Source: OHIO STATE UNIVERSITY submitted to
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
Funding Source
Reporting Frequency
Accession No.
Grant No.
Project No.
Proposal No.
Multistate No.
Program Code
Project Start Date
Oct 1, 1999
Project End Date
Sep 30, 2004
Grant Year
Project Director
Bonello, P.
Recipient Organization
Performing Department
Non Technical Summary
Certain diseases predispose conifers to bark beetle and other insect attacks. Very little is know about the actual physiological/chemical mechanisms that make diseased trees more prone to insect attack. The purpose of this project is to understand the systemic effects of disease on the secondary metabolism of the host and how these mediate host predisposition to insect infestation.
Animal Health Component
Research Effort Categories

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
Goals / Objectives
1. Characterize the role of biotic and abiotic factors in predisposing trees to bark beetle attack and subsequent mortality. 2. Characterize interactions among conifer hosts, bark beetles, their natural enemies, and vectored fungi. 3. Characterize the taxonomic diversity and genetic structure of key fungal pathogens and symbiotic fungi associated with insects on North American conifers.
Project Methods
Work to be conducted from The Ohio State University mainly addresses the effect of pathogens on host trees and subsequent effects of altered host trees on bark beetles. This is being accomplished by using both field and greenhouse studies employing different model systems. The field study is being conducted in Northern California in collaboration with Profs. D.L. Wood (Univ. of California, Berkeley, Entomology) and T.R. Gordon (Univ. of California, Davis, Plant Pathology). Both are members of W-187. The model system used in the Sierras comprises a stand of 35 yr. old ponderosa pines, the artificially inoculated root pathogen Heterobasidion annosum, and the natural populations of bark beetles resident in the experimental area. Results so far indicate that systemic effects of root disease occur at the level of secondary metabolism and that these changes may affect bark beetle colonization of the host. Further studies would highlight the persistence of these changes and their effects on some of the vectored fungi, which may or may not increase the fitness of the bark beetles. The greenhouse studies, being developed at Ohio State University, will utilize the model system comprising Austrian pine and the diplodia tip blight and canker pathogen, Sphaeropsis sapinea. This model system will be used to elucidate the physiological mechanisms underlying systemic changes in secondary metabolism similar to those observed in the field in California. These studies will contribute to the regional effort considerably, as they address hitherto unexplored aspects of the physiology of pathogen-host-bark beetle interactions.

Progress 10/01/99 to 09/30/04

The main goal of this project was to begin to unravel the role of induced defense mechanisms in pines, both locally and systemically, in the ecology of these important tree species, particularly as it pertains to interactions with bark beetles. This goal was achieved by tackling the biochemical defense responses in pine from several separate but complementary angles: 1) local and systemic effects of fungal infection on accumulation of both soluble and cell wall-bound, simple and complex phenolics; 2) local and systemic effects of fungal infection on the host's resin system, both in terms of quantity and quality; 3) local and systemic effects of fungal infection on induction/suppression of defensive enzyme activity and 4) local and systemic effects of fungal elicitors on some of the same defense responses that were induced by live inoculations. All of these defense responses are presumed to be involved in resistance to both pathogens and bark beetles. This work represents a novel approach as it integrates several different defense mechanisms that are usually investigated separately. This work has now generated a working hypothesis of clear ecological significance, which will likely be tested in the new proposal that will replace W187. This hypothesis states that pre-symptomatic, root diseased trees become more resistant to subsequent fungal infection and insect attack, due to the expression of systemic induced resistance. However, once root disease impairs physiological functions to the point of the host becoming symptomatic, then tree resistance to other pathogens and insects collapses. The significance of this process if that if trees can be induced in the absence of a root infection they could be primed to respond more effectively to bark beetle attack. Work to elucidate the molecular signals involved in the induction process has now begun and hopefully will result in the development of chemical inducers of more durable resistance.

A better understanding of host-pathogen interactions will allow us to target specific pathways to enhance disease and insect resistance in forest trees.


