Early survival of Quercus ilex subspecies from different populations after infections and co‐infections by multiple Phytophthora species

Forests in Europe are threatened by increased diversity of Phytophthora species, but effects on trees of simultaneous infections by Phytophthora and ecological consequences of their coexistence are unknown. This study explored variation in early survival of Quercus ilex to Phytophthora infections and assessed interactions between Phytophthora species when trees were co‐infected. Three Phytophthora species (P. cinnamomi, P. gonapodyides and P. quercina), seeds from 16 populations of Q. ilex (ballota and ilex subspecies) and two infection times were used as sources of variation in two experiments. The influence of Phytophthora species, Q. ilex subspecies and populations on plant germination and survival were analysed using generalized linear mixed models and survival analysis techniques. Germination rates were not influenced by Phytophthora spp. (P = 0.194) but by the subspecies and populations of Q. ilex (P < 0.001). In Phytophthora‐infested soils, Q. ilex subsp. ilex germinated at higher rates than Q. ilex subsp. ballota. Plant survival was strongly influenced by Phytophthora species (P < 0.001), not by the subspecies and populations of Q. ilex. Seedling mortality was reduced and delayed if a less virulent Phytophthora species infected plants prior to infection by a more virulent Phytophthora species. The results help to explain oak decline syndrome and the lack of natural and artificial regeneration of Q. ilex forests. Lack of interspecific variability of early survival to Phytophthora spp. discourages direct sowing for artificial reforestation programmes. Large, thick seeds, giving plants rapid growth, are advantageous traits when soils are infested with Phytophthora spp.     

First report of Pauesia silana Tremblay, 1969 (Hymenoptera: Aphidiidae), a natural enemy of the aphid Cinara pini L., in Algeria

A survey of aphids and their parasitoids in a garden park located in Algiers from March 2015 to March 2016 detected the presence of Cinara pini Linnaeus, 1758 for the first time in Algiers. This species had previously been reported in one other location in Algeria. This aphid was found on Pinus nigra and Pinus halepensis. Mummies of C. pini were found to be parasitized by Pauesia silana Tremblay, 1969. This paper provides the first report of P. silana in Algeria.     

Chemical control of isolated invasive conifers using a novel aerial spot application method

Conifer species, which have formed the foundation of commercial forestry industry in many countries, are known to be invasive in natural ecosystems, especially in the Southern Hemisphere. Controlling isolated invasive conifers before they reach reproductive maturity is an essential element of any strategy that aims to reduce spread rate of these species. Using a novel helicopter‐mounted spot‐application gun, which delivers a precise dosage to the crown of each tree, the objective of this research was to test the efficacy of three triclopyr‐based treatments against the four most vigorous wilding conifer species (Pinus contorta, Pinus nigra, Pinus sylvestris and Pseudotsuga menziesii) under New Zealand field conditions. Herbicides tested were triclopyr at two different rates and a combination of triclopyr and picloram. Treated trees covered a wide range of heights (c. 0.5–16 m), and measurements of mortality taken two years post‐herbicide application were used to examine variation in efficacy of the herbicides. Successful treatment was defined by a mortality rate of 85% or higher. A logistic regression model was fitted to the mortality data and used to derive threshold tree heights at which 85% mortality occurred, H₈₅. For all four species, the most effective treatment was application of 1000 ml of herbicide mixture per tree that contained 120 and 20 g, respectively, of the active ingredients triclopyr and picloram. There was a significant decline in efficacy of this treatment with increases in tree size for all four species. Values of H₈₅ for this treatment were 7.4 m for P. nigra, 8.3 m for P. menziesii, 9.7 m for P. contorta and >10 m for P. sylvestris. The methods developed here could be used to effectively manage emerging conifer infestations before they become problematic.     

