大豆不同亲本正交和反交后代株高遗传规律的比较研究

对中美大豆不同亲本正、反交间F2、F3、BC1F2的株高性状遗传表现进行了初步比较研究,结果表明:正交和反交间株高在F2、F3两世代的遗传规律基本一致;株高在各世代的遗传表现因正交和反交的不同而存在一定的差异;BC1F2株高因回交亲本的不同而有不同的表现;用相同亲本回交的BC1F2株高遗传表现因正、反交不同而存在一定的差异。     

大麦生育期部分双列杂交分析

以50个大麦品种(系)为试材,用 kempthorne 部分双列杂交法分析各生育期性状和单株产量。结果表明广义遗传力由大到小是成熟期、灌浆期、孕穗期、出苗期、抽穗期、单株产量。各品种(系)间的5个生育期和单株产量性状的一般配合力差异显著。     

大豆不同亲本正、反交F2、F3、BC1F2主茎节数遗传规律研究

为深入理解大豆主茎节数的遗传规律,提高杂交组配及选择效果,以中、美大豆品种为亲本,对正、反交F2、F3、BC1F2后代群体的主茎节数遗传规律进行了比较研究.结果表明:不同大豆亲本杂交及回交后代群体的主茎节数变异度不大,分离强度表现中等;F3主茎节数的超亲优势较F2增强,而分离强度小于F2;大豆杂交及回交早世代主茎节数的遗传与其亲本值相关,以主茎节数少的品种为母本的组合,其杂交和回交早世代群体的平均值比以主茎节数多的品种为母本的组合偏小,而分离强度偏大,反之则异然;采用主茎节数少的品种回交不利于后代群体平均节数的增加,有利于回交后代群体分离强度保持在较高水平,扩大选择空间;而采用主茎节数多的品种回交虽有利于后代群体平均节数的增加,但回交后代群体分离强度偏低,选择空间缩小.研究还表明,主茎节数在F2、F3都具有较高的广义遗传力,且差异较小,在这2个世代进行选择是有效的;杂交早世代主茎节数的广义遗传力与组合配置有关,母本主茎节数多的组合,主茎节数广义遗传力大于母本主茎节数少的组合.     

不同三元杂交猪肥育效果及肉质比较

用杜洛克、A系作三元杂交终端父本,分别与 (长白×大约克)、(大约克×长白),(B系×C系)、(大约克×C系)作母本杂交产生的8个杂交组合的仔猪为试验材料,对其安排活质量20～90 kg的肥育试验,并进行屠宰测定和胴体品质分析,结果表明,全期日增质量以杜洛克×(长白×大约克)最高(为704 g),显著的高于杜洛克×(B系×C系)、A系×(长白×大约克)、A系×(B系×C系),同时与A系×(大约克×C系)有极显著的差异;从表现值看,料肉比最小的组合为A系×(长白×大约克)。通过对肥育性能较好的几个组合的肉质比较,初步确定杜洛克×(长白×大约克)和杜洛克×(大约克×C系)为较理想的三元杂交组合模式。     

甘蓝型油菜与诸葛菜属间杂交F12群体的品质及遗传分析

以甘蓝型油菜（AACC,2n=38）品种Oro与诸葛菜（OO,2n=24）属间杂交F4世代中出现的五倍体单株（AACCO,2n=50）为起始材料连续自交选育、鉴定,直至获得F12群体。各F12株系间表现一定的形态差异, 但株系内植株形态特征一致。细胞学观察表明85.3%的F12单株具有与甘蓝型油菜相同的染色体数目,花粉母细胞(PMCs) 减数分裂中正常配对和分离;其余植株的染色体数目分别为37、39和40;红紫色植株在减数分裂中有落后染色体,四分体时期会出现微核。基因组原位杂交(Genomic in situ hybridization,GISH)分析未检测出整条的诸葛菜染色体;但AFLP分析表明存在渗入的诸葛菜DNA片段。F12植株的脂肪酸组成及硫苷含量表现较大的变异, 有的植株油酸含量高于Oro而硫苷降低。     

甘蓝型油菜与芽菜属间杂交新品系的形态及解剖学特征

甘蓝型油菜与荠菜属间杂交新品系ＹＤ１６的根、茎和叶的外部形态似母本美国油菜．但分枝部位较低、茎秆较矮、成熟期早等性状偏向父本荠菜。ＹＤ１６根、茎、叶大多数解剖结构特征介于双亲之间，少数性状如根中韧皮部和木质部所占的比例偏向母本，花粉粒大、叶片厚度小、叶片绿色浅等属超亲性状。     

小麦与多枝赖草耐盐纯合易位系的培育及GISH鉴定

以小麦与多枝赖草属间杂种花药培养获得的纯合后代纯系为材料，经过细胞学观察、田间选拔、抗性鉴定、综合农艺性状调查以及小区产量对比试验，从中初步筛选鉴定出具有外源耐盐性状、且农艺性状好的材料，再经分子标记(GISH)鉴定纯合易位系。表明花药培养可有效克服小麦远缘杂交后代的疯狂分离，并可促进染色体的结构变异，在短时间内获得大量具有丰富变异且可稳定遗传的后代，大大缩短了小麦远缘杂交导入外源基因的年限。     

