Differential response to foliar infection with Botrytis cinerea within thegenus Pelargonium

Foliar evaluations for Botrytis resistance of greenhouse grown plants were performed on 45 cultivars and control genotypes including diploid and tetra ploid zonal (P. xhortorum L.H. Bailey) and ivy(P.peltatum (L.) L'Her. in Ai t.) pelargoniums, Additional evaluations were performed on eight species wi thin section Ciconium and on progeny of a susceptible by susceptible cross- pollination involving the cultivars Ben Franklin and Marilyn. Differential levels of resistance were observed. Among many genotypes that exhibited res istance, two genotypes had consistently high levels of Botrytis resistance over several experiments. These two genotypes were the diploid P, peltatum accession 86-23-1 and the tetraploid P. xhortorum cultivar Fox. The diploid P, xhortorum cultivar Ben Franklin was a reliable susceptible control in a ll experiments. Plants grown outdoors generally had higher levels of resist ance than comparable greenhouse grown plants. Orthogonal contrasts indicate d no trends in resistance when comparing diploid and tetraploid pelargonium s, or when comparing among ivy, zonal, and floribunda types. Genotypes pate nted or introduced since 1990 have greater susceptibility than older genoty pes, Cross-pollinations among susceptible parents resulted in susceptible p rogeny, white self-pollinations of a resistant parent resulted in resistant progeny.