几种除草剂对当茬玉米生长发育的影响

除草剂为作物产量提供保障的同时,对作物造成的药害也频繁发生。为此,本文以目前陇东旱塬区主栽玉米品种为试验材料,选用对恶性杂草具有良好防除效果的除草剂,明确了75%二氯吡啶酸SG、90%莠去津WG和56% 2甲4氯钠盐SP 3个单剂及其2个混配配方对玉米主要农艺性状及产量的影响,以期为玉米的安全生产提供依据。结果表明：参试除草剂在药后0~7天及不同生育期对玉米生长均无直观影响。75%二氯吡啶酸SG、90%莠去津WG、75%二氯吡啶酸SG+90%莠去津WG对苗期玉米株高稍有影响,但随着玉米自身防御能力的增强,除草剂对之后各生育期的玉米株高无显著抑制作用。不同除草剂对各生育期玉米茎粗无抑制作用,玉米果穗粗、果穗有效长、穗粒数和百粒重无显著差异。各除草剂处理后玉米产量较空白对照增加21.93%~30.22%,较人工除草对照增加-2.91%~3.69%。可见,供试除草剂对玉米安全性高,可应用于玉米田的杂草防除。     

Nuclear genetic control of variation in simazine tolerance in oilseed brassicas

Summary Substantial variation in tolerance to the triazine herbicide simazine was observed among a wide range of Brassica napus cultivars grown in a hydroponic screening system. None of these cultivars was as tolerant of are simazine treatment as the Canadian cultivar Triton which carries cytoplasmic gene(s) which confer a high level of resistance through their modification of chloroplast membranes to which triazine herbicides normally bind. A field study showed that the most tolerant cultivar Haya had a significantly higher yield than Triton in both handweeded plots and plots treated with 1000 ml/ha simazine. This finding supported other observations that the yield potential of cultivars such as Triton is substantially reduced because of the impairment of photosynthesis by cytoplasmic gene(s) for triazine resistance. A slight reduction in the yield of Haya with an increase in simazine concentration from 500 to 1000 ml/ha suggested that further increases in simazine concentration required for optimal weed control are likely to have a detrimental effect on the yield of Haya and other tolerant cultivars. Genetic analyses of variation in simazine tolerance in populations derived from crosses among cultivars representative of the range in tolerance indicated that the narrow-sense heritability of tolerance was of sufficient magnitude to allow for isolation of genotypes tolerant of higher simazine concentrations. These could be utilized in developing high yielding cultivars in areas of southern Australia where simazine treatment is necessary for effective weed control in Canola crops.     

Incremental crop tolerance to weeds: A measure for selecting competitive ability in Australian wheats

Total reliance on herbicides for weed control is unsustainable with the spread of herbicide resistance and the environmental need to reduce pesticide use. Strongly competitive wheat crops that have high tolerance to weed pressure and therefore maintain high yields in the presence of weeds are a low-cost option for reducing dependence on herbicides. We examined the feasibility of selecting for wheat tolerance to weeds by crossing varieties differing for traits associated with competitiveness. Competitive ability and yield potential must be treated as separate traits for selection. Current measures of crop tolerance to weed competition do not separate the two traits so that selection based on these measures is often synonymous with selection for yield potential rather than pure tolerance. We propose a new measure, termed Incremental Crop Tolerance (ICT) that reflects the incremental yield difference between genotypes associated with tolerance, over and above differences in underlying yield potential.     

玉米成株期耐盐性评价与耐盐资源筛选

为探明玉米成株期耐盐性评价方法并筛选耐盐玉米资源,采用多个鉴定指标对16份玉米品种进行耐盐性综合评价,并划分为不同的耐盐级别。试验采用大田鉴定法,以株高、穗鲜重、茎鲜重、总鲜重和籽粒干重这5个指标的耐盐指数为评价依据,运用加权隶属函数法进行耐盐综合评价,并根据D值对耐盐性进行聚类分析。结果表明,与正常环境相比,在盐碱胁迫下,各鉴定指标的平均值均有所下降,其中籽粒干重和穗干重的变异系数在盐胁迫条件下明显高于正常条件;不同玉米种质资源的耐盐指数的表现不同,以各个耐盐指数为依据的品种耐盐性排序也不一致;相关分析表明D值与各耐盐指数的隶属函数值均呈极显著正相关,可以用加权隶属函数法综合评价玉米成株期耐盐性。根据D值和聚类分析,可将16个玉米品种划分为5个耐盐级别:其中高耐盐品种(1级) 1个、耐盐品种(2级) 2个、中等耐盐品种(3级) 9个、敏盐品种(4级)3个、高敏盐品种(5级) 1个。本研究共筛选出高耐盐普通玉米1个(天泰316)、耐盐普通玉米2个(五岳97-1,惠农609)和特用玉米1个(山农207),这些品种建议在黄河三角洲等盐碱地示范推广。     

