Callus Culture-Derived Somaclonal Variation in the Tropical Pasture Legume Stylosanthes guianensis (Aubl.) Sw.

Plants were regenerated from leaf-derived callus cultures of five genotypes of Stylosanthes guianensis. There were substantial genotypic differences in morphogenetic potential, ranging from 95–100 % of cv.‘Graham' calh to less than 1% of cv,‘Oxley' calh forming shoots. A total of 1024 regenerants (SC₁) were planted out, with 28.1 % surviving to set seed. Variant characters including albinism, reduced fertility, dwarfism and leaf morphology were observed. Variation in selfed progeny (SQ₂) of 138 SC₁ plants was assessed in a replicated field trial involving 2484 SO₂ individuals. Variant phenotypes were observed in 55 (39.9 %) SC₂ families. Many families were segregating for albinism, altered morphology or reduced fertility. Thirty families had lower yields than their parent and earlier and later flowering variants were found. Eight tetraploid families were identified. These were characterized by more erect habit, larger leaves, stems, flowers and seeds, reduced fertility and yield and a tendency to flower later.     

Enhanced productivity of the essential oil in the artificial autopolyploid of vetiver (Vetiveria zizanioides L. Nash)

Summary Artificial autotetraploids were produced by colchicine treatment in the important essential oil bearing vetiver (2n=20). The raw tetraploids were stabilised by selection for pure types in segregating vegetative progeny. The tetraploids were vigorous with thicker and longer roots. The performance data recorded on 17 months' old crop of the tetraploid taken in conjunction with diploid parent and the best available check, exhibited distinct superiority of the tetraploid. In terms of economic yield the tetraploid has the potential of producing 62.5% and 39.2% more oil over the diploid parent and the check, respectively. Although there was marginal improvement in root biomass but significant improvement was registered for percent oil content. The tetraploid produced 1.4% oil in freshly harvested roots compared to 0.98% and 1.15% in the control and check respectively. The study explicitly demonstrate the use of induced tetraploidy in attaining rapid genetic improment even for the characters associated with the secondary metabolism.This paper is dedicated to Professor AK Sharma to commemorate his 40 years association with chromosome research, (CIMAP Publication No. 719).     

A technique for identifying polyploid sectors in grass inflorescences

Summary A simple technique for counting mitotic chromosome numbers in ovaries of inflorescences has been developed and applied to grasses. The uses, as outlined, include isolating polyploid inflorescences for hybridization, and as an alternative method to root-tip squashes for chromosome morphology and banding studies.     

Cytology and reproductive behavior of diploid, tetraploid and hexaploid germplasm accessions of a wild forage grass: Paspalum compressifolium

Summary Fourteen germplasm accessions of Paspalum compressifolium native from southern Brazil were cytologically and embryologically analysed. The study revealed that one accession was diploid (2n=20), twelve were tetraploid (2n=40) and one was hexaploid (2n=60). This is the first report of diploid and hexaploid cytotypes for this species. Studies on microsporogenesis, megasporogenesis, and embryo sac development indicated that the diploid cytotype had regular meiotic behavior and reproduces sexually. Tetraploid cytotype usually had an important proportion of chromosomes that associated as quadrivalents during meiosis and reproduced by mean of aposporous apomixis. The hexaploid cytotype showed irregular meiotic behavior with about one third of the chromosomes associated as multivalents and reproduced by aposporous apomixis. Thus, P. compressifolium could be an agamic complex. Breeding in this complex is possible due to the presence of diploid sexuals which can be treated by colchicine and pollinated by apomicts.     

A strict diploid-like pairing regime is associated with tetrasomic segregation in induced autotetraploids of kale

Fertility and reproductive stability in polyploids depend on the precise control of chromosome pairing at meiosis. In this study, meiotic pairing configurations are related to isozyme segregation ratios in F₁ hybrids between colchicine‐induced autotetraploids of kale. An immediate diploid‐like pairing regime is associated with tetrasomic segregation. Although the mechanisms driving such a behaviour have yet to be identified, pairing preferences are not responsible for the cytological diploidization of autotetraploid kales.     

