Intraspecific variation in susceptibility to dothistroma needle blight within native Scottish Pinus sylvestris

Abstract

Dothistroma needle blight (DNB), caused by Dothistroma septosporum, is the most important disease currently affecting pine plantations in Britain. Intraspecific variation in susceptibility to DNB has been observed in several pine species, but it is not clear if similar variation occurs in Pinus sylvestris (Scots pine), Britain's only native pine. In three separate experiments 2‐ and 3‐year‐old Scots pine saplings from six native Scottish populations were artificially inoculated with D. septosporum conidial suspensions and incubated under conditions optimal for disease development. Conidial suspensions were produced using a single isolate from northeast Scotland. In one experiment, plants were also treated with various spore suspension concentrations to assess the impact of inoculum load on disease severity. There were no significant interactions between host population, plant height, and experiment/inoculum load (anova, P > 0·05), but population, height and inoculum load all significantly affected disease severity (anova, P < 0·05). Among the 2‐year‐old trees, those from Amat were less susceptible than those from Glen Loyne and Glen Cannich (anova, P < 0·05). Among the 3‐year‐old trees, those from Beinn Eighe were less susceptible than those from Abernethy. Plant height and DNB susceptibility had a slightly negative relationship. The use of a spore suspension with a concentration of 1·6 × 106 spores mL−1 was optimum for disease development. In an in vitro experiment, production of conidia was greater when cultures were incubated in darkness. This paper is the first to report intraspecific variation in DNB susceptibility within Scots pine.

Has Scots pine (Pinus sylvestris) co‐evolved with Dothistroma septosporum in Scotland? Evidence for spatial heterogeneity in the susceptibility of native provenances

“…High levels of variation in susceptibility to D. septosporum have been reported in all trials and significant differences among provenances were reported by Fraser, Brown et al. () and Fraser, Mullett et al. (), although the composition of their trials did not allow a heritability estimate to be derived.…”

“…Fraser, Brown et al. () and Fraser, Mullett et al. () have shown similarly high correlation between a highly infected naturally inoculated trial and artificial inoculated trials, although when there were very low levels of infection in their natural trial the correlation ceased.…”

“…Additionally, Fraser, Brown et al. () and Fraser, Mullett et al. () found significant differences in susceptibility to D. septosporum among naturally inoculated provenances in two of three assessed years, as well as in their artificial inoculation trials, despite the use of different provenances and younger trees.…”

“…Previous experimental studies on DNB on native Scots pine have been performed both in artificial conditions using a single pathotype in an ideal environment for infection (Fraser, Brown, & Woodward, ; Perry et al., ) and in a natural environment where DNB is known to affect neighbouring trees (Fraser, Mullett et al., ). High levels of variation in susceptibility to D. septosporum have been reported in all trials and significant differences among provenances were reported by Fraser, Brown et al.…”

A review of Pinaceae resistance mechanisms against needle and shoot pathogens with a focus on the Dothistroma–Pinus interaction

“…Between-provenance variation in susceptibility to DNB has been reported for several Pinus species, including Pinus caribaea Morelet (Ivory 1968), P. contorta (Gilmour and Noorderhaven 1969), P. elliottii (Gibson 1972), P. monticola (Hunt et al 2011), P. muricata (Ades et al 1992;Muir and Cobb 2005), P. nigra (Peterson and Read 1971), P. ponderosa (Eldridge et al 1980;Peterson 1984), P. radiata (Cobb and Libby 1968;Burdon and Bannister 1973;Power and Dodd 1984;Ades and Simpson 1991), P. sylvestris (Fraser et al 2015) and Pinus tecunumanii Eguiluz & J. P. Perry (Rodas et al 2016). As discussed above, one way of identifying possible resistance mechanisms is to compare the morphology and chemistry of susceptible and resistant provenances.…”