Dothistroma needle blight (DNB) is one of the most important diseases of pine. Although its notoriety stems from Southern Hemisphere epidemics in Pinus radiata plantations, the disease has increased in prevalence and severity in areas of the Northern Hemisphere, including Europe, during the last two decades. This increase has largely been attributed to expanded planting of susceptible hosts, anthropogenic dispersal of the causative pathogens and changes in climate conducive to disease development. The last comprehensive review of DNB was published in 2004, with updates on geographic distribution and host species in 2009. Importantly, the recognition that two species, Dothistroma septosporum and D. pini, cause DNB emerged only relatively recently in 2004. These two species are morphologically very similar, and DNA-based techniques are needed to distinguish between them. Consequently, many records of host species affected or geographic location of DNB prior to 2004 are inconclusive or even misleading. The objectives of this review were (i) to provide a new database in which detailed records of DNB from 62 countries are collated; (ii) to chart the current global distribution of D. septosporum and D. pini; (iii) to list all known host species and to consider their susceptibility globally; (iv) to collate Drenkhan et al. 410 |
Summary This review comprises both well‐known and recently described Phytophthora species and concentrates on Phytophthora–woody plant interactions. First, comprehensive data on infection strategies are presented which were the basis for three models that explain invasion and spread of Phytophthora pathogens in different woody host plants. The first model describes infection of roots, the second concentrates on invasion of the trunk, and the last one summarizes infection and invasion of host plants via leaves. On the basis of morphological, physiological, biochemical and molecular data, scenarios are suggested which explain the sequences of reactions that occur in susceptible and tolerant plants following infections of roots or of stem bark. Particular emphasis is paid to the significance of Phytophthora elicitins for such host–pathogen interactions. The overall goal is to shed light on the sequences of pathogenesis to better understand how Phytophthora pathogens harm their host plants.
Summary Dothistroma needle blight (DNB) caused by Dothistroma septosporum and Dothistroma pini is a damaging disease of pine in many countries. The disease led to the abandonment of planting susceptible Pinus species in parts of Africa, Asia, Australasia, Europe and North America. Although the disease can be effectively controlled using copper fungicides, this chemical is only routinely applied in forests in New Zealand and Australia. Other management tactics aimed at making conditions less favourable for disease development, such as thinning or pruning, may be effective on some, but not all, sites. Disease avoidance, by planting non‐susceptible species, is the most common form of management in Europe, along with deployment of hosts with strong disease resistance. Although D. septosporum is present almost everywhere Pinus is grown, it is important that an effort is maintained to exclude introductions of new haplotypes that could increase virulence or enable host resistance to be overcome. A global strategy to exclude new introductions of Dothistroma and other damaging forest pathogens, facilitated by collaborative programmes and legislation, is needed.
Fungal endophytes were collected from 168 Pinus halepensis trees sampled in 55 Spanish stands. In total, 229 endophytic isolates were grouped into 92 morphotypes according to their mycelium features. Thus, twigs enclosed 63.76% of the total endophyte isolates and needles 36.24%. Likewise, twig samples also yielded a higher endophyte species richness. Analysis of ITS rDNA region generated 38 different Ascomycota taxa and confirmed the endophytic stage of several pathogens previously associated with the Pinus halepensis decline in Spain. Naemacyclus minor, Brunchorstia pinea, Lophodermium pinastri, Phomopsis sp., Diplodia pinea, Pestalotiopsis besseyi and Truncatella angustata were isolated. Sequencing of LSU rDNA region verified the 38 taxa and contributed to infer their phylogenic relatedness using the Neighbour-Joining method. In the bootstrap consensus tree five classes were observed. Dothideomycetes resulted to be the dominant class because of its high isolation frequency (52.4%) and richest species composition (39.5%). On the contrary, class Eurotiomycetes was the least abundant (3.5%) and along with class Pezizomycetes harboured the lowest species richness (7.9%). Class Sordariomycetes and Leotiomycetes had intermediate abundance and species composition percentages. This study represents the first work concerning the taxonomy of the fungal endophytic community of the Mediterranean host species Pinus halepensis using molecular tools. The data provided here may help to establish the cause of Pinus halepensis decline.
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