Efficacy and Phytotoxicity of Phosphine as Fumigants for Frankliniella occidentalis (Thysanoptera: Thripidae) on Asparagus.

The insecticidal activity of phosphine (PH3) and ethyl formate (EF) toward Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) and their phytotoxicity to asparagus were evaluated. Both the PH3 and EF fumigants showed higher lethal concentration and time (LCT) values at lower temperatures. The LCT99 values of PH3 and EF at 5°C in a 12 liters desiccator for 4 h showed the following ranking: eggs (64.69 mg·h/liter for PH3 and EF indicating phytotoxicity to asparagus), nymphs (5.54 and 17.48 mg·h/liter, respectively), and adults (3.83 and 14.67 mg·h/liter, respectively). The adsorption of PH3 was approximately 11% at 2°C and 13% at 5°C, whereas the adsorption of EF increased sharply to 88% at 2°C and 97% at 5°C. The hatching rate of F. occidentalis eggs was approximately 95% at all locations (top, middle, and bottom) in the presence of 4 mg/liter PH3 at 5°C in a 0.65-m3 fumigation chamber for 24 h. However, extension of the treatment to 48 h resulted in 100% inhibition of egg hatching. The atmospheric level of PH3 decreased below the threshold limit value after 80 min, and phytotoxicity was not observed. The results revealed that EF is highly absorbed by asparagus and is not suitable as a fumigant, but PH3 is a suitable alternative to the fumigant methyl bromide for the control of western flower thrips in asparagus.

Synergetic effects of 5-aminolevulinic acid and Ascophyllum nodosum seaweed extracts on Asparagus phenolics and stress related genes under saline irrigation.

Salinity is one of the major agricultural problems that may threat food security and limit the agricultural lands expansion worldwide. Exploring novel tools controlling saline conditions and increase valuable secondary metabolites in the horticultural crops might have outstanding results that serve humanity in the current century. The current study explores the effects of weekly seaweed extracts (7 mL L-1) and/or 5-aminolevulinic acid (3, 5 and 10 ppm) sprays on Asparagus aethiopicus plants subjected to saline stress conditions (2000 and 4000 ppm) for 6 weeks in two consecutive seasons of 2016 and 2017. Under saline conditions, there were stimulatory synergetic effects of seaweed extracts (SWE) and 5-aminolevulinic acid (ALA) on branch length and number of treated plants. Similar increases were also found in fresh and the dry weight of treated plants compared to control. These morphological improvements associated with increased accumulation of specific phenols (robinin, rutin, apigein, chlorogenic acid and caffeic acid) as revealed by High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD). There were increases in the antioxidant activities of leaf extracts, chlorophyll content and sugars and proline accumulation. The transpiration and photosynthetic rates as well as the stomatal conductance were enhanced. The morphological and physiological improvements associated with increased expression of several genes responsible for water management (ANN1, ANN2 and PIP1), secondary metabolite production (P5CS1 and CHS) and antioxidants accumulation (APX1 and GPX3) in plants. Our findings indicate that SWE + ALA had stimulatory synergetic effects on the growth and secondary metabolites of A. aethiopicus subjected to saline conditions. Several mechanisms are involved in such effects including gas exchange control, sugar buildup, increasing non-enzymatic and enzymatic antioxidants control of reactive oxygen species accumulation as well as transcriptional and metabolic regulation of environmental stress.

Involvement of an autotoxic compound in asparagus decline.

Asparagus (Asparagus officinalis L.) is a widely cultivated perennial veritable and can be harvested more than ten years. However, the crop quality and yield decline after a few year's cultivation, which is called "asparagus decline". Even though those asparagus plants were replaced with new young asparagus plants, the productivity and quality of the crop remain relatively low, which is known as a "asparagus replant problem". One of the possible reasons for "asparagus decline" and "asparagus replant problem" is thought to be autotoxicity of asparagus. However, the compounds involved in the autotoxicity is not clear. The objective of this study was therefore to determine the potential role of autotoxicity in the "asparagus decline" and "asparagus replant problem". An aqueous methanol extract of 10-year-asparagus-cultivated soils inhibited the growth of asparagus seedlings and other two test plants with concentration dependent manner. The result confirmed that the asparagus soils have autotoxic activity. The extract was then purified by several chromatographies with monitoring the inhibitory activity and a potent growth inhibitory substance causing the autotoxic effect was isolated. The chemical structures of the compound was determined by spectral data to be trans-cinnamic acid. trans-Cinnamic acid inhibited the growth of asparagus seedlings at concentrations greater than 10 µM. The concentrations required for 50% growth inhibition of asparagus (IC50) were 24.1-41.6 µM. trans-Cinnamic acid accumulated 174 µM in the 10-year-asparagus-cultivated soils, which may be enough levels to cause the growth inhibition on asparagus considering its IC50 value. Therefore, trans-cinnamic acid may contribute to the autotoxic effect of asparagus soils, and may be in part responsible for "asparagus decline" and "asparagus replant problem".

Asparagus decline: Autotoxicity and autotoxic compounds in asparagus rhizomes.

