Breeding for dwarf, winter-hardy Iris domestica, blackberry lily (Iridaceae)

Iris domestica (= Belamcanda chinensis) is an ornamental native to China and Japan. At seed set, the capsules open and display rows of large black seeds; the entire dehisced capsule has the appearance of a blackberry. The species is drought tolerant (once established), flowers through the summer season, is highly self-compatible and, as a result, has become an invasive species escaped from cultivation throughout most of the southern United States and elsewhere around the globe. Despite its spread, it remains a unique ornamental with a spacious inflorescence useful for cut flower production since plants often reach 1 m in height. Conversely, if dwarf types could be bred and selected their potential as a potted flowering plant would be useful for interior and exterior containers and landscapes. The purpose of this research was to analyse phenotypic diversity of seedling populations for seed germination, plant habit (dwarf vs. cut flower types), reduced generation cycle (seed to early flowering), and the occurrence of semi- to double-flowered mutants for eventual hybrid sterility. Intra- and interspecific crosses (n=203) were made over three years and the genetic variation for all traits was analysed in the total progenies (n=4,146). Across three years of populations, variation was noted for mean % germination (13.4-51.5%) occurring in weeks G2 through G7 after sowing. The mean number of days to visible bud date ranged from 151.6 (in 2015) to 207 (in 2013), decreasing as the breeding cycles and selection progressed. Similar results were found for the mean number of days to flowering (158.9-210). Flower number on the main stem ranged from 20 to 21 flowers plant^-1 whereas the number of leaves averaged 13.3-14.5 plant^-1. Mean internode lengths were ~4 cm. While the total plant height (stem + inflorescence heights) was 85-86 cm tall, numerous dwarf genotypes that were shorter than commercial cultivars were found throughout the populations in all years. Flower petal coloration ranged from the classic orange with red spots, to pure reds, yellows, creamy white, pink, and purple; colour patterns included picotees. Several crosses were homozygous for flower colour. At least one seedling had semi-double flowers and could serve as a source for sterility in this crop.