México: CIMMYT, 2002.
México: CIMMYT, 2002.
CIMMYT Annual Report 2013: Agricultural research for development to improve food and nutritional security. 2014. CIMMYT, Int.. : 136 p.. Mexico, DF (Mexico). CIMMYT. Series: CIMMYT Annual Report
Through research, development, training and capacity building, CIMMYT works with partners to sustainably increase the productivity of maize- and wheat-based cropping systems. Focused on improving food and nutritional security and improving livelihoods in the developing world, CIMMYT is a member of CGIAR and leads the MAIZE and WHEAT CGIAR Research Programs (CRPs)..
Mujeeb-Kazi, A.; Kazi, A.G.; Dundas, I.;Rasheed, A.; Ogbonnaya, F.; Kishii, M.; Bonnett, D.; Wang, R.R.-C.; Xu, S.; Chen, P.; Mahmood, T.; Bux, H.; Farrakh, S.
Genetic diversity is paramount for cultivated crops genetic improvement, and for wheat this resides in three gene pools of the Triticeae. In wheat, access to this diversity and its exploitation is based upon the genetic distance of the wild species relatives from the wheat genomes. For several decades, these wide crosses have been a reservoir of novel variation for wheat improvement. Among these, close relatives of the primary gene pool have been preferred since this ensures successful gene transfer as they permit homologous genetic exchanges to occur between related genomes, as exemplified by the A and D genome diploid progenitors. One strategy has been based upon first producing genetic stocks that capture the potential of the diploids via bridge crossing where the D genome synthetic hexaploid wheats (2n = 6x = 42, AABBDD) are exploited. The synthetics are products of crosses between elite durum wheat cultivars (Triticum turgidum) and various Aegilops tauschii accessions. Similarly, the diversity of the A and B genomes has also been assembled as AABBAA (T. turgidum/A genome diploids Triticum boeoticum, Triticum monococcum,Triticum urartu) and AABBBB (SS) (T. turgidum/Aegilops speltoides). The utilization of these useful diversity for various biotic/abiotic stresses including in the development of molecular tools for enhancing breeding efficiency has been in the forefront of wheat improvement over the past two decades. Additional strategy employed includes the direct crosses between parental diploids and recipient wheat cultivars extended to give even swifter products by top- or backcrossing the F1 combinations with either durum or bread wheats. Relatively less progress has been made in the use of genes from tertiary gene pool often involving “intergeneric crosses.” The potency of potentially useful diversity in tertiary gene pool warrants further exploitation of this resource. Presented here are major facets of intergeneric hybridization embracing a taxonomic consideration of genetic diversity within the Triticeae, the exploitation protocols, prebreeding strategies, and some of the outputs from distant hybridization with a major focus on wheat/alien chromosomal exchanges classed as “translocations” such as T1BL.1RS and to a lesser degree the T1AL.1RS Robertsonian translocations. This chapter also attempts to relate the exploitation of the Triticeae genetic diversity with wheat productivity as a means of addressing diverse stress constraints that if pursued will provide yield enhancing outputs necessary for overriding environmental limitations of climate change, unpredictable incidences of biotic stresses, and catalyzing gains for food security with wheat.
The work of CIMMYT and its many valued partners on maize and wheat farming systems is more important now than at any time in the organization’s history. Our planet’s expanding population, changing diets, limited natural resources, demand for bio-fuels and increasingly variable climate are all putting extraordinary pressure on the global food system. The evidence is all around us. In 2012, for the third time in less than six years, we faced a global food price crisis with international maize prices reaching levels double those of just two years prior. In the wake of the Arab Spring, two major wheat production and cereal importing areas, North Africa and the Middle East, remain highly stressed by rising wheat prices. In recent years average wheat imports for all of Africa have reached more than 35 million tons annually, costing the continent’s nations more than US$12 billion and threatening the supply of wheat products for resource-poor consumers.
José Ariel Ruiz Corral, José de Jesús Sánchez González, Juan Manuel Hernández Casillas, Martha C. Willcox, Gabriela Ramírez Ojeda, José Luis Ramírez Díaz y Diego Raymundo González Eguiarte
Se trabajó con una base de datos de accesiones recientes de 54 razas de maíz de México, cuyos datos pasaporte se extrajeron de la Unidad de Recursos Genéticos del Banco de Germoplasma del INIFAP. A partir de las coordenadas geográficas de las accesiones, se hizo una caracterización por sitios de accesión, de las condiciones de disponibilidad de humedad del período mayo-octubre para el desarrollo del maíz, con base en el sistema de información ambiental del INIFAP y el sistema IDRISI Andes. Con estos datos se realizó un análisis estadístico que incluyó análisis de varianza y un análisis de taxonomía numérica (análisis cluster) con la opción de correlación de momento producto entre razas. Adicionalmente se realizó un análisis de accesiones por raza para identificar las accesiones que desarrollan bajo ambientes con deficiencia de humedad. Se seleccionaron las accesiones con adaptación a un ambiente con índice de humedad (IH) (precipitación/evapotranspiración potencial) mayo-octubre inferior a 0.5. Los resultados mostraron la identificación de cinco grupos raciales, de los cuales uno de ellos se destacó por su adaptación a un IH entre 0.39 y 0.53. Este grupo incluyó las razas Chapalote, Dulcillo del Noroeste, Tuxpeño Norteño, Cónico Norteño, Tablilla de Ocho y Gordo. El análisis de accesiones reportó la presencia de maíz en un total de 677 sitios con condiciones de semiaridez en la temporada mayo-octubre. Las 677 accesiones representan a 24 razas. Éstos resultados permiten concluir que en México existen recursos genéticos, relacionados con las razas de maíz, los cuales podrían ser de utilidad en los programas de mejoramiento genético de maíz enfocados a la adaptación a estrés por sequía.
