【作者】 刘东华；

【导师】 靳德明；

【作者基本信息】 华中农业大学 ， 作物栽培学与耕作学， 2014， 博士

【摘要】 水稻是最重要的粮食作物之一,全球半数以上人口以水稻为主食。水稻又是耗水量最大的农作物,干旱胁迫严重影响水稻的产量和品质。全球气候变化增加了水旱灾害发生频率,进一步加深了干旱胁迫对水稻生产和人类粮食安全的威胁。因此,水稻抗旱性研究已成为稻作科学研究的热点之一。迄今国内外关于干旱胁迫与水稻产量的研究相对较多,而关于干旱胁迫对水稻品质的影响的研究则相对较少,尚缺乏系统性研究。本文以不同年份(2006-2008年)、不同地点(湖北武汉和海南陵水)、不同干旱胁迫强度(中度干旱：大田试验,37个供试品种；重度干旱：具移动式雨棚田间试验,18个供试品种)共6组田间实验的米质分析数据,对干旱胁迫与稻米品质性状的关系进行了系统研究,进而利用可调节土壤含水量的PVC管进行灌浆结实期干旱胁迫盆栽实验,定量分析了干旱胁迫对水稻胚乳中Wx基因表达与直链淀粉含量的动态变化。主要研究结果如下：1.对6组田间实验的稻谷加工品质(糙米率、精米率和整精米率)、外观品质(粒形、垩白粒率和垩白度)、蒸煮和营养品质(胶稠度、糊化温度、直链淀粉含量和蛋白质含量)的方差分析表明,不同年份、不同地点、不同干旱胁迫强度与不同品种间的互作效应都达到极显著水平。表明水分胁迫对稻米品质性状的影响存在基因型差异,同时与其他环境因子有关。2.干旱胁迫对水稻加工品质性状有不利影响,干旱胁迫下糙米率和精米率相对比较稳定,但整精米率显著下降。6次试验的干旱胁迫与对照(正常水分管理)处理下稻米的平均糙米率分别为77.31%-80.80%和77.30%-80.65%,精米率分别为65.17%-70.70%和65.71%-70.50%,其中5次试验的处理间差异均不显著,但2007年海南试验中度干旱胁迫处理的稻谷平均糙米率(79.31%)和精米率(67.71%)比对照糙米率(80.30%)和精米率(68.73%)下降约1%,分别达到显著和极显著水平。不同试验的干旱胁迫与对照处理下稻谷的平均整精米率分别为55.97%-63.54%和61.42%-64.14%,6次试验干旱胁迫处理的整精米率均低于对照,其中5次试验干旱胁迫处理整精米率的降低达到显著或极显著水平。3.干旱导致外观品质各个指标的变异性增加,其中粒形因干旱导致的变异性较小,而垩白粒率和垩白度的变异较大。6次试验的干旱胁迫与对照处理下稻谷的平均粒宽分别为2.0-2.4mm和2.2-2.4mm,差异均不显著。不同试验的干旱胁迫与对照处理下稻谷的平均粒长分别为6.0-6.5mm和6.5-6.6mm,干旱胁迫处理的粒长均低于对照,其中4次试验达到极显著水平。不同试验的干旱胁迫与对照处理下稻谷的平均长宽比分别为2.8-3.0和2.8-2.9,均未达到显著水平。6次试验的干旱胁迫与对照处理下稻米的平均垩白粒率分别为21.4%-47.3%和28.0%-50.8%,垩白度分别为3.2%-15.9%和9.9%-22.9%,处理间的差异均达到显著或极显著水平。4.干旱胁迫对稻米蒸煮品质和营养品质亦有一定影响。干旱胁迫下稻米直链淀粉含量降低,而蛋白质含量有所提高,重度干旱胁迫下稻米碱消值减小(糊化温度提高)和胶稠度降低。6次试验的干旱胁迫与对照处理下稻米的平均直链淀粉含量分别为16.6%-17.3%和17.2%-17.7%,干旱胁迫处理的直链淀粉含量均低于对照,其中4组实验干旱胁迫处理的直链淀粉含量的降低达到极显著水平。6次试验的干旱胁迫与对照处理下稻米的平均蛋白质含量分别为8.9%-9.9%和9.4%-10.8%,6次试验干旱胁迫处理的蛋白质含量均高于对照,其中5次试验干旱胁迫处理蛋白质含量的增加达到极显著水平。6次试验的干旱胁迫与对照处理下稻米的平均碱消值分别为6.5-6.8和6.5-6.9,中度干旱胁迫对碱消值的影响不显著,而重度干旱胁迫则极显著地降低了稻米的碱消值。2组重度干旱胁迫试验的干旱胁迫与对照处理下稻米的平均胶稠度分别为41.8-44.0mm和50.0-53.0mm,胶稠度降低均达到极显著水平。5.干旱胁迫对稻谷品质的影响存在基因型差异,不同品种的品质性状变化幅度存在显著差异。例如,在不同干旱胁迫处理条件下,C1027的整精米率、矮三芦的垩白度、以及PRIMAVERA的直链淀粉含量变化相对较小。6.胚乳中Wx基因的表达模式与直链淀粉积累模式基本一致。胚乳中Wx基因的表达量在开花后第5天显著增加,并在第10天达到最高值,然后逐渐下降,这与籽粒灌浆期直链淀粉的积累速率变化一致。灌浆期干旱胁迫处理下,胚乳中Wx基因的相对表达量减小,致使直链淀粉的合成和累积速率降低,最终导致稻米直链淀粉含量的降低。表明干旱胁迫通过改变相关基因的表达影响稻谷品质性状。更多还原

