Vegetative incompatibility and potential involvement of a mycovirus in the Italian population of Geosmithia morbida

Studies carried out during an Italian outbreak of the Thousand Cankers Disease of walnut, demonstrated that non-coalescing cankers on host plants, separated by equidistant uninfected zones, were associated with incompatible strains of Geosmithia morbida. Confirmation of the vegetative incompatibility of paired fungal isolates, randomly collected from black walnuts, was obtained from observations of a clear separation zones and the absence of anastomoses. Pairing tests with two incompatible monoconidial strains indicated differences in morphology and growth rates. Electron microscopy revealed the presence of icosahedral mycovirus-like particles in one of the monoconidial strains that demonstrated low degrees of virulence in planta compared with a particlefree monoconidial strain. The occurrence of a vegetative incompatibility system in recently introduced populations of G. morbida has considerable implications for fungal biology. Incompatibility in G. morbida and potential direct or indirect roles of the observed virus-like particles have potential ecological and epidemiological consequences. \ua9 Firenze University Press

The Importance of Saperda Inornata and Oberea Schaumii (Coleoptera: Cerambycidae) Galleries as Infection Courts of Hypoxylon Pruinatum in Trembling Aspen, Populus Tremuloides

(excerpt) Trembling aspen, Populus tremuloides Michaux, and bigtooth aspen, P. grandidentata Michaux, are hosts of numerous species of injurious insects and microorganisms (Harrison 1959). Only a few of those organisms, however, are directly responsible for mortality of healthy trees. The fungus Hypoxylon pruinatum (Klotzsche) Cke. is most important in that respect, killing 1-2%o f the standing volume annually in the Lake States (Anderson 1964). It invades and spreads in cambial tissue, killing it and eventually the branch or stem by girdling. Initially, a canker appears as a sunken, yellowish-orange area in the bark (Anderson 1956). In a later stage the outer bark raises in blister-like patches and sloughs off exposing blackened, crumbling cortex

Spatial distribution of Sahlbergella singularis Hagl. (Hemiptera: Miridae) populations and associated damage in unshaded young cocoa-based agroforestry systems in Cameroon

The aim of this study was to analyze the spatial distribution of S. singularis populations and associated damage in young not yet shaded cocoa-based agroforestry systems. The study was carried out in six 4 years-old cocoa plantations located in the Centre region of Cameroon. Three different specialized models were used for analysis: the Taylor's power law, the binomial negative distribution and semi-variograms. The populations of S. singularis were strongly aggregated in the studied plantations. Recent damage, namely feeding lesions on flushes and pods, was also relatively aggregated yet less clearly than mirid populations. In contrast, older damage, namely cankers on trunks and branches, was more regularly distributed, although some zones of the cacao plantations were more damaged than others. These results provide information about the history of mirid infestations in these young and unshaded plantations, and suggest that, if mirid populations are usually aggregated, infestation areas vary over space and time, leading to relatively uniform cumulated damage. However, the presence of higher infestations in some areas of the cocoa plantations could indicate that there are zones that offer better ecological conditions (in the form of habitat and/or food) to mirids. Our study contributes to the understanding of the spatial distribution of S. singularis populations and its damage in young cocoa plantations, and these should be taken into consideration for integrated pest management (IPM) strategies against S. singularis, especially in unshaded cocoa plantations. (Résumé d'auteur

The Control of Apple Blotch

Exact date of bulletin unknown.PDF pages: 1

The dual nature of trehalose in citrus canker disease: A virulence factor for Xanthomonas citri subsp. citri and a trigger for plant defence responses

Xanthomonas citri subsp. citri (Xcc) is a bacterial pathogen that causes citrus canker in susceptible Citrus spp. The Xcc genome contains genes encoding enzymes from three separate pathways of trehalose biosynthesis. Expression of genes encoding trehalose-6-phosphate synthase (otsA) and trehalose phosphatase (otsB) was highly induced during canker development, suggesting that the two-step pathway of trehalose biosynthesis via trehalose-6-phosphate has a function in pathogenesis. This pathway was eliminated from the bacterium by deletion of the otsA gene. The resulting XccΔotsA mutant produced less trehalose than the wild-type strain, was less resistant to salt and oxidative stresses, and was less able to colonize plant tissues. Gene expression and proteomic analyses of infected leaves showed that infection with XccΔotsA triggered only weak defence responses in the plant compared with infection with Xcc, and had less impact on the host plant's metabolism than the wild-type strain. These results suggested that trehalose of bacterial origin, synthesized via the otsA-otsB pathway, in Xcc, plays a role in modifying the host plant's metabolism to its own advantage but is also perceived by the plant as a sign of pathogen attack. Thus, trehalose biosynthesis has both positive and negative consequences for Xcc. On the one hand, it enables this bacterial pathogen to survive in the inhospitable environment of the leaf surface before infection and exploit the host plant's resources after infection, but on the other hand, it is a tell-tale sign of the pathogen's presence that triggers the plant to defend itself against infection.Fil: Piazza, Ainelén Melanie. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Zimaro, Tamara. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Garavaglia, Betiana Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Ficarra, Florencia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Thomas, Ludivine. King Abdullah University of Science and Technology; Arabia SauditaFil: Marondedze, Claudius. King Abdullah University of Science and Technology; Arabia SauditaFil: Feil, Regina. Max Planck Institute of Molecular Plant Physiology; AlemaniaFil: Lunn, John E.. Max Planck Institute of Molecular Plant Physiology; AlemaniaFil: Gehring, Chris. King Abdullah University of Science and Technology; Arabia SauditaFil: Ottado, Jorgelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Gottig Schor, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; Argentin

