In order to study the control methods of water-nitrogen coupling on low temperature chilling damage of direct-seeded early indica rice at the seedling stage, the cold-tolerant cultivar Xiangzaoxian 6 and coldsensitive cultivar Zhongjiazao 17 were used as materials, and seven treatments including ambient temperature no nitrogen（CK）, low temperature plus no nitrogen（LT-0N）, low temperature plus low nitrogen（LT-LN）, low temperature plus high nitrogen（LT-HN）, low temperature flooding plus no nitrogen（LTF-0N）, low temperature flooding plus low nitrogen（LTF-LN） and low temperature flooding plus high nitrogen（LTF-HN） were established for five days to analyse the physiological characteristics such as agronomic characters, antioxidant enzyme activities, osmotic regulation substances, nitrogen metabolism-related enzymes and photosynthase activities, endogenous hormone contents of rice seedlings. The results showed that water-nitrogen coupling treatments could alleviate the injury caused by low temperature chilling damage to direct-seeded early indica rice, compared with LT-LN treatment, the seedling height, root number, maximum root length, fresh weight, dry weight, T1（the first leaf from top） leaf length and T3（the 3rd leaf from top） leaf length of cold-sensitive cultivar Zhongjiazao 17 significantly increased after five days of LT-HN treatment; compared with LTF-0N treatment,the root number, root length, fresh weight and T3 leaf length of different tolerant cultivars increased significantly after five days of LTF-LN and LTF-HN treatments, the number of roots and fresh weight were higher in LTF-LN than that in LTF-HN. Compared with LT-0N treatment, LT-HN and LTF-LN treatments significantly increased the nitrogen metabolism-related enzymes, photosynthase activities, nitrate nitrogenin, chlorophyll and endogenous growth-promoting hormone contents in leaves of the cold-sensitive cultivar Zhongjiazao 17, but decreased leaf antioxidant enzyme activities, soluble protein, malonic dialdehyde, and endogenous growthinhibiting hormones contents, high nitrogen and flooding low nitrogen treatments could alleviate low temperature cold damage in seedlings of direct-seeded early indica rice.

In order to investigate the effects of weeds control on the yield formation and quality of doublecropping direct-seeded high-quality late indica rice, high-quality inbred rice Meixiangzhan 2（MXZ2） and highquality hybrid rice Taiyou 871（TY871） were used as materials, the field experiment with two treatments of chemical herbicide weeding（CW） and non-weeding（NW） were conducted. Compared with NW treatment, the grain yields of MXZ2 and TY871 under CW treatment increased by 75.71% and 76.00%, respectively, mainly due to the significant increase in the effective panicles and the spikelets per panicle. Compared with NW treatment, CW treatment could generally improve the processing quality and appearance quality of direct-seeded rice, and the gel consistency significantly reduced by 7.65% and 8.03%, respectively. CW treatment significantly increased the starch peak viscosity, hot viscosity, breakdown value and final viscosity of direct-seeded late rice,decreased the setback value, and improved the palatability of cooked rice. However, NW treatment significantly reduced the consistence of MXZ2, and did not differ on the chalkiness grain rate, amylose content and protein content. In all, spraying chemical herbicides for weed control significantly increased the yield of direct-seeded high-quality late rice, and it could significantly improve the processing quality of direct-seeded high-quality late rice, while reduced the chalkiness and gel consistency of rice. In addition, chemical weed control significantly affected the values of rice starch RVA profiles, which was beneficial to the improvement on cooking and eating quality.

Late-season indica rice frequently encounters low temperature (LT) along with low light (LL) after heading in southern China, which deteriorates the grain quality by altering starch quality. However, the detailed effects on starch properties of these stressors remain unclear. Herein, two indica rice cultivars with good and poor grain quality were grown under control (CK), LT, and LT + LL conditions after heading and the structural and physicochemical properties of their starch were evaluated. Compared with CK, LT and LT + LL worsened thermal and pasting properties of starch in the two cultivars, mainly because they increased branch chain branching and A chain (DP <= 12), and decreased average branch chain length and crystallinity. Compared with LT, LT + LL deteriorated the pasting properties of the poor-quality cultivar, such as reducing breakdown (BD), final and peak viscosity, which mainly owing to decreasing the starch branching and crystallinity degrees, and increasing the small starch granules (d < 10 mu m). Gelatinization enthalpy and BD both had significant and positive correlations with amylose content, the ratio of amylose and amylopectin, B3 chain and crystallinity. Taken together, these results suggest that LT and LT + LL during grain filling can deteriorate the physicochemical properties of starch in late-season indica rice cultivars by disrupting starch multilevel structure, especially upon LT + LL. In particular, while poor-quality cultivar had poorer physicochemical properties, the good-quality cultivar had poorer thermal properties under LT + LL.

