Physiologial Plant Pathology 

About: Physiologial Plant Pathology is an academic journal. The journal publishes majorly in the area(s): Tobacco mosaic virus & Phytophthora infestans. It has an ISSN identifier of 0048-4059. Over the lifetime, 1048 publications have been published receiving 38192 citations.

Association of enhanced peroxidase activity with induced systemic resistance of cucumber to Colletotrichum lagenarium

Abstract: Inoculation of the first true leaf of cucumber with Colletotrichum lagenarium enhanced peroxidase activity in leaf 2. The increased activity was associated, at least in part, with the fastest moving anodic isozymes during polyacrylamide gel electrophoresis. All plant parts and cellular fractions exhibited enhanced peroxidase activity in protected as compared to control plants. Injury of leaf 1 with dry ice neither induced systemic resistance to C. lagenarium nor enhanced peroxidase activity of leaf 2. Inoculation of leaf 1 with C. lagenarium followed by inoculation of leaf 2, 1 week later, elicited a higher degree of protection and higher peroxidase activity in leaf 3 than did single inoculations. Increasing numbers of C. lagenarium lesions on leaf 1 progressively increased peroxidase activity and resistance in leaf 2. Induced resistance was detected 3 to 4 days after inoculation of leaf 1, whereas peroxidase activity increased after the 4th day.

The production of resveratrol by Vitis vinifera and other members of the Vitaceae as a response to infection or injury

Abstract: Trans -resveratrol (4,3′,5′-trihydroxy stilbene) has been identified as the major component responsible for the blue fluorescence of grapevine leaf tissue following fungal infection or exposure to ultraviolet light. The biosynthesis of this compound appears to be a non-specific response of members of the Vitaceae to infection or injury. The compound is not detectable in healthy leaves but accumulates to between 50 and 400 μg/g fresh weight in infected or u.v.-irradiated leaves and is a major constituent ( c. 700 μg/g) of lignified stem tissue. The biological significance of the production of resveratrol is discussed.

Involvement of superoxide anion generation in the hypersensitive response of potato tuber tissues to infection with an incompatible race of Phytophthora infestans and to the hyphal wall components

Abstract: Potato tuber tissue discs, which were aged after wounding in order to acquire hypersensitive reactivity, reduced extracellular cytochrome c and nitroblue tetrazolium (NBT) following inoculation with an incompatible, but not compatible, race of Phytophthora infestans . The cytochrome c -reducing activity rapidly increased from l to 4 h after inoculation along with an increase in the percentage of hypersensitively dead cells, and then decreased from the time when most of the penetrated cells had died. A localized activation of NBT reduction around invading hyphae of the incompatible, but not those of the compatible, race was observed at early stages of penetration before cell death. The reductive activity of the discs was also elicited by treatment with a hypersensitivity-eliciting substance, hyphal wall components of the fungus. Superoxide dismutase (SOD), an enzyme catalysing the conversion of the superoxide anion (O 2 − ) to H 2 O 2 and O 2 inhibited the enhanced reducing activity of the discs when added to the assay solution, indicating that cytochrome c and NBT may be reduced by O 2 − generated from the discs. Pre-infectional, vacuum infiltration of the discs with a solution containing SOD significantly delayed the occurrence of hypersensitive cell death caused by infection with the incompatible race as well as the accumulation of phytoalexin. Application of SH-binding reagents and NADP + , but not respiratory inhibitors, inhibited the elicitation of the reducing activity caused by infection with the incompatible race. These results indicate that an O 2 − -generating system may be activated in potato tissues during the incompatible interaction induced by invading fungi or fungal wall components, and also that the generation of O 2 − may be involved during hypersensitive cell death as a trigger of the sequence of resistance reactions.

Lignification as a mechanism for induced systemic resistance in cucumber

Abstract: Infection of the first true leaf of cucumber with Colletotrichum lagenarium induces systemic resistance (protection) against subsequent challenge by C. lagenarium or Cladosporium cucumerinum Conidia of C. lagenarium germinated and formed appressoria equally well on isolated epidermal strips from protected and control plants; however, penetration occurred less frequently into epidermal strips from protected plants. Inhibition of penetration was associated with host epidermal cell wall lignification directly under appressoria. Lignification occurred more rapidly and to a greater extent in protected than in control plants. Infection of etiolated seedlings resistant to scab with C. cucumerinum made the seedlings resistant to C. lagenarium, and elicited a rapid lignification of penetrated and adjacent host cells. This lignification reaction in the resistant cultivar was histologically indistinguishable from that at sites of penetration in a systemically protected “susceptible” cultivar challenged with C. cucumerinum. Germination of conidia and frequencies of penetration of C. cucumerinum were similar in protected and control plants, but development of the fungus in lignified tissue was markedly restricted. Coniferyl alcohol, a lignin precursor, was toxic to C. lagenarium and C. cucumerinum when only 0·3 hg were applied to thin-layer bioassay plates. This suggests that it might function as a phytoalexin. Mycelia of C. lagenarium and C. cucumerinum were “lignified” in the presence of coniferyl alcohol, peroxidase and hydrogen peroxide.

A rapid method for the chemical estimation of filamentous fungi in plant tissue

Abstract: A sensitive colour reaction is described for estimating fungi which contain chitin. The method is based on the alkaline deacetylation of chitin to chitosan, the glucosamine residues of which are susceptible to deamination with nitrous acid. This yields an aldehyde which is determined colorimetrically with 3-methyl-2-benzothiazolone hydrazone. The observed level of aldehyde, expressed as glucosamine, was related to fungal dry weight by experiments using different fungi grown in vitro. The method, requiring 5 h to complete, has been tested on five phytopathogenic fungi and three hosts, and should be applicable to a wide range of host-pathogen systems.