Reaction of selected soybean cultivars to Rhizoctonia root rot and other damping-off disease agents.
Eight soybean cultivars; Giza 21. Giza 22, Giza 35, Giza 82, Giza 83, Crawford, Holladay and Toamo were evaluated to Rhizoctonia root rot using agar plate and potted plant techniques. Data cleared that, in agar plate assay all soybean cultivars were moderately susceptible (MS), although the differences between them were significant (P=0.05). Generally, in potted assay, the reactions were resistant (R) or moderately resistant (MR) to root rots. Also, the differences between cultivars were significant (P=0.05). These cultivars were inoculated under greenhouse conditions with Fusarium solani, Macrophomina phaseolina, Rhizoctonia solani and Sclerotium rolfsii Generally, G21 had the least pre-emergence damping-off followed by Giza 35, Crawford and Giza 83 with averages of 19.0, 20.0, 20.5 and 21.5%, respectively. In case of post-emergence, Giza 35 had the least values, followed by Giza 21, Crawford and Giza 82 with averages 3.95, 4.10, 4.10 and 4.25%, respectively. Under naturally infested soil in the field conditions the reactions of the same cultivars to damping-off were evaluated in two successive seasons. In 2002 season, G35 had the least pre-emergence damping-off % followed by Giza 21 and Giza 22 with averages of 22.61, 24.33 and 29.33%, respectively. Also, G35 had the least post-emergence damping-off % followed by Toamo and Giza 21 with averages of 9.40, 10.33 and 10.41%, respectively. In 2003 season, the same trend was appeared with light grade where Giza 35 had the least pre-emergence damping of % followed by Giza 22 and Giza 21 with averages of 30.67, 31.00 and 36.67%, respectively and Giza 35 was the most resistant cultivar against post-emergence damping-off, followed by Giza 21 and Giza 22 with averages of 10.91, 11.32 and 11.80%, respectively. Generally, Giza 21 significantly surpassed the other cultivars in plant height, number of pods per plant and 100-seed weight. Moreover, also it had second grade with the other traits.
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Agricultural Botany Department, Faculty of Agriculture (Saba-Basha), Alexandria University P.O. Box 21531, Bolkley, Alexandria, Egypt.
D015169:Colony Count, Microbial; D004198:Disease Susceptibility; D004534:Egypt; D005670:Fusarium / Q000254:growth & development* / Q000472:pathogenicity; D010935:Plant Diseases / Q000382:microbiology*; D018517:Plant Roots / Q000382:microbiology; D012232:Rhizoctonia / Q000254:growth & development* / Q000472:pathogenicity*; D012988:Soil Microbiology; D013025:Glycine max / Q000235:genetics / Q000276:immunology / Q000382:microbiology*