Centro Internacional De Mejoramiento De Maiz Y Trigo Research Articles

Multi-Location Evaluation of Global Wheat Lines Reveal Multiple QTL for Adult Plant Resistance to Septoria Nodorum Blotch (SNB) Detected in Specific Environments and in Response to Different Isolates.

The slow rate of genetic gain for improving resistance to Septoria nodorum blotch (SNB) is due to the inherent complex interactions between host, isolates, and environments. Breeding for improved SNB resistance requires evaluation and selection of wheat genotypes consistently expressing low SNB response in different target production environments. The study focused on evaluating 232 genotypes from global origins for resistance to SNB in the flag leaf expressed in different Western Australian environments. The aim was to identify resistant donor germplasm against historical and contemporary pathogen isolates and enhance our knowledge of the genetic basis of genotype-by-environment interactions for SNB response. Australian wheat varieties, inbred lines from Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), and International Center for Agricultural Research in the Dry Areas (ICARDA), and landraces from discrete regions of the world showed low to moderate phenotypic correlation for disease response amongst genotypes when evaluated with historical and contemporary isolates at two locations across 3 years in Western Australia (WA). Significant (P < 0.001) genotype-by-environment interactions were detected regardless of same or different isolates used as an inoculum source. Joint regression analysis identified 19 genotypes that consistently expressed low disease severity under infection with different isolates in multi-locations. The CIMMYT inbred lines, 30ZJN09 and ZJN12 Qno25, were particularly pertinent as they had low SNB response and highest trait stability at two locations across 3 years. Genome wide association studies detected 20 QTL associated with SNB resistance on chromosomes 1A, 1B, 4B, 5A, 5B, 6A, 7A, 7B, and 7D. QTL on chromosomes 1B and 5B were previously reported in similar genomic regions. Multiple QTL were identified on 1B, 5B, 6A, and 5A and detected in response to SNB infection against different isolates and specific environments. Known SnTox-Snn interactions were either not evident or variable across WA environments and SNB response may involve other multiple complex biological mechanisms.

High yield potential, shuttle breeding, genetic diversity, and a new international wheat improvement strategy

The main elements of the international wheat improvement program of the Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), also known as the International Maize and Wheat Improvement Center, have been shuttle breeding at two contrasting locations in Mexico, wide adaptation, durable rust and Septoria resistances, international multisite testing, and the appropriate use of genetic variation to enhance yield gains of subsequently produced lines. Such an approach yielded successes known collectively as the Green Revolution. However, at the beginning of the 21st century, this “cultivar assembly line” approach needs fine tuning to address crop needs under increasingly adopted resource conserving practices, as well as those related to nutritional requirements of the end-users. International wheat improvement will therefore focus on the targeting of traits in respective mega-environments, and the use of participatory methods, especially in marginal environments. The main features of this wheat improvement strategy include the introduction of new and novel sources of genetic variation through wild species, landraces, and, potentially, the use of transgenes for intractable traits. This variation will be combined using international shuttle breeding, and increased breeding efficiency will be achieved through marker-aided methods, more targeted use of crop physiology, plant genetics, biostatistics, and bioinformatics. Likewise, CIMMYT will increase its focus on the needs of end-users by emphasizing regional efforts in participatory research and client-oriented plant breeding.

The Fourth Canadian Workshop on Fusarium Head Blight / Quatrième colloque canadien sur la fusariose

The Fourth Canadian Workshop on Fusarium Head Blight / Quatrième colloque canadien sur la fusariose

Annual Meeting, Québec, Quebec, 2006, The Canadian Phytopathological Society / Réunion annuelle, Québec, Québec, 2006, La Société canadienne de phytopathologie

Annual Meeting, Québec, Quebec, 2006, The Canadian Phytopathological Society / Réunion annuelle, Québec, Québec, 2006, La Société canadienne de phytopathologie

Fibre Analysis of Wheat Genotypes and its Association with Lodging: Effects of Nitrogen Levels and Ethephon

