Understanding the inhibitory effects of plant-derived isothiocyanates and biofumigation on potato cyst nematodes

Abstract

Management of potato cyst nematodes (PCN) has become more challenging due to nematicide restrictions. This has led to research into alternative control methods such as biofumigation. Biofumigation exploits the release of toxic isothiocyanates (ITCs) from glucosinolate (GSL) hydrolysis during the breakdown of Brassicaceae plant tissue. The type and concentration of ITCs released varies between plant species. Biofumigation and ITCs have been shown to control soil-borne pathogens however no single ITC achieves broad-range control. The main aim of this study was to determine if biofumigation can be used to control PCN, namely Globodera pallida. In vitro and glasshouse studies identified a key ITC which inhibited G. pallida, with ITC effectiveness depending upon ITC type, concentration and exposure period. The GSL profiles of different Brassicaceae spp. were analysed and results indicated that GSL content varies between species and throughout plant development. The biofumigation process was investigated in glasshouse and field trials and analysis of GSL profiles allowed a comparison of cultivars with respect to potential ITC release. Cultivars which released the identified key ITC were able to suppress encysted G. pallida under controlled conditions. External factors impacted on the effectiveness of biofumigation in field trials. In order to determine if biofumigation adversely affects soil microorganisms, shifts in soil microbial communities were investigated. ITC application under controlled conditions and biofumigation under field conditions had little effect on soil microorganisms. Transient shifts in communities occurred in response to biofumigation under controlled conditions. The greatest response of soil communities was to factors independent of biofumigation. Results from this study will feed back into the development of integrated PCN management strategies involving biofumigation as well as into biofumigant breeding programmes.