Phenolic profiles in apple leaves and the efficacy of selected phenols against fire blight (Erwinia amylovora)

The content and type of phenolic compounds in apple leaves as potential markers of resistance to fire blight were analysed. The amounts of phenolic acids and flavonoids were determined before and after E. amylovora inoculation of leaves of two cultivars: ‘Enterprise’ (highly resistant) and ‘Idared’ (highly susceptible). The basic levels of phenolics in both cultivars was similar but, following the inoculation, in the resistant one faster and more distinguishable changes were observed. The difference between the cultivars was related to the content of the compounds and the rate of release of free phenols from their glucosides. Regarding age dependency, the levels of eight out of 15 phenolics was significantly higher in young leaves of ‘Idared” than in ‘Enterprise’. In the older leaves the differences were limited to four compounds. The amount of salicylic acid in ‘Idared’ was lower than in ‘Enterprise’. In ‘Idared’ accumulation of salicylate after infection was better pronounced than in ‘Enterprise’. Higher levels of naringenin glucosides, 4-hydroxbenzoic acid and gentisic acid were found in ‘Enterprise’. The activity of 13 phenolics tested in vitro against the pathogen showed that gallic acid, phloroglucinol, hydroquinone and phloretin, suppressed its growth. The aqueous solutions of gallic acid, phloroglucinol and hydroquinone also significantly limited the development of disease on pear fruitlet slices but only hydroquinone maintained its protective activity for longer time. It also showed very high efficacy in preventing disease spread on apple shoots. The study adds novel information on the contribution of specific phenolics to apple resistance to fire blight

Efficacy of fungicides and essential oils against bacterial diseases of fruit trees

In the framework of the performed studies, the antibacterial activity of the following fungicides was evaluated: Miedzian 50 WG (active substance - a.s. 50% copper oxychloride), Ridomil MZ Gold 68 WG (a.s. 3.8% metalaxyl-M and 64%, mancozeb), Euparen Multi 50 WG (a.s. 50% tolylfluanid), Captan 80 WG [a.s. 80% N-(captan)], Dithane Neotec 75 WG (a.s. 75% mancozeb). The evaluation also concerned the essential oils: lavender, sage, lemon balm, clove, and a preparation based on thyme oil (BioZell). Each preparation and compound was tested against the following bacterial pathogens: Erwinia amylovora, Xanthomonas arboricola pv. corylina, X. arboricola pv. juglandis, Pseudomonas syringae pv. syringae, Agrobacterium tumefaciens (presently Rhizobium radiobacter). Each preparation and compound was tested at a concentration of 1,000 ppm of active substance. Copper oxychloride was also tested at a concentration of 1,500 ppm. Among the tested fungicides, metalaxyl-M with mancozeb, mancozeb alone, and copper oxychloride inhibited all of the tested strains of pathogenic bacteria. Tolylfluanid did not inhibit any of the bacteria used. Out of the investigated essential oils, the strongest inhibitors of bacteria were: sage, cloves, and BioZell. The protective activity of the above mentioned fungicides was also evaluated in vivo. They were assessed against fire blight on apple blossoms and pear fruitlets, against bacterial canker on sweet cherry fruitlets, and against crown gall on sunflower seedlings (the test plant). All fungicides were applied at the same concentrations as those in the in vitro tests. Only copper oxychloride was found to show protective activity against the studied diseases. This result indicates that the antibacterial properties of the other fungicides did not correspond with their activity on the plant organs used in the in vivo experiment

Comparative transcriptome analysis of a lowly virulent strain of Erwinia amylovora in shoots of two apple cultivars – susceptible and resistant to fire blight

