Induction of Hairy Roots on Cultivated Soybean Genotypes and Their Use to Propagate the Soybean Cyst Nematode

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Abstract
Ten soybean (Glycine max) genotypes were evaluated for hairy root induction by four strains of Agrobacterium rhizogenes. Influence of inoculation site was assessed by infecting hypocotyls and cotyledons on germinated seedlings. The presence of opines in extracts of cultured root was used to score transformed roots. A cucumopine strain, K599, induced hairy roots on 37% of the cotyledons infected on the 10 genotypes tested. Transformed root development after infection of cotyledons with the mannopine strain 8196 occurred at a frequency of 3% on four genotypes. Agropine strains 1855 and A4 induced hairy roots on 1% of cotyledons of different genotypes. No opine-positive transformed roots were induced from hypocotyl inoculations with any A. rhizogens strain-soybean genotype combination tested. However, adventitous roots containing no detectable opines developed from hypocotyl inoculations both at the wound site and at a region directly below the cotyledons. Transformed roots differentiated fromg lobular callus at the woud site on cotyledons infected with virulent A. rhizogenes. Opine-containing hairy roots were established permanently in tissue culture and exhibited typical hairy root morphologies and growth parameters. Infection of soybean cultivar Williams 82 hairy root cultures with second-stage juveniles or cysts of the soybean cyst nematode. Heterodera glycines race 3, led to the appearance of mature cysts about 3 wk later. The nematode was propagated by excising an infected root and transferring it to a fresh root culture.