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1.
Meeting demands for increased cereal production in China 总被引:1,自引:0,他引:1
Meeting demands for increased cereal production in China is a great challenge and this paper provides updated information on cereal production and the potential adaptation of cropping systems to climate change, as well as on progress in improving yield potential and developing molecular markers and GM cereals in China. Maize production and soybean imports are increasing significantly to meet the strong demand for feed by a rapidly growing livestock industry. Extension of the rice and maize growing seasons in northeastern China and improvement of the cropping system through delayed wheat planting have contributed to improving cereal productivity despite changing climatic conditions. Significant improvements in yield potential of rice, maize, and wheat have been achieved. Comparative genomics has been successfully used to develop and validate functional markers for processing quality traits in wheat, and also for developing new varieties. Although transgenic Bt rice and maize, and maize expressing phytase have been developed, their commercialization has not been officially permitted. International collaboration has contributed significantly to cereal production by providing germplasm and improved crop management practices. Full integration of applied molecular technologies into conventional breeding programs and promotion of lower-input technologies, will play a key role in increasing and sustaining future cereal production. 相似文献
2.
The importance of reduced tillage in sustainable agriculture is well recognized. Reduced-tillage practices (which may or may
not involve retention of crop residues) and their effects differ from those of conventional tillage in several ways: soil
physical properties; shifts in host–weed competition; soil moisture availability (especially when sowing deeply or under stubble);
and the emergence of pathogen populations that survive on crop residues. There may be a need for genotypes suited to special
forms of mechanization (e.g. direct seeding into residues) and to agronomic conditions such as allelopathy, as well as specific
issues relating to problem soils. This article examines issues and breeding targets for researchers who seek to improve crops
for reduced-tillage systems. Most of the examples used pertain to wheat, but we also refer to other crops. Our primary claim
is that new breeding initiatives are needed to introgress favourable traits into wheat and other crops in areas where reduced
or zero-tillage is being adopted. Key traits include faster emergence, faster decomposition, and the ability to germinate
when deep seeded (so that crops compete with weeds and use available moisture more efficiently). Enhancement of resistance
to new pathogens and insect pests surviving on crop residues must also be given attention. In addition to focusing on new
traits, breeders need to assess germplasm and breeding populations under reduced tillage. Farmer participatory approaches
can also enhance the effectiveness of cultivar development and selection in environments where farmers’ links with technology
providers are weak. Finally, modern breeding tools may also play a substantial role in future efforts to develop adapted crop
genotypes for reduced tillage. 相似文献
3.
R. M. Trethowan Alexei Morgunov Zhonghu He R. De Pauw J. Crossa M. Warburton Arman Baytasov Chunli Zhang M. Mergoum G. Alvarado 《Euphytica》2006,152(3):303-316
Spring sown bread wheat is grown at high latitudes in Europe, Asia and North America. However, it is not clear what the associations are among environments, particularly in Asia and North America, and whether or not cultivars developed in one region may adapt in another. A yield trial comprised of cultivars developed in northern Kazakhstan, western Siberia, the Canadian Prairies, northern USA, northeastern China and broadly adapted genotypes bred by CIMMYT in Mexico was planted in all the above mentioned environments in 2002–2004. In general, cultivars performed best within the regions they were developed. However, cultivars developed in northern Kazakhstan/western Siberia were the most broadly adapted at high latitudes; they were not significantly different for grain yield from the locally developed cultivars in both China and Canada. Stronger photoperiod response, greater plant height and larger seed weight appeared to be key adaptive features of these materials. At lower latitudes, the Kazakh/Siberian cultivars were significantly lower yielding than all other materials. When low latitude Mexican sites were removed from the analysis, the Chinese locations tended to associate, whereas most Canadian and Kazak/Siberian locations were negatively associated with those from China.
SSR analysis of the cultivars from each region split the materials into two general groups, one based on North American cultivars and one comprised of Kazakh/Siberian and Chinese cultivars. Lines developed in Mexico were spread across these two groupings. Evidence suggests that considerable scope exists to improve bread wheat adaptation at high latitudes globally through intercrossing materials originating from Asia and North America. 相似文献
4.
