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 |
Scots pine ( Pinus sylvestris L., Pinaceae) produces a terpenoid resin which consists of monoterpenes and resin acids that offer protection against herbivores and pathogen attacks. Methyl jasmonate (MJ) is a potential plant elicitor which induces a wide range of chemical and anatomical defence reactions in conifers and might be used to increase resistance against biotic damage. Different amounts of MJ (control, 10 m , and 100 m ) were applied to Scots pine to examine the vigour, physiology, herbivory performance, and induction of secondary compound production in needles, bark, and xylem of 2-year-old Scots pine seedlings. Growth decreased significantly in both MJ treated plants, and photosynthesis decreased in the 100 m MJ treated plants, when compared to 10 m MJ or control plants. The large pine weevil ( Hylobius abietis L.) (Coleoptera: Curculionidae) gnawed a significantly smaller area of stem bark in the 100 m treated plants than in the control or 10 m treated plants. The 100 m MJ treatment increased the resin acid concentration in the needles and xylem but not in the bark. Furthermore, both MJ treatments increased the number of resin ducts in newly developing xylem. The changes in plant growth and chemical parameters after the MJ treatments indicate shifts in carbon allocation, but MJ also affects plant physiology and xylem development. Terpenoid resin production was tissue-specific, but generally increased after MJ treatments, which means that this compound may offer potential protection of conifers against herbivores.
The cessation of shoot elongation, diameter growth and needle elongation were compared with the initiation of frost hardening of the stems and needles in an 8-year-old provenance trial of Scots pine (Pinus sylvestris L.) established in central Finland. The saplings were of six different origins ranging from Estonia to northern Finland, forming a latitudinal gradient of ca. 10°N. The frost hardiness of the stems of current-year shoots was assessed by electrical impedance analysis and that of current-year needles by electrolyte leakage and visual scoring of damage. Artificial freezing tests were used in the assessments. The pattern of growth cessation (shoot and needle elongation, diameter growth) tended to follow the latitude of origin, i.e. growth ceased in the northernmost provenance first and in the southernmost one last. Both stems and needles of the northern provenances hardened earlier than the southern ones, but the differences in hardiness disappeared as hardening progressed. Growth cessation and initial hardening to -15°C were clearly correlated at the provenance level, indicating that growth must cease prior to hardening, and that earlier cessation of growth predicts earlier frost hardening of stems and needles. No differences in frost hardiness of stems were found at the provenance level at the end of the growing period in August. At that time, the frost hardiness of needles of the northernmost provenance was higher than that of other origins. Within the provenance, the stems were less hardy than the needles.
S L' M M .\ R •^'Variations ol'terpenc, resin acid and total phenolic concentrutions in yuung seedlings of SiicitF. pine (Pinus sy L,) from nine different seed origins growing in three locations of different latitudes, in Finland and Kstonia, wert investigated in autumn 1991 and spring 1992. Seasonal variation uas remarkahle in monoterpene, resin acid and total phenolic concentrations. In spring there was more 3-carene, a-pinene, /^-pinene + sabinene and total monoterpenes m pine shoots, and less myrcene and tncyclerie compared to autumn. Concentrations of some individual resin acids, levopimaric and dehydroahietic acids, were higher in autumn. The total phenolic concentration vvas higher in spring. In the most northern location, the concentrations of total monoterpenes and total phenolics were lowest. The total resin acid concentration vvas highest in the middle location, and indi\idual resin acids, palustric and neoabietic acids, w ere more common in the most northern location. Seed origin had no significant effects either to the resin acid or total phenolic concentrations. There wt're almost equal concentrations of total phenolics and resin acids in northern and southern t)rigins. Instead some individual monoterpenes. limonene, tricyclene, camphene, /f-pinene + sabinene and hornylacetate, were more common in northern seed origins. The results suggest that the origin of the seed material is not so important in affecting the concentrations of secondary compounds as are the en\ ironmental factors.
The seasonal and latitudinal influences on the diversity and abundance of mycota of Pinus sylvestris needles were investigated. A sample of 1620 needles resulted in a total of 3868 fungal isolates, which were assigned to 68 operational taxonomic units (OTUs). The majority of these OTUs (65%) belong to Ascomycota and only 0.03% was grouped as Basidiomycota. The dominant and most frequently isolated OTU was Hormonema dematioides. Other wellknown species with a saprotrophic nutritional mode such as Lophodermium spp. were also observed. The abundance of fungi increased from fall to spring. Frequencies varied significantly in Northern and Southern Finland suggesting that factors associated with latitudinal differences have an impact on the abundance of fungi.
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