  • Luchi, N., Ma, R., Capretti, P., Bonello, P., 2004. Systemic induction of traumatic resin ducts and resin flow in Austrian pine by wounding and inoculation with Sphaeropsis sapinea and Diplodia scrobiculata. Planta, in press.
  • Blodgett, J.T., Herms, D.A., Bonello, P., 2004. Effects of fertilization on red pine defense chemistry and resistance to Sphaeropsis sapinea. Forest Ecology and Management, submitted October 2004.
  • Bonello, P., 2004. Biochemistry of localized and systemic induced defense responses in pine. Phytopathology 94, S133.

Progress 01/01/03 to 12/31/03

Our work on the biochemistry of pine defense responses against Sphaeropsis sapinea and Diplodia scrobiculata continued in 2003. Recent work has shown that induced trees contain less total soluble phenolics than control trees throughout the stem. However, the soluble phenolic fraction of pathogen-induced trees is more antifungal than extracts from control trees. We also investigated the role of selected defense proteins, namely chitinase (CHI), peroxidase (POD), and polyphenoloxidase (PPO). Results show that infection with S. sapinea resulted in decreased total protein content at the induction site. Infection with S. sapinea did not result in any effects on the activities of the three enzymes. However, infection with D. scrobiculata resulted in locally decreased PPO activity and locally and systemically decreased CHI activity. Since D. scrobiculata is less aggressive than S. sapinea these results seem to suggest that these enzymes are not involved in the resistance response of Austrian pine to these pathogens. A third defensive barrier we investigated was the resin component. This study showed that a basal infection results in systemic formation of traumatic resin ducts and increased systemic resin flow, four times higher than in control trees.

A better understanding of host-pathogen interactions will allow us to target specific pathways to enhance disease and insect resistance in forest trees.


  • Blodgett, J.T., and P. Bonello. 2003. The aggressiveness of Sphaeropsis sapinea on Austrian pine varies with isolate group and site of infection. Forest Pathology 33:15-19.
  • Blodgett, J.T., P. Bonello, and D.A. Herms. 2003. Fertilization decreases resistance of red pine to the Sphaeropsis canker pathogen. Phytopathology 93:S9.
  • Blodgett, J. T., P. Bonello, and G. R. Stanosz. 2003. An effective medium for isolating Sphaeropsis sapinea from asymptomatic pines. Forest Pathology 33:395-404.
  • Bonello, P. 2003. Current perspectives on honeylocust knot. The Buckeye, May 2003:32-35.
  • Bonello, P. 2003. Mistletoes. McGraw-Hill, 2003.
  • Bonello, P., M. Bellizzi, and H.A.J. Hoitink. 2003. Update on honeylocust knot. Pages 69-72. In: Ornamental Plants Annual Report and Research Reviews, 2002. OARDC Special Circular 189. OARDC Wooster, OH.
  • Dias, A.P., J. Brown, P. Bonello, and E. Grotewold. 2003. Metabolite profiling as a functional genomics tool. Pages 415-426. In Plant Functional Genomics: Methods & Protocols, Vol. 236, edited by E. Grotewold. Humana Press, New Jersey.
  • Graham, T. L., and P. Bonello. 2003. Pathogen resistance in plants. In McGraw-Hill Yearbook of Science and Technology. McGraw-Hill. (In press)
  • LaForest, J.H., P. Bonello, and D.A. Herms. 2003. Effect of soil type and management on ectomycorrhizal colonization of Betula papyrifera. Phytopathology 93:S48.
  • Ma, R., P. Bonello, and D. F. Cipollini. 2003. Systemic expression of defense responses in Austrian pines induced by Sphaeropsis sapinea. Phytopathology 93:S55.

