Soybean Cyst Nematode Population Development and Associated Soybean Yields of Resistant and Susceptible Cultivars in Minnesota

Abstract

The soybean cyst nematode (SCN), Heterodera glycines, is a major soybean yield-limiting factor, and the use of resistant cultivars is one of the most effective means to manage the nematode. During the past decade, a number of resistant cultivars in maturity groups I and II have been developed and made available to growers. A total of 47 resistant cultivars and nine susceptible cultivars were evaluated at 15 SCN-infested field sites and two noninfested sites during 1996 to 1998 in Minnesota. As expected, more nematodes developed on susceptible cultivars than on resistant cultivars. Egg density on susceptible cultivars increased by 1.9- to 10.6-fold during the growing season at 12 sites and did not change at the other three sites. Average egg density decreased over time for resistant cultivars at all sites, except where the initial egg density was low (≤455 eggs per 100 cm3 soil). Nematode reproduction factors (Rf = egg density at harvest/egg density at planting) for individual resistant and susceptible cultivars were highly consistent across the eight sites where initial SCN density was more than 1,000 eggs per 100 cm3 soil. Resistance, however, varied among the cultivars, with the average Rf of individual resistant cultivars across the sites ranging from 0.3 to 1.7. Resistant cultivars produced an average yield of 3,082 kg/ha compared with 2,497 kg/ha by susceptible cultivars at eight of 10 sites where egg density at planting was greater than 700 eggs per 100 cm3 soil. In contrast, no difference in yield was observed between resistant and susceptible cultivars at sites where egg density at planting was lower than 500 eggs per 100 cm3 soil. Yield differences between resistant and susceptible cultivars increased with increasing initial SCN egg density. In six fields infested with initial densities of more than 5,000 eggs per 100 cm3 soil, resistant cultivars produced 28.4% (676 kg/ha) more yield on average than susceptible cultivars. Soybean yield increased when cultivars with increasing resistance to the SCN (lower Rf or females formed on roots) were grown in fields infested with SCN. Average relative yield (yield of a cultivar/average yield of all resistant cultivars at a site) of individual resistant cultivars across all SCN-infested sites ranged from 0.76 to 1.10. Yield consistency of soybean cultivars was low among the different sites, indicating that many other factors affected yield. Our results suggest growing resistant cultivars is an effective method to manage SCN in Minnesota while minimizing yield loss due to SCN.

Short Corn Rotations Do Not Improve Soil Quality, Compared with Corn Monocultures

“…The dominant CS rotation renders higher yields for each crop than when each is grown continuously in the same field (Bullock, 1992;Kelley et al, 2003). Though reasons behind these yield benefits have proven difficult to uncover, this 'rotational effect' is considered an emergent property of the system where decreased disease, weed, and insect pressures (Chen et al, 2001;Xing and Westphal, 2009;Davis et al, 2012); reduction of greenhouse gas emissions (Halvorson et al, 2008;Wilson and Al-Kaisi, 2008); and enhanced soil fertility (Karlen et al, 2006;Villamil et al, 2006;Congreves et al, 2015) all play a contributing role. Therefore, the CCS rotation is considered to bring some of these agronomic advantages associated with growing corn and soybean in rotation compared with growing corn sequentially in the same field for several seasons.…”

The Nematode Resistance Allele at the rhg1 Locus Alters the Proteome and Primary Metabolism of Soybean Roots

“…Among soybean pathogens, the soybean cyst nematode (SCN) causes the most damage. Yield losses in the world due to SCN infection have approached $2 billion a year (Niblack et al, 2004) and amounted to $1.5 billion in the United States alone for the 1996 to 1997 period (Chen et al, 2001). SCN preventative measures include crop rota-tion, the use of resistant cultivars, and nematicides.…”

Genetic variation for disease resistance and tolerance among Arabidopsis thaliana accessions

“…Empirically, resistance is measured in several different ways. Resistance in crop varieties is usually evaluated by their relative yield with and without pathogen infection (14)(15)(16). In contrast, genetic variation for disease resistance in natural populations is usually estimated by quantitative variation in visual symptoms (9,12,17,18).…”