Abstract Background Erwinia amylovora is generally considered to be a homogeneous species in terms of phenotypic and genetic features. However, strains show variation in their virulence, particularly on hosts with different susceptibility to fire blight. We applied the RNA-seq technique to elucidate transcriptome-level changes of the lowly virulent E. amylovora 650 strain during infection of shoots of susceptible (Idared) and resistant (Free Redstar) apple cultivars. Results The highest number of differentially expressed E. amylovora genes between the two apple genotypes was observed at 24 h after inoculation. Six days after inoculation, only a few bacterial genes were differentially expressed in the susceptible and resistant apple cultivars. The analysis of differentially expressed gene functions showed that generally, higher expression of genes related to stress response and defence against toxic compounds was observed in Free Redstar. Also in this cultivar, higher expression of flagellar genes (FlaI), which are recognized as PAMP (pathogen-associated molecular pattern) by the innate immune systems of plants, was noted. Additionally, several genes that have not yet been proven to play a role in the pathogenic abilities of E. amylovora were found to be differentially expressed in the two apple cultivars. Conclusions This RNA-seq analysis generated a novel dataset describing the transcriptional response of the lowly virulent strain of E. amylovora in susceptible and resistant apple cultivar. Most genes were regulated in the same way in both apple cultivars, but there were also some cultivar-specific responses suggesting that the environment in Free Redstar is more stressful for bacteria what can be the reason of their inability to infect of this cultivar. Among genes with the highest fold change in expression between experimental combinations or with the highest transcript abundance, there are many genes without ascribed functions, which have never been tested for their role in pathogenicity. Overall, this study provides the first transcriptional profile by RNA-seq of E. amylovora during infection of a host plant and insights into the transcriptional response of this pathogen in the environments of susceptible and resistant apple plants

La Charente

14 février 18861886/02/14 (A15,N5479)-1886/02/14.Appartient à l’ensemble documentaire : PoitouCh

Additional file 6: Table S5. of Comparative transcriptome analysis of a lowly virulent strain of Erwinia amylovora in shoots of two apple cultivars – susceptible and resistant to fire blight

Differentially expressed genes of E. amylovora 650 between bacterial culture in TY medium(650-bact) and in apple shoots in two time points after inoculation (I-24 h, I-6d, FR-24 h, FR-6d). (XLSX 401 kb

The impact of phytosanitary treatments in the soil with signs of fatigue on the growth of apple seedlings and populations of bacteria and fungi

The object of research was the soil from an orchard after 27 years of apple cultivation, showing signs of fatigue re-sulting in weaker growth of apple seedlings planted into it, and the soil sampled on the same farm, but not used for growing fruit trees. The physicochemical properties of both soils did not differ significantly. In sick soil, no pathogens of fungal or fungi-like origin were found, and the number of nematodes was below the threshold of economic threat. There is a suspicion that abiotic fac-tors could be responsible for soil fatigue. It has been demonstra-ted that the cultivation of spring and winter wheat, triticale and white mustard before planting apple ‘Antonovka’ seedlings, had a positive impact on their growth. The best effect was obtained after the cultivation of white mustard or after the introduction of mustard seed meal into the soil, which was also confirmed by measurements of the intensity of apple seedlings photosynthesis. The cultivation of these phytosanitary plants or the addition of mustard seed meal positively influenced the biological potential of the soil expressed by a significant increase in the population of bacteria from the genera Pseudomonas and Bacillus. There was also a very large increase in the number of Trichoderma spp. fun-gi after the addition of mustard seed meal into the soil and winter wheat cultivation

Effects of silvicultural techniques on the diversity of microorganisms in forest soil and their possible participation in biological control of Armillaria and Heterobasidion

Effects of different pre-planting soil preparations and post-harvest wood debris applications in a clear-cut Scots pine plantation, on the abundance, diversity, and activity of culturable microorganisms were investigated. The investigation was done 9 years after the re-plantings had been done. This formed part of an investigation of silvicultural practices for conservation and the biological control of Armillaria and Heterobasidion in northern temperate forests (Poland). The treatments being compared, were expected to have altered the soil’s physical and chemical properties, and consequently, its biological properties. Only soft-rot microfungi from the Ascomycota and Zygomycota were detected in the soil. Fungi, including those antagonistic to Armillaria and Heterobasidion, were more abundant after shallow ploughing than after deep ploughing or ridging, and where chipped rather than coarse wood debris was left on the soil surface or incorporated. Scots pine trees had the most biomass and the least mortality after ridging and leaving coarse wood debris on the surface (associated with only a relatively moderate abundance of fungi)