Metabolites from Resistant and Susceptible &amp;lt;i&amp;gt;Pinus thunbergii&amp;lt;/i&amp;gt; after Inoculation with Pine Wood Nematode

Fujia Zhang,Mineko Ohira,Ryuichiro Kondo,Junko Kajiwara,Yasuhiro Mori,Yuji Tsutsumi

doi:10.4236/ajps.2013.43065

Abstract

Pine wilt disease (PWD), which is caused by pine wood nematodes (PWN), is one of the most serious forest diseases worldwide. To clarify the mechanism of resistance to PWD, we compared metabolites from resistant and susceptible Japanese black pine (Pinus thunbergii) families after inoculation with PWN. After 2 weeks to 1 month post inoculation, the number of PWN dramatically increased in susceptible plants, but not in resistant plants. At this PWN-proliferation phase, ethyl acetate soluble fractions extracted from PWN-inoculated plants were analyzed by gas chromatogramphy-mass spectrometry (GC-MS). Although most compounds were qualitatively and quantitatively similar between resistant and susceptible plants, resistant plants accumulated 2.0-fold more linoleic acid (LA) than susceptible plants. On the other hand, benzoic acid (BA) was barely detected in resistant plants, but it accumulated in susceptible plants as the number of PWN increased. Susceptible plants contained greater levels of the nematicidal compounds pinosylvin and pinosylvin monomethyl ether, compared with resistant plants. These results suggested that LA is involved in the resistance reaction against PWN-proliferation, and that BA could be a good biomarker for PWD.

Highlights

Pine wood nematode (PWN) (Bursaphelenchus xylophilus) is the causal pathogen of pine wilt disease (PWD) [1], the most serious disease in East Asian pine forests [2,3,4]
Susceptible plants contained greater levels of the nematicidal compounds pinosylvin and pinosylvin monomethyl ether, compared with resistant plants. These results suggested that linoleic acid (LA) is involved in the resistance reaction against pine wood nematodes (PWN)-proliferation, and that benzoic acid (BA) could be a good biomarker for Pine wilt disease (PWD)
Comparison with spectra in the MS library showed that linoleic acid (LA) trimethylsilyl ester was commonly detected in xylem extracts of two resistant plants

Summary

Introduction

Pine wood nematode (PWN) (Bursaphelenchus xylophilus) is the causal pathogen of pine wilt disease (PWD) [1], the most serious disease in East Asian pine forests [2,3,4]. This disease has been found in USA [5,6], Canada [7], Nigeria [8], Mexico [9], Portugal [10] and Spain [11]. Seedlings have been produced commercially from a seed orchard of resistant clones. To save time and expense in the program, it is important to identify the factors involved in PWD resistance

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Conclusion