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

台灣草苺(Fragaria hayatae Makino)是台灣之特有種，部份文獻認為是黃毛草苺(F. nilgerrensis Schlecht.)的一個亞種。但台灣草苺果實紅色且富含花青素，形態上明顯異於黃毛草苺。本研究室曾於小雪山採集得一群形態異於典型台灣草苺，但與黃毛草苺較相近之白果草苺，此群草苺在台灣尚無文獻紀錄。本試驗調查台灣草苺、白果草苺、黃毛草苺及其他草苺屬植物形態特徵及RAPD分子標誌之差異，以釐清其間之親緣關係與分類地位。性狀調查結果顯示白果草苺之葉柄及走莖為綠色，花瓣及果實均為白色；台灣草苺之葉柄及走莖為紅色，花瓣為白色基部帶有紅紫色條斑，果實為紅色；黃毛草苺之葉柄為綠色，走莖為紅色，花瓣及果實為白色。白果草苺與台灣草苺之葉片與花之大小以及果實高無顯著差異，而黃毛草苺之葉片、葉柄、花之大小及果高則顯著大於台灣草苺及白果草苺。RAPD分子標誌分析之結果顯示，白果草苺與台灣草苺的親緣關係非常接近(相似距離 = 0.94)，這兩者與黃毛草苺則有相當程度之差異(相似距離 = 0.43)。綜合形態特徵調查及RAPD分子標誌分析結果，台灣草苺應非黃毛草苺之一個亞種，且白果草苺應為台灣草苺之變種而非來自中國的黃毛草苺。 為配合種間雜交之需求，本試驗亦研究溫度與光週對台灣草苺生育之影響。結果顯示低溫會抑制台灣草苺之營養生長，低溫處理結束植株移至溫暖環境數週後，低溫處理者之營養生長反而較旺盛。以15/10℃或10/5℃配合10小時日長處理6至10週後，25%-50%之植株可開花。以15/10℃配合14小時日長或10小時日長以及15/5℃配合10小時日長處理6週後，8.3%之台灣草苺可開花。由於開花植株百分比低於50%，台灣草苺之最合適開花誘導條件仍待進一步研究。 台灣草苺(2x)與栽培種草苺(F. ×ananassa)‘桃園三號’(8x)進行互交，以台灣草苺為母本時，雜交結果率為73%，而以栽培種草苺‘桃園三號’為母本，雜交結果率為41%。以栽培種草苺‘桃園三號’作為母本得到的雜交種子之發芽率為34%，另一組合之種子無法發芽。成功存活的21個雜交後代中，7株可開花結果，但果實多為畸形。畸形果可能是授粉不完全之結果，或可能是成功雜交得到5倍體之證據。

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.