Date of this Version
Broderick, K. C. 2016. DIVERSITY AND VIRULENCE OF SOYBEAN CYST NEMATODE (Heterodera glycines Ichinohe) IN NEBRASKA. M. S. Thesis. University of Nebraska-Lincoln. Lincoln, NE.
Soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is one of the most economically important soybean pathogens in the United States. Best management practices are the use of resistant cultivars and crop rotation. Though there are several genetic sources of SCN resistance, most of the SCN-resistant cultivars are derived from a single resistance source (PI 88788). Other states have reported an increase in virulence to PI 88788 due to prolonged use of this resistance. In this thesis, two studies were conducted to characterize the diversity and virulent phenotypes of SCN populations in Nebraska.
The first study assessed the virulent phenotypes of SCN field populations and their diversity in Nebraska by conducting HG type tests on 118 populations from 36 soybean-producing counties. 46.6%, 29.7%, and 88.1% of populations were virulent on PI 88788, Peking, and PI 548316 resistance respectively. No populations were virulent on PI 437654 (Hartwig). Virulence to PI 88788, PI 209332, and PI 548316 was common and found in nearly every county. Many counties also had populations virulent on Peking, PI 90763, and PI 89772.
The second study investigated the mitochondrial diversity of SCN in Nebraska as well as the diversity within a field. Previous work examining the haplotype diversity of SCN using CO1 mitochondrial markers found low diversity and two primary haplotypes – one common and found throughout the U.S. while the second, the MNNE haplotype, was only found in Minnesota and northeast Nebraska. Markers were developed to determine if there is association of the MNNE haplotype with HG type and the incidence of the MNNE haplotype in Nebraska. No association was found between the MNNE haplotype and HG type. Populations from the original Nebraska field did not contain the MNNE haplotype, however it was confirmed to be in the original isolates suggesting the MNNE haplotype is found at very low frequencies in the field. Information on virulence and diversity of SCN in Nebraska will provide insight for development and selection of SCN resistant cultivars.
Advisor: Loren J. Giesler