从8个方面介绍了美国玉米生产的关键技术与专业化服务体系。提出我国玉米生产管理技术转型的具体建议与措施。

正玉米机械粒收是利用联合收获机摘穗、脱粒一次完成的收获方式,由于减少了果穗储运、晾晒、脱粒等作业环节,不仅大大降低劳动强度、节约人力成本,还可降低晾晒、脱粒过程中的籽粒霉烂与损失,是我国玉米机械收获的发展方向和今后玉米生产转方式的重点~([1])。美、德等国20世纪50年代玉米收获作业也以机械穗收为主,70年代全面采用田间机械粒收~([2-4])。目前我国玉米机械播种率已超过80%,但机械收获率

机械收粒(机收粒)是现代玉米生产技术体系的关键技术,是我国玉米收获技术的发展趋势。开展玉米机收粒技术推广和应用限制因素的研究,对于推动玉米机收粒技术的发展和应用,引导全国玉米高产高效生产,提高玉米产业竞争力具有重要的实践意义。本研究基于2012年新疆机收粒的研究结果,围绕不同玉米品种、不同子粒含水量、不同收获机型和不同收割速度等因素对玉米机收粒质量(子粒破碎率、杂质率和产量损失率)的影响进行了试验和统计,针对影响农户机收方式采用行为的影响因素进行了调研和分析。试验结果表明：(1)玉米子粒含水量与机收时子粒破碎率、杂质率和产量损失率呈极显著正相关,落粒率和落穗率与产量损失率均显著正相关,二者均是产量损失的主要原因。就目前推广品种和机具收获水平进行机收粒时,杂质率和田间产量损失率基本控制在国家标准范围之内,收获子粒杂质含量达标率为88.31%,产量损失为85.68%。子粒破碎率相对较高,按国家标准5%计,品种适宜度仅为32.30%,按企业标准8%计,为64.07%,品种适宜性问题比较严峻。不同品种不同收获时期试验结果表明,北京地区春玉米以子粒含水量23%左右机收粒为宜,若继续站放,子粒水分进一步下降,子粒变硬变脆,受力容易碎裂,导致机收粒时破碎率再次升高,因此为保证机收粒质量,确定各玉米品种适宜机收粒的子粒含水量非常关键。不同收获机具和收割速度测试结果显示,现阶段玉米各生态区选用的不同收割机型,在产量损失率方面都控制的较好,相当水分条件下杂质率相差不大,但是破碎率方面,不同技术来源的机型相差较大,且差异达显著水平。此外,玉米收割时机手惯用的中低匀速度并非最佳收获质量的速度。(2)调研结果表明,黑龙江农垦地区(友谊农场和852农场)玉米种植基本实现了全程机械化,影响玉米机收粒方式采用的主要因素是种植规模(96.2%)、品种(91.7%)和整地政策(88.9%)。相比机收穗(机收穗),子粒直收收售更为方便、成本投入也低,因此在852农场被大规模采用。黑龙江地方(龙江、富裕、克山)玉米生产机械化程度也比较高(83.0%以上),但主要是机械收穗(机收穗)方式,机收比人工更省力(83.3%)、没有大型收粒机具(37.3%)、收穗易存放可以待价而沽(35.2%)是机收穗采用率较高的主要原因。吉林省为人工收获较多的地区,机收质量评价差(89.6%)、芯秆留用(82.9%)和机收费用高(66.3%)是限制其机收采用的主要原因。种植规模大、机收粒成本投入低(97.4%)是决定新疆地区农户机收采用的主要因素。机收费用偏高(63.9%)、规模小劳力足(52.8%)、机收损失大(50.0%)是限制河南地区机收采用的主要原因。技术扩散影响因子模型估计结果表明,耕种面积、玉米收入占比、机收穗技术采用年数、玉米销售方式显著影响机械收获技术的扩散和推广,随耕种面积近一步扩大,玉米收后能否直接售卖极显著影响农户对机收粒技术的采用行为。综上,子粒含水量极显著影响机收粒质量,适宜品种和子粒水分含量的确定、专业机型和适宜收割速度的选择是机收粒质量的保证。耕地经营规模和技术采用效益是农业机械收获技术推行的关键,耕种规模越大,机收带来的效益越高,农户越倾向于采用机收粒等先进的农业技术以及与先进技术配套的种植经营模式,收后售卖烘干等社会配套服务设施越完备。机收粒技术要实现更大面积的推广和普及,还应根据各地玉米生产的社会、经济、环境因素分区而治。