A rapid virulence assay for the Dutch elm disease fungus Ophiostoma novo‐ulmi by inoculation of apple (Malus × domestica ‘Golden Delicious’) fruits

Large‐scale virulence tests using trees or saplings are expensive, time‐consuming and require a considerable amount of space. The suitability of using ‘Golden Delicious’ apples as a rapid screen for identifying Ophiostoma novo‐ulmi transformants with reduced virulence was thus evaluated. When a collection of O. novo‐ulmi field isolates belonging to subspecies novo‐ulmi or americana was inoculated to apples, members of subsp. novo‐ulmi induced, on average, larger necrotic lesions than subsp. americana isolates. The size of the lesions on apples was not correlated with mycelial growth rate of isolates on nutrient agar. Insertional mutants from O. novo‐ulmi subsp. novo‐ulmi isolate H327 were inoculated to ‘Golden Delicious’ apples and Ulmus parvifolia × U. americana saplings in parallel experiments. Results clearly indicated that the O. novo‐ulmi transformants included several exhibiting significantly altered levels of virulence. Variability among replicates within a treatment was reduced in apple inoculation data compared to elm sapling data. Overall, the ‘Golden Delicious’ apple assay was found to be an excellent means for rapidly assessing the virulence level of O. novo‐ulmi isolates.     

Distribution of major clonal lineages EU_13_A2, EU_2_A1, and EU_23_A1 of Phytophthora infestans associated with potato late blight across crop seasons and regions in Algeria

Potato is one of the most important agricultural crops in Algeria and worldwide. Each year, potato late blight, caused by Phytophthora infestans, is responsible for significant damage that leads to large production losses, and is thus a direct threat to food security in Algeria. In this study, 131 isolates of P. infestans and 92 DNA fingerprints captured on FTA cards were sampled from commercial and seed production fields in three major potato production regions (western, eastern, and central) during the main-season and late-season in Algeria over six cropping seasons (2010–2016). Genotypes of P. infestans and population genetic diversity were analysed using a 17-plex simple-sequence repeat (SSR) marker assay, and the mating type of all isolates was characterized. Both mating types (A1 and A2) were found, and often occurred in the same field. Differences in mating type proportion were observed between regions and between sampling periods. Analysis with SSR markers showed the prevalence of the EU_13_A2 lineage (70%) over EU_2_A1 (16%), EU_23_A1 (10%), and 4% of unknown multilocus lineage (MLL). The EU_13_A2 showed differentiation within the group. EU_23_A1 was found mainly in late-season crops. However, the cropping region did not influence the distribution of lineages due to the dispersal of the pathogen in Algeria by seeds. Genetic structure did not reveal a clear variation in distribution of the three lineages throughout the sampling regions. These data provide important new information on the composition and change over time of P. infestans populations in Algeria and open the way for a better understanding of the local epidemiology of this important pathogen.     

Isolation and pathogenicity of Phytophthora species from declining Rubus anglocandicans

Rubus anglocandicans is the most widespread and abundant blackberry species within the European blackberry (Rubus fruticosus) aggregate in Western Australia (WA). European blackberry is also one of the 32 Weeds of National Significance in Australia. A disease recorded as ‘blackberry decline’ was first observed in some blackberry sites in WA in 2006. A disease survey was conducted in the Manjimup‐Pemberton region along the Warren and Donnelly River catchments in WA between 2010 and 2012. Phytophthora amnicola, P. bilorbang, P. cryptogea, P. inundata, P. litoralis, P. multivora, P. taxon personii, P. thermophila and a P. thermophila × amnicola hybrid were recovered from declining and adjacent decline‐free sites, as well as from streams and rivers. Phytophthora cinnamomi was isolated from dying Banksia and Eucalyptus species from two non‐decline sites. Of these species, P. bilorbang and P. cryptogea were more pathogenic than the others in under‐bark inoculations using excised stems (primocanes), in planta primocane inoculations in blackberry growing wild in native forest stands, and in glasshouse pot trials. It was concluded that blackberry decline is a complex syndrome and Phytophthora species, in particular P. bilorbang and P. cryptogea, together with temporary inundation, are major biotic and abiotic factors contributing to blackberry decline.     

Effects of defoliation caused by the processionary moth on growth of Crimean pines in western Turkey

An outbreak of the pine processionary moth (PPM), Thaumetopoea wilkinsoni Tams (Lepidoptera: Thaumetopoeidae), began in spring 1998 and lasted 6 years in a Crimean pine (Pinus nigra Arnold) plantation in western Turkey. The effects of PPM on the radial, height and volume growth of Crimean pine trees were investigated by examining the increment losses for three defoliation intensities (groups). PPM activity in Crimean pine stand was assessed through radial increment analysis of cores extracted at breast height. In 2004, increment cores were collected from moderate and high defoliation and low defoliation dominant or co-dominant trees. Based on the sample, annual radial growth indices from 1998 to 2004 were calculated. Growth functions were defined as the cumulative sum of radial, height and volume increment graphically compared between Crimean pine defoliation group sample trees. The sample trees are the same subspecies and varieties. After the defoliations, radial, height and volume growth of low defoliation group trees was found to be significantly greater than that of the other affected groups. During the 1998–2004 period the total radial growth of low, moderately affected and highly affected trees was, respectively, 49, 33 and 31 mm; the total height growth was 3.1, 1.8 and 1.0 m; and the total volume growth was 50, 14 and 10 dm³.     

