抗条锈、抗穗发芽六倍体人工合成小麦Cereta/Aegilops tauschii783的SSR标记分析

Cereta/Aegilops tauschii783是由CIMMYT引进的硬粒小麦/节节麦人工合成种,具有高抗条锈和高抗穗发芽等优良特性.本文选用小麦A、B、D染色体组的91对SSR引物将人工合成小麦Cereta/Aegilops tauschii783与绵阳26在分子水平上进行了比较分析,结果表明：91对引物中有88对引物能扩增出清晰条带;88对引物中除3对引物外,86对引物（96.59%）均能揭示出Cereta/Aegilops tauschii783与绵阳26之间的差异.人工合成小麦Cereta/Aegilops tauschii783与育成小麦品种遗传差异很大,是丰富现代小麦遗传多样性的优异基因源;利用人工合成小麦Cereta/Aegilops tauschii783与绵阳26构建SSR标记群体,可有效标记双亲优良基因.     

Assessment of genetic diversity in synthetic hexaploid wheats and their Triticum dicoccum and Aegilops tauschii parents using AFLPs and agronomic traits

Synthetic hexaploid wheats are of interest to wheat breeding programs, especially for introducing new genes that confer resistance to biotic and abiotic stresses. A group of 54 synthetic hexaploid wheats derived from crosses between emmer wheat(Triticum dicoccum, source of the A and B genomes) and goat grass (Aegilops tauschii, D genome donor) were investigated for genetic diversity. Using the AFLP technique, dendrograms revealed clear grouping according to geographical origin for the T. dicoccum parents but no clear groups for the Ae. tauschii parents. The geographical clustering of the T. dicoccum parents was also reflected in the dendrogram of their derived synthetic hexaploids. Diversity of the T. dicoccum parents and their derived synthetic hexaploids was further evaluated by measuring 18morphological and agronomic traits on the plants. Clustering based on morphological and agronomic data also reflected geographical origin. However, comparison of genetic distances obtained from AFLP and agronomic data showed no correlation between the two diversity measurements. Nevertheless, similarities among major clusters with the two systems could be identified. Based on percentage of polymorphic markers, the synthetic hexaploids had a considerably higher level of AFLP diversity (39%) than normally observed in cultivated hexaploid wheat (12–21%). This suggests that synthetic hexaploid wheats can be used to introduce new genetic diversity into the bread wheat gene pool. This revised version was published online in July 2006 with corrections to the Cover Date.     

Use of the gene pools of Triticum turgidum ssp. dicoccoides and Aegilops squarrosa for the breeding of common wheat (T. aestivum), through chromosome-doubled hybrids

Summary Triticum turgidum ssp. dicoccoides (wild emmer wheat, AABB, 2n=28) and Aegilops squarrosa (goat grass, DD, 2n=14) comprise a rich reservoir of valuable genetic material, which could be useful for the breeding of common wheat (T. aestivum, AABBDD, 2n=42). Many accessions of both wild species, most of them selected for resistance to stripe rust, were used to make amphiploids. Two strategies were applied: (1) the production of autopolyploid cytotypes of the wild species, followed by hybridisation, and (2) the production of allotriploid interspecific hybrids, followed by doubling of the number of chromosomes. The first route was unsuccessful because of failure of the crosses between the autopolyploid cytotypes, possibly due to incongruity between the two species and to reduced fertility in the autopolyploid cytotypes. The second route yielded the desired synthetic hexaploids. However, the rate of success of the crosses was low and there were great differences between years, and within years between crosses. Embryo rescue was applied to obtain the primary hybrids (2n=21), which were highly sterile and had on average 0.3 bivalents and 20.4 univalents per pollen mother cell. Various abnormalities were recorded. Doubling of the number of chromosomes sometimes occurred spontaneously or was brought about by colchicine treatment. The large scale of the interspecific hybridisation programme ensured that one-third of the female and one-sixth of the male accessions were represented in the synthetic hexaploids.     

The effects of climatic variation in Europe on the yield response of spring wheat cv. Minaret to elevated CO2 and O3: an analysis of open-top chamber experiments by means of two crop growth simulation models

In the ESPACE-Wheat programme, 25 open-top chamber experiments were carried out in 1994, 1995 and 1996, on nine locations, divided over eight European countries. In most experiments, spring wheat cv. Minaret was subjected to two levels of atmospheric CO₂ and two levels of ozone. Grain yields in the control treatments (ambient levels of CO₂ and O₃) varied strongly between sites. Also, yield response to elevated CO₂ and O₃ showed great variation. The present study was conducted to determine whether climatic differences between sites could account for the observed variation.

Two simulation models were used for the analysis: AFRCWHEAT2-O3 and LINTULCC. AFRCWHEAT2-O3 simulates phenology, canopy development and photosynthesis in greater detail than LINTULCC. Both models account for the effects of radiation and temperature on crop growth. New algorithms were developed to simulate the effects of CO₂ and O₃. Weather data that were measured in the experiments were used as input, and simulated growth responses to CO₂ and O₃ were compared with measurements. No attempt was made to merge the two models. Thus two independent tools for analysis of data related to climate change were developed and applied.

The average measured grain yield in the control treatment, across all 25 experiments, was 5.9 tons per hectare (t ha⁻¹), with a standard deviation (SD) of 1.9 t  ha⁻¹. The models predicted similar average yields (5.5 and 5.8 t ha⁻¹ for AFRCWHEAT2-O3 and LINTULCC, respectively), but smaller variation (SD for both models: 1.2 t ha⁻¹). Average measured yield increase due to CO₂-doubling was 30% (SD 22%). AFRCWHEAT2-O3 expected a slightly lower value (24%, SD 9%), whereas LINTULCC overestimated the response (42%, SD 11%). The average measured yield decrease due to nearly-doubled O₃ levels was 9% (SD 11%). Both models showed similar results, albeit at lower variation (7% yield decrease at SDs of 6 and 4%). Simulations accounted well for the observation that, at elevated CO₂, the percentage yield loss due to O₃ was lower than at ambient CO₂.

The models predicted lower variation among sites and years than was measured. Yield response to CO₂ and O₃ was predicted to depend on the climate, with a predominant effect of temperature on the response to CO₂. In the measurements, these climatic effects were indeed observed, but a greater part of the variation was not related to light intensity, temperature, CO₂, or O₃. This unexplained variability in the measured dataset was probably caused by factors not accounted for in the models, possibly related to soil characteristics.

We therefore conclude that even perfect information on the climate variables examined in ESPACE-Wheat, i.e. light intensity and temperature, by itself would be insufficient for accurate prediction of the response of spring wheat to future elevated levels of CO₂ and O₃.