花蓮地區氣溫環境與水稻品種間稻米品質之相關性

Abstract

水稻是台灣最重要的糧食作物，栽培品種主要以稉型水稻為主。稉稻適種於溫帶氣候，該地區栽培之稉稻穀粒有效充實期長，充實期平均氣溫低於25℃。台灣因地處亞熱帶地區，氣溫環境高於較高緯度的日本、韓國等其他傳統稉稻栽培地區。高溫環境促使區內水稻在生育後期時的有效充實期較短且穀粒充實速度較快，導致稻米產量與品質皆不理想。Intergovernmental Panel on Climate Change (IPCC) 指出目前溫室效應已造成全球氣溫明顯上升且變動劇烈。在此因氣候暖化所帶來的高溫環境下，台灣的水稻栽培勢將面臨更嚴峻的挑戰，未來該如何藉由改善栽培方式以因應全球暖化變遷趨勢，並進一步提升稻米產量及品質，將是現今及未來國內農業的重要研究方向。 本研究主要藉由設計花蓮地區主要稉稻栽培品種台稉2號及高雄139號周年栽培試驗，配合各栽培時期所遭遇到之不同氣象條件，進而分析稻米之產量及品質性狀與氣象因素之相關性。97與98年在花蓮區農業改良場分別完成7個與8個栽培期，同時調查分析其氣象條件、產量構成要素與品質性狀。結果顯示：花蓮地區各栽培期之抽穗後日均溫以二月下旬插秧者最高，而以八月中旬插秧者最低。抽穗後氣溫影響以抽穗後15日內最為顯著，同時影響產量、穀粒外觀與食味品質，品種間則以台稉2號相較於高雄139號對高溫環境的反應較為敏感。抽穗後氣溫上升的趨勢導致單株有效穗數與稔實率的降低，導致單位面積產量之減少，其中以台稉2號表現較為明顯。在外觀方面，抽穗後15日內平均氣溫、平均單日最高溫及平均單日最低溫與糙米之完整米率、白米之正常粒率呈負相關，與未熟米率、粉質狀粒呈正相關，推測原因為高溫使穀粒充實過快，澱粉堆積不緊實所致，品種間差異仍以台稉2號變動幅度較為明顯。食味方面，抽穗後日均溫上升使直鏈澱粉含量下降，進而提高米飯的食味品質。 本研究之田間試驗結果可用於彙整影響花蓮地區主要水稻品種之稻作產量與品質之氣溫範圍，並可藉以規劃安全及優質栽培時期，及作為耐性品種育種之參考，未來將進一步進行生理層面之探討以及其他田間氣候因素之分析，期彙整試驗結果並提出栽培改善建議供水稻農友參效仿行。

Taiwan is one of the lowest latitude zones where Japonica type rice is mostly cultivated. Japonica type rice adapts to temperate climate like Japan and Korea, where has a long grain filling period and suitable grain filling temperature lower than 25℃. In resent years, the warming trend of global climate change has became a significant phenomena, it will impact Taiwan’s rice yield. The warm climate of Taiwan may lead to a lower yield and quality than other traditional Japonica type rice culture regions. Intergovernmental Panel on Climate Change（IPCC）indicated that global warming was apparent and getting severe. Thus, there will be a strict challenge on rice cultivation in Taiwan. It is important to improve the agricultural practice against the future warming climate. To understand the relationship between the yields/quality of two prevailing rice cultivars of Hualien district（Taikeng 2 and Kaohsiung 139）and climate factors, two year-round cultivation experiment with 7 and 8 culture periods were conducted in 2008 and 2009 respectively. The results revealed that the designed different culture periods covered with different accumulated temperature, daily mean temperature, daily maximum temperature and daily minimum temperature. The temperature after heading for crop transplanted in late February was highest, and for the one transplanted in middle August was the lowest among the all culture periods. The most sensitive period of temperature was within 15 days after heading. The temperature of this periods affected yields, grain appearance qualities and eating qualities. Rising temperature after heading significantly decreased panicle number and grain sterility in Taikeng 2（TK2） rather than in Kaohsiung 139（KH139）. For grain appearance qualities, significant negative correlations were found between whole kernel ratio and daily mean temperature/maximum temperature/minimum temperature of the period within15 days after heading in both two varieties. On the contrary, the correlation of opaque kernel ratio showed positive correlation with the temperature. For eating qualities, rising of temperature of within 15 days after heading decreased the accumulation of amylose. Finally, high temperature increased the eating qualities of TK2 by decreasing amylose contend. KH139 in general showed a higher stability than did the TK2. The results of this research revealed the correlation between high temperature and rice yields/qualities of two most common cultivars in Hualien region. The present results are valuable for designing appropriate culture practice and for breeding new adaptive varieties in coping with climate change.