同源四倍体水稻与非洲栽培稻杂交的效果

以4份同源四倍体水稻(Oryza sativa,2n=4x=48)和4份二倍体水稻(Oryza sativa,2n=2x=24)为母本,以4份非洲栽培稻(Oryza glaberrima,2n=2x=24)为父本进行远缘杂交配组,共配制32个杂交组合。研究结果表明,非洲栽培稻分别与亚洲栽培稻中的两种倍性水平的水稻品系进行杂交均表现出一定的可交配性,生殖隔离并不很严格。然而,不同倍性的亚洲栽培稻与非洲栽培稻杂交,其结实率表现出明显的差异。二倍体水稻与非洲栽培稻不容易杂交,其结实率比较低(0．32％—1．93％),而同源四倍体水稻与非洲栽培稻较容易杂交,其结实率比较高(1．22％—8．86％,)。由此认为,利用同源四倍体水稻为母本与非洲栽培稻杂交更容易将后者的遗传物质引入亚洲栽培稻。     

同源四倍体水稻与非洲栽培稻杂交的胚胎学观察

以同源四倍体水稻(Oryza sativa,2n=4x=48)和二倍体水稻(Oryza Sativa,2n=2x=24)为母本,以非洲栽培稻(Dryza glarri,2n=2x=24)为父本进行远缘杂交配组,对其杂交结实的胚胎学机理进行了研究。结果表明,非洲栽培稻的花粉粒能在二倍体水稻的柱头上萌发,但萌发频率仅为0．18％～0．56％,花粉管在花柱内的伸长速度比较慢,发生受精的频率比较低,因而二倍体水稻与非洲栽培稻杂交的结实率比较低。然而,非洲栽培稻的花粉粒在同源四倍体水稻的柱头上萌发频率高达12．81％～14．65％,花粉管在花柱内的伸长速度比较快,发生受精的频率比较高,因而同源四倍体水稻与非洲栽培稻杂交的结实率比较高。在同源四倍体水稻与非洲栽培稻的杂交中发现,其受精作用比较特殊,其中包括精细胞与卵细胞的单受精作用,精细胞与次生极核的单受精作用和正常的双受精作用,总受精率和总成胚率分别为7．49％～9．28％和6．61％～8．64％。     

同源四倍体水稻与狼尾草杂交结实的胚胎学证据

在以6份同源四倍体水稻为杂交母本与狼尾草进行属间杂交中发现,其结实率达到0.84%～2.06%,而在以二倍体水稻为母本的属间杂交中却没有获得结实种子.利用激光扫描共聚焦显微技术对属间杂交结籽的特殊生殖现象进行了观察研究,试图寻找其杂交结实的胚胎学证据.结果表明,狼尾草的花粉粒不能在二倍体水稻的柱头上萌发,说明二倍体水稻与狼尾草的生殖隔离很严格,两者很难杂交.然而,狼尾草的花粉粒在同源四倍体水稻的柱头上能萌发,花粉管能在花柱中伸长并能将雄配子送入胚囊内与雌配子融合成受精卵.同源四倍体水稻与狼尾草的受精作用比较特殊,包括精细胞与卵细胞的单受精作用、精细胞与次生极核的单受精作用和正常的双受精作用,总受精率和总成胚率分别为6.36%～11.68%和4.11%～9.44%.试验结果为解释同源四倍体水稻与狼尾草杂交结籽的特殊生殖现象提供了有力的胚胎学证据.     

同源四倍体水稻与非洲栽培稻杂交的后效性研究

利用亚洲栽培稻中的4份同源四倍体水稻(O.sativa,2n=4x=48)和相应的4份二倍体水稻(O.sativa,2n=2x=24)为母本,以4份非洲栽培稻(O.glaberrima,2n=2x=24)为花粉供体进行远缘杂交后,对其杂种后代的分离动态进行了研究.结果表明,不同倍性的普通栽培稻与非洲栽培稻之间杂交后代的结实率以二倍体普通栽培稻的较高.在配制的32个杂交组合中,其杂种第1代群体均表现出明显的营养生长优势.从群体的生长势来看,杂种第2代群体比杂种第1代群体要弱一些;在杂种第2代群体中,以同源四倍体水稻为母本的杂交组合的分离现象比以二倍体水稻为母本的杂交组合的分离现象更明显.在各杂交组合的第3代群体中,从植株的株叶形态和生育期来看,株系间的差异和株系内的变异依然很明显,变异频率更宽,变异种类更多.在普通栽培稻与非洲栽培稻的杂交组合中,育性变异、生长势变异、株叶形态变异、染色体变异和结实性变异等是较易发现的变异现象.     