Low temperature (LT) chilling damage often occurs at the seedling stage of rice growth, especially direct-seeded early indica rice, and flooding can alleviate the damage caused by LT chilling at the rice seedling stage. However, few studies have elucidated the molecular mechanism by which suitable flooding alleviates LT stress-induced damage. Therefore, LT, LT plus flooding (LTF) and control (CK) treatments were established at 8 °C for 3 days to determine the phenotype, agronomic traits and transcriptomic of direct-seeded early indica rice at the seedling stage. The results showed that compared with LTF, the seedling height, root number, fresh weight, dry weight and T3 (the 3rd leaf from the top) leaf length significantly decreased after LT treatment; LTF could reduce the damage of LT to the agronomic characters of rice seedlings. The physiological characteristics showed that compared with LT, LTF significantly decreased soluble protein content and CAT activity. Transcriptomic profiling showed that 5934 DEGs were identified from the rice leaves between the LT and CK comparison groups; 7658 DEGs were identified between the LTF and CK; and 2697 DEGs were identified between the LT and LTF treatment. In biological process, the ‘metabolic process’ was the most enriched subcategory. In cellular components, the three most enriched subcategories were ‘cell’, ‘cell part’ and ‘organelle’. ‘Binding’ was the most enriched subcategory in molecular function. Differentially expressed genes (DEGs) were significantly enriched in photosynthesis, carotenoid biosynthesis, flavonoid biosynthesis, glycolysis gluconeogenesis, glycine, serine and threonine metabolism and plant hormone signal transduction pathways. Photosynthesis, energy metabolism and signal transduction pathway play important roles in flooding mitigation of LT stress. The results of this study may help to elucidate changes in physiological characteristics and gene expression through which flooding mitigates LT stress.

【Objective】 To elucidate the response and mechanism of starch accumulation and its component contents of double-cropping indica rice cultivars to the future warming conditions. 【Method】 With Xiangzaoxian 45（Inbred indica rice） and Qiliangyou 2012（Hybrid indica rice） as early rice, and Jiuxiangnian（Inbred indica rice） and Taiyou 398（Hybrid indica rice） as late rice, a free-air temperature increasing facility（FATI）（1.4-1.5 ℃ increase in early rice, 2.0-2.3 ℃ increase in late rice） was used to study the effects of warming throughout the growth period on activities of enzymes involved in starch synthesis and accumulation of double-cropping indica rice. 【Result】 There was no significant change in the starch contents and amylopectin contents in rice, but the amylose content and the proportion of amylose content were reduced under warming conditions. Among them, the amylose content of Qiliangyou 2012 and Jiuxiangnian decressed by 4.2% and 3.4%, respectively. Compared with the ambient treatment, warming increased the total starch and amylose accumulation in grains at the early growth stage of grain filling（7-14 d after heading）, but the effect on the amylose accumulation in late rice was longer than that in early rice. This was mainly related to the varying degrees of increased activity of key enzymes in starch synthesis. Under warming conditions, the activity of adenosine glucose diphosphate pyrophosphorylase（ADGPase） in grains at grain filling stage of early rice increased first and then decreased, while that of late rice increased gradually. Warming decreased the activity of bound starch synthase（GBSS） in grains of early rice 14 d after heading and 7 d after heading of late rice, but significantly increased GBSS activity in grains of late rice during late heading stage（21, 28 d after heading）. The soluble starch synthase（SSS） activity in Qiliangyou 2012 and Jiuxiangnian 7 and 14 days after heading was significantly increased by warming. The activity of starch branching enzyme（SBE） in late rice grains followed an increasing trend under the warming treatment. In general,the effects of warming on ADGPase and GBSS activities in late rice grains were significantly greater than those in early rice. 【Conclusion】 FATI significantly increased the activities of ADGPase, GBSS and SSS enzymes in the grains of double-cropping indica rice at the early stage of grain filling（7-14 d after heading）, thereby improving the synthesis and accumulation of total starch and its components in grains of double-cropping indica rice at the early stage of grain filling.The effect of warming on the key enzymes of starch synthesis varied with seasons and varieties.

