Survey of Heterodera glycines Population Densities and Virulence Phenotypes during 2015–2016 in Missouri

Abstract

The soybean cyst nematode (SCN), Heterodera glycines, is one of the the roots of a set of resistant soybean indicator lines by the mean number most important pathogens of soybean. Periodic monitoring of SCN pop-of females that develop on the roots of susceptible cultivar Lee74 after ulation densities and virulence phenotypes is necessary for developing 30 days in the greenhouse then multiplying by 100 to obtain a percentage. management strategies utilizing resistant cultivars, the primary strategy Notably, all SCN populations evaluated during 2015–2016 had a FI > 10 used to combat this pest. Therefore, we conducted a statewide survey on PI 88788, the most widely used source of resistance in Missouri, in of Missouri to determine SCN population densities and virulence phenocontrast to 78% in 2005. Moreover, 50% of these populations had a FI types during 2015–2016 and compared these results with a similar survey > 50 on PI 88788, up from 16% in 2005. Forty-three percent of populaconducted in 2005. SCN population densities were determined for 393 tions tested also had a FI > 10 on Peking, the second most common soil samples representing 74 soybean-producing counties across eight source of resistance by farmers. Our results show that over the last degeographical regions of Missouri. Eighty-eight percent of samples tested cade, SCN has become more prevalent in Missouri fields. Additionally, positive for SCN, up from 50% in 2005, and population densities ranged the percentage of individuals within SCN field populations that are virufrom 125 to 99,000 eggs per 250 cm3 of soil. The virulence phenotypes of lent on PI 88788 and Peking has markedly increased. The results stress 48 SCN populations also were determined. For this, female indices (FI) the importance of rotating cultivars with different types of resistance were calculated by dividing the mean number of females that develop on when using resistant cultivars to manage SCN.