Exotic pine forestry in the Southern Hemisphere: A brief history of establishment and quarantine practices

Slippers

et al. 2003

Mycological Research

Self Cite

124

Sphaeropsis sapinea is an opportunistic pathogen causing serious damage to conifers, pre-disposed by adverse environmental conditions or mechanical damage. Three different morphological forms of the fungus have been described and are commonly referred to as the A, B and C morphotypes. Isolates of the different morphotypes have also been separated based on differences in pathogenicity and molecular characteristics. These differences, however, overlap and have not been considered sufficiently robust to justify the description of separate taxa. The aim of this study was to consider relationships between isolates representing different S. sapinea morphotypes, using multiple gene genealogies inferred from partial sequences of six protein-coding genes and six microsatellite loci. Genealogies generated for the protein-coding genes and microsatellite loci were not congruent but both consistently grouped isolates representing the A and C morphotypes in separate but closely related clades. In contrast, isolates of the B morphotype grouped together in a clade that was equally different to the A and C morphotypes as it was to the clade encompassing isolates of Botryosphaeria obtusa. These results provide strong evidence to show that the B morphotype isolates are distantly related to S. sapinea and represent a discrete taxon, which we describe here as Diplodia scrobiculata sp. nov.

Section: Discussionmentioning

confidence: 99%

“…It is also one of the best-known pathogens of Pinus spp. grown as exotics in the tropics and southern hemisphere (Burgess & Wingfield 2001). Thus, the discovery of taxonomically and ecologically meaningful differences in isolates of S. sapinea in the north central United States in the late 1980's, was relatively recent.…”

Section: Discussionmentioning

confidence: 99%

Multiple gene genealogies and microsatellite markers reflect relationships between morphotypes of Sphaeropsis sapinea and distinguish a new species of Diplodia

Wet

Slippers

et al. 2003

Mycological Research

Self Cite

124

“…J. Kickx) is an important pathogen of Pinus spp. causing shoot die-back, stem cankers, seedling mortality and under stress conditions such as hail damage, tree mortality (Swart et al 1987;Blodgett et al 1997;Burgess and Wingfield 2001;Stanosz et al 2001). Diplodia pinea can be an endophyte in asymptomatic Pinus tissue (Smith et al 1996;Burgess et al 2001a;Stanosz et al 2005;Maresi et al 2007) and is commonly encountered as a saprophyte on cone bracts and coarse woody debris (Smith et al 1996;Flowers et al 2001;Santini et al …”

Section: Introductionmentioning

confidence: 99%

Distribution of Diplodia pinea and its genotypic diversity within asymptomatic Pinus patula trees

Bihon

Australasian Plant Pathol.

Slippers

et al. 2011

Self Cite

Diplodia pinea (= Sphaeropsis sapinea) is an endophytic fungus and opportunistic canker pathogen of Pinus spp. The diversity of this fungus has been studied at broad geographic scales, but little is known regarding its population structure at smaller spatial scales such as within a single tree. This is despite the importance that diversity in a single tree might hold for understanding the biology of the fungus, especially the role of the endophytic or asymptomatic phase in disease development. Moreover there was not information regarding the distribution of the fungus within healthy trees and its persistence. The genotypic diversity of these isolates was investigated using microsatellite markers. Five polymorphic markers were developed and these were used together with eight previously developed markers and vegetative compatibility tests to study the genotypic diversity of D. pinea isolates. In this study, D. pinea was isolated for the first time in the well structured stems of healthy P. patula trees along with branches and cones. From a total of 44 isolates collected from five trees, 39 microsatellite haplotypes and 32 vegetative compatibility groups (VCG's) were identified. 2The results indicate high genotypic diversity of D. pinea within individual asymptomatic trees which will lead to disease outbreak when trees are physiologically stressed.

“…However, only D. pinea is known to have been introduced to southern hemisphere pine plantations (Swart et al 1991, Stanosz et al 1999, de Wet et al 2000, Burgess & Wingfield 2001, Burgess et al 2001a, Burgess et al 2004. The origin of D. pinea populations in exotic plantations was impossible to determine due to the lack of equivalent unique alleles in native populations (Burgess et al 2004).…”

Section: Discussionmentioning

confidence: 99%

“…in many parts of the world (Punithalingam & Waterson 1970, Swart, Wingfield & Knox-Davies 1985, Zwolinski, Swart & Wingfield 1990, Burgess & Wingfield 2002. In Southern Hemisphere plantations, P. radiata is known to be particularly susceptible to D. pinea when planted off-site in regions with summer rainfall, hail, drought or waterlogging (Marks & Minko 1969, Thomson 1969, Gibson 1979, Lundquist 1987, Zwolinski et al 1990, Davison, Tay & Peroni 1991, Burgess & Wingfield 2001.…”

Section: Introductionmentioning

confidence: 99%

Geographic isolation of Diplodia scrobiculata and its association with native Pinus radiata

Gordon

Wingfield³

et al. 2004

Mycological Research

Self Cite

Diplodia pinea (syn. Sphaeropsis sapinea) is a well-known latent pathogen of Pinus spp. with a worldwide distribution. As such, this fungus is native where pines are endemic in the northern hemisphere and it has been introduced into all countries of the Southern Hemisphere where pines are exotic. The newly described D. scrobiculata (formerly known as the B morphotype of D. pinea) is thought to have a much more limited distribution. D. scrobiculata was first reported as an endophyte and weak pathogen of P. banksiana, where it was found to coexist with D. pinea. Diplodia scrobiculata is now known to have a much broader distribution in Northern America and Europe. In this study, seven Simple Sequence Repeat (SSR) markers were used to evaluate genetic diversity and gene flow between populations of D. scrobiculata. Results indicate a strong geographic isolation between populations of D. scrobiculata from different regions in North America, with unique alleles fixed in the different populations. The data fits the isolation by distance model indicating limited dispersal. Geographic isolation in combination with isolation by distance suggests prolonged reproductive isolation. Intensive collections of endophytes from native P. radiata in California have yielded only D. scrobiculata and not the significantly more pathogenic D. pinea. SSR analysis of three populations of D. scrobiculata from native P. radiata identified many shared alleles among the populations and moderate to high gene flow between them. The three Californian populations are distant and distinct from populations of D. scrobiculata from elsewhere. Under stress conditions, P. radiata is known to be very susceptible to D. pinea in plantations in the Southern Hemisphere. Native P. radiata is currently experiencing severe stress due to pitch canker caused by Fusarium circinatum. Such stress would provide ideal conditions for an associated outbreak of D. pinea. Thus, it is critical to prevent the movement of D. pinea into the last remaining native stands of P. radiata.