Yield and adaptation of hexaploid spring triticale 总被引:2,自引:0,他引:2
Summary Gains in yield and stability were analysed using grain yield data from the 8th to the 14th International Triticale Yield Nursery (ITYN) and differences in adaptation between complete and substituted triticales (X Triticosecale Wittmack) were examined. A trend of improving yield and adaptation was observed. As highly significant genotype × site interaction each year was not adequately described using regression analysis, yield stability was examined by ranking genotypes within sites and summarizing scores for individual genotypes across sites. Cluster analysis was used to study the relationships among sites and among genotypes. There was little evidence of sites grouping on a geographical basis. Grouping of genotypes showed a tendency for complete and substituted triticales to perform differently, suggesting that diversity for adaptation is maximized by utilizing both types in breeding.Progress for grain yield is compared with more spectacular gains in test weight and reasons for the different rates of improvement are postulated.Abbreviations CIMMYT
International Maize & Wheat Improvement Centre
- ITYN
International Triticale Yield Nursery
contribution from CIMMYT/Agriculture Canada (No. R-002) 相似文献
5.
Fifty-five spring bread wheat (Triticum aestivum L.) cultivars, mostly released between 1975 and 1991 in eight leaf rust-prone spring wheat growing regions of the former USSR, were tested in the seedling growth stage for reaction to 15 Mexican pathotypes of Puccinia recondita f. sp. tritici. In total, seven known and at least two unknown genes were identified, either singly or in combinations: Lr3 (7 cultivars), Lr10 (14), Lr13 (5), Lr14a (1), Lr16 (1), Lr23 (3); the unknown genes were identified in 14 cultivars. The first unknown gene could be either Lr9, Lr19, or Lr25; however, the second unknown gene in 9 cultivars was different from any named gene. Twelve of the 15 pathotypes are virulent for this gene, hence its use in breeding for resistance will be limited. The cultivars were also evaluated at two field locations in Mexico with two pathotypes in separate experiments. The area under the disease progress curve and the final disease rating of the cultivars indicated genetic diversity for genes conferring adult plant resistance. based on the symptoms of the leaf tip necrosis in adult plants, resistance gene Lr34 could be present in at least 20 cultivars. More than half of the cultivars carry high to moderate levels of adult plant resistance and were distributed in each region. 相似文献
6.
Ram C. Sharma G. Ortiz-Ferrara J. Crossa M. R. Bhatta M. A. Sufian J. Shoran A. K. Joshi R. Chand Gyanendra Singh R. Ortiz 《Euphytica》2007,157(3):457-464
Improving the level and stability of grain yield is the primary objective of wheat breeding programs in the Eastern Gangetic
Plains (EGP) of South Asia. A regional wheat trial, the Eastern Gangetic Plains Yield Trial (EGPYT), was initiated by CIMMYT
in collaboration with national wheat research programs in Bangladesh, Nepal, and India in 1999–2000 to identify wheat genotypes
with high and stable grain yield, disease resistance, and superior agronomic traits for the EGP region. A set of 21 wheat
experimental genotypes selected from a regional wheat screening nursery in South Asia, three improved widely grown cultivars
(Kanchan, PBW343 and Bhrikuti), and one long-term cultivar (Sonalika) were tested at 9–11 sites in six wheat growing seasons
(2000–2005) in the EGP. The 21 experimental genotypes were different in each year, whereas the four check cultivars were common.
In each year, one or more of the experimental genotypes showed high and stable grain yield and acceptable maturity, plant
height, and disease resistance compared to the check cultivars. Three improved cultivars have already been commercially released
in the region through EGPYT and many germplasm lines have been used in the breeding programs as parents. Identification of
wheat genotypes with high-grain yield in individual sites and high and stable yield across the EGP region underlines their
value for regional wheat breeding programs attempting to improve grain yield and agronomic performance. 相似文献
7.
Summary The wheat area in developing countries, including China, is around 100 million ha. To address the needs of these very diverse wheat growing areas, CIMMYT has defined 12 wheat mega-environments (ME). A ME is defined as broad, not necessarily continuous often transcontinental area with similar biotic and abiotic stresses, cropping systems and consumer preferences. The factors describing each ME are presented.CIMMYT's breeding methodology is centered around the development of widely adapted germplasm with high and stable yield across a wide range of environments. Segregating populations are alternating screened in two diverse environments in Mexico. One key requirement is that all germplasm is tested under near optimum conditions for its yield potential. The second one is multi-locational testing of advanced lines at sites that represent a given ME (key locations) and careful screening of germplasm for tolerance to abiotic and biotic stresses specific to that environment. This methodology has permitted the pyramiding of a large number of multiple resistance genes for use against a wide spectrum of diseases and tolerance to abiotic stresses within each ME. In addition, the widespread testing of lines allows the identification of traits which are beneficial in several environments. Data from international nurseries are used to further delineate environments within an ME. This approach has proven to be successful since around 70% of the spring wheat area in developing countries (excluding China) is planted to varieties derived directly or indirectly from CIMMYT germplasm. The performance of the bread wheat cultivar Pastor in international trials is given as an example for a wide adaptation. 相似文献
8.
