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RESISTANCE OF SOYBEAN CULTIVARS TO A NEW ROOT-LESION NEMATODE SPECIES IN NORTH DAKOTA
EXECUTIVE SUMMARY
NORTH DAKOTA SOYBEAN COUNCIL
JUNE, 2021
Dr. Guiping Yan, Principal Investigator, Dept. Plant Pathology, NDSU
Research Conducted
Ten soybean cultivars used in ND were evaluated for resistance to a new root-lesion nematode (RLN) species recently discovered in a ND soybean field. The experiment was conducted under greenhouse conditions (Fig. 1A) and repeated to confirm research findings. A quantitative real-time PCR (qPCR) assay was developed to detect and quantify this new species in DNA extracts of field soil. Primers were tested for specificity and detection sensitivity was determined. A standard curve was generated. The qPCR assay was validated by comparing the numbers of nematodes in 15 field soil samples obtained by traditional microscopic counting and qPCR through correlation analysis.
Why the research is important to ND soybean farmers
Root-lesion nematodes are one of the most important groups of plant-parasitic nematodes. During our previous soil surveys in ND, a new RLN species was identified. In 2021, this new species was named as Pratylenchus dakotaensis, paying homage to the state in which it was discovered. RLNs have a wide host range including soybean. One of the most economical and effective ways to control RLNs is the use of cultivar resistance. This research aims to provide valuable information about resistance levels of soybean cultivars in ND to manage the new species, and an efficient DNA-based, qPCR assay for improving nematode detection to facilitate management strategies.
Final findings of the research
Resistance rating results were consistent between two trials. Although none of the cultivars tested were resistant or moderately resistant, three were found to be moderately susceptible and the remaining seven were susceptible (Fig. 1B). A new qPCR assay was developed for detection and quantification of this new species in DNA extracts of field soils. The assay was highly specific and sensitive, and had a high correlation between the numbers of nematodes in field soil samples determined through manual counting and qPCR (Fig. 2). This is the first report for detection and quantification of this species directly from field soil DNA.
Benefits/Recommendations to North Dakota soybean farmers and industry
Such research findings provide an insight into the virulence of the new RLN species on commercial soybean cultivars. Moderately susceptible cultivars identified may perform better than the susceptible cultivars. However, further research is necessary to find better performing resistant cultivars. The qPCR assay developed provides a rapid and efficient method for P. dakotaensis quantification in soil DNA and can serve as a valuable diagnostic tool for providing informed decisions to growers.
Fig. 1. A: soybean plants grown in a growth chamber maintained at 22 °C for resistance evaluation to the new root-lesion nematode species (Pratylenchus dakotaensis) identified in ND. B: classification of the resistance responses of ten soybean cultivars to this new species based on the two trials.
Fig. 2. Relationship between the numbers of Pratylenchus dakotaensis determined by qPCR and traditional microscopic counting method from 15 naturally infested field soil samples.