Accumulation Of Antifungal Compounds Research Articles

2,4-EPIBRASSIONOLIDE ACTIVATES PRIMING RESISTANCE AGAINST RHIZOPUS STOLONIFER INFECTION IN PEACH FRUIT

This study was conducted to assess the effects of 2,4-epibrassionolide (EBR) on mold decay caused by Rhizopus stolonifer and its capability to activate biochemical defense reactions in postharvest peaches. The treatment of EBR at 5 μM possessed the optimum effectiveness on inhibiting the Rhizopus rot in peach fruit among all treatments. The EBR treatment significantly up-regulated the expression levels of a set of defense-related enzymes and PR genes that included PpCHI, PpGns1, PpPAL, PpNPR1, PpPR1 and PpPR4 as well as led to an enhancement for biosynthesis of phenolics and lignins in peaches during the incubation at 20 °C. Interestingly, the EBR-treated peaches exhibited more striking expressions of PR genes and accumulation of antifungal compounds upon inoculation with the pathogen, indicating a priming defense could be activated by EBR. On the other hand, 5 μM EBR exhibited direct toxicity on fungal proliferation of R. stolonifer in vitro. Thus, we concluded that 5 μM EBR inhibited the Rhizopus rot in peach fruit probably by a direct inhibitory effect on pathogen growth and an indirect induction of a priming resistance. These findings provided a potential alternative for control of fungal infection in peaches during the postharvest storage.

Reactive oxygen species metabolism and phenylpropanoid pathway involved in disease resistance against Penicillium expansum in apple fruit induced by ϵ-poly-l-lysine.

Blue mould caused by Penicillium expansum comprises a notable disease of apple fruit during storage. ϵ-Poly-l-lysine (PL) consists of ϵ-amino and α-hydroxyl and has been used in food preservation. In the present study, apple fruits (cv. Fuji) were used to investigate the effects of PL dipping treatment, at different concentrations of PL, on the lesion diameter of fruit inoculated with P. expansum, aiming to screen the optimal concentration for controlling blue mould. The effects of PL at the optimal concentration on reactive oxygen species (ROS) metabolism and the phenylpropanoid pathway were also investigated. The results indicated that 25, 50, 100 and 200 µL L-1 PL treatment significantly decreased the lesion diameter in apple fruit inoculated with P. expansum and the smallest lesion diameter was determined for 50 µL L-1 PL-treated fruits. The results also indicated that 50 µL L-1 PL treatment increased the hydrogen peroxide content and the activities of enzymes involved in ROS metabolism, including superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and peroxidase in apple fruit. The activity of phenylalanine ammonia-lyase and the contents of lignin, total phenolic compounds and flavonoids were also enhanced by PL treatment. The disease resistance to P. expansum in apple fruits enhanced by PL treatment is related to activating ROS metabolism and the phenylpropanoid pathway and the accumulation of antifungal compounds. © 2018 Society of Chemical Industry.

BENZOTHIADIAZOLE INDUCES DEFENCE RESPONSES IN BERRY CROPS

Plants have developed multiple protection strategies during evolution in response to invading pathogens and environmental stresses. Flavonoids are a large and diverse group of over 4000 compounds, many of which are known to play an important role against UV-light stress and microbial attacks in plants. Many of these plant defence compounds are also health-promoting phytochemicals in the human diet. Strawberry (Fragaria x ananassa) contains a variety of such phenolic compounds. We found that the most disease resistant (to gray mold) strawberry cultivar contained considerably more flavonoids than the most susceptible one, but the role of these compounds in disease resistance is still unclear. Defence mechanisms in plants can be activated by biotic or abiotic elicitors, which trigger a defence pathway leading to the expression of several defence genes and the accumulation of antifungal compounds, which eventually leads to the inhibition of the fungal growth. We tested the ability of benzothiadiazole (BTH) to induce resistance to powdery mildew (Sphaerotheca macularis) in strawberry. Powdery mildew has become a serious disease in strawberry grown in greenhouses in many parts of the world. As chemical control is difficult because of the rapid development of fungicide-insensitive strains, alternative strategies are needed. We showed that foliar applications of BTH (0,6-1,2 g/l) on young strawberry leaves provide effective mildew control in greenhouses. The flavonol glycoside content of BTH-treated leaves was also analyzed by HPLC and ESI-MS method, but no clear differences were detected between BTH-treated and control plants. However, the levels of two flavonols, quercetin and kaempferol, in berries were increased in response to foliar treatments under field conditions. The results suggest that BTH and related bioactivators may become a realistic alternative for chemical control against powdery mildew in strawberries grown in greenhouses and plastie tunnels.