Annotated Bibliography of the Ambrosia Beetle \u3ci\u3eXylosandrus Germanus\u3c/i\u3e (Coleoptera: Scolytidae)

(excerpt) Xylosandrus germanus (Blandford) (= Xyleborus germanus) is an ambrosia beetle that is found in Japan, Korea, the KurU Islands, Vietnam, China, Taiwan, central Europe, and the Cnited States (Nobuchi 1981). It attacks apparently healthy plants and those that are dying or recently dead (Weber 1982). Kaneko (1967) reported X. germanus to be a serious pest on tea (Thea sp.) plants in Japan, and Heidenreich (1%0) reported it on oak (Quercus sp.) trees in Gennany. This beetle seems to be increasing in economic importance on black walnut (Juglans nigra L.) and other hardwood species in the U.S. (Weber 1982)

Evaluating the impact of Hymenoscyphus fraxineus in Trentino (Alps, Northern Italy): first investigations

The spread of Hymenoscyphus fraxineus has been causing great concern regarding the survival of European ash (Fraxinus excelsior) throughout Europe since the 1990s. The disease was first recorded in Trentino (southern Alps, Italy) in 2012 and has spread throughout the mountain landscape, where ash trees are scattered in small and isolated stands in different valleys. The status of the disease was checked by monitoring the damage to natural regeneration and adult trees in 90 sites spread over the whole region. The survey confirmed the complete colonization by the pathogen of the whole investigated area, with high levels of damage to both young and adult ash trees. Regeneration (both seedlings and saplings) was observed to be affected by the fungus in 88 plots out of 90. Out of 4486 examined young European ashes, 2261 (50.4%) were affected and 789 (17.6%) were already dead. Ten of the 384 assayed flowering ashes (Fraxinus ornus) showed symptoms on branches and apical stems, similar to those observed for European ash. Isolation and molecular analysis proved the presence of the fungus on both symptomatic European and flowering ashes. The examined 386 adult trees showed different levels of damage, sometimes reaching more than 75% of the crown. Some individual trees (42) growing close to severely damaged trees appeared fully healthy, which suggests the possible existence of some resistant/tolerant individuals in the examined populations

Nectria galligena as the cause of a collar rot disease in organically grown Topaz apple trees

Symptoms resembling collar rot were detected in organically managed Topaz trees aged 3-10 years, occur-ring one to several years after planting of the orchard. Trees were killed within the same growing season in which symptoms were first observed. The disease commonly progressed as a complete covered canker at the base of the tree trunk. Isolation attempts were negative for Phytophthora and other Oomycetes, but con-sistently yielded Nectria galligena. The possibility of latent (endophytic) infections of N. galligena as the cause of delayed collar rot symptoms is briefly discussed

Methods of inoculating cypress with Seridium species to screen for resistance and pathogen variability : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Plant Health at Massey University, Palmerston North, New Zealand

The cypress species are grown for their timber value, ornamental beauty and shelter. Their existence is threatened by the presence of cypress canker disease caused by fungal pathogens of the genus Seiridium. The long term solution for controlling this disease is to breed for cypress clones that are resistant to cypress canker. Screening for resistance is conducted by artificially inoculating cypress plants with the pathogen's inoculum. This study aimed at developing reliable methods of artificial inoculation that are suitable for New Zealand's climatic conditions. Infection of cypress plants in nature is caused by conidia but mycelial inocula are more commonly used in artificial inoculation. Several methods of inducing sporulation of Seiridium species were investigated Addition of plant substrates was shown to increase sporulation of cultures of Seiridium isolates. Studies comparing the two types of inocula (mycelial plugs and conidial suspensions) showed that mycelium inocula caused a higher percentage of canker lesions than spore inocula. Conidial inocula offer a more consistent pathogenicity. Experiments to determine the effective spore load revealed that the percentage of canker increased with the increase of inoculum load. Pathogenicity varied between species and individual colonies of Seiridium isolates. Infection of cypress in nature is thought to occur through wounds and in this work, wounding was required for infection under both glasshouse and outdoor conditions. Inoculation of the main stem and side branches showed disease symptoms develop more rapidly on side branches than on the main stem. Investigations on in vitro inoculation of tissue cultured plants and excised side shoots showed the possibility of screening cypress ramets under different environmental conditions. Temperature and percentage relative humidity were found to influence the percentage of successful inoculations on cypress plants