不同倍性栽培稻与药用野生稻种间杂交不结实性的比较胚胎学观察

以栽培稻(Oryza sativa)品种L202二倍体（L202 2x）及其同源四倍体（L202 4x）作母本分别与药用野生稻（Oryza officinalis）杂交,比较了两个杂交组合的杂交结实性及影响结实性的杂种胚胎发育细胞学。两个杂交组合所取得的一致结果是：杂交授粉后30 d所有杂交小穗均干枯死亡,不能结实;种间杂交不结实的原因在于受精和杂种胚胎胚乳发育异常。两个杂交组合的受精和杂种胚胎胚乳发育虽然均存在双受精、单受精和未受精类型,但就受精率而言,L202 2x作母本的平均总受精率为59.45％,略高于L202 4x（54.87％）; L202 4x的单受精率（24.60％）则高于L202 2x的单受精率（15.30％）。两个杂交组合的杂种胚胎胚乳发育均严重异常,虽然在授粉后1 d形成小的球形胚;到授粉后3 d,胚胎发育停滞并开始解体;至授粉后5 d,只有二倍体杂交组合的极少数胚胎可发育到梨形胚时期,四倍体组合的胚胎则基本全部解体。双受精胚囊内胚乳发育更为异常,在授粉后1 d,游离胚乳核就开始解体退化,到授粉后3 d不能形成细胞化胚乳或细胞化过程异常。与L202 2x作母本的杂交相比,以L202 4x作母本所得杂种胚胎发育更为滞后,且退化严重,形成的游离胚乳核少,解体早,不能进行细胞化。因此,利用同源四倍体栽培稻与药用野生稻杂交获得种间杂种的难度更大。     

野生二倍体鸭茅染色体加倍及杂交利用研究

对滇中朗目山野生二倍体鸭茅用秋水仙素处理萌动种子，获得了混倍体鸭茅(同一植株根尖中二倍体细胞和四倍体细胞混存)，混倍体鸭茅的形态学特征及生长发育均与二倍体无明显差异；从混倍体鸭茅自然传粉后代中，获得了纯合同源四倍体鸭茅。同源四倍体鸭茅的气孔和种子均较二倍体大，但形态、发育与二倍体差异较小。以诱导所得混倍体为母本，与四倍体栽培种杂交，杂交F1代为四倍体，其形态学特征及物候发育均介于野生二倍体和四倍体栽培种之间，早期生长与四倍体栽培种相当，优于野生二倍体，繁殖性能与野生二倍体相当，强于四倍体栽培种，分蘖、再生性及干物质产量均强于二倍体，但明显不如四倍体栽培种。以鸭茅野生二倍体为母本，与四倍体栽培种进行杂交，获得的杂交三倍体高度不孕，但早期生长、分蘖、再生等明显优于母本二倍体，杂交三倍体开放传粉后代倍性复杂，混倍体、四倍体和五倍体都有。     

不同倍性水稻的花粉发育特征分析

以水稻品种红米2x和其对应的同源四倍体红米4x为试验材料,用激光扫描共聚焦显微镜观察了不同倍性水稻的花粉发育特征。结果表明,不同倍性水稻花粉粒形成过程基本相似,但与相应的二倍体水稻相比,同源四倍体水稻在减数分裂及后期发育过程中存在多种异常现象,如纤维素壁降解不完全、细胞不均等分裂及分裂不同步等现象;在成熟花粉中,二倍体水稻的正常花粉占89.92%,败育率为10.18%,四倍体水稻的正常花粉占69.96%,败育率高达30.04%;四倍体水稻的花粉直径显著大于二倍体水稻,且四倍体水稻的花粉粒萌发延迟。认为不同倍性水稻的花粉发育存在差异,染色体加倍对水稻花粉发育产生了不良影响。     

向日葵的遗传

向日葵属(Helianthus)的染色体基数为17,类似于小麦属在进化中形成了二倍体(2n=2x=34)、四倍体(2n=4x=68)和六倍体(2n=6x=102)等几个倍性系列的种。在一些自然群体中也偶尔发生极低频率的单倍体。据Gundaev(1971)研究,双胚向日葵可能有介于单倍体和双倍体之间的染色体数目,由这个材料可获得一套连续的非整倍系列。非整倍体也能从种间杂交得到。有关性状的遗传扼述如下。     