Present study involved 12 lodging tolerant/ susceptible spring wheat (Triticum aestivum L.) genotypes grown at 180, 300 kg N/ha and 480 glha ethephon application in latter N rate at CIMMYT (Centro Internacional de Mejoramiento de Maiz y Trigo), Mexico during 1997-98 and 1998-99 under disease free and irrigated condition. During both the years, crop lodged 25 to 30 days after anthesis in varying degrees at different N levels whereas, ethephon application at DC 38 prevented lodging and decreased the ADF (acid detergent fibre), cellulose and lignin content by 8.47, 8.81 and 5.56 %, respectively in the basal intemode and increased K content of 2 n d intemode by 9.6 % as compared to without its application. However, increasing N rates from 180 to 300 kglha determined non-significant difference for ADF, cellulose, lignin and K concentrations in the 2 n d and 3 r d intemodes. ADF and cellulose concentrations of 3 r d internode were higher by 3.2-3.8 % and 4.7-5.3 %, respectively when compared with 2 n d internode whereas 2 n d internode determined 1.9-4.2 % higher lignin and 12.3-13.4 % more potassium contents than the 3 r d internode at different N levels. Pooled analysis indicated that genotypic differences for ADF, cellulose, lignin and K contents were significant for both the internodes. ADF, cellulose and lignin contents for the 2 n d and the 3 r d intemodes were negatively correlated with lodging score and in combined analysis of 3 r d intemode its phenotypic correlation was - 0.53, - 0.57 and - 0.61 with lodging score, respectively. Also, from multiple correlations study it was observed that ADF, cellulose and lignin contents had a positive impact among themselves and their cumulative effect in turn might be preventing lodging. Therefore, it could be said that higher ADF, cellulose and lignin content of basal intemode were important parameters in developing a lodging resistant cultivar under irrigated and high N conditions.

UTILIZATION OF WILD AND CULTIVATED EMMER AND OF DIPLOID WHEAT RELATIVES IN BREEDING

Different wheat relatives have contributed greatly towards economic improvement of hexaploid bread wheats. Since its discovery by Aaronsohn in 1906, wild emmer has been widely described and phenotyped for many useful traits such as stripe-rust resistance and high protein. A cultivated emmer landrace, Yaroslav emmer, has contributed durable stem-rust resistance to variety ‘Hope’, which has become a paramount germplasm for improving resistance to stem rust in bread wheats. Other lines of cultivated emmer, Triticum dicoccum, are being used for improved protein percentage. Recently, following the examples of Yaroslav emmer, the International Maize and Wheat Improvement Center, CIMMYT (Centro Internacional De Mejoramiento De Maiz Y Trigo) has embarked on utilization of Aegilops tauschii (DD genome) for resistance to Septoria tritici leaf blotch and Fusarium head scab, drought tolerance, and good bread-making quality traits. Some wild perennial members of the Triticeae genera Leymus and Thinopyrum are additiona...

The Potential for Increasing the Iron and Zinc Density of Maize through Plant-breeding

The Centro Internacional de Mejoramiento de Maiz y Trigo ( CIMMYT) maize-breeding programme has been focusing on identifying white-grained maize germplasm that has the potential to increase kernel iron and zinc concentrations, especially in sub-Saharan Africa. In addition, research at Cornell University has focused on traits such as multiple aleurone layer, which can increase kernel iron and zinc concentrations, and low phytic acid concentration, which holds promise for improving the bioavailability of iron and zinc. More than 1,400 improved maize genotypes and 400 landraces were grown and evaluated to assess grain iron and zinc concentrations. These materials represented all white-grained landraces that belonged to the core collection of CIM-MYT's germplasm bank, all white- and yellow-grained CIMMYT maize germplasm pools and populations, all white-grained materials that are currently in the active breeding programme of CIMMYT-Zimbabwe, and 57 white-grained maize cultivars currently grown in southern Africa. After a very thorough evaluation of the genetic variability of iron and zinc potentially available in white-grained tropical maize germplasm, promising genetic variability was found in both improved maize germplasm and landraces. One difficulty that maize breeders encounter is that grain iron and zinc concentrations are often correlated negatively with grain yield, which may result from the increased carbohydrate content of high-yielding materials, so that a given amount of iron and zinc is diluted. The multiple aleurone trait may be a fast track to overcome this effect. This trait is being introgressed into various materials in both the United States and southern Africa.

Breeding for Trace Minerals in Wheat

In the search for genetic material with high iron and zinc concentration in wheat grain, a significant positive correlation has been found between iron and zinc concentrations, suggesting that these two traits may be combined relatively easily during breeding. In future research, the very high values of iron and zinc in the grain seen in wild types and landraces need to be confirmed in trials in which all the best material is planted in the same location and year. In addition, it is important to determine if these high levels of iron and zinc in the grain can be maintained in high-yielding material. The production of semi-dwarf wheat through the introduction of the rht genes has resulted in substantial yield increases. However, this is associated with a reduction in iron and zinc concentrations in some bread wheat genotypes, but not in durum wheat. The presence of the 1B/1R translocation in the wheat germplasm of the Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT) to increase leaf rust resistance may have had a positive effect on the concentration of iron and zinc, but a negative effect was ruled out. There is a strong positive correlation between grain yield and year of release in the CIMMYT wheat varieties. There is a small negative but statistically significant relationship between the time of release and the concentrations of iron, zinc, total phosphorus, and phytate. The positive effect of nitrogen applications on iron and zinc concentrations is more important than declines in these concentrations due to breeding during the last 42 years

