Heritability of the Groundcover (‘wave') Plant Habit in Garden Chrysanthemums

The success of the ‘wave’™ petunia phenotype in the bedding plant market created widespread interest among flower breeding programs to create ‘me, too’ Petunia products. Soon thereafter, other crops were bred and promoted with this trait e.g. Calibrachoa, Begonia. Garden chrysanthemums (Chrysanthemum xgrandiflorum, C. xhybridum) are no exception. For the past 20 years, the University of Minnesota garden chrysanthemum breeding program has focused on an adaptable wave or groundcover phenotype. The objective of this study was to determine the heritability of this phenotype within the elite, selected parents and cultivars in the 80-year-old germplasm bank. Groundcover and non- groundcover parents (cultivars, inbred and noninbred selections) within the major flower color classes (red, purple/pink, bronze, yellow, white) and with the best combining ability (fertility, seed production, yield potential) were used to create hybrid populations for inheritance studies. Groundcover x groundcover and groundcover x non-groundcover crosses were performed, with ten replications (seed heads) per cross. Due to low seed set, crosses within color classes and cross types were pooled for analysis. Fertility (seed production), % germination, % yield potential, % flowering, and plant habit (groundcover vs. non-groundcover) were assessed.  Chi-square ratios, 1:3, 3:1, or 1:1 (groundcover:non-groundcover), were calculated to determine the genetic control. Seed set within the same flower color classes varied from 7 to 218. Percent germination ranged from 28.9% (red groundcover x groundcover) to 80.6% (pink/lavender groundcover x groundcover).  Yield potential was lowest with pink/lavender groundcover x non-groundcover crosses (8.3%), while the highest was 79% for the same color class, groundcover x groundcover crosses.  Percentage of flowering varied as well (6.5% to 94%). Surprisingly, several yellow groundcover x non-groundcover crosses with a specific parent in common produced 100% groundcover progeny. However, no groundcover x groundcover crosses produced 100% groundcover progeny. The groundcover habit is not due to a single gene and allelic configuration (homozygous recessive, heterozygous or homozygous dominant), but is most likely the result of many genes.  This complicates obtaining groundcover progeny for continued breeding and selection.

Abstracts:

• Mum 90-275-27 Waseca 170.jpg (149.1KB) - Abstract Text