Pathogenicity of Meloidogyne incognita and M. javanica on recombinant inbred lines from a crossing of Cucurbita pepo subsp. pepo × C. pepo subsp. ovifera

The response of recombinant inbred lines (RILs) from a cross of zucchini × scallop (Cucurbita pepo subsp. pepo ‘Murcia MU-CU-16’ × C. pepo subsp. ovifera ‘Scallop UPV-196’) to Meloidogyne incognita and M. javanica was determined after completion of a nematode reproduction cycle in experiments carried out in a growth chamber. The nematode differentiated the C. pepo genotypes at the subspecies level due to lower egg mass production on subspecies pepo than ovifera, and thus subspecies pepo was a poorer host than ovifera. In addition, Murcia MU-CU-16 discriminated M. incognita from M. javanica in terms of egg masses (EM), eggs per gram of root and reproduction factor (Rf), whereas Scallop UPV-196 did so in eggs per gram of root and Rf. The RILs differed in gall formation and EM production depending on the nematode × line combination. Comparisons between nematode isolates resulted in four significant combinations for pathogenic potential (galls/initial population (Pi) × 100), seven for parasitic success (egg masses/Pi × 100), and nine for host efficiency (egg masses/galls per root system × 100) which included all the lines tested against both isolates. Lines that restricted nematode development by at least 90% were considered as having intermediate resistance to M. incognita based on the definition of the International Seed Federation. They included lines 28-1, 35A, 107A, 110-3 and 153-2. All the RILs were susceptible hosts for M. javanica. The information presented here will be helpful for nematode management and also for plant breeders working on pathogen resistance on C. pepo.     

Severe modifications in source-sink ratio influence the susceptibility of bananas to crown rot and its phenolics content

Banana susceptibility to crown rot is influenced by many biotic and abiotic preharvest factors, which include source-sink (So-Si) ratio modifications through trimming of leaves and fruit. Banana plant's resistance to biotic stress has been previously correlated to its phenolic content; it is hypothesized that the crown's phenolic content may influence the fruit's susceptibility. The aim of this work was to investigate the influence of severe So-Si ratio modifications, via the removal of leaves and fruit, and the involvement of phenolics in the fruit's susceptibility to crown rot. Fruit susceptibility was evaluated 13 days postinoculation (13 dpi) with Colletotrichum musae. Banana crowns obtained on the day of harvest before inoculation (dhbi) and 13 dpi were analysed for changes in phenolics using GC-MS, HPLC, and LC-MS devices. Severe So-Si ratio modifications had a significant effect (p <.001) on susceptibility, fruits of low So-Si ratio being most susceptible. It also significantly influenced (p < .001) some tree and fruit characteristics. The less susceptible (S−) crowns had higher amounts of phenolics compared to the more susceptible (S+) ones. Catecholamines were identified as the major phenolics in banana crown, notably dopamine compared to norepinephrine and normetanephrine. Hydroxycinnamic acids (ferulic acid and its derivatives) were significantly accumulated (p <.001) the dhbi in S− crowns compared to S+ crowns, but decreased 13 dpi. Phenolics have a possible role in the biochemical defence of banana crown and could be used by producers as a chemical criterion for estimation of the level of banana's susceptibility to crown rot.     

Several subspecies and sequence types are associated with the emergence of Xylella fastidiosa in natural settings in France

