Effects of Population Density and Planting Pattern on the Yield and Yield Components of Leafy Reduced-Stature Maize in a Short-Season Area

Maize hybrids that yield well, mature earlier with low grain moisture contents, tolerate higher population densities and take advantage of narrow row spacings better than the currently available hybrids would be more suitable for production in short-season areas. Leafy reduced-stature maize hybrids, which have only recently been developed, have traits which address these criteria. The objective of this study was to evaluate the effects of different population densities (65 000 and 130000 plants ha^?1) and planting patterns (single rows 76 cm apart and paired rows with 20 cm between rows within a pair of 56 cm between rows of adjacent pairs) on the yield and yield components of two leafy reduced-stature (LRS1 and LRS2), one non-leafy reduced-stature (NLRS), and two conventional corn hybrids (Pioneer 3979, < 2500 CHU; and Pioneer 3902, 2600-2700 CHU) at two locations. All hybrids had higher kernel numbers per row and single plant grain yields at the lower population densities when in paired rows. However, as plant density increased, these variables decreased more in the conventional hybrids than the LRS and NLRS hybrids, which demonstrates the greater tolerance of the latter to the stresses associated with higher plant densities. Grain yield was higher for the two LRS hybrids and the NLRS hybrid at 130000 plants ha^?1 than 65 000 plants ha^?1 Grain yield of conventional hybrids was reduced at the higher population density. The LRS hybrids matured before both conventional hybrids and out yielded Pioneer 3979 at the higher plant population density in both row spacings at both sites. Harvest index was not affected by population density and this value was not different among the NLRS and conventional hybrids. However, the harvest index of the LRS hybrids was greater than the others. LRS and NLRS hybrids had lower moisture contents and earlier maturities than conventional hybrids. Rapid growth of the first ear and higher harvest index values might are indications that LRS hybrids are more tolerant of higher population densities than the conventional hybrids.     

A proposed mechanism for loss of heterozygosity in rice hybrids

A phenomenon, loss of heterozygosity (LOH), was discovered in hybrid plants involving a selected plant (named AMR) of the Chinese rice cultivar ‘ZhongxinNo. 1’ as one parent. In these hybrids and some of their progenies, somatic variations were manifested by molecular genotypes and/or morphological phenotypes in vegetative parts of the same plant. Random amplified polymorphic DNA (RAPD) markers for the parents have been followed through the F₃ generation. RAPD markers were uniformly present or absent in all plants within some or all F₂ panicle rows derived from F₁ hybrids involving AMR. In contrast, RAPD markers segregated in the Mendelian manner for dominant markers in panicle rows derived from control hybrids. Certain F₂ panicle rows from F₁hybrids involving the special rice became fixed for all assayed RAPD markers. Genotype fixation was confirmed by molecular assays and field observations of the F₃ progenies. We propose a new biological mechanism, called ‘assortment mitosis,’ as being responsible for the observed phenomenon. The use of this mechanism in plant hybrids allows the development of uniform progenies as early as the F₂ generation. Therefore, the time required to obtain fixed non-parental type progenies for subsequent performance trials can be drastically shortened. Utilizing this mechanism in plant breeding represents a new approach and requires the modification of conventional plant breeding procedures. This revised version was published online in July 2006 with corrections to the Cover Date.     

酯酶在烟草远缘杂种早代中的应用

远缘杂交在一定程度上打破了物种间的界限,人为地促进不同物种的基因渐渗和交流,将紫苏的DNA运用常规杂交手段转入普通烟草中,从而获得新的烟草后代。着重研究了烟草杂种早代酯酶同工酶的差异,结果表明:在子代中具有与父本相同的遗传物质,即父本部分遗传物质在烟草中的整合与表达。     

Effects of Population Density on the Yield and Yield Components of Leafy Reduced-stature Maize in Short-season Areas