Nitrate reductase (NR) is a key enzyme for nitrogen assimilation in plants, and its activity is regulated by posttranslational phosphorylation. To investigate the effects of dephosphorylation of the NIA1 protein on the growth and the physiological and biochemical characteristics of rice under different forms of nitrogen supplies, the phenotypes, nitrogen metabolism and reactive oxygen metabolism were measured in NIA1 phosphorylation site-directed mutant lines (S532D and S532A), an OsNia1 over-expression line (OE) and Kitaake (wild type, WT). Compared with WT and OE, S532D and S532A have stronger nitrogen assimilation capacities. When ammonium nitrate served as the nitrogen source, the plant heights, dry weights of shoots and chlorophyll (Chl) contents of S532D and S532A were lower than those of the WT and OE, whereas hydrogen peroxide (H2O2), malondialdehyde (MDA) and nitrite contents were higher. When potassium nitrate served as the nitrogen source, the plant heights, dry weights of shoots and Chl contents of S532D and S532A were higher than those of the WT and OE, there were no significant differences in the contents of H2O2 and MDA in the leaves of the test materials, and the difference in nitrite contents among different lines decreased. When ammonium sulfate served as the nitrogen source, there were no significant differences in the physiological indexes of the test materials, except NR activity. Compared with ammonium nitrate and ammonium sulfate, the content of NH4+-N in the leaves of each plant was lower when potassium nitrate was used as the nitrogen source. The qPCR results showed that OsGS and OsNGS1 were negatively regulated by downstream metabolites, and OsNrt2.2 was induced by nitrate. In summary, when ammonium nitrate served as the nitrogen source, the weak growth of NIA1 phosphorylation site-directed mutant lines was due to the toxicity caused by the excessive accumulation of nitrite. When potassium nitrate served as the nitrogen source, the assimilation rates of nitrate, nitrite and ammonium salt were accelerated in NIA1 phosphorylation site-directed mutant lines, which could provide more nitrogen nutrition and improve the tolerance of rice to ammonium nitrogen deficiency. These results could provide a possible method to improve the efficiency of nitrogen utilization in rice under low-nitrogen conditions.

Nitrate reductase (NR) is an important enzyme for nitrate assimilation in plants, and post-translational phosphorylation regulates NR activity. To evaluate the impact of the dephosphorylation of nitrate reductase 1 (NIA1) protein on NR activity, nitrogen metabolism and plant growth, NIA1 phosphorylation site directed mutant lines (S532D and S532A) and an OsNia1 over-expression line (OE) were constructed, and the phenotype, NIA1 protein and its phosphorylation level, NR activity, nitrate metabolism and reactive oxygen metabolism of the transgenic lines were analysed. Exogenous NIA1 protein was not phosphorylated in S532D and S532A mutant lines, and their NR activities, activity states of NR and assimilation efficiencies of NO3−-N were higher than those in Kitaake (WT) and OE. The changes in these physiological and biochemical indexes in the OE line were less than in S532D and S532A compared to WT. These results suggest that the removal of transcriptional level control had little effect on nitrogen metabolism, but the removal of post-translational modification had a profound effect on it. With the removal of NIA1 phosphorylation and the improvement in the nitrate assimilation efficiency, the plant height and chlorophyll content of S532D and S532A decreased and the hydrogen peroxide and malondialdehyde contents of rice seedlings increased, which may be related to the excessive accumulation of nitrite as an intermediate metabolite. These results indicated that the phosphorylation of NR may be a self-protection mechanism of rice. The reduced phosphorylation level of nitrate reductase improved the assimilation of nitrate, and the increased phosphorylation level reduced the accumulation of nitrite and prevented the toxic effects of reactive oxygen species in rice.

对6个优质晚籼稻品种在江西北部上高、中部吉安、南部赣州3个不同生态区下产量及品质的变化,灌浆结实期温度与产量、稻米品质的关系进行了研究,以明确优质晚籼稻的生态适应性和稳产性.结果表明,随着纬度降低,各品种产量逐渐降低,外观品质、营养品质变优;直链淀粉含量下降,峰值粘度、崩解值以及糊化温度增加.优质晚籼稻产量主要受齐穗-成熟阶段的日最高温影响,外观品质主要受齐穗-成熟阶段的日最低温影响,直链淀粉含量主要受齐穗-齐穗后20 d的日最低温影响.优质晚籼稻在赣北地区种植能发挥产量优势,而在赣南地区种植则具有品质优势.

