小麦×高粱的受精率和小麦单倍体的诱导(简报)

远缘杂交无论在植物遗传学理论的建立还是在新品种的培育上都是一项十分有用的技术,特别在小麦上成绩更为突出。近来发现小麦不但和其亲缘属(如山羊草属、偃麦草属,赖草属等)植物可以杂交,而且和亲缘关系较远的植物种属如玉米、珍珠栗、大刍草、摩擦禾等杂交也有很高的成胚率,并且通过杂种胚发育过程中父本染色体的消失,可以获得小麦单倍体。Laurie和Bennett以高粱属的     

不同倍性小麦和玉米不同群体杂交诱导小麦单倍体的研究

自从Ｚｅｎｋｔｅｌｅｒ等［１］首先报道了小麦×玉米受精现象以来,许多学者对六倍体普通小麦与玉米杂交进行了广泛的研究,获得单倍体的普通小麦,并筛选到一些杂交亲和性较高的亲本材料［２］。但四倍体小麦与玉米杂交研究报道较少。ＯＤｏｎｏｕｇｈｕｅ等用四倍体小麦与玉米杂交获得单倍体胚［３］。随后,Ａｍｒａｎｉ等［４］和孙敬三等［５］利用这一方法相继获得四倍体小麦的单倍体苗。本文报道了不同倍性的小麦基因型与玉米不同群体杂交对诱导小麦单倍体的影响１　材料和方法１．１　亲本材料用作母本的二倍体小麦有一粒小麦（…     

由小麦×玉米获得的普通小麦加倍单倍体后代的RFLP变异

用小麦（Ｔｒｉｔｉｃｕｍ　ａｅｓｔｉｖｕｍＬ．）的ｒＤＮＡ克隆ｐＴａ７１和与小麦基因组有部分同源性的玉米（ＺｅａｍａｙｓＬ．）ＤＮＡ克隆作探针,对由小麦ｘ玉米获得的普通小麦加倍单倍体（ＤＨ）后代群体进行ＲＦＬＰ分析。结果发现,不但用ｐＴａ７１在这些ＤＨ后代中检测到ｒＤＮＡ所发生的明显的减少和扩增及非转录间隔区的限制性片段长度的变化,而且用与小麦基因组部分同源的玉米克隆ＭＲ１３和ＭＲ５０在一些ＤＨ后代中检测到缺失变异,特别是用ＭＲ１３在普通小麦ＤＨ系的１８号株的基因组中检测到大幅度的限制性片段长度的变化,即原来的４．３ｋｂ的强信号带消失,取而代之的是４０．０ｋｂ、２．５ｋｂ和２．０ｋｂ三条杂交带。这可能与小麦基因组ＤＮＡ较大的重排事件有关,也可能是由外源的玉米ＤＮＡ插入造成的。     

莜麦与玉米的远缘杂交

莜麦（Ａｖｅｎａ ｎｕｄａ Ｌ．）和玉米（Ｚｅａ ｍ ａｙｓＬ．）杂交有一定的受精率和成胚率。人工传粉后玉米花粉能很快在莜麦柱头上萌发并长入莜麦花柱中,在６８％ 的莜麦花柱中可观察到不只一条玉米花粉管。对授粉后的１６３ 个莜麦子房进行制片观察,发现受精率可达１１．０４％ ,其中只形成胚而无胚乳的卵细胞单受精占３．０７％ ,只形成胚乳而无胚的中央细胞单受精占１．８４％ ,既形成胚又形成胚乳的双受精占６．１３％ 。从授过玉米花粉的大约２２００ 朵莜麦小花中收获１８ 粒种子,对１２ 株实生苗根尖染色体计数表明,其中９ 株为单倍体（２ｎ＝ ２１）,３ 株为二倍体（２ｎ＝ ４２）。结果证明,通过莜麦和玉米杂交后玉米染色体的消除可以获得莜麦单倍体     

RFLP Variations of Common Wheat Doubled Haploid Progenies from Wheat×Maize Crosses

