ABSTRACT Intensified globalisation and the movement of plant materials have increased pathways for plant invasions and the risk of plant disease establishment globally. Mango bacterial black spot (MBBS) is an invasive disease native to Africa. The disease poses a serious threat to global mango production and trade. Yet MBBS habitat‐suitability models that can guide surveillance and monitoring programmes remain poorly documented. This study predicts global climate‐suitable areas for MBBS using the Maximum Entropy model. Future projections were conducted under two socioeconomic pathways (SSPs245 and 585) and two time periods (2050s: 2041–2060 and 2070s: 2061–2080). The models showed strong predictive performance (AUC = 0.890, TSS = 0.686, and CBI = 0.705). Among the bioclimatic variables, the minimum temperature of the coldest month, the mean temperature of the warmest quarter, precipitation of the wettest month and the precipitation seasonality contributed the most to the model. Under current conditions, parts of South America, Africa, Asia and Australia were found to be suitable. These areas will become more suitable for disease establishment in the future. Areas suitable for MBBS establishment are projected to increase by 1.60% and 2.01% under SSP245 and SSP585, respectively, in the 2050s. Similarly, in the 2070s, suitability gains are projected at 1.91% and 2.78% under SSP245 and SSP585, respectively. These findings provide insight into the habitat suitability of the MBBS disease and are useful for surveillance and monitoring programs.
Cronartium pini, Scots pine blister rust, is a rust fungus that has caused severe damage in both old and young Scots pine (P. sylvestris) forest stands in northern Fennoscandia. To understand the many drivers of these outbreaks we examined putative factors and their explanatory power of C. pini incidence based on data collected in Lapland, northern Finland. Diseased stands were selected from the 10th Finnish National Forest Inventory (NFI) and control plots were randomly selected from the 11th NFI. A damage assessment was conducted in 2014, 4 years later in separate 10-15 sample plots within each stand. Stand and tree characteristics, including incidence of C. pini, were recorded. Site type (fertility) and age of trees significantly explained the incidence of C. pini in sample plots. Incidence of C. pini infection increased significantly in fertile sites, while the risk was non-significant in more arid sites. Risk of infection by C. pini was significantly reduced when the proportion of deciduous trees increased. There was an increased infection risk (up to over 50%) proportional to how well the trees grew for the last 5 years if Melampyrum spp. were present. Our results support previous observations that fertile sites are more susceptible to infection by C. pini. For the first time, we also demonstrate that an increase in the number of deciduous trees reduces the risk of C. pini infections. These results offer tools to improve forest management practices in reducing the risk of damage caused by C. pini in northern pine forests.
There are currently several Phytophthora species that are of major concern for forestry. Three of these species: P. pluvialis, P. pseudosyringae and P. ramorum, share a similar host range across the British Isles and display similar symptoms and disease progression. As P. pluvialis and P. ramorum are regulated pathogens in Great Britain, early and accurate detection is fundamental for appropriate management of these potentially invasive and highly destructive pathogens. We developed two diagnostic tests, both targeting the mitochondrial gene Cytochrome c oxidase subunit 2 (cox2): a multiplex real-time polymerase chain (RT-PCR) reaction, which enables simultaneous detection of these three Phytophthora species, and an isothermal recombinase polymerase amplification (RPA) assay for detection of P ramorum and P. pluvialis. The RT-PCR is highly specific and sensitive, with a limit of detection (LOD) ranging from 7.4 to 36 fg of mycelial DNA and is suitable for detection from infected plant material, with > 90% diagnostic accuracy. The RPA can be used at the point of sampling and provides results within 20 min. This assay showed high specificity at LODs between 1 and 10 pg of mycelial DNA, depending on species and lineage. Although less sensitive than the RT-PCR assay, this rapid, frontline test is suitable for plant matrices, with positive detections from samples with a RT-PCR positive of < 30 cycles. These new diagnostic tools improve accuracy and speed of detection, reducing cost without compromising sensitivity. The RPA assays provide rapid results in the field, borders and ports, and enable effective triage of samples for laboratory analysis.
Seed-associated fungal communities may influence forest regeneration by affecting seed viability and early seedling performance. This study investigated whether host species identity and seed origin are associated with variation in fungal community composition and taxon-specific occurrence in pine seeds. We hypothesized that fungal community composition varies among host species, individual fungal genera exhibit host-associated occurrence patterns, and seed origin influences the occurrence of specific taxa. A total of 420 seeds from four pine species, representing 21 certified seed stands, were examined using culture-based isolation, MALDI-TOF identification and ecological analyses. Fungal communities were dominated by Trichoderma spp., followed by Rhizopus arrhizus. Differences in the occurrence of several fungal genera were detected among pine species, while seed origin was associated with variation in selected taxa. Principal Coordinates Analysis illustrated variation in fungal genus composition among seed stands. These findings highlight the importance of examining fungal taxonomic composition rather than relying solely on overall fungal incidence when assessing seed-associated fungal communities. The results provide insights relevant to seed health monitoring and forest reproductive material management.
The fungus Chrysoporthe cubensis has been reported to cause significant losses in eucalypt mini-clonal hedge systems in Brazil, where the disease is characterized by wilting, xylem lesion and dieback of mini-stump. This study aimed to investigate the occurrence of Chrysoporthe species occupying an endophytic niche in asymptomatic mini-stumps, mini-cuttings and rooted mini-cuttings in a mini-clonal hedge; confirm the identity of the pathogen through phylogenetic analyses of an expanded set of fungal isolates; assess whether the pathogen is transmitted from symptomatic mini-stumps to mini-cuttings and rooted mini-cuttings; and analyse the pathogenicity of Chrysoporthe spp. recovered from mini-stumps. Chrysoporthe cubensis was recovered and identified in 88% of the symptomatic samples analysed and, at a lower frequency (12%), as an endophyte in asymptomatic samples from two hybrid clones of Eucalyptus grandis & times; Eucalyptus urophylla. Additionally, Chrysoporthe doradensis was identified in only one symptomatic sample. Chrysoporthe was not detected in asymptomatic mini-cuttings and rooted mini-cuttings. Pathogenicity tests confirmed that all C. cubensis isolates recovered from asymptomatic eucalypt mini-stumps induced necrotic lesions in the stems of rooted mini-cuttings within the same time frame as the reference isolate. The pathogenicity of C. doradensis isolate was also confirmed in rooted mini-cuttings. The proportion of rooted mini-cuttings did not differ between those from dieback-affected and asymptomatic mini-stumps. Furthermore, Chrysoporthe was not detected in rooted mini-cuttings produced from symptomatic mini-stumps, suggesting that the pathogen is unlikely to be transmitted through vegetative propagation. This is the first report worldwide of C. cubensis occupying an endophytic niche in eucalypt mini-stumps and of C. doradensis as an additional species associated with dieback in eucalypt mini-stumps in Brazil.
