Synergistic Effect of Nano-Sliver with Sucrose on Extending Vase Life of the Carnation cv. Edun

Editing of the ethylene biosynthesis gene in carnation using CRISPR-Cas9 ribonucleoprotein complex

The study aimed to edit ethylene (ET) biosynthesis genes [1-aminocyclopropane-1-carboxylic acid (ACC) synthetase 1 (ACS1) and ACC oxidase 1 (ACO1)] in carnation using the CRISPR/Cas9 ribonucleoprotein (RNP) complex system. Initially, the conserved regions of the target genes (ACS1 and ACO1) were validated for the generation of different single guide RNAs (sgRNAs), followed by the use of an in vitro cleavage assay to confirm the ability of the sgRNAs to cleave the target genes specifically. The in vitro cleavage assay revealed that the sgRNAs were highly effective in cleaving their respective target regions. The complex of sgRNA: Cas9 was directly delivered into the carnation protoplast, and the target genes in the protoplast were deep-sequenced. The results revealed that the sgRNAs were applicable for editing the ET biosynthesis genes, as the mutation frequency ranged from 8.8 to 10.8% for ACO1 and 0.2-58.5% for ACS1. When sequencing the target genes in the callus derived from the protoplasts transformed with sgRNA: Cas9, different indel patterns (+ 1, - 1, and - 8 bp) in ACO1 and (- 1, + 1, and + 11) in ACS1 were identified. This study highlighted the potential application of CRISPR/Cas9 RNP complex system in facilitating precise gene editing for ET biosynthesis in carnation.

Increasing the Vase Life of Chrysanthemum Cut Flowers by Using Silver and Zinc Nanoparticles

Cut flowers are horticultural products that have great potential to be developed. Efforts to maintain quality and extend the shelf life of cut flowers are very important to obtain a product that is accepted in the market. The main problems of chrysanthemum cut flowers are the leaves easily turning yellow, wilting, and failure to fully open flowers. This study aimed to obtain the best pulsing solution formulation that increases vase life and maintains the freshness of chrysanthemum cut flowers. Pulsing solution treatment was carried out on chrysanthemum cut flowers during the evaluation period. Pulsing solution treatment consisted of control, AgNO3, nano-Ag (NAg), ZnO, and nano-Zn (NZn). The results showed that NAg20 treatment increased the vase life of chrysanthemum cut flowers up to 23 days, which was 19 days longer than the control. Nano-Ag inhibits bacterial growth, flower wilting, color degradation, and carotenoids. In addition, nano-Ag increased the size of the bloom-flower diameter. Considering the results of all postharvest quality parameters mentioned above, NAg20 extends the vase life of chrysanthemum cut flowers.

Lemon grass essential oil improves Gladiolus grandiflorus postharvest life by modulating water relations, microbial growth, biochemical activity, and gene expression

Gladiolus (Gladiolus grandiflorus Andrews) is a high-valued bulbous cut flower. However, the shorter postharvest life of the gladiolus, limits its marketing and commercial value. In the present investigation, the effect of lemon grass (LG) essential oil as an antimicrobial agent was studied towards increasing the vase life of gladiolus. The results revealed that as compared to control (distilled water), treatment with a lower concentration of 5 µL L^-1 LG essential oil prolonged the vase life of gladiolus up to 11 days (d). Scanning Electron Microscope (SEM) observation indicated that the sample treated with 5 µL L^-1 LG essential oil showed intact vasculature, suggesting reduced microbial blockage at the stem end which was further corroborated by microbial count. Biochemical analysis suggested an increased level of total soluble sugars, carotenoid content, lower MDA accumulation, and higher activity of antioxidant enzymes in LG treated flowers. Moreover, transcripts levels of genes associated with senescence viz., GgCyP1 and GgERS1a were downregulated, while expression of GDAD1 and antioxidant genes such as GgP5C5, GgPOD 1, GgMnSOD, and GgCAT1 were upregulated in LG treated cut spikes as compared to control. Among various treatments we have concluded that, the vase life of the gladiolus cut spike was improved along with the relative fresh flower weight and diameter of flower at the lower dose of 5 µL L^-1 LG oil in the vase solution. Thus, LG oil as an eco-friendly agent has the potential to extend the postharvest life of cut flowers.

Synergistic effect of graphene oxide and silver nanoparticles as biostimulant improves the postharvest life of cut flower bird of paradise (Strelitzia reginae L.)

The bird of paradise (Strelitzia reginae L.) is one of the important tropical cut flowers. Generally, flowers like bird of paradise (BOP) grown for the commercial ornamental market must be of high pre and postharvest quality. Thus, to improve the postharvest longevity and increase marketability, the relative efficacy of two different biologically synthesized nanoparticles (NPs) was evaluated. The novel proprietary stimulants were graphene oxide (GO) and silver nanoparticles (SNPs). The NP treatments were applied as a vase (lower concentrations) solutions. Among all the applied treatments, the synergistic effect of GO + SNPs at 1 µL L^-1 vase solution significantly (p =0.05) prolongs the post-harvest life of cut flowers of BOP. Increased vase life over the deionized water (DI) control was associated with better maintenance of relative water uptake, relative fresh weight, suppressed microbial density at stem-end and delay of stem blockage, reduced electrolyte leakage, malondialdehyde (MDA), SOD, and POD activity. In contrast to control, administration of NPs gave better results for all analyzed parameters. Application of biologically synthesized NPs in combination (GO + SNPs at 1 µL L^-1) extended the vase life of cut flowers by 6 days compared with control flowers, and overall, showed better results than the control. The findings of the studies revealed that the standardized NPs could have more potential in prolonging the postharvest life of cut flowers in BOP. Thus, this technique can be used as a novel postharvest technology for commercial application in cut flowers.

