Novel Impatiens Genotype with Improved Resistance to Western Flower Thrips Feeding

in HortScience
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  • 1 University of Illinois, Natural Resources and Environmental Sciences, Urbana, IL, 61801

When breeding floriculture plants, one must have a targeted phenotype and genotype in mind before the initial cross-pollination event is performed. In the case of the floriculture breeding program at the University of Illinois, our initial goal was to develop a commercially acceptable, yet novel, Impatienswallerana(bedding plant impatiens) phenotype with improved resistance to the western flower thrips, Franklinella occidentalis, a significant insect pest in production greenhouses. This study describes the process used to obtain a large impatiens phenotype (>61 cm tall and >125 cm wide) with acceptable branching, leaf color, flower size, flower number, flower display, and flower colors with improved resistance to western flower thrips. A reliable and simple evaluation technique, based on the number of leaves expressing western flower thrips feeding damage after inoculation, was developed and utilized to create more resistant impatiens genotypes based on generation means. Using a 1 to 9 scale, mean damage ratings for the original germplasm populations 1, 2, and 3 were 5.18, 6.02, and 6.11, respectively, with the trend for populations 1, 2, and 3 skewed toward susceptible plants. Germplasm with novel phenotypes were derived from crosses with plants in populations 1 and 3 with commercial cultivars. These novel phenotypes had improved levels of resistance with a mean rating of 5.06 and a normal shaped distribution. The potential for improving resistance to western flower thrips feeding exists within available germplasm and the tools necessary for proper evaluations are available.

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