Pelargonium resistance

Host plant resistance to the two-spotted spider mite, Tetranychus urtlcae, was observed In the geranium, Pelargonium x hortorum. Initial studies Indicated an association between leaf morphology and resistance later studies concluded that resistance was due largely to the presence of glandular trlchomes which produced a toxic exudate. The active components of this exudate have been Identified as anacardlc acids. Inheritance studies Indicated that resistance was dominant to susceptibility and that two dominant complementary genes conditioned resistance. 

Winner, B. L. Inheritance of Resistance of the Two-spotted Spider Mite, Tetranychus urtlcae Koch in the Geranium, Pelargonium x hortorum Bailey. M.S. Thesis, The Pennsylvania State University, University Park, Pennsylvania. 1975. 

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