利用杂交水稻开花比例鉴定耐高温性的方法

选用水稻开花期耐高温能力强的品种,是缓解极端自然高温导致大幅减产的有效途径之一。为改进水稻品种耐高温性的鉴定技术,2013年和2014年以4个杂交水稻品种为材料,用钵栽方法,分别在开花前后不同时间将钵栽水稻移至人工气候室38.0℃高温下处理5 h,以室外常温(穗层日最高气温31.2~32.8℃)处理为对照,研究极端高温时段对结实率的影响。2015年和2016年以40个杂交中稻组合为材料进行5个分期播种试验,于水稻穗层温度达35℃以上时期,从5个播种期中选择20个同期开始抽穗、生长整齐的稻穗挂牌标记,观察不同时段开花比例,以研究品种间开花期耐高温能力与不同时间开花比例关系。结果表明,杂交水稻开花期高温下11:30前的开花比例、常温下12:00前开花比例分别与耐高温指数呈极显著正相关关系,耐高温品种主要通过提高高温下的结实率而间接增强其耐高温指数,而高温下的结实率则直接影响耐高温指数。高温下开花早的品种在常温下开花也早,杂交水稻开花时间主要集中在9:30—12:30,品种间在不同时刻开花的比例各异。开花后2 h遇高温对结实率影响不明显;穗层气温34℃、35℃且频率达80%以上的最早出现时间分别在13:30和15:30,选择日最高温度≥34℃或35℃出现前2 h开花比例高的品种,能有效地避开高温伤害。基于以上分析分别建立了利用开花期高温下11:30前开花比例、常温下12:00前开花比例和高温下结实率3个指标预测鉴定耐高温指数回归模型,准确率(预测值/实测值)高达92.29%~102.73%。为水稻品种开花期耐高温性鉴定提供了科学适用的新方法。

Identification method of high temperature resistance of hybrid rice based on flowering rate

Using cultivars with high temperature resistance is an effectively approach to reduce yield loss induced by extreme high temperature. The objective of this study was to improve the identification method for high temperature resistance of hy- brid rice varieties in both pot and field experiments. To that end, a pot experiment was conducted in an intelligent artificial climate chamber to determine the effects of extreme high temperature (38℃) on percentage grain filling at grain-filling stage in 2013 and 2014. Four cultivars were planted and exposed to extreme high temperature for 5 hours at 5.0 hours before and during flowering stage, and 1.0 hour, 1.5 hours and 2 hours after flowering stage. Also concurrently, hybrid rice cultivars were grown under normal background conditions (daily maximum temperature of panicle layer of approximately 31.2-32.8℃) as control (CK). A field experiment was conducted using 40 hybrid rice cultivars to study the relationship between high tem-perature resistance and flowering rate of hybrid rice at different times of the days based on 5 sowing dates (March 5, March 25, April 20, May 4 and May 24) in 2015-2016. In each year, 20 cultivars with same heading date were selected from 5 sowing dates to observe flowering rate at different times of the day. The results showed a significantly positive linear correlation be-tween high temperature resistance index and flowering rate of hybrid rice before 11:30 AM under high temperature condition or before 12:00 noon under normal temperature condition. The increase in seed setting rate of high temperature resistant vari-ety under high temperature condition was indirectly related with high temperature resistance index, while its' seed setting rate under high temperature condition was directly related with high temperature resistance index. Flowering of hybrid rice oc-curred earlier under high temperature condition, the cultivar flowering was also earlier under normal temperature condition. Flowering of hybrid rice was mainly concentrated around 9:30 AM to 12:30 PM. However, flowering rate differed with cultivar at different times of the day. Seed setting rate was not significantly affected by high temperature after 2 hours of flowering. When panicle layer temperature was 34℃ and 35℃, and their frequency reached 80％ at 13:30 PM and at 15:30 PM, respectively, choosing cultivars that flowered 2 hours before high temperature (daily maximum temperature greater than 34℃ or at about 35℃) could effectively resist high temperature injury. Regression equation was established based on flowering rate before 11:30 AM under high temperature and before 12:00 noon under normal temperature condi-tion and seed setting rate under high temperature condition. The equation provided a new identification method of high temperature resistance of hybrid rice cultivars at flowering stage at a percent accuracy (estimated value / measured value) of up to 92.29％-102.73％.