Location: Soil Management and Sugarbeet Research
Project Number: 3012-11120-001-10-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 15, 2016
End Date: Aug 13, 2021
Columbia root-knot nematode (Meloidogyne chitwoodi) is a major pest in commercial potato production in the northwestern, United States of America. The most widespread method for nematode control is the use of Vydate. However, the use of microorganisms antagonistic to nematodes has been reported in the literature to control the root-knot nematode (Radwan et al., 2012). The fungus Paecilomyces lilacinus preys on Meloidogyne females and reduces the population density of nematodes in the soil. In addition, bacteria such as Bacillus subtilis have been reported to have nematicidal activity. Previously, it has been shown that commercially available microbial soil inoculants can control nematodes at levels comparable to chemical treatments (e.g., Vydate). However, results are strongly influenced by region and climatic conditions. In this proposal, we aim to expand our knowledge in this area to understand how the natural soil microbiology present in the San Luis Valley could play a role in controlling nematodes, which have historically exhibited regional differences in population densities that are likely correlated with regional differences in soil microbial community differences. In addition, we will focus on the isolation and development of new soil biological amendments for the control of M. chitwoodi. Recently, it has been shown that beneficial (i.e., bacterivore) nematodes can limit plant pathogenic nematode populations. However, little is known about the feeding preferences and potential microbial regulation of beneficial nematode populations; therefore, we will also conduct the first assessment of the gut microbiome associated with bacterivore nematodes. Potato cultivars also traditionally have had low nitrogen use efficiencies. These low nitrogen use efficiencies contribute to increased losses of reactive nitrogen to the environment. This collaborative project also is aiming at developing cultivar-specific nitrogen management guidelines for Colorado potato cultivars. The project will evaluate the response of Colorado potato cultivars to source of nitrogen fertilizer, rate of nitrogen fertilizer application, and timing of nitrogen application. The Nitrogen Management goals are to: 1) Define optimum nitrogen fertilizer application rates for efficient use of nitrogen by Colorado potato cultivars, which will lead to maximum tuber yield, increased premium tuber size, and high quality tubers; 2) define optimum in-season petiole nitrate-nitrogen concentration levels for Colorado potato cultivars that will aid in efficient in-season nitrogen fertilizer management; 3) establish proper nitrogen fertilizer application timing for maximum tuber yield and quality of Colorado potatoes; and 4) test the new USDA-ARS Nitrogen Index tool’s capabilities in assessment of nitrogen uptake efficiencies of new potato varieties grown in the San Luis Valley of south-central Colorado.
Nematode Studies: Conduct complete microbiological characterization of four distinct areas in the San Luis Valley (SLV) that have dissimilar nematode problems. This particular aim was suggested by the Executive Director of the Colorado Potato Administrative Committee to get an understanding of the microbial diversity in the SLV. General Methods: Before planting, three samples per field from each of the four areas will be analyzed for soil texture, organic matter, and nutrient levels. Nematode testing will also be done on each of these samples to determine populations of plant parasitic nematodes that are present. DNA from the nine rhizosphere samples/field will be extracted and analyzed by molecular techniques to assess the microbial community associated with plant roots. Bacterial 16S rRNA genes will be amplified for each sample, pyrosequenced, and the data analyzed using appropriate bioinformatics methodologies. Thirty six samples will be pyrosequenced and analyzed. The plants derived from the four different locations will be analyzed for nematode damage at CSU. Aim 1: Correlate microbiome composition with nematode population levels and soil characteristics to determine the factors associated with decreased levels of nematode presence. Aim 2: Isolate beneficial microbes from San Luis Valley soils that could be natural antagonists of M. chitwoodi. Aim 3. Characterize the gut microbiome associated with beneficial (bacterivore) nematodes. Bacterivores from the above soils will be isolated and the internal microbiome, food source, of these nematodes will be analyzed by sequencing. Assessing nitrogen management and use efficiencies with potato varieties, Nitrogen Management Studies: Soil samples from experimental plots and water samples from the irrigation well will be taken in the spring and analyzed for their nutrient content. This will indicate the quantity of residual nitrogen and other nutrients in the soil before planting, and how much nitrate-nitrogen is supplied to the crop from the irrigation water at each time of irrigation. Soil samples will also be taken at the end of crop harvest and analyzed for nutrients that were not used by the crop. During tuber bulking, plants will be sampled to evaluate treatment effects on stem number, tuber set, mean tuber weight, and tuber bulking rate. Petiole samples will be taken at four different dates during the growing season for petiole nutrient analysis. This will help establish in-season petiole nitrate concentration curves for individual cultivars. Aim 4: Define optimum nitrogen application rates for efficient use of nitrogen by Colorado potato cultivars which maximize tuber yield, tuber size, and production of quality tubers. Aim 5: Define optimum in-season petiole nitrate-nitrogen concentration levels for Colorado potato cultivars that will aid in efficient in-season nitrogen fertilizer management. Aim 6: Establish proper nitrogen fertilizer application timing for maximum tuber yield and quality of Colorado potatoes.