The Quality Protein Maize Story

The paper describes the sequence of breeding stages that led to the development of acceptable quality protein maize (QPM) germplasm at the Centro Internacional de Mejoramiento de Maiz y Trigo ( CIMMYT). Initial emphasis was on the development of soft opaque-2 (o2) maize varieties, but these had undesirable consumer characteristics, among other problems. Research then shifted to the development of hard-textured QPM germplasm. Several breeding approaches were explored and tested in early 1970. The combined use of two genetic systems involving the o2 gene and the genetic modifiers of the o2 locus appeared to be the most promising approach. This strategy first involved the development of donor stocks from which a large volume of QPM germplasm was generated through a modified backcross programme and various recurrent selection procedures. Later merging and reorganization of QPM germplasm was undertaken, which resulted in a definite number of QPM populations and pools to meet germplasm needs for various agroclimatic conditions. This was a turning point in the breeding strategy that permitted work with homozygous o2 genetic backgrounds. In the mid-1980s, a hybrid development initiative was started. Basic information on combining ability and heterotic pattern(s) of QPM germplasm was generated. Later emphasis was shifted to development efforts for inbred and hybrid QPM. Several superior QPM germplasm products are now spreading commercially in several developing countries of Asia, Central and South America, and Africa

Research on ‘Xanthomonas translucens’ of wheat and triticale at CIMMYT1

Bacterial streak caused by ‘Xanthomonas translucens’ is a serious bacterial disease of wheat and triticale and is distributed worldwide. Contaminated seed is the main source of inoculum. As disease incidence appears to be increasing in several countries, research is needed for more resistance in both crops. However, assessment of resistance is hampered by symptom variations and diagnosis can be difficult. Moreover, the nomenclature of the pathogens causing bacterial streak on cereals is rather confusing. A seed detection method has been developed at CIMMYT (Centro Internacional de Mejoramiento de Maiz y Trigo) using a WBC semi‐selective medium. The efficiency of hot cupric acetate has been confirmed to disinfect contaminated seed sets. More research is currently under way on epidemiology to identify the environmental factors favorable for disease expression and to determine the transmission rate of bacteria under Mexican conditions.

Comparisons Among Populations of Maize for Growth at 13°C

Six populations of maize (Zea mays L.), from high altitude sources in Mexico, Peru, and a high latitude source in Germany, and their crosses as males to two United States Corn Belt dent inbred lines (‘A619’ and ‘WI53R’) were compared for growth and survival at 13 C in a controlled environment with three U.S. Corn Belt dent hybrids (‘A632’ ✕ ‘A659,’ A619 ✕ A632, and WI53R ✕ A632).The objective of this study was to determine if any of these populations had the ability to grow autotrophically at 13 C, a temperature which was expected to be below the minimum for autotrophic growth of U.S. Corn Belt dent cultivars.At 13 C all plants grew heterotrophically utilizing seed reserves. However, major differences in the ability to grow autotrophicaly at 13 C existed among the genotypes studied. All genotypes containing germplasm from the high altitude Peruvian races ‘San Geronimo,’ ‘Huancavelicano,’ and ‘Confite Puneno’ were capable of autotrophic growth at l3 C as were genotypes from the CIMMYT (Centro Internacional de Mejoramiento de Maiz y Trigo) Pool 5. ‘Criollo die Toluca,’ predominantly of the high altitude Mexican race Conico, and ‘Bergenlaender,’ of the high latitude Norllhern Flint race, per se, were unable to grow at 13 C. However, their crosses with W153R and the cross A619 ✕ Criollo de Toluca were able to grow autotrophically at this temperature. Differences in growth rates existed between A619 and WI53R in crosses. Overall, crosses with W153R had the highest growth rates and crosses with A619 the lowest. The three U.S. Corn Belt dent hybrids did not grow autotrophically at 13 C.

Impediments to Technical Progress on Small versus Large Farms

During the past four years, Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT) has been associated with a number of farm-level studies of the adoption of new wheat and maize varieties and fertilizer use. Most of these studies have now been published, and it is our purpose here to summarize some of the findings with respect to impediments to farmer adoption of new varieties. Farm-to-farm differences in the date of adoption or the extent of adoption of new technology might be explained by a number of considerations. The studies reviewed here considered farm-to-farm differences in the cost of acquiring and processing information, differences in the physical productivity of the new technology, differences in incentives due to tenure arrangements, differences in the cost of inputs, differences in prices received for the product, differential aversion to risk among farmers, and scale effects associated with farm or enterprise size. Policies to stimulate more rapid or more extensive adoption will vary in their success depending upon which of these factors are the most important in limiting the rate and extent of adoption. Of particular relevance is the extent to which small farmers lag behind large farmers in adoption and which of the above factors might account for that lag. The studies were directed toward factors