Showing papers by "International Maize and Wheat Improvement Center published in 1990"

Statistical analyses of multilocation trials

Abstract: Publisher Summary This chapter presents the statistical analysis of multilocation trials. Multilocation trials play an important role in plant breeding and agronomic research. Data from such trials have three main agricultural objectives—to accurately estimate and predict yield based on limited experimental data; to determine yield stability and the pattern of response of genotypes or agronomic treatments across environments; and to provide reliable guidance for selecting the best genotypes or agronomic treatments for planting in future years and at new sites. Agronomists use multilocation trials to compare combinations of agronomic factors, such as fertilizer levels and plant density, and on this basis make recommendations for farmers. Breeders compare different improved genotypes to identify the superior ones. Data collected in multilocation trials are intrinsically complex, having three fundamental aspects—namely, structural patterns; nonstructural noise; and relationships among genotypes, environments, and genotypes and environments considered jointly. Pattern implies that a number of genotypes respond to certain environments in a systematic, significant, and interpretable manner, whereas noise suggests that the responses are unpredictable and uninterpretable.

Yield and adaptation of hexaploid spring triticale

Abstract: 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.

Household Inventories and Marketed Surplus in Semisubsistence Agriculture

Abstract: A model of semisubsistence agriculture explicitly accounting for the ability of farm households to hold inventories of staple foods is developed. Comparative statics analysis highlights the potential importance of wealth effects attributable to price-induced changes in the value of household inventories. Empirical results for three groups of households in an Indian village confirm that failure to account for household inventories leads to an overstatement of the responsiveness of both consumption demand and marketed surplus.

Identification of resistance genes to Puccinia striiformis in seedlings of Ethiopian and CIMMYT bread wheat varieties and lines

Abstract: In a controlled environment, the reaction was observed of 42 bread wheat varieties and lines inoculated with 19 isolates of yellow rust differing in their virulence to 20 differential varieties. Five varieties and lines showed resistance to all isolates. The remaining ones appeared to have the genes Yr2, Yr3, Yr4, Yr6, Yr7, Yr9 and YrA, either singly or in combination. Yr9 derived from rye was present in 67% of the varieties and lines. Yr4 is the only effective gene in that material as, in Eastern and Central Africa, yellow rust has virulence to the other Yr genes. Recognition of virulence to Yr genes is enhanced by the use of a supplemental set of differential varieties supposedly carrying a single gene. Additional keywords: yellow (stripe) rust races, Triticum aestivum, Yr genes.

Heterotic Patterns among Mexican Races of Maize

Abstract: Collection and description of the maize (Zea mays L.) germplasma complexes of Mexico began in 1943, and efforts toward the potential utilization of the 25 recognized Mexican races were initiated in 1961. This study was conducted to determine the performance of the 25 Mexican races and 300 interracial crosses evaluated in three environments identified as high (2249 m), intermediate (1800 m), and low (1300 m) elevations. Data were analyzed with the Gardner-Eberhart model, Analysis II. At the high elevation the races Conico, Conico Norteno, and Chalqueno had high mean yields per se and in crosses. Cacahuacinthe and Maiz Dulce had equally high yield in crosses but had lower per se yield. At the intermediate elevation, the best yielding races in crosses and per se were Comiteco, Harinoso de Ocho, Celaya, Maiz Dulce, Tabloncillo, and Tuxpeno. At low elevation, the highest per se yields were exhibited by Harinoso de Ocho, Celaya, Pepitilla, and Tabloncillo. Across all elevations, the best general combiners were Cacahuacintle, Harinoso de Ocho, and Maiz Dulce. Results of this study could be used to (i) introgress varieties or populations, (ii) search for race collections with better agronomic type that belong to the racial heterotic pattern, (iii) improve gene pools based on racial heterotic patterns and geographical origins, (iv) establish reciprocal recurrent selection between two races that exhibited heterosis when crossed, or (v) develop hybrids based on lines derived from the collections studied in each environment

Genetic Evidence for Sibling Species within the Sugarcane Borer (Lepidoptera: Pyralidae)