Maize hybrids which yield well, mature earlier and tolerate higher population densities better than the currently available hybrids would be more suitable for production in short-season areas. Leafy reduced-stature maize hybrids, which have only recently become available, have traits which address these criteria. The objective of this study was to evaluate the effects of different population densities (50000, 100000, 150000, and 200000 plants ha⁻¹) on the yield and yield components of one leafy reduced-stature (LRS), one non-leafy reduced-stature (NLRS), and two conventional control hybrids (Pioneer 3979, <2500 CHU; and Pioneer 3902, 2600–2700 CHU) at two locations. All hybrids had the highest kernel number per row and single plant grain yields at the lowest population densities, however, as plant density increased these variables decreased more in the conventional hybrids than the LRS and NLRS hybrids, which demonstrates the greater tolerance of the latter to the stresses associated with higher plant densities. Grain yield was highest for all hybrids, except for NLRS, at 100 000 plants ha⁻¹ with the LRS hybrid and Pioneer 3902 having the highest yields (11.4 vs. 9.8; 12.0 vs. 10.4) at locations 1 and 2 respectively. The LRS hybrid matured before either of the conventional hybrids and out yielded Pioneer 3979 at both sites. Harvest index was not affected by population density and this value was not different among the NLRS and conventional hybrids. However, the harvest index of the LRS hybrid was greater than the others. LRS and NLRS hybrids had lower moisture contents and earlier maturities than conventional hybrids. Rapid growth of the first ear, a higher yield per unit leaf area, and a higher harvest index are indications that LRS hybrids should be more tolerant of higher population densities than the conventional hybrids.     

油菜小孢子培养技术体系研究

小孢子培养在油菜的基础研究和应用研究中均具有十分重要的意义。自1982年Lichter首次在甘蓝型油菜中进行小孢子培养获得成功以来,国内外在油菜小孢子培养技术方面已取得大量研究成果,包括油菜小孢子胚状体发生的影响因素,小孢子植株的再生、成苗、大田移栽、染色体加倍等,近年来又对一些关键技术环节加以了改进,笔者在对这些研究成果进行总结的基础上针对中国国情建立了大田条件下油菜高效小孢子培养技术体系。用该体系对甘蓝型油菜和新疆野生油菜的体细胞杂种后代进行小孢子培养的出胚率达到300枚/皿以上,采用小孢子苗直接移栽大田技术,成活率达到89.0%。此外还成功构建了含127个DH系的黄籽油菜DH群体及含115个DH系的粒重分离群体。     

New maize × Tripsacum hybrids for maize improvement

Summary Approximately 27 000 maize x tripsacum pollinations were made and 19 hybrids were identified. Fourteen of these hybrids were of the classical type, which possesses the full gametic complement of chromosomes from each parent. These hybrids are more like tripsacum than maize. They are perennial, tiller profusely, and begin to flower in approximately two years from germination. So far, none of these hybrids has produced pollen and all backcrosses have been unsuccessful.Five of the 19 hybrids were not of the classical type, and possessed a variable number of chromosomes in cells of the same root tip. Most cells examined contained 20 maize and no tripsacum chromosomes. Other cells contained 20 maize chromosomes and up to eight of tripsacum. However, in at least three hybrids some cells contained a total of 20 chromosomes, of which up to four were tripsacum substitution chromosomes. These five non-classical hybrids are more maize-like, and are annual. Most have flowered within three months of germination. Although they have produced no viable pollen, four plants have set seed after backcrossing to maize.The production of F₁ hybrids is discussed with view to their subsequent assessment and utilization for maize improvement.     

Effect of parental genotypes and colchicine treatment on the androgenic response of wheat F1 hybrids

The effect of the parental genotypes and colchicine treatment on the androgenic response of wheat (Triticum aestivum L.) F1 hybrids was studied. For this, anthers from three F1 hybrids and their parents were cultured on W14 initiation medium and W14 supplemented with 0.03% colchicine. The number of responding anthers, microspore‐derived structures/100 anthers, green plants/embryos cultured, green plants/100 anthers and albino plants/100 anthers were recorded. It was observed that embryo formation and plant regeneration ability were genetically controlled and genotype dependent. In both treatments the variety Kavkaz had a significantly higher percentage of responding anthers, microspore‐derived structures and green plants/100 anthers than the other genotypes. On the other hand, the variety Myconos also demonstrated high microspore‐derived structure production and green plant regeneration when treated with colchicine. The good response observed in these two varieties indicates the importance of colchicine treatment only for certain genotypes. Green plant production capacity of the hybrids was intermediate to that of the parental varieties. As one parent with a high or even an intermediate response to anther culture could lead to the production of sufficient (for breeding purposes) green plants from the F₁ hybrids, it was concluded that screening the inbred lines for the response to anther culture with and without colchicine treatment could contribute to utilization of breeding material with a low response to anther culture via the proper hybrid combinations.     

Fertility restoration of new CMS sources in sunflower (Helianthus annum L.)