An increased planting density and decreased nitrogen (N) rate combination may obtain a stable yield and enhance N utilization. However, the effects of an increased planting density and decreased N rate combination on the yield and nutrient utilization in different ecological regions are unclear. The aim of this research was to assess the interactive impacts of the N rates and planting densities on double cropping rice yields and nutrient utilization in two ecological regions in field experiments during 2018 and 2019. The results showed that, at Shanggao, increased planting densities of 67% and 200% compensated for the biomass, nutrient uptake and yield losses from N application reductions of 20% and 27% and increased the nutrient utilization of the early and late seasons. However, at Xingguo, compared with the N2D1 treatment (165 kg ha−1 with 57 plants per m2), the late rice yield under the N1D2 treatment (120 kg ha−1 with 114 plants per m2) decreased by 6.71% and 5.02% in 2018 and 2019, respectively. The photosynthetic rate and nutrient uptake were likely related to the positive interaction on the double cropping rice yield in the two ecological regions. Our results indicate that dense planting is a feasible cultivation strategy to decrease N inputs for double cropping rice, but the low soil nutrient supplies negatively affect stable yields in different ecological regions.

High temperature (HT) accompanied with strong light (SL) often occurs in early indica rice production during grout filling stage in southern China, which accelerates grain ripening. Two indica rice cultivars with different amylose content (Zhongjiazao17, ZJZ17, high amylose content; Xiangzaoxian45, XZX45, low amylose content) were grown under control (CK), HT, and HT+SL conditions during grout filling to determine the effects on grain yield and quality of rice. The results showed that compared with CK, HT and HT+SL significantly reduced the 1000-grain weight and filled grain rate whether in high or low amylose content early indica rice cultivars during grout filling, resulting in a significantly lower grain yield. Meanwhile, HT and HT+SL significantly decreased the milled rice rate, brown rice rate and head rice rate, whereas significantly increased chalky rate and chalky degree; and breakdown decreased and setback, pasting temperature increased in the cultivars, leading to the poor processing, appearance and cooking and eating quality of early indica rice cultivars. Compared with HT, the yield of ZJZ17 was significantly decreased under HT+SL, due to the lower 1000-grain weight. However, the effect of HT+SL on rice quality varied in the cultivars. In general, the yield and rice quality of ZJZ17 were relatively poor under HT+SL. Our results suggested that HT and HT+SL during grout filling had significant damage to the yield and quality of early indica rice cultivars, especially HT+SL, while the high amylose cultivar ZJZ17 showed a higher negative effect under HT+SL.

为探究抽穗扬花期低温胁迫对不同晚稻品种生理特性的影响,本研究以2个耐冷品种(岳优27、昌粳225)和2个冷敏感品种(泰丰优208、黄华占)为试验材料,于抽穗扬花期在人工气候室进行低温处理,分析其光合特性、抗氧化酶活性、穗部性状与稻米品质等.结果表明,随着低温处理时间的延长,各晚稻品种花粉活力均降低,除过氧化氢酶(CAT)外的抗氧化酶活性、丙二醛(MDA)及可溶性蛋白(SP)含量都有不同程度的增加,其中超氧化物歧化酶(SOD)活性和SP含量呈先增加后降低的趋势,而CAT活性呈先降低后增加的趋势,结实率和千粒重呈降低趋势.低温胁迫也会影响稻米品质及稻米RVA值,具体表现为随着低温处理时间的延长,各晚稻品种精米率降低,垩白粒率、垩白度和胶稠度增加,直链淀粉与粗蛋白含量呈先增加后降低的趋势;峰值黏度、崩解值逐渐降低,冷胶黏度、回复值和消减值逐渐升高.相较于冷敏感品种泰丰优208和黄华占,耐冷品种岳优27和昌粳225的抗氧化酶活性和SP含量较高,MDA含量较低;结实率和千粒重降低幅度较小,花粉活性降低幅度也较小,其中在第5天昌粳225降幅最小,为4.38％;稻米品质中精米率、垩白粒率、胶稠度、直链淀粉含量和蛋白质含量变化幅度较小,而垩白度增加幅度较大,RVA谱中峰值黏度降低幅度较大,热浆黏度反应较慢,而冷胶黏度和回复值较先达到最大值,崩解值和消解值的变化幅度较小.综上,耐冷品种岳优27和昌粳225抽穗扬花期相较于冷敏感品种泰丰优208和黄华占表现出较强耐受低温胁迫的能力.本研究结果可为抽穗扬花期耐低温双季晚稻的选育与栽培提供一定的理论参考.

