Management of root lesion nematodes in Montana winter wheat

Abstract

Wheat is one of the most important crops globally and a key component of Montana's economy. However, wheat production faces various challenges, including water availability and pests such as root lesion nematodes (RLNs; Pratylenchus spp). These nematodes feed on and migrate through plant roots, causing radicular lesions that impair the plant's ability to absorb water and nutrients, making it more susceptible to drought and high temperatures. In Montana, yield losses due to Pratylenchus neglectus infections are estimated at US$84 million annually, while the spread and extent of damage caused by P. thornei remains unknown. To better manage the nematode infestation, a breeding program was initiated to incorporate P. neglectus resistance into Montana-adapted winter wheat lines, resulting in the selection of resistant lines in greenhouse trials. Recent research suggests that resistant plants support specific microbial communities that may help them cope with both biotic and abiotic stressors, including pest pressure. This dissertation begins by comparing the reproduction rates of P. neglectus and P. thornei on Montana crops and selected double haploid lines under controlled conditions. Field trials were then conducted to assess agronomic performance and nematode suppression in real field scenarios. Microbiome studies were incorporated to compare microbial communities between resistant and susceptible phenotypes, providing insights into the underground interactions between nematode infections and plant resistance. The reproduction rate and host suitability of the nematodes vary by Pratylenchus species, highlighting the need for accurate diagnostics before recommending rotational crops to growers facing RLN issues. Under field conditions, P. neglectus reproduction was found to be dependent on the initial nematode density, with higher reproduction rates observed at lower initial densities. Double haploid lines selected for resistance in greenhouse settings demonstrated better agronomic performance under high nematode pressure, and lower P. neglectus multiplication at low nematode densities. The microbiome composition was more strongly associated with nematode density in the soil than with the plant phenotype. Given their low reproduction rates and improved yield and grain quality, two of the resistant lines hold potential for benefiting Montana growers dealing with high P. neglectus pressures.