单倍体小麦(n=3x=21)花药离体培养诱导的单倍体和二倍体植株

前言过去十年中,许多实验室都已发展了植物体外孤雄生殖的技术。1973年以来,我们在实验室中用花药离体培养的方法,也获得了数百个小麦花粉植株(De Buyser和Henry1979)。这些再生植株多是单倍体(n=3x=21)或二倍体(2n=6x=42),四倍体(4n=12x=84)极为罕见。     

染色体消除法诱导啤酒大麦单倍体技术研究

为了探索完善染色体消除法诱导啤酒大麦单倍体的技术体系,以7个啤酒大麦F1代材料为母本,分别以1个二倍体和1个四倍体的球茎大麦为父本进行杂交诱导。结果表明,二倍体球茎大麦的单倍体诱导率平均为28.13%,四倍体球茎大麦的单倍体诱导率为0。研究了试验期间的环境日最高温度、不同授粉时间和授粉后激素处理对授粉结实率的影响,结果表明,杂交试验期间环境日最高温度低于22℃、啤酒大麦去雄后2d进行授粉、授粉后第1～3d每天用Dicamb∶2,4-D∶GA3=1∶2∶75(质量比,各激素浓度分别为1、2、75mg·L-1)的混合激素喷授粉小花1次,可获得最高的杂交结实率。同时,分析了不同年际间授粉结实率存在较大差异的原因和不同倍性的球茎大麦对单倍体诱导率的影响。     

Comparative Embryological Studies on Infertility of Interspecific Hybridizations Between Oryza sativa with Different Ploidy Levels and O. officinalis

As maternal parents, diploid (L202-2x) and autotetraploid (L202-4x) of Oryza sativa cv. L202 were crossed with O. officinalis. Embryo development and fertilization in these two crosses were comparatively studied. There were no mature hybrid seeds obtained because all the hybridized spikelets died 30 days after pollination. The main reasons for no seed set were abnormal fertilization and development of the embryos and endosperms in the interspecific hybrids. There were double- fertilization, egg cell single-fertilization and non-fertilization in these crosses. Although 59.45% and 54.87% of hybrid embryos produced in the crosses of L202-2x/O. officinalis and L202-4x/O. officinalis, respectively, hybrid embryos ceased to develop or degenerated and plenty of free endosperm nuclei were in disaggregating state without developing cellular endosperms three days after pollination. Besides, some embryological differences in these two crosses were found, that is, the rate of double-fertilization and total rate of double- and single-fertilization in L202-2x/O. officinalis were higher than those in L202-4x/O. officinalis. The embryo and endosperm of hybrids developed more slowly, and embryos and free endosperm nuclei were more severely degenerated in L202-4x/O. officinalis than in L202-2x/O. officinalis. Five days after pollination, a few of embryos in L202-2x/O. officinalis developed into pear-shaped ones, however, embryos in L202-4x/O. officinalis were all degenerated. Therefore, it is more difficult to obtain interspecific hybrids by wide crosses between autotetraploid of O. sativa and O. officinalis.     

同源四倍体水稻胚囊内反足细胞团的多态性

利用激光扫描共聚焦显微技术对6份同源四倍体水稻在生殖发育过程中胚囊内反足细胞或反足细胞团的多态性进行了研究。结果表明，在同源四倍体水稻的雌配子体发育过程中已经存在着一些不正常的发育现象。在同源四倍体水稻的胚囊内反足细胞或反足细胞团的多态性比在二倍体水稻的胚囊内表现得更明显。反足细胞或反足细胞团的多态性主要表现为胚囊内形态的多样性和位置的多样性，这是其有性生殖能力变弱和雌配子体不正常的部分形态学特征。     

