Effects of nitrogen management on the ratoon crop yield and head rice yield in South USA

Ratoon rice cropping is an important component of the rice cropping system in Texas and south Louisiana,USA,and expanded to Asian countries in 1970.Two field studies were conducted with widely planted rice(Oryza sativa L.)cultivars at Eagle Lake,Texas,USA to determine the effects of nitrogen(N)management in main(first)crop(MC)and ratoon(second)crop(RC)on RC yield.In 2012 and 2013,one cultivar(Presidio)was adopted to determine the effects of RC N management on ratoon yield and head rice yield.In 2016 and 2017,CL153,CL163 and CL272 in addition to Presidio were adopted to examine the effect of MC N management on ratoon yield and head rice yield.N applied at preflood after MC harvest considerably improved RC yield.Application of 99 kg N ha^(–1)at preflood after MC harvest was practically adequate for RC regrowth,development and approaching the yield potential for Presidio.RC could produce quite high average grain yields of 5.90 to 6.53 t ha–1 in 2012 and 2013,respectively.Main crop N rate only significantly affected MC yield;however,given N applied of 99 kg ha^(–1)at preflood after MC harvest,ratoon yield was not significantly affected by MC N rate.Neither the main nor ratoon crop N management had a significant effect on RC head rice yield.Considerable RC head rice yields(55–65%)were observed in all of the four cultivars and 4 years except for CL272 in 2016.These results indicat that without very high N fertilizer application,rice ratoon crop could produce a considerable grain yield and an expectative head rice yield.Rice ratooning could be a practical way to increase rice yields with the minimal input in south Texas and regions with a similar climate.

Regulation of 2-acetyl-1-pyrroline and grain quality in early-season indica fragrant rice by nitrogen and silicon fertilization under different plantation methods

Fragrant rice has a high market value,and it is a popular rice type among consumers owing to its pleasant flavor.Plantation methods,nitrogen(N)fertilizers,and silicon(Si)fertilizers can affect the grain yield and fragrance of fragrant rice.However,the core commercial rice production attributes,namely the head rice yield(HRY)and 2-acetyl-1-pyrroline(2-AP)content of fragrant rice,under various nitrogen and silicon(N-Si)fertilization levels and different plantation methods remain unknown.The field experiment in this study was performed in the early seasons of 2018 and 2019 with two popular indica fragrant rice cultivars(Yuxiangyouzhan and Xiangyaxiangzhan).They were grown under six N-Si fertilization treatments(combinations of two levels of Si fertilizer,0 kg Si ha^(−1)(Si0)and 150 kg Si ha^(−1)(Si1),and three levels of N fertilizer,0 kg N ha^(−1)(N0),150 kg N ha^(−1)(N1),and 220 kg N ha^(−1)(N2))and three plantation methods(artificial transplanting(AT),mechanical transplanting(MT),and mechanical direct-seeding(MD)).The results showed that the N-Si fertilization treatments and all the plantation methods significantly affected the HRY and 2-AP content and related parameters of the two different fragrant rice cultivars.Compared with the Si0N0 treatment,the N-Si fertilization treatments resulted in higher HRY and 2-AP contents.The rates of brown rice,milled rice,head rice,and chalky rice of the fragrant rice also improved with the N-Si fertilization treatments.The N-Si fertilization treatments increased the activities of N metabolism enzymes and the accumulation of N and Si in various parts of the fragrant rice,and affected their antioxidant response parameters.The key parameters for the HRY and 2-AP content were assessed by redundancy analysis.Furthermore,the structural equation model revealed that the Si and N accumulation levels indirectly affected the HRY by affecting the N metabolism enzyme activity,N use efficiency,and grain quality of fragrant rice.Moreover,high N and Si accumulation directly promoted the 2-AP content or affected the antioxidant response parameters and indirectly regulated 2-AP synthesis.The interactions of the MT method with the N-Si fertilization treatments varied in the fragrant rice cultivars in terms of the HRY and 2-AP content,whereas the MD method was beneficial to the 2-AP content in both fragrant rice cultivars under the N-Si fertilization treatments.

Quantitative Trait Loci for Heading Date and Their Relationship with Genetic Control of Yield Traits in Rice (Oryza sativa)

Grain yield and heading date are key factors determining the commercial potential of a rice variety. Mapping of quantitative trait loci （QTLs） in rice has been advanced from primary mapping to gene cloning, and heading date and yield traits have always attracted the greatest attention. In this review, genomic distribution of QTLs for heading date detected in populations derived from intra-specific crosses of Asian cultivated rice （Oryza sativa） was summarized, and their relationship with the genetic control of yield traits was analyzed. The information could be useful in the identification of QTLs for heading date and yield traits that are promising for the improvement of rice varieties.