Asparagus (Asparagus officinalis L.) is a perennial vegetable, but its crop productivity and quality decrease gradually. One possible reason for "asparagus decline" is thought to be the autotoxicity of asparagus. However, the autotoxic property of asparagus rhizomes remains unknown. The objective of this study was to determine the potential role of rhizomes in the autotoxicity of asparagus. An aqueous methanol extract of asparagus rhizomes inhibited the growth of asparagus seedlings and six other test plants in a concentration-dependent manners: garden cress (Lepidum sativum L.), lettuce (Lactuca sativa L.), alfalfa (Medicago sativa L.), ryegrass (Lolium multiflorum Lam.), timothy (Phleum pratense L.) and barnyardgrass (Echinochloa crus-galli (L.) Beauv.). These results suggest that asparagus rhizomes contain autotoxic compounds. The extract was purified through several chromatographic steps with monitoring the autotoxic activity, and p-coumaric acid and iso-agatharesinol were isolated. These compounds inhibited the shoot and root growth of asparagus and two other test plants, garden cress and ryegrass, at concentrations higher than 0.1mM. The concentrations required for 50% inhibition of the root and shoot growth of these test plants ranged from 0.36 to 0.85mM and 0.41-1.22mM for p-coumaric acid and iso-agatharesinol, respectively. Therefore, these compounds may contribute to the autotoxicity caused by asparagus rhizomes and may be involved in "asparagus decline".

Effects of post-harvest stigmasterol treatment on quality-related parameters and antioxidant enzymes of green asparagus (Asparagus officinalis L.).

The effects of immersion of green asparagus spears in stigmasterol solution (0, 0.5 and 1.0 g l-1, 15 min, 25°C) on weight loss, surface colour, enzyme activities and content of malondialdehyde, total phenol, lignin and chlorophyll were investigated during 40 days of storage at 4 ± 0.5°C. Of the concentrations tested, 0.5 g l-1 treatment was most effective. Stigmasterol (0.5 g l-1) treatment significantly reduced colour changes and losses of fresh weight and chlorophyll content. Superoxide dismutase (SOD) and catalase (CAT) activities were maintained higher in stigmasterol-treated (0.5 g l-1) asparagus, whereas the activity of peroxidase (POD) was significantly reduced. Stigmasterol treatment (0.5 g l-1) also significantly decreased the content of malondialdehyde (MDA) and increased total phenol content. Accumulation of lignin was positively correlated to activity of guaiacol-POD (r = 0.960, p < 0.01) in stigmasterol-treated (0.5 g l-1) asparagus. The polyphenol oxidase (PPO) activity decreased and showed a significant negative correlation with the chroma L* value (r = -0.899, p < 0.01) in stigmasterol-treated (0.5 g l-1) asparagus. It was concluded that stigmasterol treatment (0.5 g l-1) could inhibit the senescence of green asparagus, and therefore prolong its shelf-life, maintaining the quality of post-harvest green asparagus.

Sucrose delays senescence and preserves functional compounds in Asparagus officinalis L.

The high metabolic rate of harvested asparagus spears (Asparagus officinalis L.) causes rapid deterioration. To extend shelf life, we investigated the effect of sucrose treatment on asparagus during storage. Asparagus spears were treated with 3%, 5%, and 10% sucrose and stored at 2 °C for 20 h. Cellular respiration decreased, but other processes were unaltered by exogenous sucrose. The overall appearance of asparagus treated with 3% sucrose and stored at 2 °C for 18 days was rated as good and excellent, unlike that of untreated spears. Asparagus treated with sucrose maintained firmness for 15 days, while untreated spears lost firmness and showed increased water-soluble pectin content during storage. Carbohydrate levels were also higher in sucrose-treated than in control samples. Transcript levels of cell-wall-related genes, including xyloglucan endotransglycosylase (XET)1, XET2, and peroxidase (prx)1, prx2, and prx3 were upregulated by sucrose. Cyanidin 3-O-rutinoside and rutin levels immediately increased upon addition of sucrose and remained high relative to the control during storage. Thus, sucrose modulates asparagus cell wall components and maintains the functionality of important compounds during storage, thus effectively prolonging shelf life.

Evaluation of mercury stress in plants from the Almadén mining district by analysis of phytochelatins and their Hg complexes.

To evaluate plant response to Hg stress, glutathione, phytochelatins, and their Hg complexes were analyzed using HPLC with amperometric detection in samples of Asparagus acutifolius grown in the Almadén mining district (Ciudad Real, Spain), one of the most Hg-contaminated sites in the world. Soils of the Almadén mining district, and specifically from the Almadenejos zone, are highly contaminated, with some zones having values above 4,000 µg Hg g(-1) soil. Although soils have an extremely high concentration of mercury, generally less than 2% is available for plants, as is shown by various soil extractions simulating bioavailability. In plants, Hg concentration increases depending on the content of Hg in soils. In addition, Hg levels in roots are higher than in aerial parts, which is a strategy of plants for protecting their more sensitive aerial parts from the deleterious effects of metal stress. The total content of phytochelatins (PCs) and their complexes are directly related with the amount of mercury in soils. These findings highlight the important role of thiol compounds and their metal complexes in capturing and fixing Hg from soils, giving plants the capacity to deal with the heavy metal toxicity of polluted soils.