【目的】机械粒收技术是现代玉米生产的关键技术,是国内外玉米收获技术发展的方向和中国玉米生产转方式的关键。明确当前中国玉米机械粒收质量的现状,研究影响收获质量的主要因素,推动玉米机械粒收技术发展。【方法】利用2011—2015年在西北、黄淮海和东北和华北玉米产区15个省（市）168个地块获得的1 698组收获质量样本数据,分析当前中国玉米机械粒收质量的现状及其影响因素。【结果】结果表明,籽粒破碎率平均为8.63%,杂质率为1.27%,田间损失籽粒（落穗、落粒合计）为24.71 g·m~（-2）,折合每亩损失16.5 kg,平均损失率为4.12%,破碎率高是当前中国玉米机械粒收存在的主要质量问题。收获玉米籽粒平均含水率为26.83%,含水率与破碎率、杂质率及机收损失率之间均呈极显著正相关。其中,破碎率（y）与籽粒含水率（x）符合二次多项式y=0.0372x~2-1.483x＋20.422（R~2=0.452＊＊,n=1 698）,在一定含水率范围内（含水率大于19.9%）,破碎率随籽粒含水率增大而增大。【结论】当前中国玉米机械粒收时破碎率偏高,而籽粒含水率高是导致破碎率高的主要原因。对此,建议选育适当早熟、成熟期籽粒含水率低、脱水速度快的品种,适时收获,配套烘干存贮设施等作为中国各玉米产区实现机械粒收的关键技术措施。

子粒破碎率是评价玉米子粒机械收获质量的重要指标。2011-2016年在全国16省(市、区)194个地块开展子粒机械收获质量测试,对获取的2450组样本数据的统计表明,当前玉米子粒机械收获破碎率均值为8.56%,高于国标["玉米收获机械技术条件"(GB/T 21961-2008)]≤5%的要求,破碎率偏高是我国玉米子粒机械收获存在的主要质量问题。破碎率与收获时玉米子粒含水率呈极显著正相关,2450组样本子粒含水率平均值达到26.65%,两者呈二次多项式关系,水分偏高是导致当前我国玉米子粒收获破碎率高的主要原因;不同收获机械及其作业对子粒破碎率也会产生显著影响;此外,玉米生育和收获期间生态环境因素、栽培措施对破碎率也有影响。培育早熟、脱水速率快、收获期含水率低及抗破碎性好的品种,研发推广破碎率低的收获机械和选择最佳收获期收获是解决破碎率高的主要措施,而在收获时根据玉米生长、成熟和子粒水分状况及时检查与调试收获机械参数也有助于降低破碎率。

【目的】机械粒收是玉米生产的发展方向,收获质量是影响其推广应用的主要因素。中国玉米机械粒收还处于起步阶段,目前在西北和东北等春播玉米区推广应用面积较大,黄淮海夏播玉米区正在积极开展试验示范。本研究通过分析黄淮海夏玉米机械粒收质量及其影响因素,为该技术的推广应用提供支持。【方法】2013—2015年累计选用了23个玉米品种,在黄淮海典型代表区河南新乡开展试验研究。2013年和2015年在收获期分别进行2次机械收获,2014年1次机械收获。收获当天测定各个品种的收获前籽粒含水率,并调查测产。机械收获后从机仓随机取一定量籽粒样品,立即测定收获后籽粒含水率,然后手工分拣样品,测定籽粒破碎率和杂质率;收获后,在田间选取3个代表性样区,调查落穗损失和落粒损失。【结果】2013—2015年,籽粒破碎率共调查131个样点,结果显示,收获时玉米籽粒含水率在20.80%—41.08%,籽粒破碎率变幅为4.98%—41.36%,籽粒破碎率随着籽粒含水率的提高明显升高;破碎率低于8%的有38个样点,占比29.01%,籽粒含水率低于26.92%时,收获的玉米籽粒能够满足破碎率8%以下的要求。机收杂质率共调查134个样点,杂质率0.37%—5.28%,杂质率低于3%的样点有107个,占比79.85%,杂质率也随着籽粒含水率的升高而增加;2013—2014年,籽粒含水率低于28.27%时,杂质率能够低于3%的国家标准;2015年收获时籽粒含水率虽然较高,但杂质率均在3%以下。田间损失率共调查108个样点,变幅为0.18%—2.85%（落穗率和落粒率）,均能满足国家标准,损失率不是影响机械收获质量的限制因素。在本试验条件下,籽粒含水率低于26.92%时,破碎率和杂质率分别低于8%和3%,田间损失率也符合国家标准,能够满足机械粒收质量要求。研究还发现,籽粒含水率相近的不同品种之间,机械收获的破碎率和杂质率也存在显著差异,17