Plant Ideotype at Heading for Super High-Yielding Rice in Double-Cropping System in South China

The newly released super high-yielding hybrid rice combinations, Yueza 122, Fengyou 428, Peiza 67, and the super high-yielding conventional cultivars, Guangchao 3 and Shengtai 1, were grown in both early and late seasons. The morphological characters of each population were investigated at the heading stage, and the data were analyzed by using ANOVY and other statistic methods. The plant ideal morphological characters at the heading stage were established as follows： 1 ） for the early-season cropping, 90-105 cm plant height; 11-12 tillers per plant; 35-40 em length and 2.1-2.2 cm width of flag leaf; 46-50 cm length and 1.8-2.1 cm width of the second leaf from the top （L2）; 59-64 cm length and 1.4-1.9 cm width of the third leaf from the top （L3）; 7°-14°, 18° and 200-33° for the ideal leaf angles of the flag leaf, L2 and L3, respectively; 2） for the late-season cropping, 90-100 cm plant height; 9-15 tillers per plant; 30-41 cm length and 1.8-2.0 cm width of flag leaf; 53-61 cm length and 1.3-1.8 cm width of L2; 52-58 cm length and 1.2-1.5 cm width of L3; 9°-19°, 15°-37° and 16°-49° for the ideal leaf angles of the flag leaf, L2 and L3, respectively. The main physiological characteristics of these varieties were also analyzed.

Yields and Agronomic Characters of New Rice Hybrids Performed at Pine Bluff, Arkansas

Yields and agronomic characters of 35 new hybrids were tested at Pine Bluff, Arkansas in 2013. These hybrids were developed from 7 female parent sterile lines, UP-1s, UP-3s, 100s, 101s, 105s, 111s, and 113A, and 5 male parent restorer lines, PB2, PB5, PB12, PB13, and PB18. The inbred variety Francis, which is a popular variety in the rice production, was used as the check (CK). Results showed that the yields of 10 hybrids were 20.3% - 31.7% higher than that of CKFrancis. The yields of other 18 hybrids were 10.1% - 19.4% higher than CK, and the yields of rest of the hybrids were 2.5% - 9.2% higher than CK. Hybrid UP-3s/PB5 had the highest yield, 12,983.8 kg/hectare and over check by 31.7%. The yield of hybrid UP-3s/PB18 and 115A/PB18 were 12,333.7 kg/hectare and over check 25%. The yields of hybrid UP-1s/PB12 was 12,324.6 kg//hectare and over check 24.9%. The sterile lines UP-3s, 113A, 105s, and 101s have good combinability and the average grain yields of their hybrids were over CKby 21.5%, 20.34%, 17.2% and 16.2%, respectively. The restorer lines PB18, PB5, and PB12 have good combinability and the average grain yields of their hybrids were over CKby 19.9%, 18.4% and 16.2%, respectively. These results indicated that these top hybrids and their parents of the sterile lines and restorer lines might be used in the hybrid rice breeding and production in the future.

Relationship Between Degree of Starch Gelatinization and Quality Attributes of Parboiled Rice During Steaming

Paddy rice samples were parboiled by soaking at 65℃ for 180 min and steaming at 96℃ for 2–10 min,and then dried to achieve the final moisture content of 11% ± 1%. The degree of starch gelatinization （DSG） andseveral quality attributes （head rice yield （HRY）, color value and hardness） of parboiled rice were measured.Results showed that DSG （46.8%–77.9%）, color value （18.08–19.04） and hardness （118.6–219.2 N） allincreased following steaming. In contrast, the HRY increased （64.8%–67.1%） for steaming times between 2–4min but decreased （67.1%–65.0%） for steaming times between 4–10 min. Linear relations between DSG andcolor value （R2 = 0.87）, and DSG and hardness （R2 = 0.88） were observed. The suitable DSG of parboiled riceleading to the highest HRY was found to be 62.5%, obtained following 4 min of steaming.

Influence of Moisture Content,Variety and Parboiling on Milling Quality of Rice Grains

The effects of moisture content （8%, 10%and 12%）, variety （Tarom and Fajr） and parboiling on milling quality of rice as a function of milling recovery （MR）, head rice yield （HRY）, degree of milling （DOM） and whiteness were investigated. The parboiled grains was prepared with three soaking temperatures of 25 oC, 50 oC and 75 oC and three steaming times of 10, 15 and 20 min. As a result of parboiling, the increasing rates of MR and HRY values were 7.8%and 14.3%for Tarom and 9.8%and 10.0%for Fajr, respectively, and the decreasing rates for DOM and whiteness were 6.6%and 10.8%for Tarom and 6.8% and 10.5% for Fajr, respectively. Moreover, decreasing moisture content to 8%maximized MR （75.8% for Tarom and 74.3% for Fajr） and HRY （65.8% for Tarom and 57.0% for Fajr） while increasing that to 12%revealed maximum values of DOM （6.1%for Tarom and 6.2%for Fajr） and whiteness （24.8%for Tarom and 28.2%for Fajr）.

