Volatiles of the entomopathogenic fungus, Metarhizium brunneum, attract and kill plant parasitic nematodes

Abstract

Root knot nematodes (RKNs) cause significant crop losses. Although RKNs and entomopathogenic fungi, such as <i>Metarhizium brunneum</i>, are associated with plant roots, very little is known about the interactions between these two organisms. This study showed that conidia and VOCs of <i>Me. brunneum</i> influenced the behaviour of <i>M. hapla</i>. The response was dependent on the fungal strain, VOC, concentration of both VOC and conidia, and time. Tomatoes planted in soil treated with the highest doses of conidia usually had a higher number of nematodes than untreated control plants. This was particularly obvious for <i>Me. brunneum</i> strain ARSEF 4556, 7 and 14-days post-treatment. The VOCs, 1-octen-3-ol and 3-octanone, lured <i>M. hapla</i> to plants when used at low doses and repelled them at high doses. In Petri dish assays. the VOCs 1-octen-3-ol and 3-octanone, caused 100% mortality of <i>M. hapla</i> at the highest dose tested (20 µl). Very few live <i>M. hapla</i> were recovered from soil treated with the VOC 1-octen-3-ol, especially at the highest doses tested.