不同水稻品種之穗上發芽與種子休眠性的調查

Abstract

種子休眠性和穗上發芽特性為兩個相關的水稻性狀，多數品種具有易穗上發芽則種子休眠性低、或不易穗上發芽而種子休眠性高之特性。本研究的目標為篩選不易穗上發芽且無種子休眠性之水稻品種，以因應一期作收穫時期異常豪大雨發生頻度加劇的情境、且能於後續二期作保持秧苗生產所需之高發芽率。本研究首先選用 196 個稉稻品種，於民國 107 年一期作時期種植於臺大農場，調查各品種的種子休眠性及穗上發芽之外表型，以期找尋休眠性低且不易穗上發芽之水稻品種。而進行種子休眠以及穗上發芽特性的調查通常需要大量費工的種子計數，故我們對於能找到替代發芽種子計數之方法具有高度的興趣。本研究另以 60 個水稻品種檢測不同泡水天數下種子之發芽率及發芽勢，並挑選 32 個稉稻品種進行 α-澱粉酶的活性測定，並計算種子發芽率與α-澱粉酶活性兩者之間的相關係數，藉以評估利用 α-amylase 活性取代計數種子發芽顆數的可行性，試驗結果可應用在未來種子休眠相關性狀上的研究及後續相關育種選拔工作。

Seed dormancy and pre-harvest sprouting (PHS) are two closely related traits in rice. Varieties prone to PHS usually possess low seed dormancy, and varieties with PHS tolerance tend to have high seed dormancy. The objective of this project is to screen rice cultivars with PHS tolerance but low seed dormancy, in order to find rice genotypes that can reduce yield damage due to more frequently occurred heavy rains around harvesting time of the first cropping season but keep high germination rate of seedling propagation in the subsequently second cropping season for rice. In this study, 196 japonica rice varieties were grown and investigated in the NTU Farm in the first cropping season 2018, in order to find rice varieties with low seed dormancy and high PHS tolerance. Investigation of seed dormancy and PHS traits usually requires a laboriously large number of seed counts. Therefore, we are very interested in finding a method to replace the direct investigation of germination rate. In this study, 60 different rice varieties were tested in different soaking days. The germination rate and germination index were obtained in 60 varieties and the activity of α-amylase was measured in 32 selected japonica rice varieties. The correlation coefficient between the activity of α-amylase and germination rate was calculated to evaluate the feasibility of using α-amylase activity instead of counting the number of germinated seeds. The results can be applied to the research for seed dormancy-related traits and breeding program in the future.