Italian Ryegrass (Lolium perenne ssp. multiflorum) and Corn (Zea mays) Competition

Italian ryegrass is an annual/biennial grass that is typically used as a pasture crop or a cover crop along roadsides, rights-of-way, and industrial areas. Glyphosate-resistant (GR) Italian ryegrass populations have been documented around the world, mostly in orchard and vineyard situations. The first evidence of evolved GR Italian ryegrass in row/agronomic crops was reported from Washington County, Mississippi in 2005. GR Italian ryegrass populations can jeopardize preplant burndown options in reduced-tillage crop production systems, thereby, delaying planting operations. The effects of competition of Italian ryegrass on crop growth and yield are poorly understood. A field study was conducted in the 2012 growing season and repeated in the 2013 growing season. GR and susceptible (GS) Italian ryegrass populations were established in the greenhouse and transplanted in prepared corn row beds in the fall of 2011 and 2012 at 0, 1, 2, 3, and 4 plants·meter> of crop row. Italian ryegrass plants overwintered and developed over the following spring-summer. Glyphosate was applied at 1.26 kg·ae/ha (1.5× of labeled rate) in the spring to burndown the Italian ryegrass plants and corn was planted into the ryegrass residue 2 - 3 wk later. Current corn production practices were followed. Corn density (early and late season), height (early season), and yield and Italian ryegrass biomass (early-mid season) measurements were recorded during both years. Corn height was greater in 2012 than that in 2013 at comparable stages of the growing season, due to a cooler and wetter early season in 2013 than that in 2012. Averaged across weed densities, corn density (both early and late season) and yield were higher in the GS than those in the GR population, but Italian ryegrass biomass was similar for both populations. Averaged across Italian ryegrass populations, corn density (both early and late season), and yield were inversely proportional to Italian ryegrass density. In summary, Italian ryegrass significantly reduced corn density and yield and reduction was greater with the GR than that with the GS population. Studies are underway to study inter population competition in Italian ryegrass and investigate allelopathic effects of Italian ryegrass on selected crops.

明矾对玉米(Zea mays L.)根尖细胞的遗传毒性效应

目的研究明矾对玉米（Zea mays L.）根尖细胞微核及异常有丝分裂的诱导,阐明明矾对玉米根尖细胞的遗传毒性效应。方法以玉米根尖为实验材料,用不同浓度的明矾为诱变剂,处理24h,测定玉米根尖细胞的有丝分裂指数、微核率和染色体畸变率。结果不同浓度明矾均能诱发较高微核率和染色体畸变率（P〈0.05）,在同样的条件下,0.1-1.0 g/L明矾处理下玉米根尖细胞微核率和染色体畸变率显著升高并达到最高值,而1.0-2.0 g/L明矾处理下玉米根尖细胞微核率和染色体畸变率下降并趋于平缓。同时在低浓度明矾作用下,玉米根尖细胞分裂有显著的加速现象。当明矾浓度到达一定程度后,表现为玉米根尖细胞分裂减少。结论明矾诱发玉米根尖细胞高微核率和有丝分裂异常,明矾对玉米根尖细胞具有明显的细胞遗传学毒性效应。

