Multiple-Species Nematode Resistance in Soybean: Effect of Genotype and Fumigation on Yield and Nematode Numbers
- D. B. Weaver ,
- R. Rodriguez-Kabana and
- E. L. Carden
Successful management of plant-parasitic nematodes without the use of fumigant nematicides is a problem in the southeastern USA, especially when both root-knot (RKN) (Meloidogyne spp.) and soybean cyst nematodes (SCN) (Heterodera glycines Ichinohe) occur in a mixed population in the same field. We studied the yield performance and nematode population numbers of several nematode-resistant soybean (Glycine max L.) cultivars near Elberta, AL, for 3 yr in a Ruston fine sandy loam (sandy, siliceous, thermic, Psammentic Paleudults) heavily infested with a mixture of RKN [Meloidogyne incognita (Kofoid and White) Chitwood and M. arenaria (Neal) Chitwood] and SCN (a mixture of races 3, 4, and other unidentified races). Objectives were to evaluate performance of a group of soybean genotypes with differing combinations of resistance to RKN and SCN in terms of yield and effect on nematode populations in soil where both RKN and SCN occur together. Comparisons were made between plots that received no nematicide, and plots fumigated with a planting-time application of 16.8 L ethylene dibromide ha−1. Four 2-yr experiments were conducted in 1984 through 1986. Fumigation increased yield and decreased RKN numbers in all years and experiments and increased SCN numbers in all except one experiment in 1984. All cultivars sustained high RKN populations 6 wk before harvest; this was especially true for ‘Kirby’ and ‘Leflore’, two of the highest-yielding cultivars in fumigated and nonfumigated plots. The RKN numbers and yield were not often correlated in nonfumigated plots. Cultivars significantly affected yield except for one experiment in 1985 and often significantly affected RKN numbers and always significantly affected SCN numbers. We concluded that even cultivars with multiple-nematode resistance show differential yield response to these mixed populations, and that breeding for multiple-nematode resistance is an effective means of reducing yield losses. If nematicide use is economical, it should be used with the most resistant cultivar available.
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