Variation among Andean races of maize for cold tolerance during heterotrophic and early autotrophic growth

Cold in the initial growth stages is an important stressfactor for maize grown in regions with a temperate climate,particularly in case of early sowing. Sources of tolerancehave been identified in adapted genotypes, but promisinggenes for cold tolerance should also be found in materialdeveloped under the lower-temperature margins of the cropdistribution. This research was conducted in order to testAndean maize accessions for cold tolerance expressed duringboth the heterotrophic and early autotrophic growth stages.Experiments were conducted in controlled environments tostudy cold tolerance traits (germination %, germinationindex and plant growth rate) at continuous 10^°C (heterotrophic growth) and at varying 10–16^°C (autotrophic growth). An experiment was also performed inthe field with early sowing (both heterotrophic and autotrophic growth). In each experiment, a control trialwas conducted in more favourable conditions (i.e. continuous25^°C in a controlled environment or late planting inthe field) so that cold tolerance traits could also beexamined as the ratio between the stress and the controltrial. None of the accessions was superior for all coldtolerance traits. However, several Andean maize accessionsoutperformed the US Corn-belt hybrid checks for one or moretraits, both in heterotrophic and autotrophic growth. Overall, BOZM 855, PMS 636, Poblacion D, Poblacion E andBOZM 696 were the best accessions, suggesting that they canbe a promising source of genes for improving cold toleranceof adapted maize genotypes.     

On-farm evaluation of integrated weed management tools for maize production in three different agro-environments in Europe: Agronomic efficacy,herbicide use reduction,and economic sustainability

The development and implementation of integrated weed management (IWM) strategies that provide good weed control while reducing dependence on herbicides, and preferably without having side effects on the overall system economic performance, is still a challenge that has to be met. In 2011 and 2012, nine on-farm experiments (i.e., real field conditions on commercial farms, with natural weed flora) were conducted in three important European maize producing regions-countries, which represent the range of climatic and edaphic conditions in Europe, to evaluate the efficacy of different locally selected IWM tools for direct weed control in maize vs. the conventional approach (CON) followed by the farms. The IWM tools tested were: (1) early post-emergence herbicide band application combined with hoeing followed by a second hoeing in Southern Germany, (2) early post-emergence herbicide broadcast application when indicated by a predictive model of weed emergence after performing one scouting in the field to supply data for the model, followed by hoeing in Northern Italy, and (3) tine harrowing at 2–3rd leaf stage of maize and low dose of post-emergence herbicide in Slovenia. Results showed that the IWM tools tested in the different countries: (1) provided sufficient weed control without any significant differences in yields, (2) greatly reduced maize reliance on herbicides, and (3) IWM implementation was economically sustainable as no significant differences in gross margin were observed in any country compared to CON.     

Contribution of autochthonous maize populations for adaptation to European conditions

Early vigor, earliness and cold tolerance are the main potential contributions of European maize (Zea mays L.) for breeding programs for adaptation to areas with short growing seasons and cold springs. The objective of this research was to determine the potential contributions of populations from different European regions to breeding for adaptation. Six Spanish and six French maize populations differing on variability for earliness, vigor and cold tolerance were crossed in a complete diallel without reciprocals. The populations and their crosses were evaluated in the field and in a cold chamber. Minimum temperatures were the main environmental trait affecting genotype × environment interaction, probably due to the cold sensitivity of the genotypes with the best performance in the field. The best population cross, based on specific heterosis for adaptation-related traits in the field, was Viana × Rastrojero, but this cross was cold sensitive. Tuy × Lazcano should be the best choice for a breeding program for adaptation, based on performance in the field and cold tolerance. As conclusions, there was variability for earliness, vigor and cold tolerance among the populations and crosses involved in this study, being tolerant to cold conditions the populations with medium growing cycle originated in areas with short growing seasons. The highest yielding crosses were cold sensitive.     