茶树倍性育种研究进展

茶树是中国重要的经济作物,自60年代以来,茶树育种一直是中国茶树研究工作的重点。为了给茶树育种工作提供新的种质资源,取得育种工作的突破性进展,国内外广泛开展了关于其多倍体育种的研究。笔者从多倍体的获得和鉴定方法两方面综述了茶树多倍体育种技术的研究进展,提出要加强多倍体诱导效率和新型诱导剂的研究,指出嵌合体是目前多倍体育种中普遍遇到的问题,茶树离体再生频率及遗传转化体系的构建,对于茶树嵌合体的分离及茶树多倍体离体诱导技术的建立具有重要意义。并分析了茶树多倍体研究的优点和未来发展前景。     

多倍体蒲公英绿茶复合饮料生产工艺研究

以多倍体蒲公英和绿茶萃取汁为主要原料,添加白砂糖、蜂蜜、柠檬酸和稳定剂,经试验确定了复合饮料最佳配方为:多倍体蒲公英萃取汁与绿茶汁的体积比2∶1,白砂糖添加量10%,柠檬酸添加量0.3%,稳定剂添加量0.25%、蜂蜜添加量1.0%。     

远缘杂交在现代月季育种中的作用

综述了远缘杂交在现代月季育种史和当代月季育种中的作用,以及克服远缘杂交不亲和与杂种不育的方法,指出多倍体技术是将来克服远缘杂交不亲和与杂种不育的一条非常有潜力的育种途径,并对远缘杂交在将来月季育种中的作用进行了展望.     

Chromosome numbers and microsporogenesis in Brachiaria brizantha (Gramineae)

The genus Brachiaria, native to the African tropical savannas, has achieved significance as a pasture grass in many tropical and subtropical countries, including Brazil. Many species and accessions are polyploid and apomictic, which complicates the improvement of breeding stocks through hybridization. In support of breeding programs, cytogenetic characterization, including chromosome counts and evaluation of the meiotic behavior in the accessions of the Brachiaria has been undertaken at the Embrapa Beef Cattle Center. In this study, 22 accessions of B. brizantha were analyzed of which one was found to be diploid (2n = 2x = 18), 18 were tetraploid (2n = 4x = 36) and three were hexaploid (2n = 6x = 54). The meiotic chromosome behavior was slightly irregular in the diploid and in some tetraploid accessions, and highly irregular in most tetra- and hexaploid accessions. Meiotic abnormalities were those common to polyploidy, i.e., multivalent chromosome association at diakinesis and irregular chromosome segregation leading to micronuclei formation in the tetrad stage. Low frequencies of multivalent chromosome associations among polyploids suggest that they may be segmental allopolyploids. This revised version was published online in August 2006 with corrections to the Cover Date.     

芽变红地球葡萄的倍性结构鉴定

芽变红地球葡萄是新近发现的自然变异新种质。为搞清其倍性结构,以芽变红地球、红地球为试材,根据组织发生层学说推断材料的倍性结构。测定保卫细胞大小和统计叶绿体数目的试验表明,芽变红地球保卫细胞长略大于红地球,宽略小于红地球;保卫细胞中的叶绿体粒数,芽变红地球为11.35个,红地球为10.63个,均没有显著差异,从而推断芽变红地球的L1层为二倍体。测定花粉粒大小的试验结果表明,芽变红地球花粉粒长度为35.46μm,宽度为22.95μm,红地球的花粉粒长度为33.03μm,宽度为18.04μm,存在显著差异,表明芽变红地球的LⅡ层为四倍体。根尖染色体数目观察结果表明,芽变红地球的染色体数目为2n=4x=76,红地球的为2n=2x=38,表明芽变红地球的LⅢ为四倍体。另外,通过对梢端切片观察,芽变红地球的LⅠ层的细胞与红地球的没有明显差异,而LⅡ、LⅢ则显著大于红地球。由此证明,芽变红地球的倍性结构为2-4-4型,为周缘嵌合体。