Temperature and inoculation method influence disease phenotypes and mortality of Eucalyptus marginata clonal lines inoculated with Phytophthora cinnamomi

Survival of 1-year-old plants of three clonal lines of Eucalyptus marginata (jarrah), two ranked as resistant (RR1 and RR2) and one as susceptible (SS1) to Phytophthora cinnamomi, was assessed after pathogen inoculation with either mycelial mats underbark or zoospores on the stem. Plants were grown at 15, 20, 25 and 30°C. Method of inoculation did not produce comparable mortalities of the clonal lines, particularly at 25 and 30°C. At these temperatures, all three clonal lines had 100% mortality when inoculated underbark, but when inoculated with zoospores, RR1 had 60% survival and lines SS1 and RR2 had 100% mortality. Generally, the level of resistance of all clonal lines declined with increasing temperature. RR2 had consistently higher mortality than SS1, and is therefore not considered resistant. Lesion development was also measured in detached stems of RR1 and a susceptible clonal line (SS2) each inoculated underbark with four different P. cinnamomi isolates. Stems were assessed for lesion development at 20, 25 and 30°C for 4 days. For all four isolates, detached stems of RR1 generally had smaller lesions than those of SS2, particularly at 30°C. The increase in lesion length with increasing temperature was greatest for SS2. Detached stems may have potential in screening for jarrah resistant toP. cinnamomi and allow identification of susceptible clonal lines at 30°C

The impact and control of Phytophthora cinnamomi in native and rehabilitated forest ecosystems in Western Australia

Botanists have likened the impact of Phytophthora cinnamomi in Australian plant communities to that of the last ice age, which affected a large number of plant families, genera and species within these families. Phytophthora cinnamomi affects the floristics and structure of many unique plant communities. We discuss the impact of this pathogen and our current knowledge of its biology, genetics and pathology in Western Australian plant communities and the current management strategies used to limit its spread and impact. We hope that the knowledge obtained from some of our experiences in managing this pathogen in Western Australian natural ecosystems will be of some benefit to researchers studying Phytophthora diseases in Quercus, Alnus and Castanea in Europe and America

Factors influencing terrestriality in primates of the Americas and Madagascar

Among mammals, the order Primates is exceptional in having a high taxonomic richness in which the taxa are arboreal, semiterrestrial, or terrestrial. Although habitual terrestriality is pervasive among the apes and African and Asian monkeys (catarrhines), it is largely absent among monkeys of the Americas (platyrrhines), as well as galagos, lemurs, and lorises (strepsirrhines), which are mostly arboreal. Numerous ecological drivers and species-specific factors are suggested to set the conditions for an evolutionary shift from arboreality to terrestriality, and current environmental conditions may provide analogous scenarios to those transitional periods. Therefore, we investigated predominantly arboreal, diurnal primate genera from the Americas and Madagascar that lack fully terrestrial taxa, to determine whether ecological drivers (habitat canopy cover, predation risk, maximum temperature, precipitation, primate species richness, human population density, and distance to roads) or species-specific traits (body mass, group size, and degree of frugivory) associate with increased terrestriality. We collated 150,961 observation hours across 2,227 months from 47 species at 20 sites in Madagascar and 48 sites in the Americas. Multiple factors were associated with ground use in these otherwise arboreal species, including increased temperature, a decrease in canopy cover, a dietary shift away from frugivory, and larger group size. These factors mostly explain intraspecific differences in terrestriality. As humanity modifies habitats and causes climate change, our results suggest that species already inhabiting hot, sparsely canopied sites, and exhibiting more generalized diets, are more likely to shift toward greater ground use

Geographical and temporal distribution of SARS-CoV-2 clades in the WHO European Region, January to June 2020

We show the distribution of SARS-CoV-2 genetic clades over time and between countries and outline potential genomic surveillance objectives. We applied three available genomic nomenclature systems for SARS-CoV-2 to all sequence data from the WHO European Region available during the COVID-19 pandemic until 10 July 2020. We highlight the importance of real-time sequencing and data dissemination in a pandemic situation. We provide a comparison of the nomenclatures and lay a foundation for future European genomic surveillance of SARS-CoV-2.Peer reviewe

Evaluation of resistance to Phytophthora cinnamomi in seed-grown trees and clonal lines of Eucalyptus marginata inoculated in lateral branches and roots

