Production of intraspecific hybrids between wild-type and petaloid-sepal cultivars in Habenaria radiata

Abstract

Orchids are commercially important plants with flowers that are unique and very specialized in shape and color. The flowers consist mostly of sepals, lateral petals, lip (labellum) and column, and are zygomorphic and resupinate. Whereas most orchid species have petaloid tepals in the first and second whorls, Habenaria radiata has a flower with greenish sepals and white lateral petals and lip. ‘Hishou’, one of the cultivars of H. radiata, is a floral homeotic mutant and has a petaloid median sepal and lip-like lateral sepals in the first whorl. Additionally, this cultivar often has non-resupinate flowers whereas wild-type H. radiata flowers are resupinate. In the present study, we investigated the genetic inheritance of these characters in the ‘Hishou’ cultivar by crossing it with wild-type plants. Some intraspecific hybrids, which were confirmed by PCR-RFLP analysis, had flowers with a petaloid median sepal and lip-like lateral sepals in the first whorl, indicating that these were dominant characters. Since the remainder of the intraspecific hybrids had wild-type flowers, these characters must be heterozygous in ‘Hishou’ plants. Although ‘Hishou’ plants had non-resupinate flowers, intraspecific hybrid flowers were resupinate, even though they had the petaloid median sepal and lip-like lateral sepals. This result indicates that non-resupination must be a recessive character. Since sepal-petalization and triple lip characters of ‘Hishou’ inherited dominantly, these characters can be utilized for the breeding of Habenaria species by intra- and interspecific crosses.