齐穗后遮阴时长对西北稻区粳稻产量和品质的影响

灌浆期光照强度对保障水稻产量和稻米品质至关重要。本研究以常规高产水稻品种(新稻41、吉粳88)和优质水稻品种(粮粳10号、吉粳515)作为研究对象,以不遮阴作为对照,于2018和2019年在新疆乌鲁木齐研究了齐穗后不同遮阴时长处理(遮阴10 d、20 d和持续遮阴)对水稻产量及稻米品质的影响。结果表明,齐穗后遮阴延长了水稻灌浆进程,降低了结实率、千粒重和产量;遮阴同时导致了籽粒直链淀粉含量显著降低,蛋白质含量显著增加,进而导致水稻垩白粒率和垩白度增加,淀粉糊化特性和食味值变差。与不遮阴相比,齐穗后遮阴10 d、20 d和持续遮阴处理2年平均水稻结实率和千粒重分别下降了3.5%、9.7%、11.1%和3.7%、7.1%、13.1%,进而导致产量分别下降了11.3%、16.5%和31.7%。直链淀粉含量和食味值受齐穗后0~10 d遮阴的影响不大,齐穗后遮阴20 d和持续遮阴处理较对照2年平均籽粒蛋白质含量分别增加了20.5%和30.8%,直链淀粉含量降低了3.6%和4.6%,崩解值和食味值分别降低了15.2%、26.1%和3.9%、7.7%。籽粒垩白粒率受齐穗后遮阴的影响因灌浆期背景光照强度而异, 2018年齐穗后遮阴10 d水稻垩白粒率增幅最大,达152.1%, 2019年为齐穗后遮阴20 d增幅最大,达345.5%。高产水稻品种对齐穗后遮阴时长的敏感程度大于优质水稻品种,其结实率和千粒重下降幅度更大,产量更易受遮阴的影响;并且高产水稻品种垩白粒率增加幅度明显大于优质水稻品种,导致其更易受遮阴影响。综上,齐穗后20d是遮阴影响稻米外观品质的关键时期,且遮阴时长的影响取决于背景光照强度;遮阴时间越长,稻米蒸煮食味品质越差。本研究将为我国优质粳稻生产应对未来气候变化提供科学依据。

鄱阳湖流域主要早稻品种耐淹试验研究

为确定鄱阳湖流域早稻抽穗开花期的耐淹水深和耐淹历时,选取流域内种植的四个主要早稻品种于抽穗开花期进行了耐淹试验,试验结果表明:抽穗开花期淹水胁迫后各处理株高均较对照组增加或显著增加;产量及其构成分析显示,淹水胁迫导致水稻减产,淹水深度和淹水历时与有效穗数、结实率和千粒重负相关;不同品种的耐淹能力不同,泰优398和湘早籼45对淹水胁迫有一定的适应能力;以水稻减产不超过10%为评价标准,株两优171和中嘉早17在抽穗开花期的耐淹水深均为1/2植株高度,耐淹历时均为1~3 d;湘早籼45的耐淹水深为2/3植株高度,耐淹历时为1~3 d;泰优398的耐淹能力较强,耐淹水深为2/3植株高度,耐淹历时为3~6 d。