Pb、Cu胁迫对玉米(Zea mays L.)生长、细胞色素合成以及重金属吸收特性的影响

通过水培试验,以玉米作为供试植株,研究Pb、Cu胁迫对玉米生长发育、细胞色素合成以及重金属吸收的影响。结果表明,Pb、Cu单一胁迫下玉米根长较对照组均偏低,复合胁迫下根长随着Pb、Cu复合浓度的增加而减小。玉米植株在重金属Pb、Cu单一胁迫下生物量变化不明显,但在不同水平Pb、Cu复合胁迫下,表现随着重金属胁迫浓度增加,玉米植株生物量先增加后减小。玉米叶绿素含量随着Pb胁迫浓度增加而增加、随着Cu浓度增加而降低;Pb、Cu单一胁迫下β-类胡萝卜素含量随着Pb浓度增加先降低后增加,随着Cu含量增加先增加后降低;Pb、Cu单一胁迫下花青素含量较对照组均增大,Cu胁迫下花青素含量增加更明显,最低增加0.65%,最高增加21.25%。玉米不同器官对Pb、Cu积累有一定差异,在单一重金属胁迫下Pb、Cu在玉米体内积累量与胁迫浓度呈正相关,分布顺序为根系>茎叶,根部是积累Pb、Cu主要器官。Pb、Cu复合胁迫下加剧了重金属向玉米体内的迁移累积,随着Pb、Cu复合胁迫浓度的增大,根部吸收Pb、Cu逐步增大,而茎叶吸收Pb、Cu趋于平稳。相关分析显示,玉米细胞色素的合成取决于被胁迫的重金属类型,β-类胡萝卜素含量与植株体内Pb含量显著正相关,花青素含量与Cu含量显著正相关,揭示Pb对β-类胡萝卜素诱导作用强、Cu对花青素诱导作用强。

Application of hybrids with cytoplasmic male-sterility in Zea mays L.in China

The abortive behaviour and the cytoplasm quality of cytoplasmic male-sterility(CMS)lines of homocaryon were investigated and the existence of C race of Bipolaris maydiswere discussed from the point of view of genetic breeding,physiology and pathology in this paper.Then the countermeasures to prevent the danger from disease of B. maydis in CMS hybrid pro-duction were proposed.

Production of Embryogenic Callus and Plant Regeneration from Elite Guizhou Waxy Maize Inbred Lines

Immature embryos from three elite Guizhou waxy maize inbred lines （W21019, B7, and QCL5036） were evaluated for their ability of forming callus and regeneration into plants. Immature embryos harvested at different physiological stages were used as explants to initiate callus on N6 basal medium with 0-3.5 mg L-1 of 2,4-dichlorophenoxy acetic acid （2,4-D）. The concentration of 2,4-D, physiological age of immature embryos and genotype had a significant effect （P0.05） on the percentage of embryogenic callus formed. The optimum 2,4-D concentration for the initiation of embryogenic callus was varied among the waxy maize genotypes from 2.0 mg L-1 （B7 and QCL5036） to 3.0 mg L-1 （W21019）. The shoots were generated from embryogenic callus which were transferred into the regeneration medium supplemented with 0-2.5 mg L-1 of 6-benzylaminopurine （6-BA）. 6-BA in the medium significantly promoted the regeneration of embryogenic callus. Embryogenic size was also an important factor that affected regeneration capacity. 0.6-0.7 cm was proved to be the best size for regeneration from embryogenic callus and the mean number of shoots per primary callus in all genotypes achieved the highest number. The ability of the plant regeneration was also affected by genotype. W21019 had the highest number of shoots formed per primary embryogenic callus. With the optimum condition, the highest mean number of shoots per primary callus was up to 12.13, 5.73, and 3.33 in line W21019, B7, and QCL5036, respectively. The successful regeneration of the two inbred lines provides a basis for development of genetic transformation to improve priority traits such as enhanced insects and drought tolerance.

Leaf Turgor Potential, Plant Growth and Photosynthesis in Organically Fertilized Sweet Corn

A greenhouse pot experiment was conducted using a complete random design with six replications. A pressure-volume curve analysis was employed to study the effects of organic fertilizers on plant water relations in sweet corn (Zea mays L. cv. Honey-bantam) in terms of leaf osmotic concentration (Cs), osmotic potentials at full turgid status (πFT) and at incipient plasmolysis (πIP), and of symplastic (ζsym) and apoplastic (ζapo) fractions in the tissue water compartment in relation to photosynthetic capacity (Pc) and dry mass accumulation. At the seedling stage (day 15), plants with chemical fertilizer treatments showed lower πFT, πIP and ζapo and higher Cs, ζsym and PC than those with organic fertilizer treatments. Compared to PC and relative growth, where values from day 15 to day 75 were first lower for organic treatments and then higher, ζsym and Cs values were similar, while πFT and πIP were opposite being higher then lower. Dry mass production with organic fertilizer was higher than or close to the chemical fertilizer treatments in the later growth stage (day 75), though dry mass production with chemical fertilizers was much higher in the early and middle growing stages (days 15 and 45). Increased photosynthesis and dry mass production in later growth stages due to organic fertilizers were associated with increased osmotic concentration in the tissue and the symplastic fraction of the tissue water compartment. These might favor stomatal opening and biochemical activities.

