Resistance of Wheat Genotypes to Root-Lesion Nematode (Pratylenchus thornei) Can be Used to Predict Final Nematode Population Densities, Crop Greenness, and Grain Yield in the Field

Abstract

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 multiexperiment analysis of final population densities of P. thornei for 1,096 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) accounted for 79 and 11% of the genetic variance, respectively, 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, crop canopy greenness (normalized difference vegetation index), and 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 (susceptible, susceptible to very susceptible, and very susceptible). However, resistant germplasm characterized in this study could be used in plant breeding to considerably improve the overall resistance of Australian wheat crops.

Impacts of Root-Lesion Nematode (Pratylenchus thornei) on Plant Nutrition, Biomass, Grain Yield and Yield Components of Susceptible/Intolerant Wheat Cultivars Determined by Nematicide Applications

“…Therefore, in these experiments, we compared plant performance against population density of P. thornei in the root-zone soil, knowing it was well correlated with P. thornei/g root. On the basis of these experiments, population densities of P. thornei have been reliably quantified in subsequent experiments by extracting from the soil and roots together [11]. Aldicarb also reduced the population density of M. brevidens in the root-zone soil in Experiment 2, from 17,450/kg soil in the nil control to 50/kg soil with 4 kg/ha aldicarb.…”

“…Use of tolerant and resistant wheat cultivars is another key component of integrated management, and tolerance and resistance ratings of wheat cultivars to P. thornei are made available to growers in annual sowing guides for the northern grain region. Resistance of wheat cultivars is assessed by final population densities of P. thornei in the plant roots and surrounding soil after 16 weeks growth in the glasshouse in soil inoculated with a standard initial population density [11]. Cultivar ratings are presented for growers in nine ordinal categories from resistant (R) to very susceptible (VS) based on data for final population densities of P. thornei from experiments combined by multi-environment trial (MET) analysis [11].…”

“…Resistance of wheat cultivars is assessed by final population densities of P. thornei in the plant roots and surrounding soil after 16 weeks growth in the glasshouse in soil inoculated with a standard initial population density [11]. Cultivar ratings are presented for growers in nine ordinal categories from resistant (R) to very susceptible (VS) based on data for final population densities of P. thornei from experiments combined by multi-environment trial (MET) analysis [11]. Tolerance is assessed by grain yield on managed field sites with high population densities of P. thornei.…”

Constitutive and Induced Expression of Total Phenol and Phenol Oxidases in Wheat Genotypes Ranging in Resistance/Susceptibility to the Root-Lesion Nematode Pratylenchus thornei

“…The temperature was maintained at 22 ± 2 • C throughout the experiment. Twenty-one wheat genotypes were selected to cover a range of resistance/susceptibility to P. thornei [65] ( Table 2). The wheat genotypes were grown using the same glasshouse conditions as described for Experiment 1.…”

Investigating the Impact of Root-Lesion Nematodes (Pratylenchus thornei) and Crown Rot (Fusarium pseudograminearum) on Diverse Cereal Cultivars in a Conservation Farming System

“…Here, we define a resistant cultivar as one that can retard nematode reproduction in its roots, resulting in lower final nematode population densities than a susceptible cultivar. Resistance of cereal cultivars to P. thornei can be determined under field conditions [19] or under more controlled conditions in the glasshouse [20]. Tolerance is best determined under the field conditions of the region where the crop is grown, so that relevant environmental conditions can interact with the nematode parasite and the host cultivar to result in a relevant yield outcome [21,22].…”