Xylella fastidiosa is a plant pathogenic bacterium emerging in Europe. In France its emergence has been demonstrated through interceptions of contaminated coffee plants and, in 2015, by a survey of natural settings. The first French focus of contamination was detected in 2015 in Corsica; since then, almost 300 foci have been found and nearly 30 plant species have been declared contaminated, with Polygala myrtifolia remaining the principal host, suffering from severe leaf scorch. This study reports on the diversity of X. fastidiosa identified in France in 2015. Multilocus sequence analysis/typing revealed the presence of mainly X. fastidiosa subsp. multiplex sequence types (STs) ST6 and ST7. A focus of X. fastidiosa subsp. pauca ST53 was identified in mainland France; one sample contaminated by X. fastidiosa subsp. sandyi ST76, one novel recombinant, and coinfections of different isolates in individual samples were also identified, but could not be confirmed by successive samplings, indicating limited or transient contamination. Koch's postulates were fulfilled for two isolates of X. fastidiosa subsp. multiplex on P. myrtifolia, one being ST6 and the other ST7. Comparative genomics of the genome sequences of three French isolates (one ST6 and two ST7) with available sequences revealed that, unlike the American Dixon strain, the French ST6 and ST7 strains are devoid of a plasmid encoding a complete type IV secretion system. Other differences regarding phage sequences were highlighted. Altogether, the results suggest that the emergence of X. fastidiosa in France is linked to several introduction events of diverse strains from different subspecies.     

Phytophthora agathidicida: research progress,cultural perspectives and knowledge gaps in the control and management of kauri dieback in New Zealand

Kauri (Agathis australis), which is one of the world's largest and longest-living conifer species, is under threat from a root and collar dieback disease caused by the oomycete pathogen Phytophthora agathidicida. The noted incidence of kauri dieback has increased in the past decade, and even trees >1000 years old are not immune. This disease has profound effects on both forest ecosystems and human society, particularly indigenous Māori, for whom kauri is a taonga or treasure of immense significance. This review brings together existing scientific knowledge about the pathogen and the devastating disease it causes, as well as highlighting important knowledge gaps and potential approaches for disease management. The life cycle of P. agathidicida is similar to those of other soilborne Phytophthora pathogens, with roles for vegetative hyphae, zoospores and oospores in the disease. However, there is comparatively little known about many aspects of the biology of P. agathidicida, such as its host range and disease latency, or about the impact on the disease of abiotic and biotic factors such as soil health and co-occurring Phytophthora species. This review discusses current and emerging tools and strategies for surveillance, diagnostics and management, including a consideration of genomic resources, and the role these play in understanding the pathogen and how it causes this deadly disease. Key aspects of indigenous Māori knowledge, which include rich ecological and historical knowledge of kauri forests and a holistic approach to forest health, are highlighted.     

Assessment of the genetic diversity of Xylella fastidiosa in imported ornamental Coffea arabica plants

A study was performed in order to assess the presence of Xylella fastidiosa in imported ornamental plants, among them Olea europaea, Coffea arabica and Nerium oleander. Positive results were only obtained from C. arabica, where 15 plant samples tested positive for X. fastidiosa by PCR, nine from Costa Rica and six from Honduras. Transmission electron microscopy observations indicated that rod‐shaped bacterial cells exhibiting the characteristics of X. fastidiosa cells were present in the xylem vessels of leaf petioles obtained from the infected C. arabica plants. Diversity of X. fastidiosa in C. arabica plants was assessed through a multilocus sequence typing (MLST) analysis of seven housekeeping genes (leuA, petC, lacF, cysG, holC, nuoL and gltT) and compared with X. fastidiosa infecting different host plants worldwide. Based on this MLST analysis, the prevalence of different sequence types (STs) of X. fastidiosa in the C. arabica ornamental plants was demonstrated and related to different X. fastidiosa subspecies, underlining the risk of introducing additional genetic diversity for X. fastidiosa to Europe. ST53, related to X. fastidiosa subsp. pauca, was frequently found in these C. arabica samples. A second ST related to X. fastidiosa subsp. pauca, ST73, has been assessed in coinfection with ST53 in one individual plant. Additionally, ST72 and ST76, related to X. fastidiosa subsp. fastidiosa, have been recorded. Next to these previously described STs, a novel ST, namely ST77 has been revealed, related to X. fastidiosa subsp. fastidiosa. Isolation of X. fastidiosa from leaf petioles and midribs of infected C. arabica plants was successfully performed only after the application of an additional ultrasonication step during the extraction procedure. Based on this approach, a number of X. fastidiosa isolates were obtained and further characterized.     

