Response Of Susceptible, Moderately Susceptible, And Moderately Resistant Soybean Cultivars To Race-14 Cyst-Nematode

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) infests soils throughout the mid and lower Mississippi River Valley, the Ohio River alley, and the southeastern Coastal Plain in the USA, and fan reduce soybean [Glycine mar CL.) Merr.] yield significantly. This study compared the yields of susceptible ('Essex'), moderately susceptible ('Cordell'), and moderately resistant ('A5474' or LA5403') Maturity Group V soybean at different levels of SCN (Race 14) infestation in a greenhouse. Level of initial infestation of SCN was 0, 200, and 600 cysts L(-1) in the top 15 cm depth of greenhouse pots. Seed yield of all cultivars declined with increasing level of infestation in 1990, but in 1992, seed yield of all cultivars declined significantly only between the 0 and 200 cysts L(-1) level. Yields of Essex and Cordell were essentially equal within all infestation levels, while yields of A5474 and A5403 were greater than those of Essex and Cordell in the infested treatments. Yield declines between the 0 and 200 cysts L(-1) treatments averaged 55% for Essex, 50% for Cordell, and 20% for A5474 and A5403. Seed yield was significantly correlated with number of pods and number of seed in both years, but not with weight of seeds or seeds per pod. These results indicate that SCN will reduce yield of moderately resistant and moderately susceptible cultivars dissimilarly. These results also indicate that the classification of cultivars for resistance to SCN reproduction is not necessarily indicative of the yield potential of these cultivars in the presence of SCN Race 14.