Wheat ( Triticum aestivum L. ) and maize ( Zea mays L. ) crosses (the chromosome elimination system) can be used to produce frequently a large number of doubled haploid (DH) wheat lines by embryo rescue and doubling treatment. The resulting DH lines are genetically homogeneous. Significant RFLP variations were detected in common wheat DH progenies from wheat and maize crosses by using wheat rDNA clone pta71 and two maize DNA clones (MR13 and MRSO) homologous to wheat genome as probes. The results revealed that the copy number and restriction fragment length of rDNA in some wheat DH progenies was changed, and also that deletion was detected in several DH plants when probed with MR13 and MR5O. In particular, the RFLP pattern of DH line No. 18 was greatly changed using MR13 as a probe. In this line, three new bands, 40.0 kb, 2.5 kb and 2.0 kb emerged while a 4.3 kb intense band from the parental common wheat genome disappeared. This change may be related to a quite large DNA rearrangement within the wheat genomic DNA or an insertion by alien maize DNA fragment.     

Naked Oat×Maize Hybridization

There is a certain frequency of fertilization and embryo productivity in naked oat (Avena nuda L. ) × maize (Zea mays L. ) crosses. The maize pollen readily germinated on the naked oat stigma and more than one pollen tubes grew into the style in about 68% of florets. In a sample of 163 florets fixed after pollination, 5 (3.07%) had only an embryo, 3 (1.84%) had only an endosperm and 10 (6.13%) had both. Overall, 9 haploid and 3 diploid naked oat plants were obtained from 12 seeds which formed following application of maize pollen to about 2200 emasculated naked oat florets. Preliminary studies indicated that elimination of the maize chromosomes occurred early in the embryo and endosperm development. This method gives a new approach for obtaining haplo!d naked oat.     

The effect of the crossability loci Kr1 and Kr2 on fertilization frequency in hexaploid wheat x maize crosses

Summary Dominant alleles of the Kr1 and Kr2 genes reduce the crossability of hexaploid wheat with many alien species, including rye and Hordeum bulbosum, with Kr1 having the greater effect. However, a cytological study of wheat ovaries fixed 48 h after pollination showed that the wheat genotypes Highbury (kr1, Kr2) and Chinese Spring (Hope 5B) (kr1, kr2) were crossable with Seneca 60 maize, fertilization occurring in 14.4 and 30.7% of embryo sacs respectively. The latter figure was similar to the 29.7% fertilization found in Chinese Spring (kr1, kr2). Most embryo sacs in which fertilization occurred contained an embryo but lacked an endosperm and where an endosperm was formed it was usually highly aberrant. All three wheat x maize combinations were karyotypically unstable and rapidly eliminated maize chromosomes to produce haploid wheat embryos.     

通过和玉米杂交诱导硬粒小麦单倍体

硬粒小麦（Ｔｒｉｔｉｃｕｍ ｄｕｒｕｍ Ｄｅｓｆ．）ＤＲ１４７授以超甜玉米（Ｚｅａ ｍ ａｙｓ Ｌ．） ｓｓ ７７００的花粉后,在８３．４％ 的柱头上观察到花粉萌发及花粉管长入胚囊,有９．９％ 的子房发生了卵细胞的单受精,１．９％ 的子房发生了中央细胞的单受精,３２．７％ 的子房发生了双受精。尽管双受精后可同时形成胚和胚乳,但胚乳往往发育迟缓,甚至败育。硬粒小麦×玉米形成的杂合子核型高度不稳定,在最初的几次细胞分裂中,来自父本玉米的染色体逐步被排除,最后形成硬粒小麦单倍体胚。在授以玉米花粉４ ｈ 后用１００ ｐｐｍ ２,４－Ｄ溶液浸蘸硬粒小麦穗部,可以有效地促进幼胚在缺乏胚乳或胚乳败育情况下的生长和发育。授粉９—１３ ｄ 后由５３３个硬粒小麦子房解剖出２５个胚,得胚率为４．７％ 。通过幼胚拯救获得１１棵正常植株,植株获得率为２．１％ 。根尖细胞染色体计数表明,它们为单倍体（２ｎ＝ ２ｘ＝ １４）。     

