Measuring yield loss in cereals caused by root lesion nematodes (Pratylenchus neglectus and P. thornei) with and without nematicide

Abstract

Yield loss caused by root lesion nematodes (Pratylenchus neglectus and P. thornei) was measured using the nematicide aldicarb (Temik 150GTM) or by correlating yield with initial or final nematode densities. In 1996, rotation trials (1 P. neglectus and 1 P. thornei) were established with susceptible and moderately resistant wheat varieties and resistant barley and triticale varieties. An intolerant oat variety (cv. Echidna) was planted over all plots in 1997. Nematode densities were 90% (P. neglectus) or 95% (P. thornei) lower in oat plots following the resistant triticale (cv. Tahara) relative to the susceptible wheat (cv. Machete). In 1997, a significant, negative correlation between both initial and final nematode density and yield was obtained. In wheat variety trials (3 sites) in 1997, a significant, negative correlation was also obtained between mean variety yield and mean final P. neglectus density or mean P. neglectus multiplication rate. Yield loss of up to 20% was calculated from the regression. In all trials, cereal varieties that were more resistant were also more tolerant. In 1996, aldicarb rate trials (1 P. neglectus and 1 P. thornei) were established to assess the affect of rate and timing of aldicarb application on yield of 2 susceptible/intolerant wheat varieties (cvv. Machete and Janz). Lower rates of aldicarb (≤1.5 kg a.i./ha) gave inconsistent nematode control and did not significantly increase yield. Rates ≥2.5 kg a.i./ha reduced nematode densities by 70–90%, resulting in up to 23% greater yield for Machete. The magnitude of yield loss caused by P. neglectus or P. thornei determined with or without nematicide was similar between trials.

Identification of quantitative trait loci for resistance to two species of root-lesion nematode (Pratylenchus thornei and P. neglectus) in wheat

“…High populations of P. thornei cause up to 85% yield loss in wheat (Triticum aestivum L.) varieties (Thompson et al 1993). Similarly, P. neglectus causes up to 27% yield loss in wheat varieties (Taylor et al 1999). In Australia, annual lost wheat production caused by P. thornei and P. neglectus is estimated at $36 million and $12 million, respectively (Brennan and Murray 1998).…”

“…Glasshouse screening of wheat lines inoculated with pure cultures of nematodes has suggested that the genetic mechanisms that confer resistance to P. thornei do not confer resistance to P. neglectus (Farsi et al 1995;Taylor et al 1999). However, mixed populations of both species can occur in the same field and therefore breeding wheat varieties with resistance to both species of nematode is a desirable goal.…”

“…Glasshouse screening of wheat lines inoculated with pure cultures of nematodes has suggested that the genetic mechanisms that confer resistance to P. thornei do not confer resistance to P. neglectus (Farsi et al 1995;Taylor et al …”

“…Similarly, P. neglectus causes up to 27% yield loss in wheat varieties (Taylor et al 1999). In Australia, annual lost wheat production caused by P. thornei and P. neglectus is estimated at $36 million and $12 million, respectively (Brennan and Murray 1998).Glasshouse screening of wheat lines inoculated with pure cultures of nematodes has suggested that the genetic mechanisms that confer resistance to P. thornei do not confer resistance to P. neglectus (Farsi et al 1995;Taylor et al …”

Characterization of Pratylenchus crenatus and P. neglectus (Nematoda: Pratylenchidae) associated with wheat crop

“…Eight species of the genus Pratylenchus infest small grains (Rivoal & Cook, 1993;Nicol et al, 2004). Among them, P. thornei Sher and Allen, 1953, P. neglectus (Rensch, 1924) Filipjev and Schuurmans Stekhoven, 1941, P. penetrans (Cobb, 1971) Filipjev and Schuurmans Stekhoven, 1941and P. crenatus Loof, 1960 have a worldwide distribution and can cause substantial yield losses (Taylor et al, 1999;Nicol et al, 2004). RLN hatch from the egg as a second-stage juvenile and starts feeding on the plant.…”