Breeding for 2n egg production in haploid × species 2x potato hybrids

The identification of diploid(2x), Tuberosum haploid × wild species hybrids (HS) which produce high frequencies of 2n eggs and have good tuber appearance is important for obtaining 4x progeny from 2x × 2x crosses in potato. More than 1700 HS clones were screened for the occurrence and frequency of 2n eggs through 2x × 4x crosses during two pollination periods. The resulting seed/fruit provides an estimate of 2n egg frequency. About 650 HS clones produced 2n eggs; 63 had 10–114 seeds/fruit; and 27 were selected for good tuber type. There was a large variation in seed set after 2x × 4x crosses, both within and between clones. Comparison of fruit and seed set between the two pollination periods using the same 595 clones indicated that environmental factor significandy affected 2n egg frequency. The mode of 2n egg formation was mainly due to omission of the second meiotic division controlled by a recessive gene (os). The gene frequency foros varied from 0.28 to 0.76 among six, 2x taxa. Both additive and dominance variance were significant for seed set after 2x × 4x crosses. Narrow sense heritability was estimated as 0.24. The average degree of dominance was equal to 1.66 which could indicate overdominance. Alternatively, this could be due to linkage disequilibrium,i.e. pseudooverdominance. However, dominance variance was greater than the additive variance indicating recurrent selection can be useful for improving the frequency of 2n egg production in the 2x population. The selected individuals, based on their phenotypic performance, should be progeny tested to identify the best parents for use in the next cycle of recombination.     

Seed set in 4x x 2x crosses as related to 2n pollen frequency

Seeds per fruit following 4x × 2x crosses in potato are roughly related to the frequency of 2n pollen. Our goal was to examine precisely the relationship between frequency of stainable 2n pollen and seeds per fruit (s/f) in 4x × 2x crosses. A 4x cultivar with high female fertility and 21 2n pollen producing 2x hybrids were used as seed and pollen parents, respectively. 2n pollen frequencies varied from 1 to 99% in the 2x hybrids and seed set ranged from 0 to 305 s/f in 4x×2x crosses. Mean seeds per fruit increased in response to increases from 1 to 50% 2n pollen, but did not increase in response to using a pollen sample with a 2n pollen frequency over 60%. Seed set averaged 11 s/f corresponding to pollen samples with 1–5% 2n pollen, 50 s/f at 10–20%, 125 s/f at 20–30%, and over 170 s/f at 2n pollen frequencies over 60%. Seed set in 210 control 4x × 4x crosses indicated that equivalent seed set occurs in 4x × 2x crosses when 2n pollen frequencies are over 20–30%. The 2x hybrids differed in mean and variation of 2n pollen frequencies and seed set in 4x × 2x crosses. One 2x hybrid with a meiotic aberration (sy-3) resulting in all univalents at Metaphase I (ordinarily leading to male sterility) and parallel spindles (ps) at Anaphase II had close to 100% 2n pollen (of the stainable pollen) and gave equivalent s/f in 4x × 2x crosses to s/f in 4x × 4x crosses. It is apparent that ample seed set occurs for using the 4x × 2x breeding scheme with 2n pollen frequencies over 10% and that even very low 2n pollen frequencies (1–10%) provide seed for the 4x×2x breeding approach.     

Haploids of tetraploid (2n=4x=48) Mexican potato species—Their extraction,cytology and crossability

Successful isolation of haploids (2n=2x=24) from 4x(2EBN) Mexican species was achieved by using Modified Wenzel (MW) and Nitsch and Nitsch (NN) media for anther culture. Both media, MW and NN, gave consistent regeneration of plantlets from 4x(2EBN) Mexican species, and responses to the media were both species and accession (PI) specific. Plantlets regenerated directly from microspores, by-passing the callus cycle, were mostly haploid (2n=2x=24). Haploid plants appeared smaller and weaker than their parents with a drastic reduction in both male and female fertility. Abnormalities observed during meiosis and the lack of success in crossing confirmed the effect of the meiotic irregularities observed in the haploids. A total of 290 seeds was obtained from the 4x × 2x crosses of 4x Mexican species with irradiated pollen of 2xS. cardiophyllum and 2xS. chancayense; however, no haploid (2n=2x=24) plants resulted. Extraction of haploids from colchicinedoubled 4x (2EBN) or natural 6x(4EBN) Mexican species using a Phureja pollinator was examined to provide clues to the potential of using 2x (1EBN) pollinators for haploid induction in 4x(2EBN) × 2x(1EBN) crosses.     

