第一章 常规杂交育种

1、第一章 常规杂交育种 (Cross Breeding)本章主要教学内容杂交育种的原理和意义杂交亲本的选择和选配杂交方式和技术杂交后代的选择和培育第一节 常规杂交育种的意义(Significant of Cross Breeding)杂交育种的基本概念(Definitions)杂交（Cross)：遗传类型不同的生物体相互交配或结合而产生杂种的过程。有性杂交（Sexual cross)无性杂交（Asexual cross)；远缘杂交（Distant cross)种内杂交（Cultivar cross).常规杂交育种：按育种目标选择选配亲本，通过人工杂交的方法将亲本的优良性状集于杂交后代，再通过对杂

2、交后代进行自交分离，选择出符合目标要求的，遗传性稳定一致的优良新品种。常规杂交育种也称做重组育种、有性杂交育种、组合育种。杂交育种的遗传学原理v 基因的自由分离和重组规律 Mendels Principle of Segregation: Pairs of alleles segregate (separate) during gamete formation. Upon fertilization, the alleles are paired up again.v 基因连锁互换规律 MORGANS LAWS：Genes occur in a linear order on chromoso

3、mes Linked genes are on the same chromosome Genes can be exchanged between chromosomes during meiosisv 细胞质遗传规律 (Cytoplasm genetic)v 数量性状遗传（Quantitative trait genetic)常规杂交育种的意义1、实现基因重组，获得变异类型。 Realizing the recombination of genes and obtaining variation.将分属于不同品种、控制不同性状的优良基因随机组合，形成各种不同的基因组合，再通过定向选择育成集

4、双亲优良性状于一体的新品种。2、打破不利基因的连锁关系。Separating the linked disadvantageous genes with the advantageous genes on the same chromosome.例：番茄抗病基因与黄化基因的连锁。3、改善基因间的互作关系，产生新性状。Changing the interaction of genes and producing the new trait.4、综合双亲优良性状(产生超亲性状)。Integrating the advantageous traits of the parents into the

5、hybrid. 例：节间长、单节结荚多的甜豌豆品种与节间短的品种杂交后代，通过自交 选育出节间短、单节结荚多的新品种。第二节 亲本的选择和选配 (Selection and mating of parent)亲本的选择：指根据育种目标选用具有优良性状的品种类 型作为杂交亲本。亲本的选配：指从入选的亲本中选用哪些亲本杂交，怎样杂交。 一、亲本的选择原则1. 广泛搜集符合育种目标原始材料，精选亲本2. 亲本应尽可能具有较多的优良性状3. 明确亲本的目标性状，分清目标性状的主次4. 重视选用地方品种5. 亲本的一般配合力要高二、亲本的选配的原则1. 父母本性状互补2. 选用不同类型或不同地理起源的亲

6、本相配 3. 以具有较多优良性状的亲本作母本4. 亲本之一的性状应符合育种目标 (Why)5. 用一般配合力要高的亲本配组第三节 杂交方式和技术1、 单交（single cross） 最简单的杂交方式，两个亲本的杂交方式，又称成对杂交。In case of single-cross hybrid, only two parents are taken. 2、多亲杂交（multiple cross） 参加杂交的亲本是3个或3个以上的杂交叫多亲杂交，又称复合杂交或复交。 根据亲本参加杂交的次序不同可分为添加杂交和合成杂交。 添加杂交 多个亲本逐个参与的杂交。 (AB) C D合成杂交: 参加杂交的

7、亲本先两两配成单交种，两个单交种 再杂交。 (AB) (CD) 特点：杂种群体的遗传基础丰富，亲本的核遗传组成均等3. 回交（Backcross ) 杂交一代及以后各世代与亲本之一再进行杂交。 Backcrossing is a form of recurrent hybridization by which a desirable allele for a character is substituted for an alternative, undesirable allele Trait of interest should be simply inherited and easily

8、 phenotypedBackcross Breeding MethodGenerally this method is practiced for diseases, insects, or stress-resistance breeding programs of vegetable crops.The backcross method is based on the principle of quick and efficient transfer of a gene by repeated backcross and then selection in F2 and subseque

9、nt segregating generations. With continuous backcrossing with the recurrent parent, the characteristics of the recurrent parents are transferred in the backcross population and this population becomes homozygous, like the recurrent parent.轮回亲本( recurrent parent)： 在回交过程中多次参与杂交的亲本。Recurrent parent is

10、the parent to which the F 1 and subsequent generations are crossed.Generally, the recurrent parent is a high-yielding, recommended variety but lacks one desirable trait. This may be susceptibility to disease, insect, or stress conditions.Recurrent parent should be a highly acceptable genotype (e.g.