玉米收获时籽粒含水率是影响机械粒收质量、安全贮藏和经济效益的关键因素,已经成为一个重要的技术与经济问题。当前玉米品种收获期籽粒含水率偏高不仅制约了中国玉米粒收技术的推广、影响到玉米收获及生产方式的转变,也严重影响了玉米品质。从国内外相关文献综述可见,收获期玉米籽粒含水率主要由生理成熟前后籽粒的脱水速率控制,该性状是可遗传的,品种间具有显著的差异;品种间脱水速率与苞叶、穗轴、籽粒特征及果穗大小等许多农艺性状有关;玉米生育后期的空气湿度（环境水分的饱和亏缺程度）、温度、日辐射、风速、降雨等生态气象因子对籽粒脱水速率具有重要影响;播期、种植密度、株行距、水肥管理等栽培措施对籽粒脱水也有一定影响。通过生理成熟时籽粒含水率和生理成熟后籽粒脱水速率参数可预测籽粒的适宜机械收获时间。本文建议,当前选择适当早熟、籽粒发育后期脱水快、成熟与收获时含水量低的品种是中国各玉米产区实现机械粒收技术的关键措施。同时,鉴于籽粒脱水速率受基因型、生态气象因素和栽培措施的共同作用,而中国玉米种植区域广、种植方式与品种类型多,因此,需要深入研究玉米籽粒脱水的生理机制,并在各产区针对籽粒脱水特征开展系统观测,为玉米机械粒收技术的推广和品质改善提供理论依据和技术支撑。

The relationship between grain moisture at harvest and the amount of kernel cracking was evaluated at Brandon, Manitoba. Grain moisture at harvest was closely correlated to percentage kernel cracking. Least amount of kernel cracking occurred with grain moisture ranging from 16.7% for K730 to 22.1% for 3979. Maize, kernel breakage, grain moisture

本文通过对黑龙江省 38个玉米自交系生理成熟期及子粒自然脱水速率的研究 ,表明中晚熟材料生理成熟期在抽丝后 5 0～ 6 0d ,此时含水量在 2 3%～ 35 % ;中早熟材料生理成熟期在抽丝后 45～ 5 0d ,此时含水量在2 8%～ 35 % ;供试自交系间子粒自然脱水速率存在显著差异 ,变幅为 0 32 6 %～ 1 371% ,其中中晚熟组的吉 846、吉16和中早熟组的龙抗 11、杂C5 46、东 91为脱水较快的玉米自交系 ,可作为快速脱水材料加以利用

分析了2008—2010年河南省审定的9个玉米杂交种生理成熟前后籽粒在田间自然条件下脱水干燥的速率,结果以豫单2670最快,达0.98百分点/d,豫单811最慢,为0.48百分点/d。但不同品种黑色层出现前后脱水速率有差异。黑色层出现前,洛玉8号最快,达2.32百分点/d;豫单811最小,为0.59百分点/d。黑色层出现后,郑单528最大,为0.77百分点/d,而新单26最小,只有0.28百分点/d。黑色层出现前品种间的脱水速率差异比黑色层出现后的大。

为明确夏玉米生理成熟期子粒含水率及其影响因素,2014-2016年,以郑单958、先玉335等玉米品种为研究对象,分别在北京和河南新乡开展品种比较和播期研究.结果表明:生理成熟期玉米子粒含水率平均27.8％,在品种间存在极显著差异,变幅为21.5％～33.1％,按80％置信区间为24.2％～31.4％;环境条件对子粒达到生理成熟的时间和含水率有极显著影响,且环境和品种之间具有明显的交互作用;生理成熟期子粒含水率高低与授粉到生理成熟经历的天数之间相关度较低.夏玉米区主栽品种郑单958、先玉335、农华101、中单909、京农科728、华美1号和农华816生理成熟期子粒含水率平均值分别为28.4％、24.9％、27.9％、29.1％、28.7％、29.2％和29.9％.

Three “fast” drying and three “slow” drying corn inbreds, whose hybrids demonstrate various rates of drying after physiological maturity, were used to study the genetics controlling differential drying rates among hybrids. Drying rate was estimated by the moisture loss from husked ears in a forced-air dryer at 38 C for 18 hours. Initial moisture range was 30 to 40% while dried ears had a range of 20 to 30%.

Field grain drying rate (FDR) after physiological maturity in maize (Zea mays L.) is an essential determinant of grain moisture at harvest. Investigating the genetic structure of FDR is of great signi

The effects on germination and early seedling growth of presowing true potato seed in water or gibberellic acid (GA) at 1500 ppm and of priming in -1.0, -1.25 and -1.5 MPa solutions of KNO3 + K3PO4 were studied using 30, 18, 6 and 3/4 month-old seed. The influence of light during presowing on the effectiveness of treatments was also investigated. Overall, priming in the light at -1.0 MPa was the most, and GA the least successful treatment for enhancing emergence and subsequent seedling growth. Though GA increased final emergence from about 20 to 70 % in the most recently harvested lot (3/4 mo), the rate and extent of final germination or emergence in this dormant seed was still much lower than that of the nondormant lots (6-30 mo), especially when the latter were primed. For all lots, dry weight per seedling was 40 % lower in dormant than in nondormant seed, and 20 % higher when seeds were primed at -1.0 MPa than when GA treated. In conclusion, the use of nondormant seed may be a requirement for both effective priming and sowing of potato crops via true seed.

