PLANT-PARASITIC NEMATODES ON SOYBEAN AND RELATIONSHIP WITH SOYBEAN CYST NEMATODE
EXECUTIVE SUMMARY
NORTH DAKOTA SOYBEAN COUNCIL
June, 2016
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 occurrence and distribution of plant-parasitic nematodes in soybean fields in North Dakota were unknown except SCN. The objectives of this project were to determine the incidence, abundance and distribution of plant-parasitic nematodes and to determine whether economically important nematode species other than SCN was present in ND soybean fields. In addition we tried to determine the relationship of SCN with other plant-parasitic nematodes in the major soybean growing regions in ND.
A nematode survey was conducted in 2015 to ascertain the occurrence and distribution of plant-parasitic nematodes in soybean fields in ND. We have collected 155 soil samples from 14 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 identified and quantified. Out of the 155 soil samples, 144 samples (93%) in these 14 counties were found to be infested with plant-parasitic nematodes.
Nine groups (genera) of plant-parasitic nematodes were detected including SCN, pin, spiral, stunt, ring, root-lesion, dagger, lance, and stubby root nematodes. SCN was found in 59% of the surveyed fields, and spiral, stunt, pin and root-lesion nematodes occurred in more than 19% of the fields. SCN had the highest mean population density followed by spiral, pin, stunt, lesion, dagger, lance, ring, and stubby root nematode. Root-lesion and lance nematodes are considered important on soybean. Moderate levels of root-lesion and lance nematodes and high populations of pin and spiral nematodes were found in some fields. These nematodes were detected in ND soybean fields, which requires more attention by researchers.
Seven groups of nematodes were identified to species using DNA-based (cloning/sequencing, direct sequencing, species-specific PCR, real-time PCR) and morphological methods. Two unknown 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. A first report of the new lance nematode on soybean in ND is being prepared. This species has been reported in the southeastern U.S. and was found to be the most predominant lance nematode on soybean in North Carolina. The effects of the new nematode species on soybean growth and yield are needed 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 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 controlling these nematode diseases to increase soybean yield.