玉米杂交种子充实期子粒增重规律研究

在相同环境条件下,研究了3个母本与5个父本玉米自交系形成的15个杂交组合在充实期子粒重量的增加与充实时间的关系.结果表明,所有杂交组合种子从授粉后10d开始,种子重量的增加均表现为典型的S形曲线增长,且不同基因型表现一致.在授粉后30d内,母本间方差达显著或极显著,父本间方差均不显著,说明在此期间内,对杂交种子粒重增加的效应可能母本比父本更明显;授粉后第35天,母本间方差极显著,父本间方差显著,说明此时母、父本对增加杂交种子粒重的效应均较明显;在授粉40d后,对杂交种子粒重增加的效应转变为父本比母本更明显.     

Tuber yields of families from open pollinated and hybrid true potato seed

This work was undertaken to compare the tuber yields, vegetative vigor and uniformity of seedling transplants obtained from different breeding methods. Twenty hybrid families from different groups of crosses involving 4x clones and 2x Phureja-haploid Tuberosum hybrids; 4x × 4x, 4x × 2x (FDR), 4x × (4x × 2x), and (4x × 2x) × (4x × 2x) and eleven open pollinated families from 4x clones, and 4x hybrids from 4x × 2x crosses were compared in a replicated yield trial. Families from 4x × 2x (FDR) crosses were the highest yielding among the hybrid groups having approximately twice the yield of the open pollinated 4x clones. They also were the best group in relation to plant vigor and uniformity. Based on these results, it appears that a good breeding scheme for high-yielding and uniform progeny from true potato seeds is the 4x × 2x hybridization method where the male parent is capable of producing 2n pollen via a first division restitution mechanism.     

The effect of direction of hybridization (4x × 2x vs. 2x × 4x) on yield of cultivated potatoes

The types of reciprocal differences found in higher plants are generally limited to those characters which are controlled by one or two major genes. There are, however, a few examples where the progeny from reciprocal crosses differ in yield or other quantitative characters. Both have been ascribed mainly to cytoplasmic inheritance. In cultivated tetraploid potatoes (Solatium tuberosum Group Tuberosum) differences in yield of the progeny from reciprocal crosses have been found. These reciprocal differences are attributed to the mode of 2n gamete formation rather than cytoplasmic differences. Preliminary experiments involving reciprocal crosses between Tuberosum cultivars (2n=4x=48) and Phurejahaploid Tuberosum hybrids (2n=2x=24) indicated that some progenies from 4x x 2x crosses yield more than progenies from reciprocal crosses. It was hypothesized that the differences in tuber yield may be due to one or more of the following factors: (i) the effect of high fruit set on yield —i.e. almost 100% of the progenies from 2x X 4x crosses are male fertile and thus higher fruit set is expected than in the 4x X 2x progenies where only about 57% of the F₁ clones are male fertile; (ii) the advantage of being in 4x cytoplasm if the nucleus is 4x; and (iii) the difference in mode of 2n gamete formation-first division restitution (FDR) gives highly heterozygous gametes and second division restitution (SDR) results in highly homozygous gametes. Six families of reciprocal crosses between three 4x cultivars (Merrimack, Superior, and Wis 639) and three 2x Phureja-haploid clones (W5293.3, W5295.7, and W5845.1) were planted in 1970 in Rhinelander in a split-plot design with two tubers of each clone in each of two replicates. Flowers were removed from one of the paired plants in each family. Even though the fruit yields were higher in 2x X 4x progenies as expected, tuber yields were not affected by fruit formation. Therefore, factor (i) is apparently not involved in the reciprocal differences observed. Significantly higher tuber yields were obtained from 4x X 2x families only with the 2x clone W5295.7. This eliminated factor (ii), since no difference in reciprocals was obtained with the other 2x clones. Factor (iii) could thus be responsible for differences in reciprocal crosses, since cytological observations indicate only W5295.7 of the 2x clones used forms 2n pollen by FDR.     

栽培稻与药用野生稻杂种后代的形态学和细胞遗传学研究

 选用两个抗褐飞虱的药用野生稻编号材料与两个感虫栽培品种杂交，通过胚培养获得了F₁、BC₁F₁和F₂植株。F₁杂种表现出野生亲本紫色柱头、长芒及抗褐飞虱等特性，其花粉母细胞中期I染色体多为单价体(仅0.77个二价体)，甚至不能形成花药，因而表现雄性不育，仅获得一株F₂，染色体数目为2n=46。用栽培稻回交获得BC₁F₁植株为异源三倍体，中期I染色体构型为12.25Ⅰ+11.85Ⅱ+0.01Ⅲ。