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    Comparison of field, greenhouse and detachedleaf evaluations of soybean germplasm for resistance to Phakopsora pachyrhizi

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    Date
    2007
    Author
    Twizeyimana, M.
    Ojiambo, P.S.
    Ikotun, T.
    Paul, C.
    Hartman, G.L.
    Bandyopadhyay, Ranajit
    Type
    Journal Article
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    Abstract/Description
    Fourteen soybean accessions and breeding lines were evaluated for resistance to soybean rust caused by the fungus Phakopsora pachyrhizi. Evaluations were conducted in replicated experiments in growth chambers using detached leaves and under greenhouse and field conditions. In growth-chamber experiments, inoculation of detached leaves with 1 × 106 sporesml resulted in a significantly (P < 0.0001) higher total number of pustules and spores per unit leaf area than inoculations with lower spore concentrations. Amending agar medium with plant hormones significantly (P < 0.0001) aided retention of green leaf color in detached leaves. Leaf pieces on a medium containing kinetin at 10 mgliter had 5% chlorosis at 18 days after plating compared with leaf pieces on media amended with all other plant hormones, which had higher levels of chlorosis. Leaf age significantly affected number of pustules (P = 0.0146) and number of spores per pustule (P = 0.0088), and 3- to 4-week-old leaves had a higher number of pustules and number of spores per pustule compared with leaves that were either 1 to 2 or 5 to 6 weeks old. In detached-leaf and greenhouse screening, plants were evaluated for days to lesion appearance, days to pustule formation, days to pustule eruption, lesion number, lesion diameter, lesion type, number of pustules, and spores per pustule in 1-cm2 leaf area. Plants also were evaluated for diseased leaf area (in greenhouse and field screening) and sporulation (in field screening) at growth stage R6. There were significant (P < 0.0001) differences among genotypes in their response to P. pachyrhizi infection in the detached-leaf, greenhouse, and field evaluations. Accessions PI 594538A, PI 417089A, and UG-5 had very low levels of disease compared with the susceptible checks and all other genotypes. Detached-leaf, greenhouse, and field results were comparable, and there were significant correlations between detached-leaf and greenhouse (absolute r = 0.79; P < 0.0001) and between detached-leaf and field resistance (absolute r = 0.83; P < 0.0001) across genotypes. The overall results show the utility of detached-leaf assay for screening soybean for rust resistance.
    https://doi.org/10.1094/PDIS-91-9-1161
    Multi standard citation
    Permanent link to this item
    https://hdl.handle.net/20.500.12478/3473
    Digital Object Identifier (DOI)
    https://doi.org/10.1094/PDIS-91-9-1161
    IITA Subjects
    Nutrition; Soybean; Food Security; Diseases Control; Genetic Improvement; Pests Of Plants; Plant Diseases; Livelihoods; Plant Production; Handling, Transport, Storage And Protection Of Agricultural Products; Plant Breeding; Plant Genetic Resources
    Agrovoc Terms
    Disease Resistance; Soybeans; Plant Hormones; Chlorosis; Spores Per Pustule; Genotypes; Phakopsora Pachyrhizi; Detached-Leaf
    Regions
    Africa; Acp; West Africa; North America
    Countries
    Nigeria; United States
    Collections
    • Journal and Journal Articles4835
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