A latitudinal cline in disease resistance of a host tree

• Published in: Heredity Vol. 110; no. 4; pp. 372 - 379
• Main Authors: Hamilton, M G, Williams, D R, Tilyard, P A, Pinkard, E A, Wardlaw, T J, Glen, M, Vaillancourt, R E, Potts, B M
• Format: Journal Article
• Language: English
• Published: England Springer Nature B.V 01-04-2013; Nature Publishing Group
• Subjects: Age Factors; Disease resistance; Disease Resistance - genetics; Dispersal; Environment; Epidemics; Eucalyptus - genetics; Eucalyptus - microbiology; Eucalyptus globulus; Gardens & gardening; Genetic diversity; Genetics, Population; Health risks; Inbreeding; Leaves; Mycosphaerella; Original; Pathogens; Plant diseases; Plant Diseases - genetics; Plant Diseases - microbiology; Plant Leaves - genetics; Plant Leaves - microbiology; Plant populations; Plant resistance; Plant species; Seasons; Selection, Genetic - genetics; Trees
• ISSN: 0018-067X; 1365-2540
• DOI: 10.1038/hdy.2012.106

The possible drivers and implications of an observed latitudinal cline in disease resistance of a host tree were examined. Mycosphaerella leaf disease (MLD) damage, caused by Teratosphaeria species, was assessed in five Eucalyptus globulus (Tasmanian blue gum) common garden trials containing open-pollinated progeny from 13 native-forest populations. Significant population and family within population variation in MLD resistance was detected, which was relatively stable across different combinations of trial sites, ages, seasons and epidemics. A distinct genetic-based latitudinal cline in MLD damage among host populations was evident. Two lines of evidence argue that the observed genetic-based latitudinal trend was the result of direct pathogen-imposed selection for MLD resistance. First, MLD damage was positively associated with temperature and negatively associated with a prediction of disease risk in the native environment of these populations; and, second, the quantitative inbreeding coefficient (QST) significantly exceeded neutral marker FST at the trial that exhibited the greatest MLD damage, suggesting that diversifying selection contributed to differentiation in MLD resistance among populations. This study highlights the potential for spatial variation in pathogen risk to drive adaptive differentiation across the geographic range of a foundation host tree species.