The use of two complementary DNA assays,AFLP and MLSA,for epidemic and phylogenetic studies of pectolytic enterobacterial strains with focus on the heterogeneous species Pectobacterium carotovorum

Amplified fragment length polymorphism (AFLP) markers and multilocus sequence analysis (MLSA) were used to analyse 63 bacterial strains, including 30 soft‐rot‐causing bacterial strains collected from Syrian potato fields and 33 reference strains. For the MLSA, additional sequences of 41 strains of Pectobacterium and Dickeya, available from the NCBI GenBank, were included to produce a single alignment of the 104 taxa for the seven concatenated genes (acnA, gapA, proA, icd, mtlD, mdh and pgi). The results indicate the need for a revision of the previously classified strains, as some potato‐derived Pectobacterium carotovorum strains were re‐identified as P. wasabiae. The strains that were classified as P. carotovorum during the analyses demonstrated high heterogeneity and grouped into five P. carotovorum highly supported clusters (PcI to PcV). The strains represented a wide range of host plants including potatoes, cabbage, avocados, arum lilies, sugar cane and more. Host specificity was detected in PcV, in which four of the six strains were isolated from monocotyledonous plants. The PcV strains formed a clearly distinct group in all the constructed phylogenetic trees. The number of strains phylogenetically classified as subspecies ‘P. c. subsp. brasiliensis’ in PcIV dramatically increased in size as a result of the characterization of new isolates or re‐identification of previous P. carotovorum and P. atrosepticum strains. The P. carotovorum strains from Syria were grouped into PcI, PcII and PcIV. This grouping indicates a lack of correlation between the geographical origin and classification of these pathogens.     

Heterogeneity of Pseudomonas savastanoi populations infecting Myrtus communis in Sardinia (Italy)

Genetic, phenotypic and host range diversity among Pseudomonas savastanoi isolates from Myrtus communis were investigated. Thirty‐one isolates from six Sardinian commercial myrtle orchards and three isolates from plants growing spontaneously on the island of Rhodes (Greece) were compared with reference strains of P. savastanoi from olive, oleander, ash and myrtle. Multilocus sequence analysis (MLSA) indicated the presence of a monomorphic population with a very low level of variability. Conversely, Biolog phenotypic fingerprinting and phytohormone production analyses showed a considerable metabolic diversity, as bacteria obtained from single infected tissue differed more than bacteria obtained from different orchards. When pathogenicity tests were carried out on myrtle plants, different types of symptoms were induced: knots, canker lesions with or without tissue proliferations and, occasionally, wilting of the inoculated twig, a symptom never reported before for P. savastanoi. Comparable symptoms were also observed in the natural environment both on spontaneous and cultivated plants. Moreover, the host range of the myrtle population was heterogeneous and not well defined. Some isolates showed a wide host range whilst others were pathogenic only to their natural host. Overall these findings suggest that the diversity of the P. savastanoi population from myrtle does not depend so much on the locality or the natural host and does not allow the Sardinian and Greek isolates, together with previously characterized myrtle strains, to be ascribed to a known pathovar of P. savastanoi, nor to propose their belonging, as a whole, to a new pathovar.     

Development of a Pseudomonas syringae–Eutrema salsugineum pathosystem to investigate disease resistance in a stress tolerant extremophile model plant

To improve the ability to understand how plants respond to multiple and/or concurrent stresses, disease resistance was investigated in Eutrema salsugineum, an extremophile model plant that is highly tolerant of abiotic stress. Compared to Arabidopsis (Col‐0), both Yukon and Shandong Eutrema accessions exhibit increased resistance to Pseudomonas syringae pv. tomato DC3000 (Pst) and pv. maculicola (Psm), with Shandong Eutrema exhibiting greater resistance to Pst than Yukon Eutrema. RT‐PCR of the EsPR1 (Pathogenesis‐related 1) defence marker gene confirmed RNA‐Seq data that healthy Shandong Eutrema constitutively expresses EsPR1. The data suggests that Shandong Eutrema exists in a highly primed state of defence preparedness, as it displays heightened resistance compared to defence‐primed natural accessions of Arabidopsis (Can‐0, Bur‐0). Pathogen‐triggered PR1 expression was delayed in Yukon Eutrema; however, these plants were resistant to Pst suggesting that Yukon Eutrema employs a PR1‐independent mechanism to resist Pst. This study demonstrates that Eutrema is an excellent model to investigate biotic stress tolerance. The Eutrema–P. syringae pathosystem will facilitate future studies to understand how this extremophile tolerates both abiotic and biotic stress, and will allow exploration of the interplay of these responses to inform efforts to improve stress tolerance in crops.     