in yield over wider rows as reported by Porter et al. (1997). Nielsen (1988) reported a 2.7% increase in corn Continued genetic improvement in the ability of hybrid corn (Zea grain yield across nine Indiana locations when corn was mays L.) to withstand high plant density stress requires agronomists to periodically reassess optimal plant density and row width. Further- grown in narrow rows. The greatest advantage with nar- more, the optimal plant density level and row width for corn grain row row systems seems to be in northern locations. yield may vary with location, primarily latitude, in the Corn Belt. This Paszkiewicz (1997) summarized 84 university and indus- study was conducted to evaluate corn grain yield, harvest moisture, try studies and reported corn grown north of the Inter- test weight, and stalk lodging with modern corn hybrids, as affected state 90 (I-90) corridor responded on average with an by row width and plant density in the northern Corn Belt. At six 8% increase in yield when row width was narrower than locations in 1998 and 1999, four hybrids differing in relative maturity,

Two methods were employed to study field drying in corn L.: First, a set of treatments (removal, enclosure, or other modification of plant parts) was imposed on a series of hybrids at the time of approximatep hysiologic maturity of the grain. Second,m orphologicadl ifferences amongm oret han 150 plant introductions were evaluated. In both methods an attempt was made to determine cause and effect relationships betweend ifferences in plants (natural or imposed) and field drying rate of the ear. The results indicated the following: Premature death speeds rate of drying. Rate of drying is relatively independent of number of leaves or amount of green leaf area (including husks) available for transpiration. Husks limit air movement around the grain; loose, short husks, of a low number are conducive to fast drying.

Flint and dent endosperm type versions of several hybrids were grown under field conditions to determine the effects of endosperm type on field drying rate following physiological maturity. The results indicated there was no inherent major difference in field drying rate between the flint and dent endosperm types. This does not suggest that all flint endosperm material has equivalent drydown rates to the dent germplasm so widely used in North America. However, the findings do suggest that the flint endosperm type per se is not responsible for slow drydown in the field. In this study the dent hybrids were found to have a higher moisture level at physiological maturity than the flint hybrids.

In studies of nine endosperm mutants in three hybrid backgrounds, grain of du, ae, sh1 and su1 had a significantly faster drying rate than normal at each of seven harvests from 35 to 77 days after pollination. Opaque-2 had a faster drying rate at the first five harvests. Sugary-2 had a lower drying rate than normal at the first five harvests while h was slower at 35 and 70 days after pollinatio...

Responses and limits to selection are found to differ invarious maize (Zea mays L.) populations and traits. Twenty-four cycles of recurrent selection for high oil concentration have been completed in maize population Alexho Synthetic. The objectives of this study were to determine the response of oil concentration to direct selection and correlated responses of fatty acid concentration, grain yield, and other agronomic traits. Cycles 0, 3, 5, 9, 11, 15, 18, 21, and 24 per se, the same cycles crossed to inbreds B73 and R802A, and hybrid check B73 X Mo17, were evaluated in six environments at Yugoslavia and at Urbana, IL in 1985 and 1986. Selection was effective in increasing oil concentration. Total oil concentration increased by 118, 51, and 57 g kg-1 of dry matter in cycles per se B73 and R802A testcrosses, respectively. The rate of response in oil concentration was 4.9, 2.1, and 2.4 g kg-1 cycle-1 for the cycles per se for B73 and R802A testcrosses, respectively. The quadratic response was significant in testcrosses, but not in cycles per se. Thus, oil concentrations has not yet shown evidence of plateauing. Oleic and linoleic acid concentration changed with selection for oil concentration in cycles per se -1.39 and 1.39 g kg-1 cycle-1, respectively. Total grain yield of the cycles per se decreased by 1718 kg ha-1, which corresponds to a response of -71.6 kg ha-1 cycle-1. Yield of the testcrosses to inbreds B73 and R802 decreased 19.7 and 15.2 kg ha-1 cycle-1, respectively. Plant height, ear height, 500 kernel weight, ear length, and lodging decreased, while grain moisture and ear row number increased with selection for oil concentration. No change was found in days to silk.

为选育脱水速率快的玉米新品 种,以黑龙江省10个熟期相近而脱水速率差异较大的优良玉米自交系为试验材料,采用完全双列杂交设计配置杂交组合,对玉米的百粒重、穗粗等12个农艺性状 与玉米生理成熟后籽粒脱水速率进行遗传相关和通径分析。结果表明:穗粗、穗行数、粒宽和胚重/胚乳重与玉米生理成熟后籽粒脱水速率之间均表现为显著或极显 著正向相关;百粒重、穗长、胚占籽粒体积比和果皮厚度与玉米生理成熟后籽粒脱水速率之间均表现为极显著负向相关。通径分析结果表明:穗粗、穗行数、粒宽和 胚重/胚乳重与玉米生理成熟后籽粒脱水速率直接通径系数为正值,百粒重、穗长、胚占籽粒体积比和果皮厚度与玉米生理成熟后籽粒脱水速率直接通径系数为负 值。为获取脱水速率快的玉米,应主要选育果穗短粗、籽粒宽度较大、果皮薄和百粒重小的基因型的玉米杂交种。