Abstract: Collections of the sugarcane borer, Diatraea saccharalis (F.), from Brazil and Louisiana differ in morphology, physiology, and behavior. These samples, along with one from Mexico, were examined electrophoretically to aid in determining the basis of this variation. Two other species, D. grandiosella Dyar and D. lineolata (Walker), were also examined. Genetic differences were minor between Mexican and Louisiana samples (Nei's distance = 0.02) and an order of magnitude greater in pairwise comparisons with the Brazilian sample (average distance = 0.23). The Brazilian collection was significantly different at all polymorphic loci, and one locus was diagnostic. Although D. grandiosella and D. lineolata are nearly identical morphologically, they differed greatly genetically (Nei's distance = 0.36; three diagnostic loci). Variation within the sugarcane borer is well within the range of interspecific differences, suggesting D. saccharalis may be composed of two species. Interstrain crosses performed using Louisiana and Brazilian laboratory colonies indicated no incompatibilities in parental, interhybrid, or backcrosses, suggesting postreproductive barriers may not exist. Further studies are required to determine the geographical ranges of the two taxa, and, if sympatric, whether they are completely reproductively isolated in nature.

Wide Hybridization — Potential of Alien Genetic Transfers for Triticum aestivum Improvement

Abstract: In the Triticeae, hybridization of alien species with those of Triticum goes back to 1876 when Wilson consciously made the first wide hybrid involving wheat and rye. Rimpau in 1891 obtained seed on a presumably doubled sector in a wheat × rye hybrid and described 12 plants that must represent the first triticale. A more divergent hybrid (wheat × barley) was first reported by Farrer in 1904 that was considered rather improbable to be a true hybrid (Shepherd and Islam 1981).

Food Aid and Food Security: A Cautionary Note

Abstract: A simple model is presented to examine the effects of instability in global food aid supplies on foreign exchange expenditures and food availability in recipient countries. When global food prices rise, food aid recipients are doubly affected through decreased availability of food aid, and through higher costs of additional commercial imports needed to make up the shortfall. Empirical estimates of key parameters of the model suggest that countries with a high dependence on food aid may place their food security at risk. Suit un modele simple qui permet d'analyser les consequences de l'instabilite des approvi-sionnements destines a l'aide alimentaire sur les depenses en devises etrangeres et l'offre d'aliments dans les pays beneficiaires. Lorsque le prix mondial des aliments augmente, les beneficiaires de l'aide alimentaire subissent le contrecoup a la fois d'une aide alimentaire reduite et du cout plus eleve des produits importes pour repondre a la penurie. Une estimation empirique des principaux parametres du modele suggere que les pays qui dependent fortement de l'aide alimentaire compromettent leur securite alimentaire.

A comparison of inoculation techniques for assessment of germplasm susceptibility to Karnal bunt (Tilletia indica) disease of wheat.

Abstract: Summary Three inoculation techniques for Karnal bunt (Tilletia indica) disease of wheat were compared: 1) boot inoculation - injection of inoculum with a hypodermic syringe into the boot; 2) spray inoculation - inoculum sprayed at growth stages between heading and anthesis, and 3) cotton wool inoculation - small pieces of cotton wool saturated in inoculum placed either inside the floret or between the spikelet and rachis. Each inoculation technique was assessed using susceptible cultivars to determine the optimum inoculum concentration, the ideal plant growth stage and the humidity requirements for successful infection. Boot inoculation did not require high humidity and gave reliable infection with low secondary sporidia concentrations (1000–10 000/ml). The ideal plant growth stages for inoculation were early-boot and mid-boot. Spray inoculation required high secondary sporidia concentrations (50 000/ml) and 48 h of high humidity, but infection was initiated over a range of growth stages throughout heading and anthesis. Cotton wool inoculation gave low levels of infection at growth stages throughout heading and anthesis, even with high secondary sporidia concentrations (100 000/ml).