不同类型晚稻品种安全齐穗下限温度及湖北双季稻区晚稻安全齐穗期研究

【目的】确定不同类型晚稻品种安全齐穗下限温度和湖北省不同双季稻区二季晚稻安全齐穗期,为各地合理布局和科学安排双季稻生产提供指导。【方法】以适宜湖北省双季稻区不同种植方式的粳型、籼型和籼粳杂交型二季晚稻品种为材料,分别于2020年和2021年在湖北省咸宁赤壁市、荆州公安县、武汉洪山区、黄冈团风县、孝感孝昌县5地进行分期播种大田试验,并结合对孕穗抽穗期盆栽试验材料进行模拟低温处理,通过调查结实率和单株产量,分析齐穗前气温与结实率的关系,以结实率降低到最适温度下结实率的82%时的温度为安全齐穗下限温度;在此基础上,根据近30年气象资料绘制湖北省不同双季稻区不同类型晚稻品种在9月份逐日齐穗风险图,并以齐穗日在80%以上的年份可以避开低温的影响作为各地的安全齐穗期。【结果】随着播期的推迟,各类品种抽穗期延迟。在迟播条件下单株(穴)产量显著降低。结实率是影响各类品种产量的主要因素,并与齐穗前4 d平均气温呈二次曲线关系。齐穗前4 d安全齐穗下限温度,粳稻品种为19.6℃,较传统标准低0.4℃;籼稻品种为22.4℃,较传统标准高0.4℃;籼粳交品种为22.2℃,与籼稻品种接近。湖北省双季稻区粳稻、籼稻和籼粳交品种的最迟安全齐穗期,在湖北东南地区分别为9月25—28日、9月16—19日和9月17—20日;在东部地区分别为9月23—27日、9月13—19日和9月14—20日;在江汉平原分别为9月25—27日、9月10—17日和9月10—18日;在北部地区分别为9月22—26日、9月7—15日和9月7—17日。【结论】不同类型晚稻品种及其在湖北省不同地区的安全齐穗期存在较大差异,从南到北呈提早趋势,籼稻品种早于粳稻品种,籼粳交品种与籼稻品种接近。为保证二季晚稻安全生产,各地应根据气候条件和品种特性选择适宜的品种并安排合理的播期;种植粳稻品种有利于抵御抽穗扬花期低温的危害。

抽穗扬花期温度对水稻产量和稻米品质的影响

为探索水稻抽穗扬花期高温对产量性状和稻米品质的影响,以泰优390和隆晶优1212为材料,在抽穗扬花期期于人工气候室以32、35、38℃处理7 d,以同时期田间自然温度条件作对照(CK,平均温度30.6℃),研究不同处理水稻的产量性状和稻米品质。结果表明:38℃处理下泰优390和隆晶优1212的结实率分别为51.52%、54.38%,千粒重分别为19.6、22.98 g,产量分别为43.41、52.32 g/盆,均显著低于对照和其他处理,但高温对有效穗和穗粒数影响较小。高温处理的2个品种稻米的出糙率、精米率、整精米率和胶稠度显著降低,而直链淀粉含量显著提高。综上,水稻抽穗扬花期高温可致使结实率和产量下降,同时影响稻米的加工品质和蒸熟品质,但不同品种受高温的影响表现存在差异。

高温连续干燥与干燥-通风联合对稻谷品质的影响

利用不同的干燥方式对稻谷进行干燥,降至安全水分含量12%(湿基),测定干燥后稻谷的整精米率(head rice yield,HRY)、脂肪酸值以及RVA特征值。结果表明:对于连续干燥作业,缓苏过程中存在一个临界缓苏时间,达到临界缓苏时间能显著提高整精米率,且干燥温度越高,该临界缓苏时间的出现越明显;但干燥温度高于60℃,且一次降水幅度不小于9.4%,缓苏温度与干燥温度相同时,通过延长缓苏时间,整精米率难以达到70%;对于干燥-通风联合作业,干燥温度高于60℃,且缓苏温度不低于干燥温度时,虽能保持较高整精米率(>72%),但稻米的RVA特征值(峰值黏度、最低黏度、崩解值、最终黏度、回生值)总体上随着干燥温度、缓苏温度的升高和缓苏时间的延长而增加,且存在一些波动,干燥温度、缓苏时间对其影响显著性低于缓苏温度。两种干燥方式的脂肪酸值都存在不同于恒低温干燥持续增加的变化趋势。

我国稻米整精米率特点及环境影响因素分析

为我国稻米整精米率的提高、品种品质的改善提供参考,本文对2002-2009年度全国稻米普查抽征的5574份稻谷样品的整精米率进行影响因素分析。结果表明,我国稻米整精米率年均值总体徘徊在55.0%,地域特点为北高南低;稻米整精米率与粒长、垩白粒率呈负相关性;地理位置、气候效益等环境因素对整精米率均有一定的影响。

真空干燥-常压缓苏后稻米品质指标的相关性研究

以不同干燥温度、相对真空度为因素对稻谷进行真空干燥-常压缓苏实验,研究其干燥后稻米爆腰增率、整精米率及蒸煮质构品质变化,分析其相关性,并通过扫描电镜观察不同干燥条件对稻谷籽粒显微形态的影响。结果表明:干燥温度和真空度对稻谷干燥后爆腰增率及整精米率影响极显著(p<0.01)。干燥温度、真空度且二者交互作用对米饭质构特性有极显著影响(p<0.01)。经过对稻谷干燥后各品质相关性分析,得出稻谷爆腰增率与其蒸煮硬度、胶黏性及胶着性呈极显著的正相关性(p<0.01),稻谷整精米率与硬度、胶黏性、胶着性呈极显著负相关性(p<0.01),且二者均与弹性、咀嚼性及内聚性没有相关性。干燥温度越高,相对真空度越大,干燥速率越大,淀粉粒与蛋白质的结合度越小,结构越稀松,干燥裂纹越粗大,数量越多。