Kernel water relations play a key role in controlling the duration of grain filling. This duration is controlled by the relationship between kernel water and biomass development, as it determines the timing kernels reach a critical percent moisture content (MC, measured on a fresh weight basis) at which biomass accumulation stops. The time in which this critical percent MC is attained can be affected by the timing kernel net water uptake stops (i.e. maximum water content is reached), or by the relationship between water loss and biomass deposition after maximum water content is attained. Which of the two mechanisms could be behind genotypic differences in maize ( Zea mays L.) grain-filling duration was unknown. We also studied the relationship between kernel water and volume development, as it was unknown in this species. Thirteen commercial hybrids were evaluated under different growing environments, and weight, water content and volume of their kernels were measured throughout grain filling. There were no differences among hybrids in their kernel percent MC at physiological maturity ( p > 0.05), showing that hybrid differences in grain-filling duration (from 1117 to 1470 C day) were related to variations in the accumulated thermal time from flowering to this critical percent MC. There were no differences in the accumulated thermal time from silking to kernel maximum water content, and this stage was always reached at the same kernel percent MC (ca. 540 g kg 1). Differences in grain-filling duration were explained by the pattern of percent MC decline after maximum water content was reached. This percent MC decline was dependent upon the relationship between water loss and biomass deposition; the higher the water loss rate and the higher the kernel growth rate the shorter the duration ( r 2 = 0.60; p < 0.001). Maximum kernel volume was achieved after maximum water content, and close to physiological maturity. Hybrids differed ( p < 0.05) in the kernel volume generated after maximum water content, and this was also related to the relationship between biomass and water development late in grain filling. Results showed the importance of understanding and predicting percent MC development throughout grain filling, as there were no differences between hybrids and environments in their kernel percent MC at specific developmental stages (i.e. maximum water content or physiological maturity). Our results highlighted the importance of the relationship between water loss and biomass deposition during late kernel development in the duration of maize grain filling.

Moisture content influences harvest timing and the consequent drying process and drying costs, and the development of spoilage fungi during pre- and post-harvest phases. Maize kernel development in the field can be partitioned into three phases: i) lag phase, ii) grain filling and maturation drying, and iii) post-maturity dry-down. A model simulating maize kernel moisture content during maturation can help either monitoring or foreseen maize kernel humidity during the harvest period. Also, it would be useful in simulation studies via crop models to estimate the infield feasibility of harvest but also the interaction with diseases responsible for mycotoxin production, against weather scenarios. A process-based model was developed, called MIMYCS.Moisture. When the hybrids were analyzed all together, MIMYCS.Moisture showed a good general predictive capability with an average error in moisture estimation of 卤3.28% moisture (considering the root mean square error 鈥 RMSE). The model efficiency (EF) was positive (0.85) and the model was able to explain the 89.7% of variation. When the two sub-models were analyzed separately, the RMSE remained approximately at the same level of the general model, while the other indicators changed revealing the different characteristics of the two models. The developmental moisture sub-model has a slight tendency to overestimate, while the dry-down sub-model tended to underestimate final moisture content. However, when the model was analyzed separately for each hybrid, both calibration and validation results suggested that more data are needed to improve the model likely with respect to kernel characteristics of hybrids. Finally, the equilibrium moisture content equation used, taken from industrial drying models, might not be adequate for simulating the field conditions where temperature is well below the one in dryers and environmental air humidity may vary considerably across sites and harvest periods.

The second edition of this book includes new information and concepts in areas of the subject where considerable advances have been made since the publication of the first edition in 1985. While some sections have been altered relatively little, others covering seed development, effects of abscisic acid and gibberellins on gene expression and some aspects of dormancy have been extensively revised. Seed development is now covered in two chapters so that reserve synthesis and its regulation could be separated from the developmental aspects of embryogenesis and seed maturation. The final chapter on some agricultural and industrial aspects of seeds and germination includes new sections on viability and longevity, and somatic embryos and synthetic seeds.

Synopsis: Husk and shank characteristics and shape or size of ear were not found to be major factors associated with differing rates of drying among strains of corn.

Development of maize ( Zea mays L.) kernels follows a predictable pattern involving rapid increase in dry weight and large changes in water content (WC). We showed previously that final kernel weight (KW) was closely correlated with maximum WC achieved during rapid grain filling. The objectives of the current work were (i) to test if percent moisture content (MC, measured on a fresh weight basis) could be used to normalize genetic and environmental variations in kernel development shown to affect final KW and (ii) to determine whether final KW could be predicted from kernel WC prior to rapid grain filling. The data examined included results from five hybrids varying more than 2-fold in final KW grown in the field, and from previously published results. When KW and WC were expressed relative to their maximum values obtained during kernel development, a single model described the relationship between dry weight accumulation and MC for the larger seeded hybrids (199–352 mg kernel 611) and published results (222–359 mg kernel 611). Two smaller seeded yellow-flint popcorn hybrids, however, accumulated less dry matter per unit moisture than expected. Nonetheless, all genotypes exhibited a common developmental relationship between kernel WC (expressed as a percent of the maximum value) and MC under well-watered conditions. A new model was developed to couple this developmental relationship to final KW. This model accurately predicted final KW from kernel WC values measured prior to rapid grain filling (6580% MC; root mean square error, RMSE, of 28.9 mg kernel 611) for all hybrids examined and all published results for which KW and kernel WC data were available. The model also provided a simple means to determine whether final KW was limited by photosynthate supply during kernel development.