Progress 01/01/02 to 12/31/02

Concentrations of soluble phenolics and lignin in the phloem of ponderosa pines inoculated with the pathogen Heterobasidion annosum, were assessed over a period of two years in a 35-year-old plantation in northern California, USA. The major effect of the pathogen on phloem soluble phenolics consisted of a significant accumulation of ferulic acid glucoside compared with mock-treated and control trees. Lignin content was negatively correlated with ferulic acid glucoside concentration and there was an indication of lignin reduction in the cell walls of inoculated trees. Lignin had a negative effect on the in vitro growth of two common bark beetle fungal associates, Ceratocystiopsis brevicomi and Ophiostoma minus. For this reason it is hypothesized that lower lignification may facilitate the growth of beetle-associated fungi, resulting in greater susceptibility of the pre-symptomatic host to bark beetle colonization. In studies of feeding by the bark beetle, Ips paraconfusus, two pine stilbenes (pinosylvin and pinosylvin methyl ether), ferulic acid glucoside, and enantiomers of the four most common sugars present in ponderosa pine phloem (sucrose, glucose, fructose, and raffinose) did not stimulate or reduce male feeding when assayed on wet alpha-cellulose with or without stimulatory phloem extractives present. When allowed to feed on wet alpha-cellulose containing sequential extracts (hexane, methanol, and water) of ponderosa pine phloem, methanol and water extractives stimulated feeding but hexane extractives did not. Males confined in wet alpha-cellulose containing aqueous or organic extracts of culture broths derived from phloem tissue and containing the root pathogen, Heterobasidion annosum, ingested less substrate than beetles confined to control preparations. In an assay using logs from uninoculated ponderosa pines, the mean lengths of phloem in the digestive tracts increased as time spent feeding increased. Males confined to the phloem of basal logs cut from ponderosa pines artificially inoculated with H. annosum ingested significantly less phloem than beetles in logs cut from trees that were (combined) mock inoculated or uninoculated and did not contain the pathogen. However, individual pathogen-containing treatments were not significantly different from uninoculated controls. It was concluded that altered feeding rates are not a major factor in explaining why diseased ponderosa pines are colonized by I. paraconfusus.

A better understanding of host-pathogen interactions in trees will allow us to target specific pathways to enhance disease and insect resistance in forest trees, particulalry under controlled situations, e.g. in plantations.


  • Blodgett, J. T., and P. Bonello. 2002. Induction of systemic resistance/susceptibility in Pinus nigra inoculated with Sphaeropsis sapinea. Phytopathology 92 (6 Supplement):S8.
  • Blodgett, J.T., Bellizzi, M. and P. Bonello. 2002. The Induction of systemic resistance and systemic susceptibility in Sphaeropsis sapinea inoculated Pinus nigra. In Proceedings of the 50th Western International Forest Disease Working Conference, Powell River, British Columbia, Canada, Oct. 7-11, 2002.
  • Bonello, P. 2002. Pest resistance, the natural way. American Nurseryman 196 (3):59-65.
  • Bonello, P., J. T. Blodgett, and D.A. Herms. 2002. Progress in research on systemic induced resistance in Austrian pine against shoot blight (formerly known as Diplodia tip blight). Wooster, OH: Ohio State University/Ohio Agricultural Research and Development Center.
  • Bonello, P. and S. Woodward. 2002. Conifer defense mechanisms against root-infecting fungi. In Proceedings of the 50th Western International Forest Disease Working Conference, Powell River, British Columbia, Canada, Oct. 7-11, 2002.
  • Bonello, P., A.J. Storer, T.R. Gordon, D.L. Wood, and W. Heller. 2003. Systemic effects of Heterobasidion annosum on ferulic acid glucoside and lignin of pre-symptomatic ponderosa pine phloem, and potential effects on bark beetle-associated fungi. Journal of Chemical Ecology accepted.
  • McNee, W.R., P. Bonello, D.L. Wood, A.J. Storer, and T.R. Gordon. 2003. Feeding response of Ips paraconfusus to phloem and phloem metabolites of Heterobasidion annosum-inoculated ponderosa pine, Pinus ponderosa. Journal of Chemical Ecology accepted.