不同生育阶段洪涝淹没时长对水稻生长发育及产量构成的影响

夏季小流域洪涝常常导致南方稻田受淹并成灾。为探究小流域洪涝淹没时长对水稻生长发育及产量的影响,于2015—2016年在广西象州县选用丝香1号和百香139进行双季稻淹水试验,分别设分蘖期、孕穗期和开花期淹没0(对照CK)、2、4、6、8、10 d处理,测定淹没前后的茎蘖数变化、抽穗期及收获后的每穗粒数、结实率、千粒质量和每盆稻谷产量,并对产量构成因素进行相关分析和通径分析。结果表明:与对照组相比,同一生育期内淹没时间越长茎蘖死亡率越高、植株恢复生长越慢,但不同的淹没时期影响程度和主要影响对象存在差异。分蘖期淹没超过6d则死苗率大于80%,且不能完全恢复生长,收获时水稻茎蘖数显著低于对照组;孕穗期淹没超过6d则死苗率大于50%,而淹没小于4 d的处理水稻能恢复生长,收获时水稻茎蘖高于对照组;开花期淹没10 d死苗率不足50%,收获时茎蘖数与对照组差异不显著。分蘖期淹没小于4 d水稻始穗期及抽穗持续时间均无显著变化,大于8 d则水稻始穗期显著推迟,抽穗持续时间增加;孕穗期受淹没则会使水稻始穗期推迟,抽穗持续时间显著增加,甚至收割时也未能达到齐穗期标准。分蘖期淹没小于4 d,单株产量无显著下降,淹没6 d及以上则减产率大于80%;孕穗期及开花期淹没超过2 d则减产率大于50%。不同生育期淹没处理下产量的主要因素不同,分蘖期主要受有效穗数和结实率影响,孕穗期受结实率及每穗粒数影响,开花期受结实率和有效穗数影响。研究可为建立西南地区双季稻洪涝灾害指标体系和提出减灾管理措施提供依据。

国内外稻谷出糙率、出米率和整精米率测定方法的比较研究及相关国际标准修订

介绍了国内出糙率检测方法、整精米率检测方法、稻谷和糙米潜在出米率测定方法等国家标准以及稻谷和糙米潜在出米率测定方法国际标准的主要技术内容,研究比较了国际标准与我国相关国家标准的技术差异和各自的优点,介绍了我国承担修订《稻米——稻谷和糙米潜在出米率的测定》国际标准的工作情况以及该国际标准修订前后的技术差异。

水稻抽穗期QTL及其与产量性状遗传控制的关系

产量和抽穗期是评价水稻品种应用价值的基本性状。水稻QTL分析已经历了从初定位到基因克隆的发展过程,并以抽穗期和产量性状最受重视。总结了亚洲栽培稻抽穗期QTL的基因组分布,分析了这些QTL与产量性状遗传控制的关系,为进一步筛选和鉴定具有较高育种应用潜力的水稻抽穗期QTL和产量性状QTL提供参考。

稻谷干燥过程中整精米率的影响因素研究

该试验依据我国南方农村的稻谷干燥习惯,以大粒溪香优质稻品种为试材,对稻谷干燥过程中整精米率的影响因素进行研究。试验结果表明,稻谷干燥过程中不同处理对最终整精米率影响较大,不同处理之间整精米率最大相差6.8%。稻谷晾晒过程中采用篾席晾晒比水泥地直接晾晒所得整精米率高3.6%,晾晒过程中夜间存放于室外比存放于室内整精米率高2.2%,这些处理对稻谷最终含水量影响不大。

水稻抽穗期叶型特性及其与产量因子关系的研究

分析了10份水稻品种抽穗期的叶型特性及其与产量构成因子的关系,结果表明:(1)不同水稻品种叶片长度和宽度之间差异较大;(2)不同水稻品种之间叶片角度的差异明显;(3)随着施氮浓度的增加叶角有所增加,叶长先增后减,叶宽也随之增加;(4)结实率与叶角之间呈线性正相关,千粒重和每穗颖花数与叶角之间呈线性负相关;(5)千粒重和叶长之间呈线性正相关,结实率和每穗颖花数与叶长之间呈线性负相关。