台灣草苺(Fragaria hayatae Makino)之植物性狀及其與‘桃園三號’草苺(Fragaria ×ananassa Duch.)之種間雜交

Abstract

Fragaria hayatae Makino is endemic to Taiwan. It was considered as a subspecies of F. nilgerrensis Schlecht. in some literature, but F. hayatae is characterized with red fruit and anthocyanin in all parts of the plant, and it is significantaly distinct from F. nilgerrensis in morphological characteristics. A white-fruited strawberry population that is morphologically distinct from typical F. hayatae but similar to F. nilgerrensis was found in Shiaoshueshan by our lab, this white-fruited form was never reported in Taiwan. Morphological characteristics and RAPD markers were studied to clarify the relationship among F. hayatae, the white-fruited strawberry, F. nilgerrensis, and some other Fragaria species. The white-fruited strawberry had green petiole, green runner, white petal, and cream-white colored fruit which were distinct from the red petiole, red runner, white petal with purplish-red blush at base, and red fruit of F. hayatae. Fragaria nilgerrensis and the white-fruited strawberry both lack of anthocyanin coloration in petiole, petal, and fruit, but F. nilgerrensis had red runners whereas the white-fruited strawberry had green runners. Despite the color of the plants, the white-fruited strawberry and F. hayatae was similar in size of leaf, petiole, flower, and fruit height. Fragaria nilgerrensis was significantly larger than F. hayatae and the white-fruited strawberry in size of leaf, petiole diameter, and size of flower. RAPD marker analysis indicated closer relationship between the white-fruited strawberry with F. hayatae (similarity index = 0.94) rather than F. nilgerrensis (similarity index = 0.43). We suggested that the white-fruited strawberry should be a mutant of F. hayatae and not F. nilgerrensis from China. For the need of interspecific hybridization, the effects of temperature and photoperiod on growth and flowering in F. hayatae were studied. Cool temperature slowed down the vegetative growth rate during treatment, but accelerated the growth after transferring the plants into warm temperature condition for several weeks. Flowers were initiated in plants treated under 15/10℃ or 10/5℃ under 10 hour day length for 6-10 weeks, and plants treated under 15/10℃ 14 hour day length, 15/10℃ 10 hour day length, and 15/5℃ 10 hour day length for 6 weeks. The rate of plants flowering was 8.3% to 50% under the above condition, and the optimal inductive condition for flower initiation in F. hayatae awaits further investigation. Reciprocal cross was made between F. hayatae (diploid) and the cultivated strawberry ‘Taoyuan No. 3’ (octoploid) to study the interspecific hybridization compatibility. 34% of seeds from F. ×ananassa ‘Taoyuan No. 3’ × F. hayatae germinated while no seed germinated in the other combination. Seven out of the 21 survived hybrid seedlings bloomed and bore fruits. The fruits were usually misshaped, which should result from partial pollination, or might be the evidence of obtaining pentaploids from successful hybridization.