The Comparison of Sugar Components in the Developing Grains of Sweet Corn and Normal Corn

The sugar components and their dynamic variation in the developing grains of sweet corn(Zea mays L. seccharata Sturt)and normal corn (Zea mays L. indentata Sturt) were compared. There are WSP (water-soluble polysaccharides), sucrose, fructose, glucose, mannitol and sorbitol in both sweet corn and normal corn, but no maltose. Two components with different degrees of polymerization (D. P. N) were detected in the sweet corn; only one of them was detected in the normal corn 20 days after pollination. With the development of grains, the total soluble sugar content(TSS)in sweet corn increased, but in normal corn it decreased. The dynamic variation of WSP, sucrose, glucose, fructose, mannitol and sorbitol in sweet and normal corn grains are different. The contents of sugar components in the sweet corn grains are higher than that in the normal corn. Sweet corn accumulates less starch than normal corn.

Differences in Physiological Age Affect Diagnosis of Nitrogen Deficiencies in Cornfields

Many studies have shown that chlorophyll meter readings （CMRs） can be used to diagnose deficiencies of nitrogen （N） during the growth of corn （Zea mays L.） in small-plot trials, but there is need to address additional problems encountered when diagnoses are made in fields of the size managed in production agriculture. A noteworthy difference between smallplot trials and production agriculture is the extent to which the effects of N are confounded with the effects of other factors such as tillage, landscape, soil organic matter and moisture content. We illustrate how some of these factors can cause differences in the physiological age of plants and introduce errors in the diagnoses of N deficiencies. We suggest methods （measuring the height to the youngest leaf collar and assigning leaf numbers by using the first leaf with pubescence and the ear leaf as references to identify growth stages） for minimizing these errors. The simplified method of growth stage identification can be used to select appropriate plants and leaves for making diagnoses in fields and to distinguish the effects of N from the effects of other factors that influence plant growth.

Weed Control, Environmental Impact and Profitability of Weed Management Strategies in Glyphosate-Resistant Corn

Eleven field trials were conducted over a three-year period (2006-2008) at three locations in southwestern Ontario, Canada to evaluate the effect of various weed management strategies in glyphosate-tolerant corn on weed control, crop injury, corn yield, environmental impact and profit margin. No visible injury resulted from the herbicide treatments evaluated. Overall, the effect of all factors assessed were location specific. By 56 days after treatment, depending on location, glyphosate applied at the 7 - 8 leaf stage (LPOST), preemergence (PRE) herbicides followed by (fb) glyphosate LPOST and sequential glyphosate applications (EPOST (3 - 4 leaf stage) followed by LPOST) provided more consistent control of annual broadleaf weeds and annual grasses compared to glyphosate applied alone EPOST. Weed control at 56 days after treatment was lower when glyphosate was applied alone LPOST compared to sequential applications of glyphosate or PRE herbicides fb glyphosate. There were no differences in corn yield among the sequential programs evaluated;however, a yield benefit was found when a sequential program was used compared to glyphosate applied alone LPOST. Among the sequential programs the lowest environmental impact was isoxaflutole/atrazine fb glyphosate. The lowest profit margins were associated with atrazine, S-metolachlor/atrazine/benoxacor, dicamba/atrazine and glyphosate LPOST treatments compared to all other treatments. Overall, profit margins tended to be somewhat higher for treatments that included glyphosate applications. Based on these results, the most efficacious and profitable weed management program in corn was a sequential application of glyphosate;however, isoxaflutole/atrazine fb glyphosate was the treatment with the lowest environmental risk while also adding glyphosate stewardship benefits.

