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Chitinase is a Potential Molecular Biomarker for Detecting Resistance to Fusarium oxysporum in Acacia koa

Rushanaedy, Isabel, Jones, Tyler C., Dudley, Nicklos S., Liao, Richard J. F., Agbayani, Ricelle, Borthakur, Dulal
Tropical plant biology 2012 v.5 no.3 pp. 244-252
Acacia koa, Fusarium oxysporum, Fusarium wilt, biomarkers, cell walls, chitin, chitinase, complementary DNA, fungi, gene expression regulation, genes, hydrolysis, legumes, pathogens, reverse transcriptase polymerase chain reaction, risk, screening, seedlings, trees, wilting, Hawaii
The populations of Acacia koa (koa), a tree legume native to Hawaii, are currently at risk due to infection by the wilt-inducing fungal pathogen, Fusarium oxysporum. To identify koa families that are resistant to F. oxysporum, it is necessary to develop a screening method through use of a biomarker gene. The purpose of this study was to develop a molecular method for detecting resistance through the use of genes for chitinase that catalyzes the hydrolysis of fungal cell wall chitin. Four distinct chitinase cDNAs corresponding to chitinase genes of classes I, II, and III were isolated from koa, which were designated Akchit1a, Akchit1b, Akchit2, and Akchit3. The expression of these chitinases in Fusarium-wilt resistant and -susceptible koa seedlings following inoculation with virulent F. oxysporum was monitored using quantitative reverse transcription PCR (qRT-PCR). Significant differences (p < 0.05) in chitinase expression between resistant and susceptible seedlings were observed for the Akchit1a and Akchit1b genes at 48, 72, and 96 h post inoculation, in which chitinases were up-regulated among resistant seedlings. The differences between the two groups for expression of Akchit2 and Akchit3 were less pronounced. These results indicate that F. oxysporum-induced expression of the chitinase genes Akchit1a and Akchit1b can be used as a biomarker for selecting for wilt resistance in koa.