The pathogenicity and virulence of four Ophiostomatoid fungi on young Longleaf pine trees

Abstract

In southeastern USA, insect vectors transfer pathogenic ophiostomatoid fungi that cause disease in southern pines. During 2007 and 2008, potted longleaf pines (P. palustris Mill.), of similar ages ranging in height from 58 to 198 cm, were inoculated with the following fungi to assess their pathogenicity (and virulence): Grosmannia huntii, Leptographium procerum, L. serpens and L. terebrantis. Seventeen weeks after inoculation, L. terebrantis, L. serpens and G. huntii were found to cause significantly larger lesions and more sapwood discolouration than wounded uninoculated controls. Leptographium terebrantis caused significantly more sapwood discolouration than all other fungi. Despite significant sapwood occlusion after fungal inoculation, no reductions in needle water potentials were observed between treatments. All fungal species were successfully re-isolated from longleaf pine trees. Résumé: Dans le sud-est des États-Unis, des insectes agissent comme vecteurs de champignons ophiostomatoïdes pathogènes qui causent des maladies chez les pins du Sud. En 2007 et 2008, des pins des marais en pots (Pinus palustris Mill.), d'à peu près du même âge et mesurant de 58 à 198 cm de hauteur, ont été inoculés avec les champignons suivants afin d'évaluer leur pathogénicité (et leur virulence): Grosmannia huntii, Leptographium procerum, L. serpens et L. terebrantis. Dix-sept semaines après l'inoculation, L. terebrantis, L. serpens et G. huntii causaient des lésions significativement plus graves et provoquaient davantage de décoloration de l'aubier que les arbres témoins blessés, mais non inoculés. Leptographium terebrantis a causé davantage de décoloration que tous les autres champignons. Malgré une occlusion significative de l'aubier après inoculation fongique, aucune réduction du potentiel hydrique des aiguilles n'a été observée. Toutes les espèces fongiques qui se trouvaient dans les pins des marais ont été de nouveau isolées.

Susceptibility of longleaf pine roots to infection and damage by four root-inhabiting ophiostomatoid fungi

“…Although the pathogenicity of several southeastern ophiostomatoid fungi has been shown experimentally in young longleaf pine trees and certain fungal species were determined to be more virulent (Matusick and Eckhardt, 2010a), inoculations of large tree roots provide the most accurate measure of pathogenicity and virulence. A large-scale root inoculation experiment incorporating a range of tree ages, during two seasons, was established in 2006 and 2007 in order to determine if ophiostomatoid fungi cause significant root damage in longleaf pine.…”

The Impact of Drought and Vascular-Inhabiting Pathogen Invasion inPinus taedaHealth

“…Seven seedlings per family within a box received each inoculation treatment. These fungal isolates have been used in previous artificial inoculation studies [15,16,21]. The fungal isolates were maintained at 4 ∘ C in MEA before use and were placed on 2 % MEA plate, 14 days prior to the inoculation experiment.…”

“…[14,15]. Host, Pinus spp., defends against these fungi by producing resins that clog the plant vascular conducting tissues [16]. A tremendous amount of carbon is required in defense which results in the scarcity of carbon required for the plant growth and functioning.…”

“…Many pathologists have had a false dichotomy of drought vs. biotic attack [17]. Many studies have focused primarily 2 International Journal of Forestry Research on individual factors: (i) drought and its subsequent effect on plant physiology [18,19] or (ii) Biotic agents and its subsequent impact tree health [15,16]. However, the evidence for the mechanisms suggested by these individual factors is inconclusive and a more integrated approach focusing on relations between drought and biotic agents on tree growth and functioning is needed.…”

Microsatellite and mating type markers reveal unexpected patterns of genetic diversity in the pine root‐infecting fungusGrosmannia alacris

“…Grosmannia alacris has the widest distribution of all species in the recently described G. serpens complex (Duong et al ., 2012a). It has been associated with pine decline in various studies as well as in fungal–insect association studies in the USA and South Africa (Zhou et al ., ; Eckhardt et al ., 2004a, ; Matusick & Eckhardt, ,b; Zanzot et al ., ; Duong et al ., 2012a). However, nothing is known regarding the centre of origin nor the genetic diversity of the fungus in these countries.…”