Influence of Adjuvants on the Efficacy of Tolpyralate plus Atrazine for the Control of Annual Grass and Broadleaf Weeds in Corn with and without Roundup WeatherMAX^®

Tolpyralate is a new HPPD-inhibiting herbicide that is efficacious on annual grass and broadleaf weed species in corn. For maximum herbicide performance of tolpyralate, it is recommended that atrazine is tank mixed with tolpyralate along with the adjuvants methylated seed oil concentrate (MSO) plus urea ammonia nitrate (UAN). A common use pattern of tolpyralate plus atrazine will be in a tank mix with Roundup WeatherMAX®due to the high proportion of corn acres that are seeded to Roundup Ready®hybrids in Eastern Canada. There is no information in the peer-reviewed literature if the adjuvant system in Roundup WeatherMAX®is adequate for optimal herbicide performance of tolpyralate plus atrazine, or if MSO and UAN are still required. Six field trials were conducted over two years near Ridgetown and Exeter, ON, Canada to determine if adjuvants are still required when tolpyralate plus atrazine is tank mixed with Roundup WeatherMAX®in corn. Tolpyralate plus atrazine plus MSO and Roundup WeatherMAX®plus tolpyralate plus atrazine provided excellent control of velvetleaf, pigweed spp, common ragweed, lambsquarters, ladysthumb, wild mustard, flower-of-an-hour, barnyardgrass and green foxtail in this study. Results of this study show that in the absence of Roundup WeatherMAX®, weed control with tolpyralate plus atrazine was improved substantially with the addition of MSO;however, there was little to no increase in weed control with the addition of UAN. When tolpyralate plus atrazine was co-applied with Roundup WeatherMAX®, there was no improvement in weed control with the addition of MSO and/or UAN.

ClO_2杀菌复合壳寡糖涂膜对鲜食糯玉米的保鲜效果

分别采用ClO_2杀菌处理、壳寡糖(chitosan oligosaccharide,COS)涂膜处理以及ClO_2杀菌复合COS涂膜(ClO_2-COS)处理鲜食糯玉米,对比不同保鲜处理对鲜食糯玉米贮藏期间的抑菌情况、多酚含量、木质素含量、木质素积累速率、苯丙氨酸解氨酶活力、过氧化物酶活力的影响。结果发现:200 mg/L的ClO_2杀菌复合15 mg/mL COS涂膜处理表现出良好的抑菌能力,贮藏35 d时霉菌和酵母菌总数为(2.30±0.12)(lg(CFU/g)),显著低于ClO_2杀菌处理组((3.78±0.16)(lg(CFU/g)))和COS涂膜处理组((4.18±0.09)(lg(CFU/g)))(P<0.05);ClO_2-COS处理能够降低木质素积累速率,降低多酚含量并使其基本保持较低水平;ClO_2-COS处理可以抑制苯丙氨酸解氨酶活力过快上升,降低苯丙烷代谢水平,还能降低过氧化物酶活力,使其在贮藏期间一直保持较低水平,从而减少木质素积累。

甜玉米穗位叶面积QTL定位

选用穗位叶面积有显著差异的超甜玉米（Zea mays L.）自交系T4和T19为亲本配制杂交组合，以232个单株的F2群体为作图群体，构建了一张包含77个位点全长868.7 cM的玉米SSR标记遗传连锁图谱，标记间的平均间距为11.28 cM。在F2群体中用复合区间作图法在玉米全基因组上检测穗位叶面积QTL，共检测到4个与甜玉米穗位叶面积相关QTL，分别位于玉米第4、5、9染色体上，可解释5.98%~11.12%的表型变异。这一结果将加快高产、耐密和抗倒伏甜玉米育种进程，实现玉米的分子标记辅助选择育种。

玉米大斑病抗性基因的QTL定位

以Mo17和黄早四为亲本,构建了包含239份F9代重组自交系的分离群体,并用103个微卫星标记构建了遗传连锁图谱,该图谱覆盖了玉米基因组1455.4 cM,标记间的平均间距为14.1 cM。通过人工接种分析了亲本及R IL群体对大斑病菌的抗性表现,并用复合区间作图法对抗性QTL进行了作图分析,结果在玉米第2染色体定位了3个与标记Bn lg1520、Um c1635和Bn lg125连锁的QTL,可分别解释表型方差的13.89%、19.33%和14.36%;另外还在第8染色体上定位了相邻的与标记Um c1327和Bn-lg2235紧密连锁的2个QTL,可分别解释表型方差的9.33%和7.62%。