禾本科植物染色体消除型远缘杂交的研究进展

植物远缘杂交是作物育种中广泛应用的技术。除了核型稳定的种间杂交可以获得杂种以外,还可以利用核型不稳定的种间杂交后父本染色体消除的现象,通过胚培养和染色体加倍处理获得加倍单倍体（ＤＨ）植株。然而从小麦×玉米杂交获得的ＤＨ后代与其理论上应完全同质的遗传表现却不相符,总有２～５％的ＤＨ植株发生了形态学变异。最近的研究证明,通过小麦×玉米的受精作用,一些玉米特异ＤＮＡ可以被转移到小麦ＤＨ后代的基因组中。     

硬粒小麦与珍珠栗远缘杂交的受精作用和胚胎发育

对硬粒小麦（ＴｒｉｔｉｃｕｎｄｕｒｕｍＤｅｓｆ．）和珍珠栗（Ｐｅｎｎｉｓｅｔｕｍｇｌａｕｃｕｍｓｙｎ．Ｐ．ａｍｅｒｉｃａｎｕｍ）远缘杂交的受精作用和胚胎发育进行了研究。对授粉后的１９２个硬粒小麦子房进行制片观察,７．８１％发生双受精,具胚和胚乳,但胚乳发育往往落后于胚的发育;３．１３％只发生了单卵受精,只产生胚而无胚乳;１．０４％发生了单极核受精,只产生胚乳而无胚。总受精率为１１．９８％,成胚率为１０．９４％。由于胚乳的缺乏或发育异常及败育,最终难以获得有生活力的种子     

小麦与赖草远缘杂交的受精和胚胎发育

对小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ Ｌ．）和赖草（Ｌｅｙｍ ｕｓｓｅｃａｌｉｎｕｓＴｚｒｅｌ．）杂交的受精和胚胎发育进行了观察．赖草花粉在小麦柱头上萌发良好,花粉管可顺利长入花柱和胚囊,在检查过的３１９个小麦子房中,６２个（１９．４４％ ）发生了双受精,产生了胚和胚乳,但胚乳的发育往往落后于胚的发育;４９个（１５．３６％ ）发生了单卵受精,只产生胚而无胚乳;７个（２．１９％ ）发生了单极核受精,只产生胚乳而无胚．小麦×赖草虽然总受精率可高达３６．９９％ ,然而由于胚乳的缺乏或发育不完全,致使最后结实率很低．从１５０朵授过赖草花粉的小麦颖花中,只得到１粒种子．表明利用胚培养技术对杂种胚进行早期离体培养,可望提高杂种植株的获得率     

Efficient production of wheat-barley hybrids and preferential elimination of barley chromosomes

Summary Intergeneric hybridization between four common wheat cultivars, Triticum aestivum L. cultivars Chinese Spring, Norin 12, Norin 61, and Shinchunaga, and cultivated barley, Hordeum vulgare L. cultivars Betzes, Nyugoruden, Harunanijou, and Kinai 5 were carried out in a greenhouse under 15 – 20 °C and long-day (15 h) photoperiod conditions. Two days prior to pollination, a 100 mg/1 2,4-D solution was injected into wheat stems. Among wheat cultivars, Norin 12, Norin 61, and Shinchunaga showed higher crossabilities than that of Chinese Spring, suggesting the presence of crossability gene(s) other than the kr system of Chinese Spring. Variation was also found among the barley cultivars as male parents. Betzes barley showed the highest crossability with wheat. Thus, the cross Norin 12×Betzes showed the highest crossability (8.25%), followed by Norin 61 ×Betzes (6.04%), Shinchunaga×Betzes (5.00%), and Shinchunaga×Kinai 5 (5.00%). The embryos were rescued by culture at 15–20 days after pollination. Seventyfour plants were obtained from 82 embryos. The morphology of the hybrid plants resembled that of wheat parents. Among 60 seedlings observed, 28 had 28 chromosomes, 8 had 21, 23 had aneuploid numbers of chromosomes (22–27), and 1 had 29 chromosomes. About half of the aneuploid hybrids showed mosaicism for chromosome number. By analyzing five isozyme markers of barley chromosomes, the chromosome constitutions of the aneuploid hybrids were determined. Barley chromosomes 1 and 5 were found to be preferentially eliminated in the hybrids, while chromosomes 2 and 4 were eliminated infrequently. The conditions and genetic factors for high crossability and the tendency of barley chromosome elimination are discussed.     

