Ability of weeds to host the root lesion nematodes Pratylenchus neglectus and P. thornei - I. Grass weeds

Nine grass weed species common to cropping rotations in southern Australia were assessed as hosts of the root lesion nematodes, Pratylenchus neglectus (Rensch) Filipjev Schuurmans & Stekhoven and P. thornei Sher & Allen. Weeds were grown at 20 degreesC and individual plants inoculated with 1000 P. neglectus or P. thornei. Weed species were classified as non-hosts, poor hosts or good hosts, based on comparison of the reproductive factor (final population/initial population, or Pf/Pi) with the cereal controls, triticale cv. Abacus (moderately resistant to P. neglectus and moderately susceptible to P. thornei) and wheat cv. Machete (susceptible to both nematodes). Hordeum glaucum Steudel, H. leporinum Link, Lolium rigidum Guadin and Bromus diandrus Roth were not hosts of P. neglectus (Pf/Pi = 0.35-0.77). B. rubens Roth, Vulpia bromoides (L.) Gray and V. fasciculata (Forssk.) Gray (Pf/Pi = 0.94-1.19) were poor hosts, and Avena sterilis L. and A. fatua L. (Pf/Pi = 4.10-5.93) were good hosts of P. neglectus. The Avena spp. were more susceptible (P<0.05) to P. neglectus than triticale cv. Abacus, and were as susceptible as wheat cv. Machete. V. bromoides, V. fasciculata, L. rigidum and A. fatua were resistant to P. thornei (Pf/Pi = 0.15-0.54). H. glaucum, B. diandrus and B. rubens were poor hosts of P. thornei (Pf/Pi = 1.06-1.46). A. sterilis and H. leporinum (Pf/Pi = 1.58-1.92) were good hosts of P. thornei, and both were as susceptible as wheat cv. Machete. Growth of susceptible weeds will allow increase and persistence of nematodes in cropping soils, compromising the use of resistant crops in rotations for management of P. neglectus and P. thornei.