Clonal performance of perennial Oryza sativa/O. rufipogon selections and their combining ability with O. sativa cultivars for survival, stolon production and yield

In Southeast Asia, upland rice (Oryza sativa) is an annual crop typically grown for subsistence on hilly lands that are at risk for soil erosion. If perennial cultivars of upland rice were developed, they would provide farmers with an inexpensive tool to produce a preferred food while conserving soil. O. rufipogon, the undomesticated progenitor of O. sativa, includes perennial and stoloniferous forms. To evaluate the feasibility of developing perennial cultivars by combining genes of O. sativa and O. rufipogon, four trials were conducted in an upland field at IRRI: O. sativa/O. rufipogon F₁ clone and cutting height trial, F₂ family trial, and two O. sativa/stoloniferous-selection factorial mating design trials. Plants were established at the beginning of the rainy season, then subjected to a 6-month dry season and evaluated for survival after 1 year. Of the 2101 cultivar control plants, only three IR47686-1-4-B individuals survived and none produced stolons. The 18 F₁ clones, which were selected from previous trials with less drought stress, ranged in survival from 4.4 to 91.4%. Cutting height at harvest did not affect survival. Survival among the F₂ families ranged from 9.4 to 31.9%. Segregation for stolon presence did not differ from a 3:1 ratio for five of the six F₂ families, suggesting the effect of a single dominant gene. Average yields per plant for the F₂ families were 1/3 to 1/9 of yields for the cultivars. However, by crossing the F₁s to cultivars, yield potential was almost fully recovered. For the full-sib families of the factorial trials, survival ranged from 0.0 to 48.6%. Azucena and IR47686-1-4-B, both japonica cultivars, exhibited greater general combining ability for survival relative to the six other cultivar parents. Thus, the process of developing perennial cultivars of rice should include screening annual cultivars to identify those with the best combining ability for survival. To develop cultivars of perennial upland rice, drought avoidance and/or tolerance from annual upland cultivars must be combined with the capacity for perennial growth from wild perennial species. The frequency of stolonifereous testcross progeny was lower than expected and was affected by the O. sativa parent. Thus, additional genes likely affected stolon penetrance and expression. Analyses of covariance indicated that stolons improved the likelihood of survival for progenies of the factorial trials but the effect was small (b < 0.1), and that yield (g/plant) had a small negative effect on percent survival (b = −0.13 to −0.32). This study demonstrated that it was possible to introgress genes for perennial growth from wild O. rufipogon accessions into domesticated O. sativa. Additionally, strategies for developing perennial cultivars of upland rice were improved.     

籼粳杂交偏籼型恢复系产量相关性状的遗传效应与杂种优势分析

选用通过籼粳杂交、籼型育种目标选择以及育性恢复能力测定等手段选育的6个偏籼型早熟恢复系Gmh01、Gmh03、Gmh05、Gmh06、Gm4006、Gme24与2个籼型三系不育系,按照2×6不完全双例杂交试验设计配制遗传材料。采用等位基因的加性-显性遗传模型(AD模型)分析其产量相关性状的遗传效应与杂种优势。结果表明,每穗总粒数和每穗实粒数主要受到基因加性效应的影响;播始历期、主穗长、单株有效穗数和结实率主要受到基因显性效应的影响。杂种一代产量相关性状均具有一定的杂种优势,但因受到等位基因遗传效应的不同而存在程度和方向上的差异。其中,籼粳交偏籼型恢复系Gmh01、Gmh03和Gme24的遗传改良效果显著,综合性状优良,在今后籼粳亚种间杂种优势利用中具有较好的应用前景。     

Integration of breeding and technology into diversification strategies for disease control in modern agriculture

While diversity for resistance has been recognised for more than 60 years as a key factor in disease management, and diversification strategies such as cultivar mixtures and multilines are described and advocated in almost every plant pathology textbook, the general view in modern agriculture is that diversity would be too difficult and expensive to implement. In addition, difficulties in marketing the produce are emphasised. The question thus arises if and how such strategies can be designed to find a place in modern agriculture. Considering the general ecological benefits of diversification and the possible economical benefits for growers and society, several possible approaches to the solution of actual and perceived problems in modern agriculture are discussed. An important route towards achieving diversity would be to integrate it into the breeding process. Selection criteria would include inducibility of resistance and competitive ability, in order to produce diversified varieties able to adapt both to unpredictable environmental conditions (especially climatic) and to changing pest and pathogen populations through co-evolution. Evolutionary breeding methods such as composite crosses and modern landraces and some of the legal problems associated with these approaches are discussed. Technical solutions are integral to the future use of diversification strategies and range from more or less simple adjustments to machinery for planting and harvesting to devices designed for separation of the harvested products.