Investigating koa wilt and dieback in Hawai'i: Pathogenicity of Fusarium species on Acacia koa seedlings

Fusarium isolates obtained from diseased Acacia koa Gray (Fabaceae) plants, adjacent soil, and seeds and seedpods may or may not be pathogenic on young seedlings under greenhouse conditions. This includes isolates of Fusarium oxysporum, the putative cause of koa wilt and dieback disease ("koa w...

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Bibliographic Details
Published in:Native plants journal 2007-10, Vol.8 (3), p.259-266
Main Authors: Dudley, N.S, James, R.L, Sniezko, R.A, Yeh, A
Format: Article
Language:English
Subjects:
Acacia koa
dieback
Disease etiology
disease resistance
Flowers & plants
Forest service
fungal wilt
Fungi
Fusarium
Fusarium oxysporum
Fusarium pallidoroseum
Fusarium solani
Genetic diversity
Gibberella fujikuroi var. subglutinans
greenhouse experimentation
indigenous species
Microbiology
Pathogens
Phytopathology
Plant diseases
Plant pathology
Plants
Seedlings
Seeds
Stems
Studies
tree mortality
trees
Virulence
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Summary:Fusarium isolates obtained from diseased Acacia koa Gray (Fabaceae) plants, adjacent soil, and seeds and seedpods may or may not be pathogenic on young seedlings under greenhouse conditions. This includes isolates of Fusarium oxysporum, the putative cause of koa wilt and dieback disease ("koa wilt") in Hawai'i. We tested 10 Fusarium isolates, made up of 4 different species (F. solani, F. subglutinans, F. oxysporum, F. semitectum), for their pathogenic potential on koa seedlings under greenhouse conditions. All tested Fusarium isolates completely colonized seedling root systems and became systemic, spreading to aboveground plant tissues (stems, branches, and leaves). Virulence was quantified on the basis of disease symptoms (mortality, wilting, foliar chlorosis, or necrosis) and effects on seedling height, stem diameter, and root volume. Results varied, ranging from nonpathogenic to high levels of virulence. Pathogenic screening of many more isolates will be necessary to identify pathogens that can be effectively used to screen families of koa for potential resistance to the koa wilt and dieback disease that is seriously affecting this important Hawaiian tree species.
ISSN:1522-8339
1548-4785
DOI:10.2979/NPJ.2007.8.3.259