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PLANT-PARASITIC NEMATODES ON SOYBEAN AND RELATIONSHIP WITH SOYBEAN CYST NEMATODE
EXECUTIVE SUMMARY
NORTH DAKOTA SOYBEAN COUNCIL
June, 2017
Dr. Guiping Yan, Principal Investigator, Dept. Plant Pathology, NDSU
Co-investigators: Dr. Sam Markell and Dr. Berlin Nelson, Dept. Plant Pathology, NDSU
Plant-parasitic nematodes are an important group of pests on many field crops. Soybean cyst nematode (SCN), root-lesion nematode, lance nematode and root-knot nematode are considered highly aggressive on soybean and can cause significant yield suppression. However, the information on occurrence and distribution of plant-parasitic nematodes in soybean fields in North Dakota was very limited except SCN. The objectives of this project were to determine the incidence, abundance and distribution of plant-parasitic nematodes, whether economically important nematode species other than SCN was present in ND soybean fields, and the relationship of SCN with other plant-parasitic nematodes in the major soybean growing regions in ND.
A nematode survey was conducted in 2016 to ascertain the occurrence and distribution of plant-parasitic nematodes in soybean fields in ND. We have collected 141 soil samples from 12 counties. Soil samples were processed and nematodes were extracted from all the samples. Vermiform (motile) and cyst nematodes (sedentary) were extracted separately from each soil sample (100 cc soil) and then were identified and quantified. Out of the 141 soil samples, 126 samples (89%) in these 12 counties were found to be infested with plant-parasitic nematodes.
Nine groups (genera) of plant-parasitic nematodes were detected including SCN (Figure 1), pin, spiral, stunt, ring, root-lesion, dagger, lance (Figure 2), and stubby root nematodes. SCN was found in 46% of the surveyed fields, and spiral, stunt, pin and root-lesion nematodes occurred in more than 30% of the fields. SCN had the highest mean population density followed by pin, spiral, stubby root, stunt, root-lesion, dagger, lance, and ring nematodes. Root-lesion and lance nematodes are considered important on soybean. Moderate levels of root-lesion nematodes, low levels of lance nematodes and high populations of pin and spiral nematodes were found in some fields. These nematodes were detected in ND soybean fields, which needs more attention from researchers.
Eight groups of nematodes were identified to species using DNA-based (cloning/sequencing, direct sequencing, species-specific PCR, real-time PCR) and/or morphological methods. Two unnamed root-lesion nematode species were detected, and importantly the populations of these nematodes were found to have increased greatly on soybean roots from preliminary greenhouse experiments. Four new species of other nematodes were identified. Four first reports describing the discovery of new species were prepared and published. The effects of these new nematode species on soybean growth and yield are unknown and need to be examined.
Correlation analysis was performed to evaluate the relationship between SCN and other plant-parasitic nematodes. Poor or no correlations were observed between population densities of each group of the vermiform nematodes and SCN.
This research provided baseline information on the incidence, density and distribution of vermiform plant-parasitic nematodes in soybean fields in ND and their relation with SCN. Such information is important to help farmers be aware of nematode species and population levels in infested fields to make the best management strategies for managing these nematode diseases to increase soybean yield.