The development of commercial sunflower hybrids based on new CMS sources is of special interest for reducing the potential risk of vulnerability to pathogens and for increasing genetic diversity. From 263 test crosses involving nine new CMS sources, i.e. ANL1, ANL2, MAX1, PEF1, PET2, ANN1, ANN2, ANNS and ANN4, five lines were selected as potential restorers for PEF1, PET2 and ANN4. In test crosses between all nine CMS sources and these five restorer lines evaluated in 2 years, seven fully restored hybrids could be identified. These hybrids, based on ANL1, ANL2, MAX1, PEF1, PET2, and ANN4, showed good agronomic performance for plant height, days to flowering, maturity and oil content. Segregation analyses of the F2 populations indicate that a single dominant restorer gene was sufficient to restore pollen production of hybrids based on ANL2, PEF1 and PET2. For restoration of ANN4, two dominant complementary genes are required. In restoration of fertility in the crosses of ANL1 and MAX1 investigated, two dominant genes are involved each of which on its own allows the production of fertile plants.     

黑龙江省不同年代玉米杂交种产量对种植密度和施氮水平的响应

明确不同年代春玉米生产力对种植密度和氮肥水平的响应特征及其趋势,对高产高效的耐密品种选育和密植抗倒栽培具有重要的理论参考和技术指导意义。本文以黑龙江近50年来第一积温带大面积种植的8个典型春玉米品种为材料,于2009和2010年进行密度和施肥的田间试验,比较不同年代主栽品种生产力演变特征。结果显示,黑龙江省1970s—2000s玉米品种更替过程中,单株生产力与群体产量均明显提高,平均增幅分别为16.96 g 10年^-1和790 kg hm^-2 10年^-1;植株空秆率和倒伏率显著下降,株高、穗位、单株叶面积、穗粒数、千粒重显著提高。随着密度的提高,各年代玉米的单株产量呈显著下降趋势,群体产量呈抛物线形上升,群体最高产量的理论密度增幅为3 507株 hm^-2 10 年^-1;空秆率显著提高,但倒伏率仅1970s和1980s的品种呈递增趋势;株高、单株叶面积、棒三叶面积、穗粒数与千粒重均呈现下降趋势,穗位随密度增加呈显著上升趋势。各年代品种株高、穗位、单株叶面积和千粒重随氮肥水平提高呈增加趋势。在150~450 kg hm^-2的施氮水平范围,随着氮肥水平的提高,各年代品种增产效果不明显。各主要指标在年代、密度和氮肥水平之间存在显著的互作效应。对照东北玉米现有的品种特性、种植密度和施肥现状表明,选育耐密品种和实施密植抗倒栽培的增产潜力大,在现在的施肥水平上进一步提高种植密度是东北春玉米高产增效耕作栽培的技术创新方向。     

植物根结线虫分子鉴定研究进展

从RFLP、RAPD和SCAR、rDNA-ITS-PCR、AFLP等几方面概述了分子技术在植物根结线虫鉴定中的应用现状。分子技术用于检测植物根结线虫种间和种内群体间在DNA水平上的根本差异,为根结线虫的鉴定提供快速、准确的方法。     

Wheat embryogenesis and haploid production in wheat × maize hybrids

Summary Embryogenesis was analyzed in wheat × maize hybrids using paraffin sectioning. Embryogenesis in wheat × maize hybrids is different from that in self-pollinated wheat plants. Development of the embryo is not accompanied by the formation of an endosperm. The endosperm nuclei remain free in the cytoplasm, fail to advance into the cellular stage, and degenerate at a later time. The antipodal cells quickly degenerate in the fertilized ovaries of wheat × maize hybrids similar to self-pollinated ovaries. The antipodal cells remain normal in unpollinated ovaries. The pre-embryo will abort if it is allowed to develop on the plant, because of a nutritional shortage in the absence of an endosperm. Therefore, embryo rescue is necessary for haploid production from a wheat × maize hybrids. Haploid polyembryos were obtained from spikelet culture of wheat × maize hybrids. The formation of polyembryos is due to the cleavage of the pre-embryo and the effect of 2,4-D. The frequency of haploid embryo production and plant regeneration is affected significantly by maize genotypes, but not by wheat genotypes. The concentration of 2,4-D affects only the size of the embryo.     

哺乳动物异种克隆的研究进展

（河南省农科院生物技术研究所,郑州,450002）     

Breeding for resistance to rhizomania in sugar-beet (Beta vulgaris L.)

