Production of Haploid Sugar Beet (Beta vulgaris L.) by Culturing Unpollinated Ovules

The culture of unpollinated ovules is shown to be a suitable system for the production of haploid sugar beet (Beta vulgaris L.). The yield of haploids depended upon the genotype and varied between 0 and 13 % with a mean of 1.0 %. Haploid plants could be produced from approximately 50 % of all genotypes examined. The majority of the haploids isolated (about 90%) maintained the haploid genome level during the in vitro culture and propagation; 10% of the haploid clones showed a spontaneous doubling to the diploid genome level.     

Plant transposable elements,with an emphasis on grass species

Transposable elements are presents in all known genomes so far, and have the faculty of changing their genomic location and/or number of copies within the genome. They are mobile endogenous genetic elements, with a large variety of structure and transposition mechanism. In crops, they compose the major part of the nucleic DNA, up to 80% in some cereals like maize and wheat. Despite their omnipresence, they are largely unknown and uncharacterized within the Poaceae family. In this review, we describe a possible classification of the elements present in this family, some of their known transposition mechanism, their known activity and possible action in crops, and their possible origin.     

Soyabean-seed Yield Response in Row- and Hill-plots under a Recurrent Selection Programme

Several studies have indicated a possible link between genome size and earliness in maize. In this study, an original maize population, South African photo-period insensitive maize composite II (C₀) and several selected generations were analyzed for days to flowering, plant height, ear height, and yield. The selection criterion was earliness. Over six cycles of selection a 14-day decrease in days to flowering was obtained with no significant reduction in grain yield. In the initial population (C₀) and the most advanced selection (C₆) 101 plants were analyzed for nuclear DNA content. A significant decrease in the mean nuclear DNA content of the C₀ population (102 AU) was observed with respect to the C₀ population (105 AU). This reduction was the result of a decrease in frequency of plants in the C₆ population with large genome sizes. Therefore it was concluded that selection for earliness resulted in selection against plants with large genome sizes. Hence, the nucleotype of a maize plant can be modified by selection such as early flowering time.     

Enhancement of RAPD Analysis by Restriction-endonuclease Digestion of Template DNA in Wheat

Random amplified polymorphic DNA (RAPD) analysis has proven to be an effective procedure for molecular marker applications in plant breeding, although non-specific amplification may limit its utility in some species. The objective of this study was to determine the effectiveness of restriction-endonuclease digestion of template DNA for elimination of non-specific amplification and generation of heritable RAPD markers. Restriction endonucleases digested wheat DNA to completion in amplification buffer, suggesting that the restriction endonuclease can be added directly to the reaction mixture prior to amplification. A 1-h 37°C step was programmed into the thermal cycler for restriction-endonuclease digestion which was followed immediately by amplification. Non-specific amplification was reduced and DNA marker patterns were altered in digested samples when compared to undigested samples. Genetic segregation of two polymorphic markers tested in F₅ inbred progeny fit expected 1:1 ratios. These results suggest that heritable DNA markers may be generated with reduction in non-specific amplification when restriction-endonuclease digestion of template DNA is conducted as part of the RAPD procedure.     

In vitro androgenesis of wheat: from fundamentals to practical application

Wheat anther cultures have a history of almost 30 years and are nowemployed efficiently in many countries of the world for the developmentof doubled haploid lines for breeding. The present paper discusses keyquestions of the elaboration and perfection of the method: cytologicalaspects of in vitro androgenesis, the conditions required for theembryogenic development of microspores and the applicability of anthercultures in the Martonvásár wheat breeding programme.     

Metaphase-I analysis of a Triticum aestivum x T. monococcum hybrid by the C-banding technique

Summary The meiotic pairing behaviour at metaphase I of a Triticum aestivum×Triticum monococcum hybrid has been studied by means of the C-banding technique to ascertain the homology between the chromosomes in the A genome of the two species. The technique allowed the A and B genome chromosomes and the 2D, 3D and 5D chromosomes to be identified. Differences in the level of chromosome pairing in the A genome were noted. The T. monococcum 4A chromosome did not pair with any of the T. aestivum chromosomes in any of the metaphase I cells analysed. Two reciprocal translocations between the 2B and 2D chromosomes on one side and the 2A and 3D on the other side have been identified. The usefulness of the C-banding technique in the study of chromosome homology among species related to wheat is discussed.     

Meiotic studies of spontaneous hybrids of Amaranthus: genome analysis

The meiotic behaviour of 13 spontaneous interspecific F₁ hybrids of Amaranthus was studied. The hybrids between species with n= 16 chromosomes had 16 bivalents but varied considerably in pollen stainability (0–55%). These results suggest the existence of cryptic structural hybridity. The hybrids involving A. cruentus (n = 17) and species with n = 16 (A. caudatus and A. quitensis) always formed 15II+1 III with very low pollen stainability (5–7%). Further observations indicated that Amaranthus species are allotetraploids with basic numbers of x= 8 and x= 9 but exhibit x= 16 and x= 17 as secondary basic numbers, as demonstrated by (a) the frequent presence of 811 + 171 in the meiosis of the hybrid A. spinosus (n = 17) × A. hybridus (n= 16); and the occurrence of secondary associations between bivalents in MI. Genomic formulae are proposed for each species, on the basis of the meiotic behaviour of the hybrids studied.     

花生基因组SRAP-PCR体系的优化

【研究目的】研究花生基因组SRAP-PCR的扩增条件,建立其优化扩增体系;【方法】对模板DNA、引物、dNTP mixture、Taq DNA聚合酶浓度及退火温度设置不同梯度,研究各因素对PCR结果的影响;【结果】扩增程序为:94℃变性2min,1Cycle;94℃变性30s,48℃复性30s,72℃延伸1min,40Cycles;72℃延伸7min。反应体系成份为:DNA模板80ng,左右引物各200ng,dNTP mixture2.0mmol/L,Taq DNA聚合酶3U,10×Buffer8μl,总体积60μl。【结论】建立了满足花生基因组SRAP-PCR的优化扩增体系。     

Marker‐assisted backcross breeding to combine multiple rust resistance in wheat

A widely grown but rust susceptible Indian wheat variety HD2932 was improved for multiple rust resistance by marker‐assisted transfer of genes Lr19, Sr26 and Yr10. Foreground and background selection processes were practised to transfer targeted genes with the recovery of the genome of HD2932. The near‐isogenic lines (NILs) of HD2932 carrying Lr19, Sr26 and Yr10 were individually produced from two backcrosses with recurrent parent HD2932. Marker‐assisted background selection of NILs with 94.38–98.46% of the HD2932 genome facilitated rapid recovery of NILs carrying Lr19, Sr26 and Yr10. In the BC₂F₂ generation, NILs were intercrossed and two gene combinations of Lr19+Yr10, Sr26 + Yr10 and Lr19+Sr26 were produced. A total of 16 progeny of two gene combinations of homozygous NILs of HD2932 have been produced, which are under seed increase for facilitating the replacement of the susceptible HD2932 with three of the sixteen improved backcross lines with resistance to multiple rusts.