Induced responses in stilbenes and terpenes in fertilized Norway spruce after inoculation with blue-stain fungus, Ceratocystis polonica

In conifers, attacks by bark beetles and associated pathogenic fungi cause an induced wound response, which is characterized by accumulation of antifungal compounds and morphological changes that aid wound healing. In this article the stilbene and terpene concentrations of Norway spruce phloem were monitored as symptoms of induced wound responses in relation to changed nutrient conditions caused by fertilization. Plots of mature Norway spruce were fertilized with N, P or NPK. One year after fertilization the trees were artificially infected with Ceratocystis polonica, a pathogenic fungus associated with the bark beetle Ips typographus. The response of stilbenes to fungal inoculation was mainly qualitative. The concentration of stilbene glycosides in the phloem decreased, and in the immediate vicinity of the site of fungal inoculation, stilbene glycosides were less frequent than in mechanically wounded or unwounded phloem. Corresponding stilbene aglycones were most frequent inside the reaction lesion. The concentration of total stilbene aglycones near the inoculation site was significantly lower in N-fertilized trees than in unfertilized trees. Fungal inoculation caused a strong quantitative response in terpenes. The total terpene concentration of the phloem increased significantly, to almost 100 times greater near the inoculation site compared to the constitutive values. N fertilization significantly reduced the total terpene and total stilbene aglycone concentrations near the inoculation sites. Thus, N fertilization may reduce the ability of Norway spruce to defend itself against fungal pathogens.

Accumulation of antifungal compounds in tea leaf tissue infected with Bipolaris carbonum.

Varietal resistance of tea towards Bipolaris carbonum was tested following detached leaf inoculation technique. Among the fourteen varieties tested, three were found to be highly susceptible, while other three were resistant. Leaf exudates and diffusates collected from the resistant varieties were more fungitoxic than those from the susceptible ones. Two antifungal compounds isolated from healthy and B. carbonum-infected tea leaves exhibited clear inhibition zones at RF 0.8 and 0.65, respectively, in a chromatographic bioassay. On the basis of their color reaction on TLC and UV-spectra these were identified to be catechin and pyrocatechol. Resistant and susceptible varieties accumulated 439-510 and 187-212 micrograms/g fresh mass tissue of pyrocatechol, respectively, 2 d after inoculation with B. carbonum, while a low concentration (45-58 micrograms/g) of this compound was detected in healthy leaf tissue.

Resistance of narcissus to infection by Fusarium oxysporum f.sp. narcissi

Single hyphae of Fusarium oxysporum f.sp. narcissi were capable of direct penetration of intact, unwounded, root tips of the susceptible narcissus cv. Golden Harvest. In other parts of the root, penetration involved the formation of infection cushions. In general, advance of the fungus in roots was by inter- and intracellular growth. In bulb scales spread occurred via ducts prior to invasion of surrounding tissue. In roots of the resistant cv. St Keverne, epidermal cell walls were modified in the presence of the fungus and lignituber-like structures were deposited about invading hyphae. Such structures were not produced in root cap cells. Isolated bulb scales expressed differential resistance to F. oxysporum f.sp. narcissi, indicating that a significant part of the resistance of cv. St Keverne has a physiological basis. The accumulation of antifungal compounds, including 7-hydroxyflavan and 7,4′-dyhydroxy-8-methyflavan, was compared in bulb scales of Golden Harvest and St Keverne following wounding or inoculation with the pathogen. It was concluded that resistance involves a complex interaction between the accumulation of antifungal compounds following infection, cell wall modification, and the formation of lignituber-like structures.

The Limiting Effect of Disease Resistance on Yield

The great majority of vascular plants possess natural means of defense that enable them to avoid or resist infection by the majority of plant pathogens present in their environments. In general, the means used by plants to defend themselves against attack by pathogens can be divided into two categories: those that are preformed and those that are induced by infection. The former includes morphological or histological structures that may primarily serve other purposes in the plant and that exist irrespective of the presence of the pathogen. Such constitutive means of resistance are most often associated with race-nonspecific resistance. Induced or active resistance is due to defense mechanisms activated in the host plant as a response to 'infection or attempted infection. It includes the formation of physical or chemical barriers and the synthesis and accumulation of antifungal compounds that inhibit or prevent pathogen growth. Active defense is most often implicated in gene-specific resistance, but it may also be involved in nonspecific and nonhost resistance. It has been used widely by plant breeders in their effort to produce disease-free cultivars. Although disease resistance has proven an invaluable tool to be used in plant breeding and hence in plant production, this article will be devoted to the fact that active defense processes in plants occur at the expense of the energy resources of the host and therefore may be a limiting factor in plant growth and yield.

Effect of Ethanol on the Accumulation of Antifungal Compounds and Resistance of Tomato toFusarium oxysporumf. sp.lycopersici

Effect of Ethanol on the Accumulation of Antifungal Compounds and Resistance of Tomato to<i>Fusarium oxysporum</i>f. sp.<i>lycopersici</i>

Accumulation of antifungal compounds on wound surfaces of carrot root tissue

Accumulation of antifungal compounds on wound surfaces of carrot root tissue

Production of antifungal compounds in cowpea (Vigna sinensis) and pea (Pisum sativum) after virus infection.

SUMMARY: Tissues of cowpea and pea underwent cellular browning following infection by tobacco necrosis virus and pea early browning virus respectively. In both species antifungal isoflavanoids accumulated in the brown tissues. The phytoalexins, phaseollidine, kievitone and phaseollin were isolated from virus-infected cowpea; pisatin from virus-infected pea. These results agree with previous indications that the destruction of host cells promotes the formation and accumulation of antifungal compounds within the tissues.