Discovering an Indirect Field-Based Method for Determining Pratylenchus Spp. Resistance in Wheat.

Root-lesion nematodes, Pratylenchus thornei and P. neglectus, are soil-borne pathogens that challenge wheat production in the Pacific Northwest, USA and worldwide. Pratylenchus species can cause severe root damage resulting in drought-like symptoms and reduced grain yield. Identifying wheat genotypes that are resistant to Pratylenchus is considered the most feasible means of reducing population densities and increase yield. Phenotyping Pratylenchus resistance is time consuming and expensive so new methods are desired. An initial greenhouse trial found that photosynthetic rates were reduced in plants inoculated with Pratylenchus. Field trials conducted at several locations in Oregon State over three years measured the impact of Pratylenchus on photosynthesis yield (PhiPSII), canopy temperature, grain yield, and grain quality in resistant and susceptible wheat genotypes. A multiple linear regression found grain volume weight, photosynthesis yield, canopy temperature, and grain protein and moisture content could significantly predict nematode population densities with an Adj. R-sq value of 0.7478. These parameters were used to estimate resistance in a recombinant inbred line population (RIL) segregating for dual-resistance to P. thornei and P. neglectus. This same RIL population was also phenotyped for resistance using traditional greenhouse methods. A comparison between the two methods showed the field method called a larger portion of the population susceptible to Pratylenchus than the greenhouse method. This could be due to environmental factors causing the resistance to breakdown that cannot be seen in the greenhouse. It is also possible that drought tolerance is also being measured in the field method and cannot be distinguished from the Pratylenchus resistance. Field trials planted this year will examine if the field method is also measuring drought tolerance.