Microbiota and Mycotoxins in Trilinear Hybrid Maize Produced in Natural Environments at Central Region in Mexico

Mycotoxigenic fungi and mycotoxins in 3 inbred lines (hybrids resistant to corn ear rot) were identified in twenty samples. The maize (Zea mays) accessions were collected in five plots of two municipalities in High Valley, state of Hidalgo. The fungal population was determined with a microbiological dilution method used two culture media (PDA and ELA), for the detection of mycotoxins with thin layer chromatography with visual inspection in UV light and a direct competitive enzyme-linked immunosorbent (ELISA). The results showed high moisture content in all hybrids evaluated on an average of 38.3% and a 1.8 × 103 UFC/g fungus, values within the permitted limits by the Mexican legislation;however the most prevalent fungi were Fusarium sp. (76%), Alternaria sp. (14%), Penicillium sp. (4%) and Aspergillus sp. (5%), and the species Aspergillus nidulas, Aspergillus flavus, Fusarium verticillioides, Fusarium poae, and Penicillium ochraceum. The aflatoxin concentration was observed in a range from 2 to 13 ng/g and 370 to 660 ng/g to fumonisins. It is concluded that trilinear corn hybrids have a variety of pathogenic potential fungi. The two genetic hybrids showed levels of aflatoxins and fumonisin safe for human consumption, contrary to one hybrid, with a content not suitable for human consumption. A better understanding of genetic hybrids corn will improve predictive mycotoxin contamination.

Comparison of the Effectiveness of Different Traditional Soaking Processes on the in Vitro Digestibility of Taro(Colocasia esculenta L.SCHOTT)Flour

A traditional process used by farmers in Chad consists in soaking slices of taro (Colocasia esculenta L. SCHOTT) in tamarind infusion, or in corn solution or in water over a 24-hour period to reduce the acridity of taro and facilitate cooking. The aim of this study was to assess the effect of traditional soaking on the in vitro digestibility of taro flour using or not using an α-amylase enzyme. The digestion without the enzyme has shown that the soaking processes improve the digestibility of taro flour (from 39.30% for the control sample to 75.11% (after tamarind infusion) and 78.67% (treatment with water) after 24 hours of soaking). Soaking over a 6-hour period and preferentially in tamarind infusion or in corn solution obtains highly digestible flour (around 95% of digestibility rate after 3 hours of enzymatic digestion).

Proximate Composition,Fatty Acid Profile and Mycotoxin Contamination in Several Varieties of Mexican Maize

In Mexico maize (Zea mays L.) is an important cereal due to excellent taste and nutritional value. Nutritional content and fatty acid profile has been reported in white maize, however, there are several genotypes natives (red, yellow, black, blue, pinto), and many improved hybrids maize of which little is known. Fumonisins and aflatoxins are mycotoxins present in 25% of the world’s cereals, mainly in tropical and subtropical regions around the world. This study presents the analysis of proximate composition (ash, protein, lipids), as well as mycotoxins (fumonisins and aflatoxins) and five different fatty acids, two of saturated fatty acids (palmitic and stearic) and three of polyunsaturated fatty acids (oleic, linoleic and linolenic), evaluated by Gas Chromatography and Flame Detector (GC-DF). Thirty varieties of maize (native and hybrid maize) were collected in states of central region. The total fumonisins were determined using the QuickTox TM extraction and quantificated by QuickScan fumonisins;the aflatoxins were analyzed by commercial ELISA kit. The highest protein level was 10.43 g/100g, 5.63 g/100g for fat, 1.62 g/100g for ash in hybrid maize. In native maize, the highest levels of protein and ash were 10.94 g/100g and 1.45 g/100g for pinto maize. The higher value for fat was 5.45 g/100g in yellow maize. The palmitic and stearic acids, in native maize were higher that hybrid maize, for linoleic acid and linoleinic fatty with a significant difference between native corn. Fumonisins and aflatoxins were contaminated in all genotypes of maize, in allow levels. This information obtained may be considered in maize breeding programs, industrialization processes and healthy diets.