A selection procedure to change the drying rates of maize ( Zea mays L.) ears was developed and tested. Results indicated that drying rates were affected by hybrid genotype, ear maturity at harvest, number of kernels per row, ear diameter, and moisture content at harvest. Mass selection was initiated in an early synthetic, NDSG, in an attempt to produce both fast and slow drying strains. After two cycles resultant substrains were evaluated in the laboratory for direct and in the field for correlated selection responses. Laboratory results indicated that selection effectively changed moisture loss rates in NDSG, and confirmed earlier observations that an ear's moisture content at harvest affects its drying rate. Data from field experiments grown at five locations in 1980 revealed that each of two selection cycles for slow laboratory drying rate significantly reduced ear moisture content at harvest, in the field. This lower harvest moisture content appeared to result from a lower moisture content at physiological maturity rather than a faster drying rate. Other correlated selection responses included lowered yield, plant height, and ear weight due to selection for fast laboratory drying, and lowered plant height and ear weight from selection for slow drying. Data indicated that this selection procedure can be used to change moisture loss rate and ear moisture content at harvest. Results also contributed to understanding of factors involved in ear drying rates which may lead to more effective selection procedures.

The objective of this research was to determine the potential for selection of maize (Zea mays L.) genotypes that are superior for resistance to kernel breakage and to evaluate the relationships among several kernel characteristics affecting grain quality. Eighty random inbreds and 40 of their single-cross hybrids were grown at two locations in 1976 to 1979. Data taken included date of anthesis, endosperm type, harvest moisture, Stein breakage test, 300-kernel weight, 300 kernel volume, specific gravity, and a Fast Green dye test. The combined analysis of variance for inbreds and hybrids indicated highly significant differences among genotypes for all traits. Heritability estimates (entry mean basis) were relatively high for all traits (77 to 87%), except for specific gravity (39%). The estimated variance component for genotype x environment was significant for all traits, but the relative magnitude was 25% to 58% as large as the estimate for genotype. Breakage-resistant genotypes tended to have smaller flinty-type kernels. Inbred-hybrid correlations were calculated for the midparent values with their hybrid progeny. Correlations for an inbred trait with the same trait of the hybrid were relatively large (r = 0.54 to 0.79). Endosperm type (r = 0.34) and 300-kernel weight (r = 0.53) of parents may predict resistance to breakage in hybrids. Selection differentials showed a restricted selection index controlling seed size would most likely improve resistance to kernel breakage.

The objectives of this study were to evaluate seeding date, plant density, moisture availability, and soil N fertility effects on maize (Zea mays L.) kernel breakage susceptibility. Three hybrids within each of three relative maturity (RM) groups (90, 100, 110 days by Minnesota Relative Maturity Rating System) were grown in separate seeding date and plant density studies at Arlington, WI [Plano silt loam (fine-silty, mixed, mesic, Typic Argiudoll)], in 1983 and 1984. Maize was seeded four times at 10-day intervals beginning 1 May. Average densities were 1.75,3.75,5.75, and 7.75 plants m&#8211;2. Hybrids were also evaluated in separate irrigated and dryland trials at Hancock, WI [Plainfield sandy loam (mixed, mesic, Typic Udipsamment)]. In a soil N study, grain samples were collected from an experiment at Arlington in which three N rates (0,11, and 22 g m&#8211;2 were applied. Grain was combine-harvested at 25% kernel moisture (except at Hancock where moistures ranged from 21 to 32%) and dried at 82&#176;C in 1983 and 60&#176;C in 1984. Kernel breakage susceptibility, test weight and kernel weight, volume, density, and grain yield were measured. Delayed planting, high plant densities, and low applied N increased kernel breakage susceptibility. At Hancock, higher kernel breakage susceptibility occurred with irrigated- vs. dryland-produced maize. Kernel physical parameters measured were not closely related to kernel breakage susceptibility, except in the soil N study, where the largest range occurred for each variable. The 110-day RM hybrids had lower kernel breakage susceptibility than 90- and 100-day RM hybrids.

从玉米品种熟期选择、农事操作及玉米生育进程、土壤耕作类型与整地、灌溉与施肥、绿色覆盖作物及精准农业技术等方面介绍美国玉米生产的技术特点，并比较分析中美玉米生产的气候条件、生育进程差异，提出高产与高效协同发展、简化农事操作、推进子粒收获等建议。

Moisture data for 12 years from the period 1940 to 1963 were summarized to determine the relation between kernel moisture and time. The rate of kernel moisture reduction was determined for five arbitrary moisture phases and used to predict when specified moisture levels would be attained from pollination date. Correlation studies were made between rate of kernel moisture reduction and four weather factors (air temperature, saturation deficit, wet bulb depression, and relative humidity).

