Root Response of Tolerant and Intolerant Soybean Cultivars to Soybean Cyst Nematode

Abstract

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.

Influence of Heterodera glycines infection, plant age and water availability on foliar symptoms of sudden death syndrome, root symptom severity and root morphology of soybean plants infected by Fusarium virguliforme

“…In our study, root tip production on plants inoculated with SCN alone was not different from that observed on non-inoculated controls. This trend was observed on both cultivars, and contrasts with research by Miltner et al (1991) showing an increase in root tip production on an SCN-tolerant cultivar. This discrepancy may be due to differences in cultivars, sources of resistance to SCN, or different SCN HG types tested in the two studies.…”

“…One of the previously reported effects of SCN infection is increased branching of soybean roots, which has been observed in SCN tolerant cultivars (Radcliffe et al, 1990;Miltner et al, 1991). In our study, root tip production on plants inoculated with SCN alone was not different from that observed on non-inoculated controls.…”

The growth of nematode ‘tolerant’ and ‘intolerant’ soyabeans as affected by phosphorus, Glomus intraradices and light

“…The proportionately smaller root system of cv, Wright (Table 3) can be considered to be more efficient than that of cv, Bragg (Radcliffe et al, 1990;Miltner et al, 1991), Differences in root efficiency and nutrient absorption have been investigated in a number of species, including soyabean (Foote & Howell, 1964;Barber, 1982), In the greenhouse, overall SRR was greater in plants infested by SCN, The root systems may have increased their activity in order to compensate for the nematode-induced reduction in their size, as has been demonstrated elsewhere (Price et al, 1982), Differences between greenhouse and growth-chamber experiments also provide evidence of differences in the physiological characteristics of the root systems of the two varieties. In the greenhouse, cv, Wright responded to P with a much increased SRR, indicating a more efficiently functioning root system under conditions of higher fertility, whilst the SRR of cv, Bragg remained unchanged.…”

Role of Mineral Nutrition on Root Growth of Crop Plants – A Review

“…Miltner et al, (1991) reported that cyst nematodes suppressed soybean root growth on susceptible cultivars, whereas root growth of tolerant cultivars was stimulated by the presence of soybean cyst nematodes. The use of tolerant or nutrient-use-efficient cultivars may be an important practice to improve root growth in stress environments.…”