Matthew Reynolds, John Foulkes, Robert Furbank, Simon Griffiths, Julie King, Erik Murchie, Martin Parry and Gustavo Slafer
Wheat provides 20% of calories and protein consumed by humans. Recent genetic gains are <1% per annum (p.a.), insufficient to meet future demand. The Wheat Yield Consortium brings expertise in photosynthesis, crop adaptation and genetics to a common breeding platform. Theory suggest radiation use efficiency (RUE) of wheat could be increased ∼50%; strategies include modifying specificity, catalytic rate and regulation of Rubisco, up-regulating Calvin cycle enzymes, introducing chloroplast CO2 concentrating mechanisms, optimizing light and N distribution of canopies while minimizing photoinhibition, and increasing spike photosynthesis. Maximum yield expression will also require dynamic optimization of source: sink so that dry matter partitioning to reproductive structures is not at the cost of the roots, stems and leaves needed to maintain physiological and structural integrity. Crop development should favour spike fertility to maximize harvest index so phenology must be tailored to different photoperiods, and sensitivity to unpredictable weather must be modulated to reduce conservative responses that reduce harvest index. Strategic crossing of complementary physiological traits will be augmented with wide crossing, while genome-wide selection and high throughput phenotyping and genotyping will increase efficiency of progeny screening. To ensure investment in breeding achieves agronomic impact, sustainable crop management must also be promoted through crop improvement networks.
Mauricio R. Bellon, David Hodson and Jon Hellin
Climate change is predicted to have major impacts on small-scale farmers in Mexico whose livelihoods depend on rain-fed maize. We examined the capacity of traditional maize seed systems to provide these farmers with appropriate genetic material under predicted agro-ecological conditions associated with climate change. We studied the structure and spatial scope of seed systems of 20 communities in four transects across an altitudinal gradient from 10–2,980 m above sea level in five states of eastern Mexico. Results indicate that 90% of all of the seed lots are obtained within 10 km of a community and 87% within an altitudinal range of ±50 m but with variation across four agro-climate environments: wet lowland, dry lowland, wet upper midlatitude, and highlands. Climate models suggest a drying and warming trend for the entire study area during the main maize season, leading to substantial shifts in the spatial distribution patterns of agro-climate environments. For all communities except those in the highlands, predicted future maize environments already are represented within the 10-km radial zones, indicating that in the future farmers will have easy access to adapted planting material. Farmers in the highlands are the most vulnerable and probably will need to acquire seed from outside their traditional geographical ranges. This change in seed sources probably will entail important information costs and the development of new seed and associated social networks, including improved linkages between traditional and formal seed systems and more effective and efficient seed-supply chains. The study has implications for analogous areas elsewhere in Mexico and around the world.
Matthew Reynolds, M. John Foulkes, Gustavo A. Slafer, Peter Berry, Martin A. J. Parry, John W. Snape and William J. Angus.
Abstract. Recent advances in crop research have the potential to accelerate genetic gains in wheat, especially if co-ordinated with a breeding perspective. For example, improving photosynthesis by exploiting natural variation in Rubisco’s catalytic rate or adopting C4 metabolism could raise the baseline for yield potential by 50% or more. However, spike fertility must also be improved to permit full utilization of photosynthetic capacity throughout the crop life cycle and this has several components. While larger radiation use efficiency will increase the total assimilates available for spike growth, thereby increasing the potential for grain number, an optimized phenological pattern will permit the maximum partitioning of the available assimilates to the spikes. Evidence for underutilized photosynthetic capacity during grain filling in elite material suggests unnecessary floret abortion. Therefore, a better understanding of its physiological and genetic basis, including possible signalling in response to photoperiod or growth-limiting resources, may permit floret abortion to be minimized for a more optimal source:sink balance. However, trade-offs in terms of the partitioning of assimilates to competing sinks during spike growth, to improve root anchorage and stem strength, may be necessary to prevent yield losses as a result of lodging. Breeding technologies that can be used to complement conventional approaches include wide crossing with members of the Triticeae tribe to broaden the wheat genepool, and physiological and molecular breeding strategically to combine complementary traits and to identify elite progeny more efficiently.