Genetic Differentiation of Populations of the Southwestern Corn Borer (Lepidoptera: Pyralidae) from the United States and Mexico

Abstract: Southwestern corn borers, Diatraea grandiosella (Dyar), obtained from seven localities in the United States and from Morelos, Mexico, were subjected to starch and cellulose acetate gel electrophoresis and assayed for 14 enzymes encoded by 17 putative gene loci. Thirteen of the loci expressed no variation. Each of the four polymorphic loci displayed statistically significant site-to-site variation in allele frequencies. Most of the geographic variation occurred between the grouped U.S. samples and the Mexican sample. Particularly notable was a fixed allelic difference between the Mexican sample and the U.S. samples at the mannose phosphate isomerase locus. The geographic variance in allele frequencies was quantified using Wright's Fst measure of population structure. Combined across the four polymorphic loci, Fst equaled 0.272. The average genetic identity (I) between the Mexican sample and each of the U.S. samples was 0.92 when based on all 17 loci. This finding suggests that considerable genetic differentiation has occurred between moths in the United States and a Mexican form and is consistent with previous documentation of physiological and morphological differences between the two groups.

Breeding wheat (Triticum aestivum) for aluminium toxicity tolerance at CIMMYT

Abstract: CIMMYT launched a breeding program in 1974 primarily to combine A1 toxicity tolerance of Brazilian wheats with high yield potential and wide adaptability of Mexican semidwarfs. This experiment has been a success as numerous advanced lines and cultivars have been produced with at least a 25% increase in yield potential combined with increased tolerance to A1 toxicity in acid soils. Laboratory screening methodology combined with shuttling of alternate segregating populations between locations in Mexico and Brazil were utilized as the breeding methodology. This paper outlines historical perspective, genetical variability in wheat varieties, screening methodology, shuttle breeding, and future prospects and development in Al toxicity research at CIMMYT.

Building institutional capacity for on-farm research: Call system training courses

Abstract: A training program in on-farm research for national agricultural research and extension institutions is described. The training is carried out in a series of 1to 2-wk meetings over two agricultural seasons, and concerns the application of research techniques in diagnostic surveying, planning, onfarm experimentation, and analysis. It is argued that this type of long-term, hands-on training is not only effective for transferring research methods, but also serves to develop institutional capacities for planning and managing research and extension directed at well-defined client groups. Implications are discussed regarding the organization of interdisciplinary research, the development of linkages between research and extension institutions, the prospects for training in research planning, and the relative merits of problemoriented training. ONE OF THE PRINCIPAL GOALS of national agricultural research services in developing countries is the provision of technology to improve the productivity of small farm agriculture. A major problem in achieving that goal is a lack of experience in planning agricultural research based on an understanding of the conditions and circumstances of client farmers. In response, a wide variety of research methods and procedures has been developed, many under the rubric of "Farming Systems Research" (22). This article discusses a training program for one such set of research methods, referred to as call system training in on-farm research. The training program not only attempts to transfer research methods, but also gives attention to assuring that research and extension organizations are able to effectively incorporate those methods in their work. On-farm research (OFR) is a set of research methods with a farming systems perspective (3) that has been adopted by a number of national agricultural research institutions (6, 13). It includes methods for assessing farmers’ circumstances and problems, planning a research program to be carried out on farmers’ fields, and developing recommendations consistent with farmers’ priorities. Several characteristics of OFR have important implications for the organization of research and for the development of training strategies. First, OFR is location-specific and presumes the identification of welldefined groups of farmers who are targets of a research R. Tripp, CIMMYT Economics Program, Apdo. Postal 6-641,06600 Mexico, D.F., Mexico; and P. Anandajayasekeram, CIMMYT Economics Program, P.O. Box 25171, Nairobi, Kenya. Received l l Sept. 1989. *Corresponding author Published in J. Agron. Educ. 19:131-136 (1990). effort. Second, it starts from an understanding of the system of crops, animals, and off-farm labor that characterizes small farm agriculture, and attempts to provide innovations that are consistent with that system. Finally, OFR is necessarily interdisciplinary, integrating the work of biological and social scientists. TRAINING OBJECTIVES FOR ON-FARM RESEARCH Several challenges present themselves to any training program aimed at introducing the methods of OFR to national research and extension institutions. The most immediate challenge is the transfer of an integrated set of research methods, including techniques for observing farmers’ fields and discussing production practices and problems with farmers, setting research priorities based on this type of diagnosis, carrying out experimentation on farmers’ fields, and analyzing the results of those experiments using criteria important to farmers. If such training is to succeed, it also requires some changes in the way that research priorities are set. Opportunities and formats need to be established at all levels of research and extension institutions for setting priorities that reflect farmers’ conditions and concerns. The process by which agricultural research priorities are currently established is quite complex and often not formally articulated (1). The establishment of appropriate planning methods for national agricultural research institutions is further complicated by the way in which these institutions are organized. There are often separate commodity programs [e.g., legumes, maize (Zea mays L.) pastures] and disciplinary departments (e.g., entomology, soils, economics). In addition, some researchers may be assigned area-specific or project-related duties. The successful introduction of OFR to such an institution must envision a way of encouraging an interdisciplinary approach to priority setting that would be relevant to various units of the research organization. A further challenge to establishing effective training in OFR is the fact that agricultural research is usually separated from the technology delivery system. The extension service is often part of a different institution, with its own procedures and organization (12). A training program must often find ways of addressing two separate institutions simultaneously. Finally, any training program must be concerned with questions of efficiency and continuity. Choices must be made regarding the participants and venue for training, the training methods to be used, and the possibilities for establishing local training capacity. J. Agron. Educ., Vol. 19, no. 2, 1990 131 Table 1. Call system training courses presented by CIMMYT. No. of Country Institution(s) Year(s) Topicst calls Ecuador Instituto Nacional de 1979, 1981, P,E,A 3 Investigaciones 1982, 1983 Agropecuarias (INIAP) Venezuela Fondo Nacional de 1980-1981 D,P,E,A 5 Investigaciones Agropecuarias (FONAIAP) Honduras Programa Nacional de 1982-1983 D,P,E,A 5 InvestigaciSn Agropecuaria (PNIA) Per5 Programa Nacional de 1983-1984 P,E,A 4 Cereales, Instituto Nacional de Investigaciones y PromociSn Agropecuaria (INIPA) Zambia Adaptive Research 1983-1984 D,P,E,A 5 Planning Teams, Research Branch, Ministry of