Effect of chitosan coatings on postharvest green asparagus quality.

Fresh postharvest green asparagus rapidly deteriorate due to its high respiration rate. The main benefits of edible active coatings are their edible characteristics, biodegradability and increase in food safety. In this study, the quality of the edible coatings based on 0.50%, 0.25% high-molecular weight chitosan (H-chitosan), and 0.50%, 0.25% low-molecular weight chitosan (L-chitosan) on postharvest green asparagus was investigated. On the basis of the results obtained, 0.25% H-chitosan and 0.50% L-chitosan treatments ensured lower color variation, less weight loss and less ascorbic acid, decrease presenting better quality of asparagus than other concentrations of chitosan treatments and the control during the cold storage, and prolonging a shelf life of postharvest green asparagus.

Effect of salicylic acid treatment on postharvest quality, antioxidant activities, and free polyamines of asparagus.

The effects of salicylic acid (SA) on the quality and antioxidant activity of asparagus stored at 18 ± 2 °C were investigated by analyzing the color, chlorophyll, shear force, and the activity of antioxidant compounds such as ascorbic acid, phenolics, flavonoids, 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity ferric reducing antioxidant power (FRAP), and polyamines (PAs). The results showed that SA improved the color and maintained the chlorophyll, phenolic, flavonoid, and ascorbic acid content of asparagus. High concentrations of SA caused a deterioration in asparagus would harm to color and had no effect on shear force within 6 d. SA induced the maximum concentration of phenolics in postharvest asparagus, promoted the increase in total flavonoids before 6 to 9 d, affected the antioxidant activity positively as indicated by the resultant increase in FRAP concentration; however, SA was only active with regard to DPPH scavenging activity within 6 d of treatment. Spermidine (Spd) is the most common form of PA in asparagus, and free putrescine (Put) contents increased over the first 3 d following harvest and then decreased. Spd and Spm concentrations evolved in a similar way and decreased during storage. Higher Spd and Spm contents in the SA pre-treatment Put was inhabited and its peaks appeared later.

Effects of hydrogen peroxide treatment on thiol contents in fresh-cut asparagus (Asparagus officinalis) spears.

In this work, the impact of hydrogen peroxide (H2O2) was investigated on the thiol content of asparagus. Fresh-cut asparagus was treated with H2O2 at varied oxidant concentrations and contact times. A significant decrease (alpha=0.05) was observed in N-acetylcysteine levels treated with 2.5% H2O2 for 10 min and with 5% H2O2 for 3, 5 and 10 min. Captopril and cysteine levels significantly decreased (alpha=0.05) in all and most treatment conditions, respectively. Glutathione levels only significantly decreased with 2.5% and 5% H2O2 for 10 min treatment. In order to determine whether asparagus undergoes oxidative stress, a well-known oxidative stress indicator-the glutathione/oxidized glutathione ratio-was calculated. This study showed that the common use of H2O2 as a disinfectant/sterilizer by the food industry could markedly diminish the important biothiols and develop oxidative stress in asparagus, and potentially in other vegetables as well.

Electroporation modulates the embryogenic responses of asparagus (Asparagus officinalis L.) microspores.

Microspores of three genotypes of Asparagus officinalis L. were mechanically isolated without affecting their viability and were submitted to electric fields in order to modulate their competence for embryogenesis. When a constant pulse length and various field strengths (250, 500, 750, 1000, 1500, and 2000 V/cm) were tested, the viability of electro-treated microspores decreased as the field strength increased, for all genotypes. Conversely, the embryogenic competence was genotype dependent and was enhanced by low voltages for two clones when microspores were cultured in the presence of auxin. When the effect of pulse duration was studied, despite a strong genotype effect on responses, a short pulse coupled with a low voltage appeared to improve the competence for proembryo formation compared with nonelectroporated microspores, while longer pulses significantly improved microspore division.

Preparation and Characterization of Fully Active Biotinylated Analogs of Phytosulfokine-α.

We report the preparation of biotinylated analogs of phytosulfokine-α (Tyr(SO3H)-Ile-Tyr(SO3H)-Thr-Gln; PSK-α), an endogenous peptide growth factor in plants. Because the modification of the N-terminal amino group leads to significant loss of the activities, a Lys residue was incorporated in the C-terminal region of PSK-α, and its e amino group was reacted with biotinylation reagent. Results of the binding assay showed that [N(ε)-(biotinyl)Lys(5)]PSK-α retained the same binding activity and mitogenic activity as that of native PSK-α. Insertion of a single or double 6-aminohexanoic acid spacer between the ε amino group of Lys(5) and the carboxyl group of biotin did not significantly alter the activities of biotinylated [Lys(5)]PSK-α. Structure-activity information obtained here would be useful for the detection and isolation of PSK-α receptors.