鲜食甜玉米除草剂安全性评价

以甜玉米(Zea mays L.)中农甜488为材料,采用盆栽法,在甜玉米播种后出苗前的土壤上分别喷施不同剂量(4倍推荐用量、2倍推荐用量、推荐用量、推荐用量的1/2、推荐用量的1/4、推荐用量的1/8)的除草剂(38%莠去津SC、50%乙草胺EC、15%硝磺草酮SC、720 g/L异丙甲草胺EC),研究4种除草剂对牛筋草、稗草、鬼针草、牛膝菊的防效及甜玉米的安全性。结果表明,使用除草剂时甜玉米播种适宜深度为4~5 cm;药后30 d,在推荐用量下4种除草剂对杂草鲜重的防效为62.52%~74.37%,在推荐用量2~4倍用量下4种除草剂对杂草鲜重的防效为70.40%~97.98%,在4倍推荐用量下除草剂对不同类型杂草的防效明显增加;38%莠去津SC和15%硝磺草酮SC对甜玉米安全,甜玉米对50%乙草胺EC和720 g/L异丙甲草胺EC较敏感。

播种期对黑糯玉米自交系生长、雌雄穗开花期及产量的影响

为了研究不同播种期对黑糯玉米(Zea mays L.)品种桂黑糯609父本和母本生长发育、花期调控以及产量的影响,基于广西的气候特征,以父本黑糯系102和母本绿秆糯为试验材料,设计6个不同播种期(父本为2月25日、2月29日、3月4日和3月8日,母本为2月25日和3月8日),调查父本和母本自交系主要生长时期的发生时间、叶片生长速度,并测量产量及产量相关性状。结果表明,随着播种期的推迟,2个亲本的开花期都相对延迟,相同播种期(2月25日和3月8日)父本的散粉期和母本的吐丝期相遇最好,不同播种期相遇一般甚至不相遇;播种期早(2月25日)的亲本叶片生长最快,雄穗最长;随着播种期的推迟,各亲本的株高、穗位高、穗长、穗行数等性状逐渐升高,但差异相对较小,穗粗、出子率和产量也逐渐升高,且处理间差异显著(P<0.05)。由此表明,在广西进行桂黑糯609制种生产,为了能确保父本和母本花期正常相遇,同时避免气温因素的影响,最好以同播种期为主,最适宜的播种期为3月上旬,且不宜超过3月中旬。

控释肥施用量对鲜食玉米生长的影响

为探究控释肥施用量对鲜食玉米(Zea mays L.)生长状况的影响,以仲甜5号和西星五彩鲜糯为材料,开展不同肥力的田间小区试验,比较不同生育时期玉米的生长指标,并筛选最佳的控释肥施用量。结果表明,控释肥施用量与鲜食玉米除糖度外的各指标的拟合模型决定系数均在0.8以上,均达极显著水平(P<0.01),说明施用控释肥能显著增加鲜食玉米各生长指标。600 kg/hm^(2)为本试验条件下的最佳控释肥施用量;当过量施肥时,大部分指标呈下降趋势,肥料利用率降低。

鲜食型糯玉米(Zea mays L.)产量和出籽率的配合力分析

为了进行鲜食型糯玉米(Zea mays L. sinensis Kulesh)种质资源的创新、改良加工品质、选育优质高产的新品种。本试验以7个糯玉米自交系为亲本,按照GriffingⅣ配制21个杂交组合,分析了糯玉米产量和出籽率的配合力效应。结果表明,糯玉米的产量和出籽率受加性基因和非加性基因共同控制;7个亲本的产量一般配合力效应大小顺序为N23>N17>N28>N47>N51>N15>N27,出籽率一般配合力效应大小值为N51>N27>N47>N23>N28>N17>N15;综合一般配合力效应及特殊配合力效应结果表明,N15×N23是相对高产的组合;N27×N51是出籽率相对较高的组合;对自交系综合评价表明,N23、N17可作为选育高产优良组合的理想亲本,N27可作为选育高出籽率的理想亲本。本研究结果可为糯玉米育种实践提供一定的参考。