Field resistance of annual pasture legumes to the root lesion nematode,Pratylenchus neglectus

Abstract

The multiplication of root lesion nematode (Pratylenchus neglectus) was compared for 13 species of annual pasture legume (eight Medicago spp., two Lotus spp., two Trigonella spp. and Trifolium balansae), triticale (Secale cereale × wheat hybrid cv. Tahara) and wheat (Triticum aestivum cv. Machete) at two field sites in South Australia. At sowing, the initial population density of P. neglectus (P i) ranged from 22 to 39/g soil at Two Wells and from 6 to 15/g soil at Maitland. After senescence of the plant hosts, final population density of P. neglectus (P f ) ranged from 5 to 69/g soil at Two Wells and from 10 to 90/g soil at Maitland. This variation was strongly influenced by plant genotype. Nematode multiplication (P f /P i) was greatest (3.4 and 11.6, respectively) under the susceptible control (Machete) at both sites and least under the resistant control (Tahara, P f /P i =0.2) at Two Wells and Medicago scutellata line Kelson (P f/P i =1.2) at Maitland. Compared with the susceptible control (wheat cv. Machete), the pasture legumes resulted in a low level of nematode multiplication overall (P f/P i=1.3). The findings indicate that it is appropriate that annual medics be classified as moderately resistant to P. neglectus and that the five other pasture legume species in this study can be ascribed provisionally to this classification.