Constitutive Expression of Pea Defense Gene DRR206 Confers Resistance to Blackleg (Leptosphaeria maculans) Disease in Transgenic Canola (Brassica napus)

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Abstract
To identify genes effective against the blackleg fungus Leptosphaeria maculans (Phoma lingam), we have transformed canola (Brassica napus) with four pea (Pisum sativum) genes under constitutive control by the cauliflower mosaic virus 35S promoter: PR10.1, chitinase, DRR206, and defensin. Transgenic lines containing single-copy T-DNA insertions for each gene were screened for both seedling (cotyledonary) and adult plant resistance. Lines for which pea DRR206 mRNA was expressed showed decreased disease scores, compared with non-expressing transgenic lines. Transgenic plants expressing pea defensin showed a slight enhancement of resistance, while for PR10 and chitinase transgenics there was little or no enhancement of resistance. Resistance to L. maculans cosegregated with DRR206 transgenes. Extracts from DRR206 and defensin transgenic plants inhibited fungal germination in vitro. DRR206 transgenic plants also demonstrated decreased hyphal growth at inoculation sites. While the precise function of DRR206 remains to be determined, these results suggest that it does play an important role in defense against fungi.