| Resumo: | In the subtropical grain region of eastern Australia, two experiments were conducted, one initially with 2490 <i>P. thornei</i>/kg soil, the other with 8150 <i>P. thornei</i>/kg soil at 0–0.9 m soil depth. We determined the effect of <i>P. thornei</i>, residual from a weed-free fallow and pre-cropping with several cultivars each of barley (<i>Hordeum vulgare</i>), faba bean (<i>Vicia faba</i>), chickpea (<i>Cicer arietinum</i>), and wheat (<i>Triticum aestivum</i>) (Phase 1), on the growth of wheat cultivars with intolerance or tolerance to <i>P. thornei</i> (Phase 2). <i>Pratylenchus thornei</i> substantially increased after growing all cultivars of the Phase 1 faba bean, barley, and most cultivars of chickpea and wheat, and decreased after two moderately resistant wheat cultivars and the fallow treatment. The biomass of the Phase 2 tolerant cultivar ranged from 5070 to 6780 kg/ha and the intolerant cultivar 1020 to 4740 kg/ha. There was a negative linear relationship between <i>P. thornei</i> population densities and biomass of the Phase 2 intolerant cultivar but not of the tolerant cultivar. Growers are at risk of financial loss because they are restricted in their choice of crops to reduce damaging population densities of <i>P. thornei</i>. The development of resistant and tolerant crop genotypes can maximize production in <i>P. thornei</i>-affected farming systems.
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