Seed-grown trees and six clonal lines of 3-5-4-5-year-old Eucalyptus marginata (jarrah) growing in a rehabilitated bauxite mine site in the jarrah forest were underbark-inoculated on lateral branches (1995) or simultaneously on lateral branches and lateral roots (1996) with isolates of Phytophthora cinnamomi in late autumn. Individual seedlings from which the clonal lines were derived had previously been assessed as either resistant (RR) or susceptible (SS) to P. cinnamomi. At harvest, the acropetal lesion and colonization lengths were measured. Overall, the length of colonization in roots and branches was more consistent as a measure of resistance than lesion length, because colonization length recorded the recovery of P. cinnamomi from macroscopically symptomless tissue ahead of the lesion which, on some occasions, was up to 6 cm. In both trials, one RR clonal line was able to contain the P. cinnamomi isolates consistently, as determined by small lesion and colonization lengths in branches and roots. In contrast, the remaining two RR clonal lines used in both trials were no different from the SS line in their ability to contain lesions or colonization. These latter two RR lines may therefore not be suitable for use in rehabilitation of P. cinnamomi-infested areas. Differences in lesion and colonization lengths among P. cinnamomi isolates occurred only in the 1995 trial. Colonization and lesion lengths in branches were up to eight times greater in 1996 than in 1995, but the relative rankings of clonal lines were consistent between trials. Although colonization was always greater in branches than roots, the relative rankings of the lines were similar between branch and root inoculations. Branch inoculations are a valid option for testing the resistance and susceptibility of young jarrah trees to P. cinnamomi

Temperature changes resistance of Eucalyptus marginata to Phytophthora cinnamomi

Eucalyptus marginata (Jarrah) varies in its resistance to infection by the introduced pathogen, Phytophthora cinnamomi. This trait has been exploited to yield jarrah clones ranging in resistance to P. cinnamomi. However, isolates of P. cinnamomi vary in their capacity to induce disease in resistant jarrah clones. We have shown that isolates differ in their growth rates in jarrah and marri (E. calophylla) tissue and in agar media. Disease outbreaks in jarrah, other native vegetation and horticultural crops due to P. cinnamomi are more likely to occur in warm moist conditions. These factors raise questions about the interactions between the pathogen, hosts and temperature, and the consequent disease development

Selecting plants resistant to Phytophthora cinnamomi

Phytophthora cinnamomi is the most devastating forest disease world wide. It is mostly an introduced pathogen as in southern Australia where it devastates native forests, woodlands and heaths, directly and indirectly affecting vegetation types from a wide range of families. P. cinnamomi has also been introduced into European and North American hardwood and softwood forests. The pathogen is now cosmopolitan in the horticultural industry and it is a particular problem in nurseries. The significance of this is that P. cinnamomi has the opportunity to interact with and the potential to evolve in association with a wide range of new hosts and in a wide range of ecosystems. Distribution of the pathogen at the local, national and international level is of concern to the management of forest, native vegetation and horticulture industries

Temperature changes resistance of clonal Eucalyptus marginata to Phytophthora cinnamomi

Eucalyptus marginata (jarrah) varies in its resistance to colonization by the introduced pathogen, Phytophthora cinnamomi. This trait has been exploited to yield jarrah clones ranging in resistance to P. cinnamomi. However, isolates of P. cinnamomi vary in their capacity to induce disease in resistant jarrah clones, with no association between pathogenicity levels and either A1 and A2 mating types or isozymes types. We have shown that isolates differ in their capacity to colonize jarrah and marri (E. calophylla) tissue. Disease outbreaks in jarrah, other native vegetation and horticultural crops due to P. cinnamomi are more likely to occur in warm moist conditions. These factors raise questions about the interactions between the pathogen, hosts and temperature, and consequent disease development

Measuring resistance in Eucalyptus marginata to Phytophthora cinnamomi: What factors change disease expression?

The interaction between Eucalyptus marginata (Jarrah), the dominant and important timber species in jarrah forests, and Phytophthora cinnamomi, is not a co-evolved one. Jarrah appears to have a wide range of variability in resistance to P. cinnamomi in the forest. Jarrah clonal lines resistant (RR) and susceptible (SS) to the pathogen have been produced. Our glasshouse mortality trial showed that the capacity of 73 isolates to cause disease ranged from killing all plants (59 days) to plants being symptomless (182 days). Comparison of branch and root inoculations in situ confirmed that branches are a valid option for testing resistance of young jarrah. No jarrah clonal line (100% =immune) maintained its resistance level in a series of experiments using different inoculation methods, different environmental conditions and when challenged by individuals from a large range of P. cinnamomi isolates. Even the most promising RR line had replicates that became diseased with time in various treatments. To develop robust resistance, further screening work may be required using more isolates varying in their capacity to cause disease and a broader range of environmental conditions that favour the pathogen, particularly at 25-30°C. Jarrah trees are affected by many environmental conditions during their life cycle (500-1000 years). Consequently, clonal lines that survive such rigorous screening may be durably resistant and survive in disease impacted sites