding of the genetic control of sugar metabolism and accumulation in plum fruits.