Dry-matter and water content of kernels, rachii and ears of maize ( Zea mays L.) cultivar Pioneer 3901 were measured during the period from silking to harvest maturity in order to (a) determine when net loss of water from the kernels and ear commenced, (b) investigate the use of ear moisture-content (% wet-weight basis) as a scale for kernel development during grain-filling, and (c) use this scale to investigate the relationships between ear moisture, physiological maturity and the environment. Water loss occurred in two phases. The first phase, ending at physiological maturity, had a constant rate of water loss, and was interpreted as a evelopmental loss of water associated with grain-filling. The second phase, which commenced at physiological maturity, showed a falling rate of water loss characteristic of the drying process. This pattern of water loss was consistent for 17 other genotypes studied in less detail, with maximum water content of the ear occurring between 80 and 60% ear moisture in all cases. Below 70% ear moisture, dry-weight per kernel increased linearly with decreasing ear moisture, enabling a direct and precise estimate to be made of ear moisture-content at the onset of physiological maturity. This method of analysis proved to be useful for evaluating the influence of the environment on grain-filling in a single cultivar. The relationship between dry-weight per kernel and ear moisture was consistent for ten crops of Pioneer 3901 studied over five seasons, but the stage at which grain-filling ceased varied. In six unstressed crops, physiological maturity was attained at between 41 and 43% ear moisture. In other crops, where cessation of grain-filling was associated with the occurence of air frosts, physiological maturity was attained at ear moistures ranging from 45 to 55%. Ear moisture at physiological maturity was also influenced by genotype, with values ranging from 34.3 to 44.5% for the 18 genotypes studied. Differences in ear moisture at physiological maturity among 12 of these genotypes were associated with different absolute levels of water in the ear during grain-filling. Strategies for lowering grain moisture at harvest through breeding should therefore take account of the absolute levels of water in the ear, as well as the more usual expression of moisture content on a wet-weight basis.

采用裂区设计方式，对5个极早熟玉米品种的籽粒含水率及脱水速率进行了研究，结果表明品种间生理成熟时的籽粒含水率存在显著差异，变化幅度为35.61%～42.17%；收获时的籽粒含水率品种间差异极显著，变化幅度为15.49%～28.50%。抽丝后35d至生理成熟前籽粒平均脱水速率品种间差异显著，变化范围为0.5296%/d～0.9007%/d；生理成熟后至收获期籽粒的平均脱水速率品种间差异显著，变化范围为0.4246%/d～0.5935%/d。出苗至抽丝的天数、株高、灌浆期绿叶数、单穗产量等性状与籽粒含水量存在显著的相关关系，穗长和穗粗等性状对脱水速率有显著影响。另外试验条件下相对湿度对生理成熟后部分品种的脱水速率影响显著。