11、existing commercial cultivar or inbred line)非轮回亲本( nonrecurrent /donor parent) ：在回交过程中只参加一次杂交的亲本，也叫做“供体”。 Donor parent donates the desirable allele but does not enter into the backcross.The nonrecurrent parent is mostly low yielding, but possesses a desired trait which the recurrent parent lacks. In

12、 most of the cases, wild species are used as nonrecurrent parents. The best BC donor parent will possess the desired trait but will not be seriously deficient in other traits.Backcross Breeding MethodRecovery of the recurrent parent genotype follows this pattern: % recurrent % donorF1 50 50BC175 25B

13、C287.5 12.5BC393.75 6.25BC4 96.875 3.125BCm1-(1/2)m+1(1/2)m+1Line Improvement through Backcross MethodFour backcrosses to recipient with selection for desired traitFinish with selfing or DH to isolate homozygous line二、 有性杂交技术 (Hybridization techniques ) For hybridization, raising of crop, equipment

14、required, preparation of female flowers, and pollination are the important aspects. A vegetable breeder should have a working knowledge of vegetable crop production. A 制定杂交计划； B 了解育种对象的开花生物学习性； C 必要的生产资料购置； D 杂交工具准备。 A pair of fine-tipped forceps, a spear-pointed needle, a pair of scissors, a magnif

15、ying lens, a small vial of alcohol, tassel bags, crossing or pollination bags, a hand stapler, label tags, electric pollen collector, pollen carrier, and apron are the common facilities required in hybridization programs. （一）亲本株的培育和选择1. 种株培育的三项基本要求是：生长健壮、典型性及无病虫危害。 Before starting emasculation, it s

16、hould be ensured that all the plants of the breeding line are true to the type. 2. 采取各种措施调整亲本花期，使之相遇。 In order to widen the hybridization period, multiple dates of planting may be adopted. 3. 选择杂交用花应根据不同园艺植物选择适当开花节位或花序，选留数量适中，健壮饱满的花蕾。 The proper size of the bud selected for emasculation decides to a

17、 great extent the success of hybridization. Usually buds about to open or due to open the following day are selected. Generally, lower buds are better than the terminal buds for hybridization. （二）隔离措施防止非目的性杂交，应采取适当的隔离措施。通常用半透明羊皮纸或硫酸纸进行花序或单花套袋隔离。（三）父本花粉采集、贮存和生活力检验 Collecting, storage and testing of p

18、ollen 父本花粉应从隔离条件下，亲本株当天盛开花朵上取得。也可在花前一天取回父本花蕾，取出花药干燥后取粉。 Either pollen is collected from the flower or the flower is used as such for pollination. In cloudy weather and at low temperature, Pollen collection is needed for later pollination. （四）母本花去雄授粉(Emasculation) 两性花园艺植物的母本在授粉前必须去除雄蕊以防自交。去雄可在开花前一天下午

19、进行。授粉可在去雄后马上进行，也可在第二天开花后进行。（五）杂交标记与登记 杂交后的花应挂牌标记。并建立有性杂交登记表。（六）杂交后的管理 检查纸袋等隔离物； 及时去除隔离物； 加强母本种株的栽培管理。（七）杂交种子的收获和贮存1. 及时采收；2. 收获过程中严格防止不同杂交组合的错乱和混杂；3. 种子脱落后晒干，装于纸袋内，袋外写明组合名称，袋内放入相应的标签；4. 种子贮存于低温、干燥、防虫、防鼠的条件下。第四节 杂交后代的选择培育 杂交后代的选择系谱法（pedigree method） 混合法（ mass or bulk selection ） 单子传代法（single seed des

20、cent method） 一、系谱选择法的基本程序1、杂种一代（F1） 以组合为小区种植， 每小区30-50株。F1一般不做选择，按组合混收留种。2、杂种二代（F2） 将每组合混收的种子按小区种植。根据目标性状控制基因对数多少计算F2群体大小。 人选的目标株应单株自交留种。若一对显性基因自交后代出现目标性状的比例为3/4，一对隐性基因自交后代出现目标性状的比例为1/4，则：具有r对隐性基因，d对显性基因的目标个体在F2出现的比率 （1/4） r （3/4） d - p当选出目标株的几率为a时，出现1株目标个体所需种植的株数要满足 （1p）n 1a 则种植株数nlog（1a）/log（1p） 当

21、r和d都为3 , 选出目标株的几率a为95% n=log（10.95）/log1（1/4）3（3/4）3 =451.39（株） 当条件允许时，一般按10002000种植Phase I: Creating Initial VariationGrow 50 to 100 F1 plants in a bulk plot Grow 2000 to 3000 F2 plants. Select and harvest plants or spikes that seem to combine desired parental characteristics. 3. 杂种三代F3 ： 按F2人选的单株后

