LAUSR

The root-lesion nematode Pratylenchus thornei is a major pathogen of wheat (Triticum aestivum) in many regions globally. Resistance of wheat genotypes to P. thornei can be determined from final nematode population densities in glasshouse experiments, but combining results across multiple experiments presents challenges. Here we use a factor analytic method for multi-experiment analysis of final population densities of P. thornei for 1096 unique wheat genotypes in 22 glasshouse experiments. The resistance to P. thornei of the genotypes was effectively represented by a two factor model with rotation of the axes to a principal components solution. Principal axes 1 and 2 (PA1 and PA2) respectively accounted for 79% and 11 % of the genetic variance over all experiments. Final population densities of P. thornei as empirical best linear unbiased predictors (PA(1+2)-eBLUPs)) from the combined glasshouse experiments were highly predictive (P<0.001) of final nematode population densities in the soil profile, of crop canopy greenness (NDVI) and of grain yield of wheat genotypes in P. thornei infested fields in the Australian subtropical grain region. Nine categories of resistance ratings for wheat genotypes from resistant to very susceptible were based on subdivision of the range of PA(1+2)-eBLUPs for use in growers' sowing guides . Nine genotypes were nominated as references for future resistance experiments. Most (62%) Australian wheat genotypes were in the most susceptible three categories (S, S-VS and VS). However, resistant germplasm characterized in this study could be used in plant breeding to considerably improve the overall resistance of Australian wheat crops.