为探究施氮量和播种密度相互作用对机直播双季稻(Oryza sativa L.)产量与氮素利用率的影响,2018-2019以优质稻柒两优2012与美香占2号为材料进行试验,设4个施氮量(早稻分别为0、120、150、180 kg·hm-2,晚稻分别为0、120、165、210 kg·hm-2,早、晚稻均以N0、N,、N2、N3表示)与3个机直播密度(早稻分别为86、143、200粒·m-2,晚稻分别为57、114、172粒·m-2,早、晚稻均以S1、S2、S3表示)分析双季稻群体生长发育、产量、产量构成及氮素吸收利用的特征.结果表明,施氮与增密促进双季稻增产,早、晚稻分别在N3和N2时产量最高,较N1增产11.41％～12.32％和8.58％～9.21％;早稻S2与S3分别较S1增产8.71％～10.38％和8.33％～10.89％,晚稻增产6.33％～8.11％和6.78％～8.56％;早稻 N2S2与 N3S2间产量无显著差异.施氮与增密的增产因素是机直播双季稻较高的抽穗后干物质量、叶面积指数及氮素积累量,在分蘖期具备碳、氮物质积累优势.机直播双季稻中,N2S2的抽穗后叶面积指数、干物质量及氮素积累量较高,同时具备较高的氮素农学利用率、氮素生理利用率及氮素吸收利用率.因此,机直播早、晚稻的施氮量与直播密度组合分别为150 kg·hm-2与143粒·m-2处理、165 kg·hm-2与114粒·m-2处理时,可以达到增产与氮高效协同.本研究为机直播双季稻密植与优化氮素管理提供了理论依据.

Low temperature (LT) and extreme humidity constantly threaten direct-seeded early indica rice production during the seedling stage. However, the physiological mechanism and damage induced by LT combined with high/low humidity are still unclear. A pot experiment was conducted to study seedling growth performance and physiological traits of two indica rice cultivars (i.e., the cold-sensitive cultivar Zhongjiazao17 and the cold-tolerant cultivar Xiangzaoxian6) under LT plus low humidity treatment (LL, 8 degrees C; relative humidity, 25 %), LT plus high humidity treatment (LH, 8 degrees C; relative humidity, 95 %) and a control treatment (CK, 25 degrees C; relative humidity, 75 %). The results showed that seedling height, rubisco concentration, and APX, PDH and alpha-KGDH activity significantly decreased under LL and LH compared to CK, and large decreases were found under LH, especially for the cold-sensitive cultivar Zhongjiazao17. However, LH significantly increased the reactive oxygen species O-2(-) and the soluble protein, GSH and ABA concentrations. Moreover, the APX, PDH and alpha-KGDH activities, rubisco and chlorophyll concentrations, and GA(3) induced by LH also significantly decreased after treatment. The differences in physiological traits of Zhongjiazao17 after LL and LH were significant. During three days of recovery, the physiological activity of the two cultivars under LL tended to recover to the level of CK, and the cold-tolerant cultivar showed reduced damage caused by humidity-cold combined stress. The results suggested that the double stress of low temperature plus high humidity rather than low temperature plus low humidity could decrease the growth performance by hampering photosynthetic and respiratory systems and altering the endogenous hormonal regulation of direct-seeded early indica rice, whereas it could significantly enhance the antioxidant protective system derived from the osmotic damage of leaves.