玉米是粮、经、饲三元作物。作为我国三大粮食作物之一,自新中国成立以来的近60年间,在解决温饱问题、保证粮食和饲料安全、发展国民经济以及缓解能源危机等方面发挥了重要作用。2009年,我国玉米种植面积已经超过水稻成为种植面积最大的作物,但是随着畜牧业和玉米深加工的发展,玉米作为粮经饲兼用作物的需求量日趋增加,玉米育种的任务仍然艰巨,而玉米改良的重点在可预见的将来仍集中在产量和品质的改良。粒用玉米的品质,除本身的蛋白质,赖氨酸、淀粉和脂肪含量外,另一个重要方面就是籽粒外观色泽。要保持籽粒外观色泽鲜美、洁净,就要求籽粒能迅速脱水和干燥。在一些高纬度高海拔地区,由于秋后气温迅速下降、雨水偏多、日照不足以及有效活动积温低,部分品种在收获时或遇到早霜时甚至不能正常成熟,或者引起籽粒霉烂；与此同时,玉米生产的全程机械化是世界和我国玉米生产的不可逆转趋势,玉米果穗脱水快和收获时籽粒含水量低,利用机械化收获可大大减少破碎率,减少产量损失；还可大大减少籽粒烘干的时间,节约能源和低碳,保护环境。鉴于此,玉米籽粒脱水慢、收获时籽粒含水量过高已成为世界玉米生产特别是高纬度或高海拔玉米生产区的主要问题。因此,籽粒快速脱水成为了玉米育种的一个重要的目标性状。本研究以5个自交系为材料,利用一种改良后的探针水分测定仪对全穗、苞叶、籽粒以及穗轴四部分的水分进行测定,并采用传统的烘箱法对这四部分的水分进行测定并与水分测定仪的测定值进行比较,优化了利用水分测定仪进行籽粒含水量测定的方法,并建立真实水分读数的标准曲线；以6个玉米自交系及8个F1为供试材料,对其抽丝后不同时间段进行水分测定,评价环境因子包括玉米热单位(CHU,Corn Heat Unit)及降雨量对籽粒脱水速率的影响,并提出利用水分测定仪进行快速脱水玉米选择的最佳时间；以上述研究结果为基础,通过对262份自交系进行鉴定,筛选出快速脱水自交系,供快速脱水育种用；以6个玉米自交系为材料,配制8个F1组合,对亲本及组合进行脱水性状的遗传分析,为组配快速脱水杂交种提供理论依据；对籽粒脱水速率与穗粒腐病抗性及农艺性状进行相关分析,探讨籽粒脱水速率与其它性状的相关性；搜集已发表的控制水分含量及抗穗粒腐病的QTL研究,通过元分析得出两个性状相关的真实QTL位点,并综合元分析结果,分析两个性状的一致性QTL区域。主要研究结果如下： 1.利用水分测定仪(读数法)和烘干法测定的各部分含水量均具有显著相关性。其中全穗含水量和籽粒+穗轴含水量的相关系数最高,达到了0.98(2006年)和0.99(2007年)。用读数法进行含水量测定时,苞叶对全穗水分读数的影响不大。当籽粒含水量大于60%或者低于20%时,穗轴对籽粒含水量的影响较小；而当籽粒含水量位于20%至60%之间时,穗轴对籽粒含水量的影响相对偏大。当利用烘干法进行含水量测定时,穗轴对籽粒含水量影响较小。对全穗水分读数及籽粒含水量进行相关性分析,发现全穗水分读数可以利用线性模型(y=1.11x,R2＝0.79)来预测籽粒含水量。 2.2007、2008及2009年间,降雨量及CHU均与籽粒含水量具有显著相关性。抽丝后的累积CHU可以利用模型y=c+dx2预测收获时的籽粒含水量。对不同的材料而言,籽粒含水量在抽丝后第4周开始出现差异,第5周开始出现显著差异。试验筛选出20个材料在抽丝后第5至6周(35-42天)具有较低的籽粒含水量,而其中的16个在收获时也具有较低的籽粒含水量。因此,使用水分测定仪MT808进行脱水速率测定时,最佳测定时间是从抽丝后的第5周至第8周。 3.抽丝期对脱水速率具有显著影响,可使用分值进行籽粒快速脱水自交系筛选。具体的评分标准为：得分值=第5周含水量差异值+第8周含水量差异值-抽丝期差异值。其中,差异值=(总体平均值-该基因型平均值)／总体标准差。根据以上评定标准,对评价分数大于1的自交系作为快速脱水自交系进行选择。2008年筛选出22份自交系,2010年筛选出24份自交系。综合两年的研究结果,共筛选出5份在两年的脱水速率得分值均大于1的自交系,分别为：A679,B73-10,C0308、C0314和C0328。 4.玉米籽粒脱水速率性状主要受加性遗传效应(87.48%)影响,也受少量非加性效应(12.52%)影响；籽粒脱水速率的广义遗传力(hB%)为79.16,狭义遗传力(hN%)为69.25,说明脱水速率是高度遗传的,实践中对籽粒快速脱水育种可进行早代选择；通过对不同组合的配合力效应值分析,发现C0431和C0441均表现出较高的GCA效应值,表明这两个自交系具有良好的育种应用价值,在籽粒快速脱水育种中可利用C0431和C0441组配组合。 5.籽粒脱水速率与镰刀穗腐(籽粒接种)和水处理在0.1的水平上具有显著相关性。镰刀穗腐(籽粒接种)和串珠穗粒腐(籽粒接种),镰刀穗腐(籽粒接种)和水处理间均具有极显著相关性,相关系数分别为0.760和0.821。株高、穗位高和粒长与籽粒脱水速率均表现出显著负相关。其中,穗位高和脱水速率的相关系数最大(r＝-0.607),株高与脱水速率的相关系数其次(r=-0.577),粒长与籽粒脱水速率的相关系数为-0.535。秃尖长在0.1的水平上也与脱水速率具有显著相关性(r=0.521)。 6.研究发现44个控制籽粒含水量的“一致性”QTL,并筛选出6个热点区域(bins 1.03,2.09,8.03,8.05,8.06和10.04)。控制穗粒腐抗性的“一致性”QTL有29个,主要分布的热点区域为bin 2.08和bin 3.04。在第2、第3、第6和第7条染色体上,共存在14个玉米籽粒含水量及穗粒腐病抗性“一致性”QTL的重叠区域,这些重叠区域主要集中在5个区段。在这些区段内共发现13个已知基因,可将这些基因归纳为5类：压力相关基因(htl,和abal),光合系统相关基因(lhcal、psbsl和ij1形态相关基因(eif5α和lg2),动力学相关基因rop6和sarl)以及生殖相关基因(dfr1和zmm7)。