【Abstract】 Rice is one of the most important food crops. It is the staple food for more than half of the global population. Rice is a crop with the largest water consumption and drought stress can cause severe lose in yield and adversely affect grain quality. Global climate change has increased frequency of flood and drought disasters, and drought stress has become a serious threat to rice production and human food security. Therefore, rice drought resistance study has become one of hot topics in rice science. Many researches have been done on drought stress and rice yield in China and abroad. However, there are few researches on the effects of drought stress on rice grain quality, and no systematic research has been reported up to present. Using grain quality data of a total of6sets of experiments in different years (2006-2008), different locations (Wuhan, Hubei province and Lingshui, Hainan province), different drought stress intensity (moderate drought: field trials,37varieties tested; severe drought:field tests with movable rain-out shelter,18varieties tested), systematic studies on the relationships between drought stress and rice quality traits have been made in this thesis, In addition, using PVC pipes with adjustable soil moisture content, a pot experiment with drought stress during grain filling stage was done and quantitative analysis was made on the dynamic changes of Wx gene expression and amylose content in rice endosperm. The main results were as follows:1. Variance analysis on6sets of different field tests on rice processing quality traits (brown rice rate, white rice rate, and whole polished rice rate), exterior appearance quality traits (grain shape, chalky rice rate and chalkiness degree), cooking and nutrition qualities (gel consistency, gelatinization temperature, amylose content and protein content) showed that there are extremely significant interaction effects between different years, different locations, different drought stress intensity and different varieties. This indicates the effect of water stress on rice quality traits has genotypic differences, and it is also related to other environmental factors.2. Drought stress has negative effects on rice processing quality traits. The brown rice percentage and white rice percentage are relatively stable under drought stress, but the whole polished rice rate dropped significantly. Under drought stressed and control (normal water management) treatments, the average brown rice percentages ranged from77.31%to77.31%and77.30%to80.65%respectively, and polished rice rate ranged from65.17%to70.70%and65.71%to70.50%respectively in6sets of drought stress tests. No significant difference has been found in5sets of tests. However, both brown rice rate (79.31%) and white rice rate (67.71%) under moderate drought stress were about1%lower than the brown rice rate (80.30%) and white rice rate (68.73%) of control in Hainan trial in2007, which reached significant and extremely significant levels respectively, the average whole polished rice rate ranged from55.97%to63.54%and61.42%64.14%respectively under drought stressed and control treatments, the whole polished rice rates under drought stress were lower than that of control. The differences between the treatments in5out of the6sets of experiments reached significant or extremely significant levels.3. Drought increased the variability of all exterior appearance traits. The variability of grain shape caused by drought is relatively small, while that of chalkiness is larger. Average grain width under the drought stressed and control treatments in6sets of tests were2.0-2.4mm and2.2-2.4mm respectively, no significant difference was detected between the treatments. Average grain length under drought stressed and control treatments were6.0-6.5mm and6.5-6.6mm. The grain length under drought stress were lower than that of control, and4out of the6trials reached extremely significant level. Average length/width ratio under drought stressed and control treatments were2.8-3.0and2.8-2.9respectively, no significant difference was detected between the treatments. Average chalky rice rate under drought stressed and control treatments were21.4%-47.3%and28.0%-50.8%respectively. And average chalkiness degree under the drought stress and control treatments were3.2%-15.9%and9.9%22.9%respectively. The differences in both chalkiness indexes reached significant or extremely significant levels.4. Drought stress also has an impact on rice cooking and nutrition traits. Amylose content decreased while protein content increased under drought stress. Alkali value decreased (gelatinization temperature increased) along with decreased gel consistency under severe drought stress. Average amylose content under drought stressed and control treatments were16.6%-17.3%and17.2%17.7%respectively. The average amylose contents under drought stress were lower than that of control, and4out of the6trials reached extremely significant level. Average protein content under drought stressed and control treatments were8.9%-9.9%and9.4%-10.8%. The average protein contents under drought stress were higher than that of control, and5out of the6trials reached extremely significant level. The average alkali value were6.5-6.8and6.5-6.5under drought stressed and control treatments, no significant difference was detected between moderate drought stressed and control treatments, while extremely significantly reduction in alkali value were found in2trials with severe drought stress. Average gel consistency under severe drought stressed and control treatments were41.8-44.0mm and50.0-53.0mm respectively, the reduction of gel consistency has reached extremely significant level.5. Genotyic difference was found in the impacts of drought stress on rice grain quality. There are significant differences among the tested varieties in their range of variation in grain quality traits. For example, relatively small changes were observed in whole polished rice rate of C1027, chalkiness degree of Aisanlu, and amylose content of PRIMAVERA under different drought stress conditions.6. The Wx gene expression patterns in endosperm are generally consistent to the amylose accumulation patterns. Wx gene expression in rice endosperm significantly increased in the5th day after flowering, and reached to its maximum in the10th day, and then gradually declined, which was consistent to the amylose accumulation during grain filling stage. Drought stress treatments decreased the relative expression quantity of Wx gene in endosperm and reduced the synthesis and accumulation rate of amylose, and*eventually resulted in a reduction of amylose content in rice. This indicates that drought stress affects grain quality traits via regulating the expression of related genes.更多还原