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Abstract Detail

Host/Plant Pathogen Interactions and Plant Health Management

Marchand, Geneviève [1], Yan, Miaoyi [1], Giorgetti, Corrine [1], Cober, Elroy R. [1], Xue, Allen [1].

Pathogenicity of Pythium species to soybean and resistance in a Canadian short-season cultivar set.

Pythium species cause seed root, seedling damping-off and root rot of numerous crops worldwide. In Canada, this pathogen hinders the establishment of short-season soybean crops in the cool, wet conditions often prevalent in the spring in the main Canadian soybean production areas. The objectives of this work were (i) to characterize the pathogenicity of a collection of Pythium isolates from soybean fields and (ii) to evaluate resistance to highly pathogenic species within a set of short-season soybean cultivars and breeding lines. The pathogenicity of a collection of 99 Pythium isolates from soybean fields was initially investigated using an in vitro seed rot assay. Pythium attrantheridium and P. hypogynum (one isolate each) were not pathogenic, causing no inhibition of seed germination, and five isolates of P. dissotocum were weakly pathogenic, causing low inhibition of seed germination. The pathogenicity of P. irregulare (two isolates) and P. sylvaticum (32 isolates) as measured by inhibition of seed germination was moderate. Pythium ultimum was highly pathogenic, with high inhibition of germination caused by P. ultimum var. sporangiiferum (four isolates) and P. ultimum var. ultimum (54 isolates). Five pathogenic isolates were selected for further evaluation of pathogenicity using an in vivo seedling damping-off assay (layer inoculum method) in the greenhouse on susceptible cultivar Williams. Pythium ultimum var. ultimum was highly pathogenic, with two isolates causing a high percentage of seedling mortality compared to the untreated control. Two isolates of P. sylvaticum and one isolate of P. irregulare caused low to moderate seedling mortality. Work is ongoing to characterize the pathogenicity of the remaining 94 isolates in vivo. A set of 92 Canadian short-season soybean cultivars or breeder lines was screened for partial resistance to this pathogen using the same methodology (greenhouse seedling damping-off assay) and two isolates of P. ultimum var. ultimum. Most cultivars showed high (50% or greater) or moderate (25-49%) seedling mortality, on average of both isolates and compared to the untreated control), although a subset of cultivars showing less than 25% of seedling mortality was identified. These cultivars constitute a source of resistance to improve future short-season soybean cultivars and study the mechanisms of resistance to this pathogen. Keywords: genetic resistance, pathogenicity, Pythium spp., soybean

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1 - Agriculture and Agri-Food Canada, Eastern Cereal and Oilseed Research Centre, 960 Carling Avenue, Ottawa, ON, K1A 0C6, Canada

none specified

Presentation Type: Poster:Posters for Topics
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PPA040
Abstract ID:165
Candidate for Awards:None

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