Identification of Key Root Volatiles Signaling Preference of Tomato over Spinach by the Root Knot Nematode Meloidogyne incognita

The root knot nematode, Meloidogyne incognita (Kofoid and White) Chitwood, is a serious pest of tomato (Solanum lycopersicum) and spinach (Spinacea oleracea) in sub-Saharan Africa. In East Africa these two crops are economically important and are commonly intercropped by smallholder farmers. The role of host plant volatiles in M. incognita interactions with these two commodities is currently unknown. Here, we investigate the olfactory basis of attraction of tomato and spinach roots by the infective second stage juveniles (J2s) of M. incognita. In olfactometer assays, J2s were attracted to root volatiles from both crops over moist sand (control), but in choice tests using the two host plants, volatiles of tomato roots were more attractive than those released by spinach. Root volatiles sampled by solid phase microextraction (SPME) fiber and analyzed by gas chromatography/mass spectrometry (GC/MS) identified a total of eight components, of which five (2-isopropyl-3-methoxypyrazine, 2-(methoxy)-3-(1-methylpro...