Harvest management based on leaf stage of a tetraploid vs. a diploid cultivar of annual ryegrass

Leaf stage‐dependent defoliation is linked to the plant's physiological status and may be a more suitable criterion than time‐based intervals for harvesting forage grasses, but no reports of research with annual ryegrass (Lolium multiflorum Lam. var. westerwoldicum) were found. To address this, a 2‐year field study was carried out at Raymond, MS, on a Loring silt loam soil (fine‐silty, mixed, thermic Typic Fragiudalfs). Forage production, morphological characteristics and nutritive value responses to defoliation based on leaf stage (2, 3 and 4 leaves per tiller) and two residual stubble heights (RSH; 5 and 10 cm) of a tetraploid (“Maximus”) vs. a diploid (“Marshall”) cultivar of annual ryegrass were quantified. Forage harvested, in 2011, increased linearly as leaf stage increased from 7.3 to 8.8 Mg/ha, but during 2012 was least (7.0 Mg/ha) at 3‐leaf stage and similar at the other two leaf stages (7.6 Mg/ha). Tiller density was less for Maximus (1,191 tillers/m²) than for Marshall (1,383 tillers/m²). Leaf blade proportion decreased with increasing leaf stage and was greater by 9% for Maximus than for Marshall. Generally, forage nutritive value became less desirable with increasing leaf stage. There was a dichotomy in forage harvested and nutritive value responses, but maximum forage productivity was achieved when annual ryegrass was defoliated at the 4‐leaf stage interval.     

二倍体月季F_1群体的SSR鉴定与遗传分析

以中国古老月季品种‘月月粉’(Rosa chinensis‘Old Blush’,用OB表示)为母本,‘无刺光叶蔷薇’(Rosa wichuriana‘Basye’s Thornless’,用W表示)为父本,构建F_1代共296个单株。从146对SSR标记中筛选出亲本间多态性好且条带清晰的23对SSR标记,对随机选择的94株F_1进行杂种鉴定和遗传分析。结果表明:筛选到3个纯合显性标记分别为Fv512、Fv609和305,可单独一次性鉴定全部杂种真实性;随机筛选的94株子代均为真杂种;20个SSR标记用于基因型分析,有9个标记出现了偏分离,并在统计上达到显著或极显著水平,偏分离率45%,说明该F_1群体基于SSR位点的基因型偏分离率较高,在进行高密度遗传图谱构建时应重视偏分离标记对作图的影响;UPGMA聚类分析显示,94株F_1的遗传变异大,且遗传多样性丰富,可划分为2个大类7个亚类。     

提高马铃薯双单倍体花药培养产生胚状体及再生植株频率的研究

用三种不同温度前处理和三种培养基相配合对７个从双单倍体马铃薯（Ｓ．ｔｕｂｅｒａｓｕｍＬ，２ｎ＝２ｘ＝２４）中随机抽取的品系进行了花药培养，选择出了较好的培养基和前处理的适宜温度及方法．从双单倍体花药中诱导产生胚状体及再生植株频率有所提高达２７．５％和８．８％．倍性鉴定表明，从双单倍体诱导的胚状体分化的植株绝大多数为二倍体，而且多数为纯合体，说明这些胚状体来自己减数的配子，可能是由在胚状体发育过程中的体细胞染色体加倍形成的．     