Precision hill-drop direct seeding via mechanical drilling is a novel planting pattern that provides benefits such as high grain yields and lodging resistance in direct-seeded rice in South China, however, the effects of different fertilization methods on yield performance and lodging resistance capacity under mechanical direct seeding systems are still unclear. Hence, a field experiment was conducted over two years with two early indica cultivars to determine the grain yield formation and lodging characteristic of the rice plants under three fertilization methods, including furrow ridging fertilization (FRF), surface fertilization (SF), and whole-layer fertilization (WLF). We found that FRF significantly increased the grain yields of the two cultivars by 6.04 %-28.25 % compared with SF and WLF; this result was attributed to the high panicle and biomass production. FRF also significantly improved the seedling emergence rate of the early indica rice cultivars and increased the aboveground total dry weight and harvest index. In addition, compared with SF and WLF, FRF significantly enhanced the stem lodging resistance of direct-seeded rice cultivars and reduced the lodging index, especially at the third internode. The physical parameters of the stem, including the internode length, thickness and wall thickness, dry weight of internode, and lignin content of the test internodes, improved under FRF due to the high associated breaking-resistance strength and lodging index. These results indicate that furrow ridging fertilization was beneficial for increasing the grain yield and lodging resistance of direct-seeded early indica rice.

调整播期可以改变水稻生长发育中的环境气候条件,对于充分利用自然资源、调节水稻生育进程及提升产量和品质具有重要意义.为明确南方双季晚籼稻优质丰产与温光资源相适应的播种期,本研究选用万象优华占、象牙香珍和美香占2号等3个晚籼稻品种为试验材料,设置6月10日、6月20日、6月30日共3个播期,研究播期对双季晚籼稻品种温光资源利用、产量及稻米品质的影响.结果 表明,随着播期推迟,供试品种在不同生育阶段日均温度和有效积温、全生育期和齐穗至成熟期阶段的日照时数均呈递减趋势,而全生育期天数无明显变化;产量以6月20日播种的最高,早播(6月10日)会导致显著减产,而晚播(6月30日)虽然也会导致减产,但差异不显著;随播期推迟,晚籼稻品种加工品质、外观品质和蒸煮品质变优,但不利于改善食味品质,对营养品质无显著影响.在南方双季晚籼稻实际生产中,不建议早播,应根据品种不同进行适期播种或适当晚播,能使水稻更合理有效地利用温光资源,有利于协调水稻高产和品质提升.

为明确南方晚粳稻适宜的氮肥运筹,设计3个不同施氮水平,分别为N210(210 kg/hm2)、N255(255 kg/hm2)及N300(300 kg/hm2),基肥、分蘖肥、穗肥的施氮比例为5∶2∶3,并在N255施氮水平下设置4种不同基肥、分蘖肥、穗肥的施氮比例,分别为BR6(6∶2∶2)、BR5 (5∶2∶3)、BR4(4∶2∶4)及BR3 (3∶2∶5),研究氮肥运筹对晚粳稻产量、干物质生产及氮素利用率的影响.结果 表明,随施氮量增加,晚粳稻产量先增后降,与N255处理相比,N300及N210处理分别降低1.8％～2.0％和6.0％～7.2％.随施氮量增加,晚粳稻氮素总积累量增加,抽穗至成熟期氮素积累量及该阶段占总氮素积累量的比例、氮素偏生产力及氮素收获指数均降低.随基肥施氮比例降低,晚粳稻产量、氮素偏生产力及氮素收获指数均先增后降,镇稻11号和甬优2640分别在BR5和BR4处理时最高,但两品种在这2个处理间的差异均不显著.随基肥施氮比例降低,晚粳稻成熟期氮素积累量、抽穗期至成熟期氮素积累量及该阶段积累量占总积累量的比例均增加.在江西等双季稻区,建议施氮量以255 kg/hm2,基肥、蘖肥、穗肥的施氮比例以(5∶2∶3)～(4∶2∶4)为宜,具体因品种特性而异.

Direct seeding of rice has become a main planting method due to the low labor input and high economic benefit in South China. Dry direct seeding (DDS) has been widely used for single-season rice planting establishment. However, few studies have examined the performance of early-season indica rice under mechanical dry direct seeding. A two-year field experiment was conducted with two indica rice cultivars (i.e., Zhongjiazao 17 and Zhuliangyou 819) to study lodging characteristics and grain yield formation under DDS, flooded direct seeding (FDS) and wet direct seeding (WDS) patterns. The results showed that the annual grain yield in DDS was higher by 14.42–26.34% for cultivar ZLY819 and 6.64–24.58% for cultivar ZJZ17 than in WDS and FDS, respectively, and these increases were mainly attributed to the improvement of the panicles. The DDS pattern significantly increased the seedling emergence rate of early indica rice cultivars, and increased total dry weight and crop growth rate. Meanwhile, shorter basal internodes, better stem diameter and stem wall thickness and lower lodging index were found in DDS in contrast to FDS and WDS. In particular, DDS improved the stem lodging resistance. Our results suggested that the appropriate direct seeding method was beneficial for improving the grain yield and lodging resistance of early indica rice.