小麦×长穗偃麦草的受精和早期胚胎发育

用石蜡切片法,对小麦（Ｔｒｉｔｉｃｕｍａｅｓｔｉｖｕｍ）和长穗偃麦草（Ｅｌｙｔｒｉｇｉａｅｌｏｎｇａｔａ）杂交的受精和早期胚胎发育进行了观察。结果表明,长穗偃麦草花粉在小麦柱头上萌发良好,花粉管可顺利长入花柱和胚囊。观察的１７０个小麦子房中,１７６５％发生了双受精,产生了胚和胚乳;９４１％发生了单卵受精,只产生胚而无胚乳;４７１％发生了单极核受精,只产生胚乳而无胚;总受精率为３１７７％;成胚率为２７０６％。由于胚乳的缺乏或发育异常及败育,最终难以获得有生活力的种子。为小麦与长穗偃麦草远缘杂交提供了细胞胚胎学证据。     

The influence of temperature on chromosome elimination during embryo development in crosses involving Hordeum spp., wheat (Triticum aestivum L.) and rye (Secale cereale L.)

Summary Several interspecific and intergeneric crosses involving five Hordeum species, Triticum aestivum and Secale cereale were carried out to investigate the influence of two contrasting temperatures on chromosome elimination during embryo development. In four of the interspecific Hordeum crosses, chromosome elimination was significantly increased at the higher of the two temperatures, resulting in greater proportions of haploid plant progenies. However, there was no significant effect of temperature in the other interspecific cross between H. lechleri x H. bulbosum nor in the two intergeneric crosses between H. vulgare x S. cereale and T. aestivum x H. bulbosum whose progeny were exclusively hybrid and haploid, respectively.     

山羊草(Aegilops)物种作母本与小麦远缘杂交的评价

研究了山羊草不同物种作母本,在不借助胚培等特殊措施的情况下与不含隐性可杂交基因的小麦推广品种杂交、回交及杂种自交情况,结果表明(1)山羊草物种作母本,小麦推广品种作父本进行杂交是一种很有效的方式;山羊草物种作母本容易与小麦进行杂交,但回交和自交较困难;回交与自交相比时,回交容易些;(2)同一物种的不同基因型材料在与小麦杂交、回交及杂种自交时存在大量变异;(3)杂交结实率与以后的回交或自交并不相关,但是杂种的回交和自交之间相关;(4)山羊草物种与小麦杂交、回交及其杂种自交的结实率与其染色体组构成并无明显相关.     

High frequncies of fertilization and embryo formation in hexaploid wheat x Tripsacum dactyloides crosses

The Hexaploid wheat variety Fukuho was crossed with Tripsacum dactyloides (2n=4x=72). The total fertilization frequencies for the egg cell, polar nuclei, and both, were 58.3%, 26.8% and 58.9% of the 168 ovaries examined. However, the fertilization frequency of single polar nuclei was much lower at only 0.6%. The total frequency of fertilization was higher than that in wheat x maize crosses. A total of 49 hexaploid wheat varieties, including Hope carrying the dominant genes Kr1 and Kr2, were crossed with T. dactyloides, and most gave embryos. The embryoformation frequencies ranged from 0.5% to 59.0%. A higher frequency of 32.0% embryo formation was obtained following pollination of the variety Hope. In comparison with embryo formation in wheat x maize crosses the difference of embryo-formation frequencies between the two crosses was significant. The results of high frequencies of fertilization and embryo formation in wheat x T. dactyloides crosses indicated that the Kr genes are as inactive in wheat x T. dactyloides, as they are in wheat x maize crosses, and also that the efficiency of fertilization and embryo formation is higher in wheat x T. dactyloides than in what x maize crosses. The potential of wheat x T. dactyloides crosses for wheat haploid production and wheat improvement is discussed.