The root-lesion nematode, Pratylenchus thornei, is a serious constraint for agricultural production systems worldwide. Under optimal soil temperature and moisture levels, P. thornei can complete its life cycle in 3-8 weeks (Agrios, 1988), enabling it to increase its population density several times in one cropping cycle. Pratylenchus thornei feeding destroys lateral roots, limiting their ability to draw water and nutrients from the soil (McGawley & Overstreet, 1998). Susceptible plants growing in fields with high P. thornei infestations show various above- and below-ground symptoms (Loof, 1978), although nematode damage is often difficult to estimate and quantify as symptoms may be indistinct or affected by several biotic and abiotic factors (Vanstone & Russ, 2001). Aboveground symptoms include uneven growth with dying, unthrifty, and/or yellowish plants, which can be confused with symptoms of water or nitrogen deficiency (Smiley, 2009). Below ground, infected plants show brownish roots, with fewer and shorter root branches. In severe cases, plants can be easily pulled from the soil as a result of root destruction (Smiley et al., 2004a, b). In addition to direct root damage, P. thornei invasions can also facilitate the penetration of other root pathogens, creating disease complexes that further deteriorate root function (Castillo et al., 1998). Assessing nematode damage solely on visible root symptoms may therefore be misleading due to concomitant infections with other fungi (Lasserre et al., 1994; Taheri et al., 1994). The addition of fertiliser to offset the poor growth caused by nematodes may exacerbate the problem as nitrogen enhances nematode reproduction, creating greater inoculum densities that can be destructive for a successive crop (Thompson et al., 1995). The extent of nematode damage is generally densitydependent, with field studies showing a linear correlation between P. thornei population densities and yield losses of wheat and other crops (Owen et al., 2014). Yield losses due to P. thornei typically range from 10 to 30% but can reach up to 70% in some crops. For wheat, studies have.