为了明确不同直播方式对早晚兼用双季籼稻产量和稻米品质的影响,该研究以常规早籼稻湘早籼45号和杂交晚籼稻泰优398为材料,进行早晚双季直播种植,比较人工撒直播(AS)和同步开沟起垄精量穴直播(PHDD)对早晚兼用双季直播稻出苗、产量和稻米品质的影响.结果表明,与AS相比,PHDD显著提高供试品种的出苗率,早晚季增幅分别为7.4％～14.2％和6.9％～8.0％;PHDD有利于提高供试品种周年产量,2个品种的增产幅度为3.23％～21.66％,其中湘早籼45号早晚2季增产均显著,泰优398为晚季增产显著;从产量构成因素来看,PHDD下供试品种的产量提高主要与有效穗数、每穗粒数有关;PHDD显著提高湘早籼45号早季的精米率、整精米率和垩白度以及泰优398晚季的垩白粒率,显著降低泰优398早季的整精米率及湘早籼45号晚季的垩白粒率、垩白度和蛋白质含量,直链淀粉含量无显著差异;PHDD显著提高泰优398晚季米粉的峰值黏度、热浆黏度、崩解值和最终黏度,显著降低糊化温度.总体来说,PHDD有利于提高优质水稻品种周年产量,主要与穗粒数协调有关,增产途径因品种和季节而异,同时显著改善湘早籼45号早季加工品质及晚季外观品质,降低泰优398的早季加工品质及晚季外观品质,但改善其晚季蒸煮食味品质,PHDD下晚季直播稻稻米品质改善明显.研究结果可为南方双季直播籼稻优质丰产栽培提供理论依据.

The effects of water irrigation management including conventional irrigation (CK), constant flooding irrigation (CFI) and alternate wetting and drying (AWD) on starch structure and physicochemical properties of two indica rice cultivars with good- and poor-quality were evaluated in the field condition with two years. The results showed that AWD could significantly increase peak viscosity, breakdown and gelatinization temperature, decreased setback and gelatinization enthalpy in two indica rice cultivars. However, starch granule size and amylopectin chain length distribution were differed the trends in the rice cultivars and treatments. AWD reduced starch granules size and amylopectin short chain, especially for large starch granules, but increased medium and long chain, which might contribute to better thermal stability and pasting viscosity for good-quality cultivar. Our study indicated that water irrigation management affected starch structure and physicochemical properties of indica rice starch, and would provide favorable information for improvement of rice starch in food industry.

[目的]水分管理影响着水稻的颖花分化与产量形成,旨在研究不同水分灌溉方式对南方优质晚籼稻稻穗枝梗和颖花发育特性及产量形成的影响.[方法]以优质籼稻泰优871和非优质籼稻荣优华占(对照)为试验材料,设置常规灌溉(CK)、持续淹水灌溉(CFI)和间歇灌溉(AWD)3种灌溉方式,测定水分灌溉、颖花发育、产量形成等指标.[结果]与CK相比,AWD显著增加供试品种水分利用效率,CFI则显著降低;CFI和AWD处理均提高了供试品种产量,但CFI与AWD差异不显著,品种间趋势一致,CFI增产趋势与有效穗数与每穗粒数提高有关,而AWD增产则是来自每穗粒数和结实率协同提高.从稻穗枝梗和颖花发育特性来看,相比CK、AWD,CFI有利于提高稻穗颖花分化数,主要是因为枝梗与颖花分化较高,且退化较低,其中泰优871品种一次颖花分化差异显著;AWD相比CK尽管总颖花分化数差异不显著,但可显著减少颖花退化.不同灌溉方式对供试品种二次枝梗及颖花分化影响要大于一次枝梗及颖花,CFI相对增加两品种不同部位一次枝梗上二次枝梗与颖花分化数,且主要体现在稻穗中上部枝梗.[结论]间歇灌溉有利于提高水分利用效率,间歇灌溉与持续淹水灌溉可增加水稻产量,但为增加稻穗枝梗和颖花分化,形成大穗,促进水稻高产高效生产,应注意水稻幼穗分化期采用浅层淹水灌溉.