不同玉米种子萌发期耐旱性分析

种子萌发期是研究玉米生长和耐旱性的关键时期。为了鉴定不同玉米自交系的萌发期耐旱性,采用聚乙二醇(PEG)模拟干旱条件,对42份不同玉米自交系进行干旱处理,通过研究发芽指数、发芽率、发芽势等种子发芽性状,以其相对值为指标,鉴定不同玉米自交系种子萌发期的耐旱性。结果表明,在PEG-6000处理胁迫下,玉米自交系种子萌发受到抑制,不同自交系的耐旱性存在较大差异,通过隶属函数法结合抗旱分级标准筛选出丹3140为萌发期强耐旱自交系,农系1315、YML 1615、京2416为萌发期中等耐旱材料。     

Chilling Tolerance of Maize Seedlings in the Field during Cold Periods in Spring is Related to Chilling-Induced Increase in Abscisic Acid Level

Recent studies on chilling tolerance mechanisms in maize revealed a significant positive correlation between genotypic chilling tolerance and chilling‐induced accumulation of the stress hormone abscisic acid (ABA) under controlled growth chamber conditions. Based on this and other results, the hypothesis was developed that chilling tolerance in maize is related to the ability to accumulate large amounts of ABA rapidly, as a protection against chilling injury. The objective of the present study was to test this hypothesis under field conditions during natural cold weather periods in spring, which often cause severe chilling injury in maize fields. In two experiments at two locations in Europe with contrasting climates, eight maize genotypes with different genotypic chilling tolerance were cultivated in spring in the field according to agronomic practice for maize. Before and at the end of cold weather periods, ABA levels and water contents were determined in the third leaves. It was found that chilling‐tolerant genotypes accumulated higher amounts of ABA during the chilling period than chilling‐sensitive genotypes. A significant positive correlation between chilling tolerance and the levels of ABA in the leaves was found. These results support the above‐mentioned hypothesis. In contrast to earlier studies performed under growth chamber conditions, the water content in chilled leaves was mostly higher than in non‐chilled leaves. The increase in ABA is therefore not attributable to chilling‐induced water deficit, but probably to the low temperature itself.     

Frost tolerance in wild potato species: Assessing the predictivity of taxonomic, geographic, and ecological factors

The use of genetic resources could be more effective and efficient if we were able to predict the presence or absence of useful traits in different populations or accessions. We analyzed the extent to which taxonomic, geographic and ecological factors can predict the presence of frost tolerance in wild potatoes. We used screening data for 1646 samples from 87 species that had been collected in 12 countries in the Americas. There was a strong association of frost tolerance with species and to a lesser extent with taxonomic series. There was significant geographic clustering of areas with wild potatoes with similar levels of frost tolerance. Areas with a high level of frost tolerance are the central and southern Peruvian Andes, the lowlands of Argentina and adjacent areas, and a small area in the central Chilean Andes. There is a greater chance of finding wild potatoes with high levels of frost tolerance in areas with a yearly mean minimum temperature below 3 ^°C than there is in warmer areas. However, temperature is only a weak predictor of frost tolerance. Temperature data alone did not predict observed frost tolerance in eastern Argentina/Uruguay and falsely predicted it in the southwestern United States. Because many wild potato species occur over small areas, taxonomic, ecological, and geographical factors are difficult to disentangle. This revised version was published online in July 2006 with corrections to the Cover Date.     

Identification of quantitative trait loci for agronomic and physiological traits in maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) under high-nitrogen and low-nitrogen conditions

Low-nitrogen (LN) tolerance is a compound character with a complex genetic basis. Many agronomic traits have been shown to be closely related to LN tolerance in maize. In this study, 150 F₇ recombinant inbred lines derived from a cross between inbreds 178 and K12 were evaluated for agronomical and physiological traits under high-nitrogen (HN) and LN conditions in 2 years. Inclusive composite interval mapping (ICIM) was used to identify the quantitative trait loci (QTLs) for traits recorded under different treatments (LN and HN) in 2 years. In total, 86 QTLs were detected: 38 for HN and 35 for LN, while 13 QTLs were detected under both nitrogen levels, suggesting that LN-specific QTLs may play a role in improving LN tolerance in maize. Overlapping QTLs for different traits were located on all chromosomes except chromosome 4 and chromosome 9. Many of these regions overlapped with previously reported QTLs. Several consensus major QTLs and LN-specific major QTLs found in the study can be used in marker-assisted selection breeding for genetic improvement and LN tolerance in maize in the future.     