In breeding for resistance to rhizomania, breeding material was routinely examined for resistance to the rhizomania virus over several years. This study was performed in order to investigate the value of virological examination of sugarbeet breeding material in breeding for resistance to the rhizomania virus. Tests were conducted with varieties susceptible or partially resistant to rhizomania, as well as with several new and more-resistant hybrids. A test on young plants showed that all genotypes contained beet necrotic yellow-vein virus (BNYVV), but that the virus content differed widely. Plants of two commercially used partially resistant varieties had, on average, only half the virus content of susceptible varieties in their roots, and plants of eight new hybrids still in the process of registration contained less than one third of that amount. There was a significant negative correlation between the quantity of BNYVV in young plant roots and final yield under disease conditions in the field. Opportunities for further improvement in the level of the resistance to BNYVV in sugarbeet by means of conventional breeding programmes are discussed.     

Characterization of seed producing pearl millet x elephantgrass hexaploid hybrids

Summary Successful widespread use of a forage or biomass plant depends largely on its ease of establishment. Elephantgrass (Pennisetum purpureum Schum.) is used for both forage and biomass production, due to its high dry matter production, aggressiveness, perenniality, and forage quality. However, lack of high quality seed has limited the use of elephantgrass and its hybrids to pearl millet (P. glaucum L. R.Br.). Development of a seed-propagated pearl millet x elephantgrass hexaploid cultivar, which would combine desirable characteristics from both of these species, would be highly desirable. The objectives of this study were to characterize morphological and seed-related traits from the selfed progeny of seven hexaploid hybrids, and to determine whether seed size had any influence on these traits. Traits studied included number of tillers, height, leaf length and width, panicles per plant, days to flowering, panicle length, seed set, seed production, and weight of 100 seeds. Genetic differences were found among the progeny of the seven hybrids. Differences were also found between plants derived from large- and small-seed lots within families. Plants descended from larger seed had better growth and seed-related characteristics, which resulted in more desirable plants. These hexaploid hybrids showed potential for direct seeding into the field for biomass or forage production.     

A new cytoplasmic-nuclear male sterility system in pearl millet

Among the cytoplasmic-nuclear male sterility (CMS) systems reported in pearl millet, Pennisetum glaucum (L.) R. Br., the A_m= A₄ system produces the highest frequency of male-sterile hybrids. A CMS source identified in a large-seeded gene pool (LSGP) was compared with the A₄ system. Seven diverse restorer lines of the A4 system produced hybrids with 81A4 that were all fertile (pollen-shedding score 4 and 68–89% selfed seedset). In contrast, all the hybrids of these inbreds made with the isonuclear line with the LSGP cytoplasm were sterile (pollen-shedding score 1 and 0–3% selfed seedset). Topcross hybrids of four diverse composites made with 81A4 had 10–35% plants that had good fertility (> 50% selfed seedset). In comparison, no plant of any topcross hybrid with the isonuclear line having LSGP cytoplasm exceeded 20% selfed seedset, and it was rare for a plant to exceed even 10% selfed seedset. These differential fertility restoration patterns of hybrids indicate that the LSGP cytoplasm represents a CMS system that is different from the A4 and, by implication, from all those reported to date. This new CMS system is designated A₅.     

密植对不同玉米品种产量性能的影响及其耐密性分析

提高种植密度是玉米高产的重要措施之一,并且群体密度对冠层光合特性与产量有重要影响,为阐明不同基因型玉米品种的耐密性,本研究以先玉335、郑单958、吉单209为供试品种,设置60 000株 hm^-2、75 000株 hm^-2、90 000株 hm^-2、105 000株 hm^-2 4种密度处理,测定并计算6个生育期的叶面积指数(LAI)、光合势(LAD)、净同化率(NAR)以及产量性能参数平均叶面积指数(MLAI)、平均净同化率(MNAR)、收获指数(HI)、单位面积穗数(EN)、单穗粒数(GN)、千粒重(GW),并结合产量性能参数的变化对各品种进行耐密性分析。结果表明,不同品种产量性能参数对密度胁迫的反应相同,MLAI、EN与密度呈显著正相关,MNAR、HI、GN、GW与密度呈显著负相关;各品种产量对密度的响应呈一元二次方程关系,并具有良好的相关性;在试验密度范围内,品种耐密性表现以先玉335最好、郑单958次之,吉单209较差,其中,先玉335的适宜密度范围为90 000~105 000株 hm^-2,郑单958与吉单209的适宜密度范围为75 000~90 000株 hm^-2。     