二倍体雌核发育鲫鲤卵子发生的DNA含量和细胞学分析

以产生单倍体卵子的二倍体雌性红鲫为对照,对远缘杂交起源的二倍体雌核发育鲫鲤早期卵巢组织中的生殖细胞进行了流式细胞术分析,在此基础上结合组织学切片方法和染色体制片,对相应的卵巢组织细胞学观察和生殖细胞减数分裂特征进行了探讨.结果显示,雌核发育二倍体鲫鲤卵母细胞的DNA含量呈现两个主要的峰值,检测样本中的2号峰值显示的DNA含量是二倍体红鲫卵母细胞的1倍,代表减数分裂前染色体数未加倍的细胞群,其减数分裂Ⅰ前期分裂相呈现同源染色体部分配对,该细胞群在组织学切片上呈现空泡化等败育现象;另外,检测样本中的3号峰值显示的DNA含量是二倍体红鲫卵母细胞的2倍,代表减数分裂前染色体数已加倍的细胞群,其减数分裂Ⅰ前期分裂相呈现染色体数目加倍的完整的染色体配对,该细胞群由于染色体数加倍,可以越过杂种鱼的异源染色体之间的减数分裂配对障碍,正常发育为体积不断增大的初级卵母细胞,为产生后续的染色体数不减半的二倍体卵子奠定基础.该结果丰富了不减数配子的发生机制研究,在鱼类遗传育种方面具有重要意义.     

不同二倍体和四倍体小麦成熟胚再生体系研究

为了研究不同基因型和培养条件对小麦成熟胚愈伤组织诱导和分化的影响,以硬粒小麦、墨西里卡、野生一粒麦Tu和野生一粒麦Tb为实验材料,对其成熟胚在不同激素配比下愈伤组织的诱导和植株分化进行研究。结果表明,不同基因型小麦成熟胚愈伤组织诱导、分化及再生均存在很大差异。其中硬粒小麦的成熟胚培养效果最佳,其愈伤组织在不同2,4-D浓度（1.0~4.0 mg/L）下诱导率均在93%以上。不同激素配比对成熟胚愈伤组织绿点率、再生率均有显著影响。硬粒小麦、墨西里卡、野生一粒麦Tb在激素配比为KT 1.5 mg/L+NAA 0.5 mg/L的分化培养基中培养效果最好,其绿点率分别为85.22%,61.67%,8.50%,成苗率分别为40.40%,32.06%,1.72%;而野生一粒麦Tu的最适分化培养基激素配比为KT 1.0 mg/L +NAA 1.0 mg/L,其绿点率和再生率分别为18.64%和8.47%。研究表明,基因型是影响二倍体和四倍体小麦成熟胚培养的主要因素,愈伤组织的诱导和植株的再生是相互独立的。     

温度对不同规格长牡蛎三倍体和二倍体代谢影响的比较

用试验生态学方法研究了温度对不同规格的长牡蛎Crassostrea gigas三倍体(3n)和二倍体(2n)呼吸和排泄的影响。试验设12、18、24、30℃4个温度水平,并根据牡蛎倍性、规格分别设3n-L、3n-M、3n-S、2n-L、2n-M、2n-S 6个组别。结果表明:在12~24℃条件下,牡蛎的耗氧率随着温度的升高而增加,并在24℃时达最大值,之后,耗氧率随温度的升高而降低;3n和2n牡蛎软体部干重(W)与耗氧率(R)的回归关系符合幂函数方程R=aWb-1,3n的a值为1.532~1.737,b值为0.728~0.887,2n的a值为1.197~2.173,b值为0.823~0.854。牡蛎软体部干重(W)与排氨率(N)的关系符合幂函数N=c Wd-1,2n的c平均值为194.992,d平均值为0.669;3n的c平均值为251.746,d平均值为0.611。以体重为协变量进行协方差分析结果表明:温度引起耗氧率和排氨率的差异达到显著水平;倍性效应引起排氨率的差异达到显著水平,且3n的排氨率大于2n,倍性效应引起的耗氧率的差异不显著。     

四倍体和二倍体泥鳅及大鳞副泥鳅营养成分分析

利用常规肌肉营养分析方法测定了四倍体泥鳅、二倍体泥鳅和大鳞副泥鳅的肌肉营养成分。结果表明: 四倍体泥鳅、二倍体泥鳅和大鳞副泥鳅肌肉中蛋白质含量(鲜重) 分别为18. 68%、18. 69%和18. 20%; 脂肪含量分别为0. 796%、0. 106%和1. 203%; 水分含量分别为79. 81%、79. 52%和78. 40%; 灰分含量分别为0. 951%、11188%和1. 162%。3种泥鳅肌肉中都含有常见的17种氨基酸, 其中包括9种人体必需氨基酸。氨基酸总量(占鲜重)分别为17. 57%、18. 11%和17. 47%; 必需氨基酸总量分别为7. 84%、7. 98% 和7. 76%, 必需氨基酸的构成比例符合FAO /WHO 的标准。鲜味氨基酸含量分别为6. 98%、7. 33%和6. 95%。经比较分析, 四倍体泥鳅和二倍体泥鳅肌肉中蛋白质含量、17种氨基酸含量、氨基酸总量和必需氨基酸总量均很接近, 但都明显高于大鳞副泥鳅。     