Technical Change, Productivity, and Sustainability in Irrigated Cropping Systems of South Asia: Emerging Issues in the Post-Green Revolution Era

Abstract: Recent trends in South Asia's irrigated cropping systems are analyzed, giving particular attention to systems in which wheat is an important crop. Much of the recent success in increasing food production In South Asia is due to success in wheat production. The paper presents an overview of the stages of technical and Institutional changes in South Asian agriculture from the pre-Green Revolution era through to the current post-Green Revolution stage. The paper then identifies emerging problems, both technical and institutional, which will Impinge on the ability to maintain gains in food grain productivity and sustain the resource base over the next 10-20 years. A new strategy Is proposed to ensure productivity increases in South Asian cropping systems in the future. This strategy not only implies profound changes in agricultural research priorities, but also in the institutions that foster technical change in agriculture.

Damage by southwestern corn borer (Diatraea grandiosella Dyar) on resistant and susceptible maize at three plant growth stages in Mexico.

Abstract: Two resistant varieties, MBRV‐SWCB and P47R, and one susceptible variety, P47S, were infested with southwestern corn borer (SWCB), Diatraea grandiosella Dyar, larvae at the 4–5, 6–8 and 9–11 fully extended leaf stages. Leaf damage ratings were highest in all varieties when plants were infested at the 4–5 leaf stage and declined with the age of plants at infestation, the decline being less between the 4–5 and 6–8 leaf stages than between the 6–8 and 9–11 leaf stages. There was greater variation in leaf damage when infested at the 4–5 leaf stage than at the 6–8 leaf stage. Variation was lowest at the 9–11 leaf stage, but the ratings did not indicate any real differences between varieties. The MBRV‐SWCB and P47R had significantly less leaf feeding damage than P47S across infestation stages. Yield, compared to that of an uninfested check, was reduced at all infestation stages in all cultivars; the greatest reduction occurred when plants were infested at the 4–5 leaf stage. The MBRV‐SWCB and P47R show...

Comment: Maize research in Malawi

Abstract: Jonathan Kydd's analysis of the history of maize research in Malawi argues successfully that the reasons for the low rate of adoption of high yielding maize varieties lie in an insufficient appreciation of local processing and storage requirements. The analysis, however, raises further questions. In particular, Kydd's conclusion that maize research by multinational seed corporations might be more effective than public sector research is not supported by adequate evidence. The existing evidence suggests that though these corporations are likely to play an increasing role in developing counties, they are unlikely to direct their efforts to the needs of the poor.