22、代（株系）为小区分别播种，每小区50株。10个小区设一ck，淘汰不良株系，优系中选优株自交，单株留种。系内高度一致者可升级鉴定。4. 从F4以后，均重复F3工作，优系中选优株自交直致系内纯合一致。Phase II: Pedigree MethodF3 to F5 generation: Grow progeny rows with seed harvested from superior plants harvested in the previous generation Select 3 to 5 of the best plants within these rows 25 to 50

23、families may be retained at the end of the F5 generation Identity of plant and row is maintained and superior traits of the plants are recorded5. 品种比较试验 条件一致、三次重复、设置对照（ck），保护行。人选最佳品系。6. 区域试验（多点试验） 在与品比试验方法相似的基础上，按不同地区多点设置。 一般由省或省级以上品种审定委员会安派，相应级别种子管理部门组织实施。7. 品种审定。Phase III: Pedigree MethodF6 Grow f

24、amilies of 1 plant in rows Selected seed lots are designated experimental lines (EL)F7 Grow EL together with adapted lines in a preliminary field trial F8 to F10 Yield trials are continued at two or three environmentsF11 to F12 Increase seed and distribute the new cultivarPedigree Method Main object

25、ive is to isolate superior, recombinant, homozygous lines Selection is performed from the F 2 generation onward Response to early generation selection of quantitative traits may be low because of heterozygosityPedigree Method Advantages1. Eliminates unpromising material at early stages2. Multi-year

26、records allow good overview of inheritance and more effective selection through trials in different environments3. Multiple families (from different F2 individuals) are maintained yielding different gene combinations with common phenotypePedigree Method Disadvantages1. Labor, time and resource inten

27、sive; usually must compromise between # crosses and population sizes;2. Very dependent on skill of breeder in recognizing promising material;3. Not very effective with low h2 traits;4. Slow; can usually put through only one generation per year, and the right environmental conditions must be at hand

28、for accurate selection.二、 混 合 法 (bulk method)混合法的工作要点 在杂种分离世代，按组合混合种植，除淘汰明显的劣株和杂株外，一般不加选择，直到杂种后代纯合百分率达到80以上时(约在F5F8)或在有利于选择时(如病害流行或某种逆境条件如旱害、冻害严重年份)才进行个体(如单株或单穗)选择，下一代种成系统(株系或穗系)，然后选拔优良系统升入比较试验。 Mass Selection or Bulk Method A procedure for inbreeding a segregating population until a desired level o

29、f homozygosity is reached Seed used to grow each selfed generation is a sample of the seed harvested in bulk from the previous generation. Seeds harvested in the F1 through F4 generations are bulked without selection Selection is delayed until advanced generations (F5-F8) when most segregation has s

30、topped. Short term, time and labor saving practical breeding procedure for the management of segregating generations to attain a sufficient level of homozygosity prior to initiation of individual plant selectionBulk Method Advantages Less record keeping than pedigree method Inexpensive Easy to handl

31、e more crosses Natural selection is primarily for competitive ability Large numbers of genotypes can be maintained Can be carried on for many years with little effort by the breederBulk Method Disadvantages Less efficient than pedigree method on highly heritable traits (because can purge undesirable

32、 phenotypes in early generations of pedigree method) Not useful in selecting plant types at a competitive disadvantage (dwarf types) Final genotypes may be able to withstand environmental stress, but may not be highest yielding If used with a cross pollinated species, inbreeding depression may be a

33、problem 混合法与系谱法的比较 优点：1、分离世代群体大，不会丢失优良的基因型；2、方法简单易行；3、充分利用自然选择，易获得对生物有利的性状；4、可能得到育种目标以外的优良类型。缺点：1、人工选择与自然选择目标不一致的性状易丢失；2、未选择，存在许多不良基因类型；3、杂种后代要求大群体；4、高代选择工作量大；5、亲缘关系无法考证。三、单籽传代法 Single Seed Descent Method Single Seed Descent procedure is based on advancing generations through single seed from each p

34、lant in each generation; This separates the inbreeding phase from the selection phase - reach the F6 generation faster; Carries forward maximum number of F2 plants to a stage near homozygosity;Single Seed Descent Procedures Cross selected parents and produce sufficient F1 seed Grow enough F1 plants

35、to produce 1000-2000 F2 plants Grow F2 plants under constrained conditions that force early maturity and harvest 1 seed form each plant; no observations need to be recorded Repeat through approximately F5 generation Select superior F6 plants and test progeny in replicated trials Release new varietiesSingle Seed Descent MethodSingle Seed Desc