Evaluation of Crossability of 20 Bouvardia Cultivars/Lines by Reciprocal Crosses

Abstract

We evaluated the crossability of 20 Bouvardia cultivars/lines and determined their usefulness as breeding materials. A total of 20 Bouvardia cultivars/lines were examined: one Bouvardia longiflora line, two B. ternifolia lines, four 4x-hybrid cultivars, nine 8x-hybrid cultivars, and four polyploid (8x) lines produced from the 4x-hybrids treated with colchicine. Reciprocal crosses were performed using all 20 cultivars/lines as seed parents, and 13 cultivars/lines as pollen parents. The seed set percentage, number of seeds per capsule, germination rate, and number of seedlings per flower were recorded. Based on crossing results, female and male fertility was scored from 0 to 5, and self-fertility was scored from 0 to 4. There were 137 cross combinations in total. Seeds were obtained from 68 combinations (50%) and seedlings were obtained from 59 combinations (43%). Female fertility was recorded in 18 cultivars/lines (scores 2–5) and was generally low in the 4x-hybrid cultivars. However, fertility significantly recovered in their polyploid lines (8x). Male fertility was recorded in 10 cultivars/lines (scores 2–5) and was medium to high (scores 3–5) in the lines of two species (B. longiflora and B. ternifolia) and many 8x hybrid cultivars. Five cultivars/lines were self-fertile. Sixteen cultivars/lines, including polyploids, had medium to high scores (≥3) for one or more fertility type (male, female, and self), and were considered to be useful cross-breeding materials.