National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba 305-8604, Ibaraki, Japan.
Taiyo Keiki Co. Ltd, 1-12-3, Nakajujo, Kita-ku 114-0032, Tokyo, Japan.
Rice (N Y). 2014 May 21;7(1):6. doi: 10.1186/s12284-014-0006-5. eCollection 2014.
Heat-tolerant rice cultivars have been developed as a countermeasure to poor grain appearance quality under high temperatures. Recent studies showed that elevated CO2 concentrations (E-[CO2]) also reduce grain quality. To determine whether heat-tolerant cultivars also tolerate E-[CO2], we conducted a free-air CO2 enrichment (FACE) experiment with 12 rice cultivars differing in heat tolerance.
The percentage of undamaged grains of five standard cultivars (Akitakomachi, Kinuhikari, Koshihikari, Matsuribare, Nipponbare) averaged 61.7% in the ambient [CO2] (AMB) plot and 51.7% in the FACE plot, whereas that of heat-tolerant cultivars (Eminokizuna, Wa2398, Kanto 257, Toyama 80, Mineharuka, Kanto 259, Saikai 290) averaged 73.5% in AMB and 71.3% in FACE. This resulted in a significant [CO2] by cultivar interaction. The percentage of white-base or white-back grains increased from 8.4% in AMB to 17.1% in FACE in the sensitive cultivars, but from only 2.1% in AMB to only 4.4% in FACE in the heat-tolerant cultivars.
Heat-tolerant cultivars retained their grain appearance quality at E-[CO2] under present air temperatures. Further improvements in appearance quality under present conditions will be needed to achieve improvements under E-[CO2], because E-[CO2] will likely lower the threshold temperature for heat stress.
耐热水稻品种已被开发出来，作为应对高温下稻谷外观品质下降的对策。最近的研究表明，高浓度二氧化碳（E-[CO2]）也会降低稻谷品质。为了确定耐热品种是否也能耐受 E-[CO2]，我们在 12 个耐热性不同的水稻品种上进行了自由空气 CO2 富集（FACE）实验。
五个标准品种（秋田小町、金辉、越光、松露白、日本晴）在大气[CO2]（AMB）处理下的完整粒率平均为 61.7%，在 FACE 处理下为 51.7%，而耐热品种（新农 6 号、W2398、关东 257、富山 80、美浓穗、关东 259、塞凯 290）在 AMB 下的平均为 73.5%，在 FACE 下为 71.3%。这导致了显著的[CO2]与品种互作。在敏感品种中，白腹或白背粒的比例从 AMB 的 8.4%增加到 FACE 的 17.1%，而在耐热品种中，该比例仅从 AMB 的 2.1%增加到 FACE 的 4.4%。
在目前的气温下，耐热品种在 E-[CO2]下保持了其稻谷外观品质。在目前的条件下，需要进一步提高外观品质，才能在 E-[CO2]下实现改善，因为 E-[CO2]可能会降低热应激的阈值温度。
