Root Response of Tolerant and Intolerant Soybean Cultivars to Soybean Cyst Nematode
- E. D. Miltner,
- K. J. Karnok and
- R.S. Hussey *
Tolerance to soybean cyst nematode (SCN), Heterodera glycines Ichinohe, has been identified in soybean [Glycine max (L.) Merr.] and has potential as a management strategy to limit SCN yield suppression. Little information is available on the growth and morphology of roots of tolerant soybean cultivars parasitized by SCN. This study was conducted to compare root and vegetative responses of a moderately tolerant soybean, ‘Wright’, with an intolerant soybean, ‘Bragg’, to parasitism by SCN. In 1986, Bragg and Wright soybean was grown in the University of Georgia rhizotron in rooting medium infested with SCN Race 3 at initial population densities (Pi) of 0,1000, or 10 000 eggs/L. Measurements were made of soybean root growth and development, vegetative and reproductive growth stage, leaf number, flower and pod numbers, and nematode activity (development and infection). Number of growing roots on Bragg at Pi 10 000 was suppressed throughout the season, whereas root growth of Wright was stimulated by the presence of SCN. Although not statistically significant, root lengths followed these same trends. Seed yield of Bragg was progressively suppressed as Pi increased, in contrast to that of Wright which was suppressed at Pi 1000, but was not suppressed further at Pi 10 000. Vegetative development of Bragg was suppressed at Pi 10 000 compared to Pi 0 from 18 and 39 d after planting (DAP), respectively, in contrast to Wright which was unaffected. Reproductive development of Bragg at Pi 10 000 was also suppressed between 79 and 133 DAP. The stimulation of root development of Wright in the presence of SCN was probably critical to maintenance of vegetative and reproductive development.
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