Polymorphism analysis of housekeeping genes for identification and differentiation of <Emphasis Type="Italic">Clavibacter michiganensis</Emphasis> subspecies

The utility of polymorphism analysis was determined for differentiation of the following subspecies of the Gram-positive plant pathogenic bacterium, Clavibacter michiganensis: C. m. subsp. michiganensis, C. m. subsp. sepedonicus, C. m. subsp. insidiosus C. m. subsp. nebraskensis, and C. m. subsp. tessellarius. Specific primers designed for amplification of the housekeeping genes recA, rpoB, and rpoD generated 827-, 1037-, and 862-bp DNA fragments, respectively. PCR products obtained from 40 C. michiganensis strains were analysed using RFLP with four restriction endonucleases, and those PCR products with specific RFLP patterns were sequenced. The genotypes discriminated after PCR–RFLP were specific for each subspecies and also allowed for differentiation of C. m. subsp. michiganensis strains. Sequence analysis of the recA, rpoB, and rpoD gene fragments also distinguished C. michiganensis subspecies and was useful for phylogenetic analysis of all subspecies. For rapid, inexpensive, and effective differentiation of the five subspecies in this research, we recommend the amplification of recA and/or rpoD gene fragments and digestion of the PCR products with the restriction endonuclease FnuDII.     

Virulence of Pectobacterium carotovorum subsp. brasiliense on potato compared with that of other Pectobacterium and Dickeya species under climatic conditions prevailing in the Netherlands

In western Europe, Pectobacterium carotovorum subsp. brasiliense is emerging as a causal agent of blackleg disease. In field experiments in the Netherlands, the virulence of this pathogen was compared with strains of other Dickeya and Pectobacterium species. In 2013 and 2014, seed potato tubers were vacuum infiltrated with high densities of bacteria (10⁶ CFU mL^?1) and planted in clay soil. Inoculation with P. carotovorum subsp. brasiliense and P. atrosepticum resulted in high disease incidences (75–95%), inoculation with D. solani and P. wasabiae led to incidences between 5% and 25%, but no significant disease development was observed in treatments with P. carotovorum subsp. carotovorum, D. dianthicola or the water control. Co‐inoculations of seed potatoes with P. carotovorum subsp. brasiliense and D. solani gave a similar disease incidence to inoculation with only P. carotovorum subsp. brasiliense. However, co‐inoculation of P. carotovorum subsp. brasiliense with P. wasabiae resulted in a decrease in disease incidence compared to inoculation with only P. carotovorum subsp. brasiliense. In 2015, seed potatoes were inoculated with increasing densities of P. carotovorum subsp. brasiliense, D. solani or P. atrosepticum (10³–10⁶ CFU mL^?1). After vacuum infiltration, even a low inoculum density resulted in high disease incidence. However, immersion without vacuum caused disease only at high bacterial densities. Specific TaqMan assays were evaluated and developed for detection of P. carotovorum subsp. brasiliense, P. wasabiae and P. atrosepticum and confirmed the presence of these pathogens in progeny tubers of plants derived from vacuum‐infiltrated seed tubers.     

The effect of salt stress on Arabidopsis thaliana and Phelipanche ramosa interaction

Salinity and Orobanche or Phelipanche spp. infection are important crop stress factors in agricultural areas. In this study, we investigated the effect of salt stress on Phelipanche ramosa seed germination and its attachment onto Arabidopsis thaliana roots. We also evaluated the effect of both stresses on the expression of genes regulated by abiotic and biotic stresses. According to our results, high concentration of NaCl delayed P. ramosa seed germination in the presence of a strigolactone analogue (GR24). A similar pattern was observed in the presence of A. thaliana plants. Furthermore, we found that salt‐treated A. thaliana seedlings were more sensitive to P. ramosa attachment compared with the untreated plants, indicating that there was a positive correlation between salt sensitivity and the ability of P. ramosa to infect A. thaliana plants. At the molecular level, a synergystic effect of both salt and P. ramosa stresses was observed on the cold‐regulated (COR) gene expression profile of treated A. thaliana seedlings. Our data clarify the interaction between parasitic plants and their hosts under abiotic stress conditions.     

Ceratocystis species on Quercus robur with oak decline symptoms in southern Poland1

In southern Poland during 1986–1989, six species of Ceratocystis were found on sick and dead Quercus robur. The frequency of their occurrence in above-ground portions and roots of trees is given. The possibility is discussed whether oak decline, caused by a complex of abiotic and biotic factors, is intensified when trees are colonized by Ceratocystis.