Genetics of Growth Habit and Development of New Coleus (Solenostemon scutellarioides (L.) Codd) Varieties with Trailing Habit and Bright Color

Abstract

A high level of genetic variability for growth habit types is observed in tetraploid, cultivated coleus (Solenostemon scutellarioides (L.) Codd). Very few cultivars with trailing habit exist, and those that are available generally have dark green or purple foliage color. Coleus with trailing growth habit is desirable as it increases its utility for use in hanging baskets, mixed containers, and as ground cover. There is a lack of published information on the genetic mechanism controlling growth habit and the development of new trailing types with orange colors. Two commercial cultivars, "Red Trailing Queen" (RQ) with trailing habit and "Sedona" (S) with upright stature, were selfed and crossed (RQ x S) to produce self and F(1) populations. F(2) populations were produced by selfing plants in the F(1) population. For each population analyzed, growth habit was rated on a visual 1-5 phenotypic scale, where 1 = upright, 2 = semi-upright, 3 = prostrate, 4 = semitrailing, and 5 = trailing. Genotypes were assigned to each phenotype, assuming that upright was dominant to trailing. In this study, growth habit was observed to be controlled by a single gene (U) with additive effects, with upright growth habit designated with a UUUU genotype and trailing growth habit designated with a uuuu genotype. In addition, foliage color was rated on a visual 1-5 phenotypic scale, and purple foliage color was found to be dominant to yellow-orange color. Several new coleus selections with trailing growth habit and orange foliage color were successfully developed.