Effects of Elevated Air Temperature under the RCP4.5 and RCP 8.5 Scenarios on Yield Quantity, Starch and Brix Value of Thai rice : Kor-Khor29 and Riceberry Cultivar

Abstract

The aims of this research were to examine the effects of increased air temperature under global warming trend base on RCP4.5 and RCP8.5 scenarios on yield component, starch (amylose and amylopectin) and brix value of 2 rice cultivars; KorKhor29 and Riceberry. Nine field-open top chambers (OTCs) with electric systems were applied to simulate expected future global warming situation (elevated temperature) into 3 conditions. Rice seedlings were planted in 9 OTCs under 3 temperature levels as follows,  CT treatments (control); 32.55±1.48°C, HT4.5 treatments (elevated temperature based on RCP4.5 scenario);  35.16±1.4°C  and  HT8.5 treatments (elevated temperature based on RCP8.5 scenario); 37.05±1.49°C, respectively through harvest stage. These constant 3 situations were operated for 10 hr daily through growing season, The results in harvest stage showed the most obvious significant decrease by 28.5% and 68.7% in seed  yield (ton/hectare) under HT8.5 situation in KorKhor29 and Riceberry, respectively. The results also showed that the positive effects on amylose content were obviously found in HT4.5 and HT8.5 but the negative effects of amylopectin were found in the same conditions. In addition, the parallel results between amylopectin and brix value were shown in Riceberry. The results showed that exposure to simulated global warming situation in HT4.5 and HT8.5 treatments also caused a significant reduction in brix value. In conclusion, overall results indicated that under future estimated temperature based on RCP8.5 caused more obvious negative effects on yield and seed chemical than RCP4.5 condition. In addition, it seemed that Riceberry was more sensitive to high temperature than Kor-Khor29. Finally, the results are the important data to climate change adaptation of rice cultivation management under future elevated temperature conditions in Thailand.