Combined Nano Silver, α-Aminoisobutyric Acid, and 1-Methylcyclopropene Treatment Delays the Senescence of Cut Roses with Different Ethylene Sensitivities

Flower senescence varies among cut roses (Rosa hybrida L.), and it is known that the postharvest life of ethylene-sensitive flowers is strongly related to the transcriptional accumulation of ethylene biosynthesis genes, whereas that of ethylene-insensitive flowers is shortened by water stress. These different responses of flowers to hormone and water stresses limit the action of preservatives in inhibiting the postharvest deterioration of cut rose flowers. This study was conducted to investigate the effects of the combined application of antibacterial agents and ethylene biosynthesis and binding inhibitors on the postharvest life and quality of the cut rose cultivars ‘Matador’ (ethylene-sensitive) and ‘Dolcetto’ (ethylene-insensitive). Cut flowers were treated with nano silver (NS), a combination of NS and α-aminoisobutyric acid (NS+A), or a combination of NS+A and 1-methylcyclopropene (NS+AM), and they were subsequently exposed to ethylene for 24 h. Treatment effectiveness was compared with that of control (CON) flowers, which were kept in distilled water and exposed only to ethylene. The results showed that all treatments significantly improved the postharvest quality and vase life of both rose cultivars. However, NS+AM most markedly delayed senescence and prolonged the vase life of cut flowers by 217% in ‘Matador’ and 168.4% in ‘Dolcetto’, compared with those of CON flowers. NS+AM also effectively increased the flower diameter and maintenance time of positive water balance and initial fresh weight by enhancing solution absorption as well as suppressing bacterial growth at the cut stem ends of the cut roses. Furthermore, NS+AM greatly suppressed the ethylene-inducible increase of ethylene biosynthesis genes and the reduction of ethylene receptor genes in petals, which resulted in a reduced flower response to exogenous ethylene in both rose cultivars. These findings show that NS+AM effectively delays flower senescence in both ethylene sensitive and insensitive cultivars by synergistically preventing ethylene response and water stress in cut flowers.

Editing of 1-aminocyclopropane-1-carboxylate oxidase genes negatively affects petunia seed germination

Editing of ACO genes involved in ethylene biosynthesis pathway reduces ethylene production in petunia seeds and inhibits seed germination. Ethylene production in the seeds of Petunia hybrida cv. 'Mirage Rose' was associated with expression of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO) genes (PhACO1, PhACO3, and PhACO4). Suppression of their expression by ethylene inhibitor silver thiosulphate (STS) significantly reduced ethylene production and inhibited seed germination. When it was combined with ethylene precursor ACC, ethylene production was re-promoted via activation of the genes and higher seed germination was restored. This was confirmed using the mutants editing the genes and WT. In the present study, compared with wild type plants, three different mutants (phaco1, phaco3, and phaco4) showed significantly decreased germination percentages as well as delayed germination time and seedling growth. These reductions were associated with lighter seed weight, lower ACO transcript levels, and lower ethylene production in mutants. Inhibited seed germination owing to reduced ethylene production was further verified by the supplementation of exogenous ACC and gibberellic acid (GA₃) to growth medium, which restored high seed germination activity in all mutants via enhanced ethylene production. In this study, we reported a key regulatory role of ethylene in seed germination mechanisms in petunia. Further, we highlighted on need to consider the negative effects of ethylene reduction in seed germination and plant growth when editing genes in the ethylene biosynthesis pathway for the maintenance of postharvest fruit, vegetable, and flower quality.

Regulation of Botrytis cinerea Infection and Gene Expression in Cut Roses by Using Nano Silver and Salicylic Acid

Botrytis cinerea (B. cinerea) is one of the necrotrophic pathogens resulting in the heaviest commercial losses in cut rose flowers, and the severity of gray mold disease partly depends on the presence of ethylene during the storage and transport. The effectiveness of nano silver (NS) and salicylic acid (SA) was assessed as a novel control agent in protecting the cut rose flowers against B. cinerea infection and ethylene damages. The efficacy of NS and SA was compared with an inoculated control (CON). A non-treated control (NT) was also used to evaluate the natural infection process. The results indicated that pretreatment with 20 mg L-1 NS significantly reduced B. cinerea growth in rose petals during vase periods. NS effectively suppressed the mRNA levels of ethylene biosynthesis genes (RhACS2, RhACS4, and RhACO1) and the reduction in expression levels of ethylene receptor genes (RhETR1, RhETR2, and RhETR5) and the downstream regulator RhCTR2 in rose petals after B. cinerea inoculation. NS application also decreased the expression of the B. cinerea snod-prot-like 1 (Bcspl1) gene which acts as the virulence factor in cut roses. In NS flowers, the maximum quantum yield of PSII (Fv/Fm) value was higher and the leaf temperature was lower on day 1, suggesting that these factors can be used for detecting B. cinerea infection and water stress in cut rose flowers. Furthermore, NS improved water relations and extended the vase life of cut rose flowers by 3.3 d, compared with that of NT flowers. In contrast, SA had no inhibitive effects on both B. cinerea growth and ethylene response in cut roses. The findings from the present study highlight NS as a promising new candidate for preventing B. cinerea infection and ethylene damages and for improving the postharvest quality of cut roses exported overseas.