四川盆地及盆周山区玉米地方种质耐低磷胁迫研究

以来自四川盆地及盆周山区的22个玉米地方种质为材料,在低磷胁迫下对苗期缺磷症状,成株期株高、穗行数、百粒重、行粒数以及穗粒重等性状表现进行了研究。结果表明,低磷胁迫对玉米的主要农艺、经济性状均有不同程度的影响,其中对苗期缺磷症状及成株期穗粒重的影响最大,且不同玉米地方种质在苗期和成株期对低磷胁迫的反应不同,以苗期缺磷症状和成株期穗粒重的耐低磷胁迫系数的平均值作为耐低磷综合指数,能较好地反映玉米地方种质的耐低磷胁迫能力。将耐低磷综合指数按最短距离法进行聚类,可将22个玉米地方种质划分为三类。其中,第一类材料包括:汉源红包谷、汉源白包谷、汶川二白、江北大板牙,占鉴定总数的18.2%,它们的耐低磷综合指数在0.81以上,属于对低磷胁迫不敏感基因型;第二类材料包括南充秋子等4个玉米地方种质,占鉴定总数的18.2%,它们的耐低磷综合指数在0.73~0.77之间,属于对低磷胁迫反应中间型;第三类材料包括小金金皇后等14个地方种质,占鉴定总数的63.6%,它们的耐低磷综合指数在0.73以下,属于对低磷胁迫敏感基因型。     

Mass selection for improved cold and density tolerance of two maize populations

Summary Data of planting and plant density are two cultural practices influencing grain yield of maize (Zea mays L.). Our study was designed to evaluate the usefulness of a mass selection scheme to improve cold and density tolerance of the BS2 and BS3 maize populations. Populations were planted at an early planting date and a high plant density, and three cycles of mass selection for well-filled ears on erect plants were conducted at earch of three Corn Belt locations (i.e., Waseca, MN; Ames, IA; Portageville, MO).Results showed that selection improved cold tolerance traits of BS3, but not of BS2. Mass selection did not increase density tolerance of either population at any location. Selection did not improve response to planting dates, although the early planting date did improve agronomic performance and grain yield of all entries. We concluded that mass selection at high plant densities and early planting dates at diverse geographical locations did not produce cycles adapted to specific environmental conditions.     

玉米自交系苗期耐酸的生物学和营养学特性

以13个玉米自交系为材料, 在红土(pH4.24)和潮土(pH7.95)两种土壤条件下, 对玉米苗期的生物学和营养学性状进行了比较研究。 结果表明, 耐酸玉米自交系的苗期耐酸特性表现在生长速度较快、 叶色较绿、 干重累积较多, 对钙的吸收效率较高, 能抑制锰过量的毒害。 与国外引进的已知耐酸自交系比较, 不同玉米自交系对酸性土     

玉米耐寒性鉴定研究进展

玉米是对低温逆境较为敏感的重要的禾谷类作物。早春低温冷害是影响玉米产量水平提高的重要因素之一。选育和创造耐寒玉米种质是减少此种危害的有效途径。耐寒性鉴定则是耐寒育种研究的基础。综述了国内外玉米耐寒性的鉴定方法和评价指标,分析了目前玉米耐寒性鉴定存在的问题,探讨了未来研究的方向,为深入开展玉米耐寒性研究提供参考。     

Variation in sweet potato for tolerance to some physical and biological stresses

Summary Sweet potato cultivars, breeding lines and unselected seedling clones were grown under 9 stress conditions in field and greenhouse; heavy soil, space competition, competition with maize, shading, flooding, drought, acidity, salinity, and weevil infestation. High root yield was considered to be a sign of stress tolerance. Stresses were shown to reduce the growth of shoots and roots, except flooding, which increased fibrous root production. The percentge of plants showing high stress tolerance varied from 0.35 to 30.90 for the different stress situations. Tolerances to stresses tended to occur together, as shown by low but significant correlations, significant chi-squares for numbers of plants with multiple stresses, and by low but significant correlations between yield and multiple stresses. Root flooding, space and fertility competition, and soil acidity appear to be the stress factors most closely related to production in heavy soils. Yet the magnitude of the correlations suggest that other factors or random variation also affect yield, and thus the predictive value of greenhouse stress test is presently limited.     