马铃薯4x-4x和4x-2x杂种后代高世代选系总产和商品薯产量比较

传统的4x-4x杂交方法很难进一步提高马铃薯（Solanum tuberosum L.）产量，倍性操作育种技术为提高马铃薯产量提供了新途径。试验比较4x-4x和4x-2x杂种后代高世代选系总产、商品薯产量的差异，探讨利用倍性操作育种的可能性。从4x-4x和4x-2x组合根据块茎性状和产量各选出17个高世代无性系，按随机区组设计，3次重复，在黑龙江省加格达奇比较两种组合类型高世代选系总产和商品薯产量的差异。4x-4x和4x-2x组合后代高世代选系在总产量方面无差异，但从4x-2x组合中可以选出更多的高产无性系。4x-2x组合高世代选系商品薯产量显著低于4x-4x组合，这主要是由于4x-2x组合后代选系单株结薯多，但单薯重低。采用4x-2x组合方式育种可有效利用具有丰富遗传变异的二倍体种质资源，但要注意在二倍体水平上选择，重点改良二倍体种或二倍体杂种对长日照的适应性，以及块茎性状，提高大薯率。     

小白菜杂交组合配制及自交系选育试验研究

把小孢子培养获得的22个小白菜加倍二倍体（DH）纯合植株分为 A、B两组进行组间杂交以及自交，对获得的41份杂交组合的叶片形状和叶柄色等外观品质性状进行观测分析，并对相应数据进行聚类分析，结合植株的田间表现，筛选出优良的杂交组合和亲本。结果表明：1）两个相同亲本的正反交组合外观商品性状可能存在差异；2）6个抗性强、耐衰老的杂交组合，其单株产量均高于0.4 kg，属于商品性状优良的杂交组合，其中A7 B2可作为特色分蘖组合；3）筛选出 A2、A5、A7、B6、B8、B9、B10、B118份骨干亲本自交系，以及 A1、A3、A9、B2和B75个特殊配合力高的亲本。     

Modes of inheritance of two apomixis components,diplospory and parthenogenesis,in Chinese chive (Allium ramosum) revealed by analysis of the segregating population generated by back-crossing between amphimictic and apomictic diploids

To investigate the mode of inheritance of apomixis in Chinese chive, the degrees of diplospory and parthenogenesis were evaluated in F₁ and BC₁ progenies derived from crosses between amphimictic and apomictic diploids (2n = 16, 2x). The F₁ population was generated by crossing three amphimictic diploids 94Mo13, 94Mo49 and 94Mo50 with an apomictic diploid KaD2 and comprised 110 diploids and 773 triploids. All the diploid F₁ plants examined were completely or highly eusporous and completely syngamic. All the triploid F₁ plants examined were highly diplosporous and highly parthenogenetic. KaD2 could not transmit its high level of apomixis via monoploid pollen grains. The BC₁ population, generated by crossing 94Mo49 with apomictic triploids found in the F₁ offspring, exhibited heteroploidy; it comprised haploid, diploid, triploid, tetraploid and various aneuploid individuals. In this generation, clear segregation was observed between diplospory and parthenogenesis. Analysis of the BC₁ population suggests that diplospory and parthenogenesis are each controlled by single dominant genes, D and P, respectively. However, all the BC₁ plants characterized as parthenogenetic were diplosporous. The absence of phenotypically eusporous parthenogenetic plants can be explained by assuming that the presence of diplospory gene is a prerequisite for the parthenogenesis gene expression in Chinese chive.