VIGS技术在观赏植物中的应用

后基因组时代,基因功能研究备受关注,病毒诱导基因沉默(virus-induced gene silencing,VIGS)技术便是一种高效的基因功能鉴定方法。VIGS虽然在模式植物以及经济作物上已经有了大量的研究基础,但在观赏植物领域研究较少。观赏植物具有一定的经济、生态和社会价值,在对其基因功能进行研究时,利用高效的技术方法有利于更好地提高其观赏性、耐胁迫等品质,实现这些价值。所以,为降低观赏植物栽培成本,提高质量,将VIGS技术用于观赏植物研究,可有效解决传统方法效率低,存在技术瓶颈等问题并实现其价值的统一。本综述对VIGS这项简便、快速的技术的分子机理、体系的优化与发展以及其在观赏植物生长发育、遗传改良、抗胁迫等方面基因功能研究上的应用进行总结,希望该技术在不断优化的同时能够在观赏植物基因功能研究中得到更广泛的运用,为观赏植物基因功能鉴定、品质改良和定向育种提供新思路。     

Field analyses of horizontal gene flow among Vigna angularis complex plants

Recent studies have indicated that spontaneous interspecies crossing commonly occurs among vascular plants, and therefore that horizontal gene flow from transgenic plants into wild relatives is unavoidable. Few surveys, however, have been conducted to determine an actual flow frequency for individual plant species. For the present estimation of gene flow among Vigna angularis complex (small red bean) plants, randomly amplified polymorphic DNA was analysed, the patterns of which differ between a cultivar, var. angularis and its wild counterpart, var. nipponensis. Cultivars and wild‐type plants were planted alternately and approximately 1% of the screened F₁ beans of wild type were hybrid. These F₁ hybrids were selected, allowed to self to produce F₂ beans, and subsequent crossing between the F₂ plants and wild type resulted in that 3.7% of the F₃ generation possessed DNA fragments specific to the cultivar. These results indicate that gene flow actually occurs among V. angularis complex plants, and that transferred genes might be stably maintained by the offspring. The present observation cannot be directly applied to transgenic plants due to the lack of information as to whether or not artificially introduced genes behave as do native genes after horizontal movement. However, as gene flow is found to be inevitable in this species, specific assessment of whether or not the gene to be introduced confers a significant selective advantage to the host is critical for utilization of genetically modified plants in future.     

种植密度对不同株高夏玉米品种茎秆性状与抗倒伏能力的影响

倒伏是影响夏玉米在密植条件下获得高产的重要限制因素之一,本研究旨在探讨种植密度对不同株高夏玉米品种茎秆性状与抗倒伏能力的影响。以矮秆品种登海661 (DH661)和高秆品种鲁单981 (LD981)为试验材料,通过设置4.50×10⁴株 hm^-2、6.75×10⁴株 hm^-2和9.00×10⁴株 hm^-2 3个种植密度,研究茎秆节间长度、茎秆穿刺强度、茎秆显微结构以及倒伏率等方面的变化。结果表明,随种植密度增加,夏玉米的基部第3茎节间和穗位节间变细,茎秆穿刺强度显著下降,较密度4.50万株 hm^-2,DH661和LD981 6.75万株 hm^-2、9.00万株 hm^-2地上第3节间茎秆穿刺强度分别降低了8.5%、22.6%和13.3%、29.6%;茎秆皮层和维管束内部厚壁细胞厚度及维管束数目均随种植密度的增加显著下降,倒伏风险增加,但矮秆品种的下降幅度小于高秆品种,而产量的增加幅度大于高秆品种,说明矮秆品种在高密度下能够保持较好的抗倒伏性能,有助于其在高密度种植条件下获得高产、稳产。     

中棉所12配制的2个杂交棉DNA甲基化遗传与传递

DNA甲基化在真核生物的生长发育过程中起着重要的调控作用。本研究用MSAP方法分析了中棉所12配制的2个杂交棉和亲本不同发育时期的基因组DNA 5′-CCGG位点胞嘧啶的甲基化水平及其遗传传递模式。研究表明: (1)杂交棉及其亲本不同发育时期的胞嘧啶甲基化水平不同,随着生育期的逐步推进,出现两头低而中间高现象;(2)两个杂交棉组合的DNA 甲基化总体水平为12.41%~20.05%,其中以内侧胞嘧啶全甲基化为主(约占6.90%~11.47%);(3)棉花中绝大多数CCGG胞嘧啶甲基化位点是由亲本稳定遗传给杂交种的,但杂交棉仍有1.14%~3.39%的位点显示了变异,其变异频率在不同亲本组合之间和不同发育时期都存在差异;(4)对甲基化差异条带测序分析发现,其功能涉及到富含亮氨酸重复、类PDR的ABC转运蛋白、GTP结合蛋白、病程相关蛋白、磷酸激酶、功能未知的蛋白质和反转录酶等,部分差异序列没有产生有意义的匹配。