Large-scale screening maize germplasm for low-phosphorus tolerance using multiple selection criteria

Phosphorus (P) deficiency is one of the major limiting factors in maize production in many developing countries. This experiment was conducted to evaluate multiple low-P tolerance criteria and identify the suitable maize germplasm for our future low-P tolerance breeding. A total of 456 diverse maize inbreds were evaluated for low-P tolerance at seedling stage using four shoot-related traits and six root-related traits measured under applied phosphorus (AP) and non-applied phosphorus (NAP) conditions. Analysis of variance revealed significant genetic variation among genotypes for all tested traits. Medium-to-high heritability estimates were obtained for most traits. Total dry weight (DW) was highly inheritable while the widely used root/shoot ratio had only an intermediate level of heritability. Based on the synthetic index (SI), the tested inbreds were classified into three groups representing low, moderate and high tolerance to low-P stress. Regression model built based on selection criteria for low-P tolerance explained 67.8 and 76.8 % of variation for DW under NAP and AP conditions, respectively. Using low-P tolerance index for DW and SI as selection criteria, 23 and 109 maize inbreds were identified as germplasm resources that were extremely tolerant and sensitive to low-P stress, respectively, which could be further used for genetic improvement of low-P tolerance.     

Glyphosate tolerance in maize (Zea mays L.). 1. Differential response among inbred lines

Summary Variation in susceptibility to the safe broad-spectrum herbicide glyphosate was investigated in maize. Eleven inbred lines, grown in a growth chamber, were evaluated for their tolerance to the herbicide at 2.4 mM (0.2 kg a.i. in 400 I ha^-1 of water). Following treatment with glyphosate at the three-leaf stage, significant variation in damage, expressed as visual injury ratings scored 7, 14 and 21 days after the application of the herbicide, was found. Effects on dry weight and shoot height were consistent with visual scores and the carbon-exchange rate was found to be a sensitive index of differential injury.Biochemical characterization of 5-enol-pyruvyl-shikimate-3-phosphate (EPSP) synthase, the main target of the herbicide, ruled out the possibility that this differential susceptibility was due to variations in the sensitivity of the enzyme. On the contrary, a positive correlation was found between in vivo tolerance and EPSP synthase levels, measured at different stages during seedling growth. This result suggests that a naturally occurring difference in EPSP synthase levels in the tissues may contribute to the differential response observed in vivo in maize inbreds.Abbreviations CER carbon-exchange rate - EPSP 5-enol-pyruvyl-shikimate-3-phosphate - ID₅₀ concentration causing 50% inhibition     

Genetic regulation of root traits for soil flooding tolerance in genus Zea

Flooding stress caused by excessive precipitation and poor drainage threatens upland crop production and food sustainability, so new upland crop cultivars are needed with greater tolerance to soil flooding (waterlogging). So far, however, there have been no reports of highly flooding-tolerant upland crop cultivars, including maize, because of the lack of flooding-tolerant germplasm and the presence of a large number of traits affecting flooding tolerance. To achieve the goal of breeding flooding-tolerant maize cultivars by overcoming these difficulties, we chose highly flooding-tolerant teosinte germplasm. These flooding-tolerance-related traits were separately assessed by establishing a method for the accurate evaluation of each one, followed by performing quantitative trait locus (QTL) analyses for each trait using maize × teosinte mapping populations, developing introgression lines (ILs) or near-isogenic lines (NILs) containing QTLs and pyramiding useful traits. We have identified QTLs for flooding-tolerance-related root traits, including the capacity to form aerenchyma, formation of radial oxygen loss barriers, tolerance to flooded reducing soil conditions, flooding-induced adventitious root formation and shallow root angle. In addition, we have developed several ILs and NILs with flooding-tolerance-related QTLs and are currently developing pyramided lines. These lines should be valuable for practical maize breeding programs focused on flooding tolerance.     

新型玉米除草剂的防效与评价研究

为了筛选既对玉米生长无明显影响又能有效防除玉米地杂草的新型除草剂,2005-2006年对宝玉、玉邦和金玉黄龙3种除草剂进行了药剂试验,结果表明,玉邦除草剂用于苗前和苗后玉米4~8叶期、杂草2~4叶期防除杂草均有很好的防效,3种除草剂对杂草防效的排序为:玉邦>宝玉>金玉黄龙。