Global wheat (Triticum aestivum L.) production must increase 2% annually until 2020 to meet future demands. Breeding wheat cultivars with increased grain
yield potential, enhanced water-use efficiency, heat tolerance, end-use quality, and durable resistance to important diseases
and pests can contribute to meet at least half of the desired production increases. The remaining half must come through better
agronomic and soil management practices and incentive policies. Analyses of the recent International Yield Trials indicate
that grain yields of the best new entries were usually 10% higher than the local checks globally, as well as within a country
across sites. Variation in yield across sites within a country/region underline the role of genotype × environment (GE) interaction
and provides opportunities to select for stable genotypes, which is not often done. The lack of proper analysis undermines
proper utilization of germplasm with high yield potential and stability in the national wheat breeding programs. Some of the
best performers in irrigated areas were amongst the best in semiarid environments, reinforcing the fact that high yield potential
and drought tolerance can be improved simultaneously. The best performing lines often had genotypic base of widely adapted
genotypes Kauz, Attila, Baviacora, and Pastor, with genetic contributions from other parents including synthetic wheat. We
recommend within country multilocation analysis of trial performance for a crop season to identify lines suiting particular
or different locations within a country. The immediate feedback on GE interaction will also help in breeding lines for countries
having substantial variation across locations and years. 相似文献
9.
The effect of two major dwarfing (Rht-B1b and Rht-D1b) genes varies with environment. Near-isogenic pairs (i.e., tall and
semidwarf) of six spring wheat lines, included in the International Adaptation Trial (IAT), were grown in 81 trials around
the world from 2001 to 2004. Trial yields ranged from 1 to 8 t ha−1 with a mean of ca. 4 t ha−1. Overall, the yield advantage of the lines possessing the dwarfing gene was ca. 10% and was particularly evident in trials
where the mean height of semidwarf isolines exceeded ca. 80 cm. However, the yield advantage was greater in the slightly taller
and older lines (Pavon and Galvez) than in the newer lines Nesser and Kauz and the two durum lines. Sixteen pairs of semidwarf/tall
near-isolines were grown in six managed drought environment trials at CIMMYT in northwestern Mexico. In these trials, height
and yield differences were small and/or negligible in the most droughted environment (2.5 t ha−1) and the slope of yield versus height for each isoline pair became consistently negative with increase in irrigation. In
the IAT, the slope of the yield versus height was much more variable at low heights or yields, presumably due to the fact
that there were many more factors driving the response. Even at the point where the slope became consistently negative (ca.
between 2 and 4 t ha−1), there were some trials where tall isolines equaled or exceeded the yield of semidwarf isolines, particularly in the most
recent developed cultivar, Kauz.
For submission to Euphytica as part of special issue “Challenges to International Wheat Breeding”. From the International
Symposium on Wheat Yield Potential: Challenges to International Wheat Breeding, Days Inn, Ciudad Obregón, Sonora, Mexico,
March 19–24th, 2006. 相似文献
10.
Summary The endosperm storage proteins of 205 Chinese bread wheat cultivars and advanced lines were fractionated by SDS-PAGE to determine their high molecular weight (HMW) glutenin subunit composition. Seventeen alleles were identified: three at Glu-A1, eight at Glu-B1, and six at Glu-D1. The most common alleles were Null, 1, 7+8, 7+9, and 2+12. The results indicate that wheats from different regions differ in their frequencies of HMW glutenin subunits, however, none of the subunits could be related to specific environments. The glutenin quality scores of Chinese wheats ranged from 3 to 10, with an average of 6.7. Increasing quality scores have implications in improving steam-bread making quality for Chinese consumers. On the basis of HMW glutenin subunit composition, Chinese wheats are close to European wheats, especially Italian wheats because several Italian introductions are widely distributed in the pedigrees of Chinese wheat. 相似文献