Fertility and Inheritance of Variegated and Purple Foliage Across a Polyploid Series in Hypericum androsaemum L.

Abstract

Inheritance of two mutant foliage types, variegated and purple, was investigated for diploid, triploid, and tetraploid tutsan (Hypericum androsaemum). The fertility of progeny was evaluated by pollen viability tests and reciprocal crosses with diploids, triploids, and tetraploids and germinative capacity of seeds from successful crosses. Segregation ratios were determined for diploid crosses in reciprocal di-hybrid F1, F2, BCP1, and BCP2 families and selfed F2s with the parental phenotypes. F2 tetraploids were derived from induced autotetraploid F1s. Triploid segregation ratios were determined for crosses between tetraploid F2s and diploid F1s. Diploid di-hybrid crosses fit the expected 9: 3: 3: 1 ratio for a single, simple recessive gene for both traits, with no evidence of linkage. A novel phenotype representing a combination of parental phenotypes was recovered. Data from backcrosses and selfing support the recessive model. Both traits behaved as expected at the triploid level; however, at the tetraploid level the number of variegated progeny increased, with segregation ratios falling between random chromosome and random chromatid assortment models. We propose the gene symbol var (variegated) and pl (purple leaf) for the variegated and purple genes, respectively. Triploid pollen stained moderately well (41%), but pollen germination was low (6%). Triploid plants were highly infertile, demonstrating extremely low male fertility and no measurable female fertility (no viable seed production). The present research demonstrates the feasibility of breeding simultaneously for ornamental traits and non-invasiveness.