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Heterosis and combining ability among CIMMYT's mid-altitude early to intermediate maturing maize (Zea mays L.) populations

Bindiganavile Vivek Jose Crossa Gregorio Alvarado (2009)

Maize is an important food crop in sub-Saharan Africa. There is an increasing demand for early maturing maize cultivars even though long-season maize cultivars yield more than early maturing cultivars under favourable conditions. This is because vast areas of maize are routinely affected by drought and low N fertility and early maturing maize cultivars offer more flexibility than full season cultivars for a farmer with respect to cultivation and food security. CIMMYT’s early maturing maize program, which aims to supply seed to approximately 3 million hectares of maize area in east and southern Africa lacks adequate information on heterotic relationships of its germplasm. 190 crosses (generated from a diallel of eighteen populations and two within heterotic group single crosses) and their 20 parentals were evaluated for heterotic relationships at six locations in Zimbabwe (four optimal conditions of rainfall and fertilizers (but different agro-ecological regions / mega-environments), one managed low nitrogen environment and one managed drought environment). Three heterotic patterns were seen under stress while six heterotic patterns were seen under optimal conditions. P9 (CML312/CML442) expressed a consistent heterotic pattern across stress and non-stress environments thus justifying its continued use as a tester. Moving towards the use of multiple heterotic groups in the CIMMYT-Zimbabwe program may be worthwhile provided that the budgetary scenario still supports its core mandate of germplasm development, germplasm ex-change and strengthening of national research systems.


Combining ability Heterosis diallel Open pollinated variety Maize CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA

Comportamiento de variedades precoces de maíz en la región semiárida y árida del centro-norte de México

Maximino Luna Flores (2005)

Twenty early corn (Zea mays L.) varieties were evaluated under

the rainfed conditions prevailing in the northern highland region of

México (250-500 mm of rain, 60 to 100 d of growing season, and

mean temperature from 16 to 21°C), and at Etla, Oax. with similar

environmental conditions (645 mm of rain in 80 to 100 d, and mean

temperature of 20.6 °C). The study was carried out from 1997 to

1999. A randomized complete blok design with four replications was

used for all locations. The corn yield was analyzed by combinig years

and varieties, and localions and varieties. The combination of years,

localitions and varieties was not evaluated because of the variable

number of traits through years and locations. The late varieties were

more productive in locations with higher precipitation and longer

growing season. Intermediate and early varieties over yielded the late varieties when growing under deficient rainfed conditions. The mean

yield of landraces varieties used as controls, was higher than most of

the other varieties, thus suggesting a delailed evaluation of these

landraces taking into account traits such as plant sanity and uniformity,

and yield potential.

Se evaluaron en temporal o secano 20 variedades precoces de maíz

(Zea mays L.) durante los años 1997-1999, en cinco localidades de

la región templada semiárida y árida del centro norte de México

(250–500 mm de precipitación en 60-100 d; temperatura media 16-

21 ºC) y en Etla, Oax. (645 mm de precipitación en 80-100 d; temperatura

media 20.6 °C). Se usó un diseño experimental de bloques

completos al azar con cuatro repeticiones, y se registró el rendimiento

de grano al que se hicieron análisis de varianza al combinar años con

variedades, y localidades con variedades. Se consideró inconveniente

el análisis combinado de años, localidades y variedades, debido a que

hubo diferente número de observaciones de las variedades en localidades

y años. Las variedades más tardías mostraron mayor rendimiento

en los ambientes con mayor precipitación y ciclo de cultivo;

las de ciclo intermedio y algunas precoces mostraron mayor rendimiento

que las tardías en los ambientes con condiciones ecológicas

intermedias o deficientes. El rendimiento medio de los maíces criollos

usados como testigos fue de los más altos, por lo que se sugiere evaluarlos

en sanidad y uniformidad, y rendimiento potencial.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ


CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA Zea mays L. variedades de polinización libre temporal o secano regiones semiáridas y áridas open pollinating varieties rainfed conditions semiarid and arid regions

Exploring the marketing environment for maize seed in Kenya: how competition and consumer preferences shape seed sector development

Pieter Rutsaert Jason Donovan (2020)

During the past decade, sizable investments have been made to strengthen maize (Zea mays L.) seed production in Eastern and Southern Africa by private seed companies. However, efforts have generally overlooked downstream issues, such as how seed companies market their products and position their business in a competitive market. This paper assesses competition and customer preferences in Kenya at the retail level for varieties from the parastatal, private domestic and international companies. Data were collected from agro-dealer surveys (n = 80) and farmer intercept interviews (n = 377). Compared to the market leader, the parastatal Kenya Seed Company, private domestic and international companies provide greater value to farmers by selling varieties that are, on average, 10 years younger. However, these companies offer few late-maturing varieties, thus giving the parastatal a near monopoly in that market segment. Kenya Seed Company also excels at being present at all sales locations with their varieties. If private domestic companies focus more on smallholders with lower budgets (luding travel budget), they should consider the most cost-effective ways to extend their networks to remote areas as well as compete with the lower prices of Kenya Seed Company. Modern breeding programs should explicitly consider these marketing challenges when designing strategies for seed production and engagement with seed companies.



Misidentification by farmers of the crop varieties they grow: lessons from DNA fingerprinting of wheat in Ethiopia

Moti Jaleta Kindie Tesfaye Bekele Abeyo Ayele Badebo Huluka Olaf Erenstein (2020)

Accurate identification of crop varieties grown by farmers is crucial, among others, for crop management, food security and varietal development and dissemination purposes. One may expect varietal identification to be more challenging in the context of developing countries where literacy and education are limited and informal seed systems and seed recycling are common. This paper evaluates the extent to which smallholder farmers misidentify their wheat varieties in Ethiopia and explores the associated factors and their implications. The study uses data from a nationally representative wheat growing sample household survey and DNA fingerprinting of seed samples from 3,884 wheat plots in major wheat growing zones of Ethiopia. 28-34% of the farmers correctly identified their wheat varieties. Correct identification was positively associated with farmer education and seed purchases from trusted sources (cooperatives or known farmers) and negatively associated with seed recycling. Farmers' varietal identification thereby is problematic and leads to erroneous results in adoption and impact assessments. DNA fingerprinting can enhance varietal identification but remains mute in the identification of contextual and explanatory factors. Thus, combining household survey and DNA fingerprinting approaches is needed for reliable varietal adoption and impact assessments, and generate useful knowledge to inform policy recommendations related to varietal replacement and seed systems development.



Impacts of international research on intertemporal yield stability in wheat and maize: an economic assessment

Douglas Gollin (2006)

Critics of modern maize and wheat varieties (MVs) have suggested that, in developing countries, yields of these varieties vary more from season to season than yields of farmers’ traditional varieties, thereby exposing consumers and producers to greater risk. Drawing on country-level data for MV diffusion, as well as aggregate data on production and yields from FAOSTAT, this study makes novel use of the Hodrick-Prescott filter to disentangle changes in trend from annual fluctuations. The outcomes suggest that, over the past 40 years, the relative variability of grain yields—that is, the absolute magnitude of deviations from the yield trend—has declined for both wheat and maize in developing countries, and that the reduction is statistically associated with the spread of MVs, even after controlling for expanded use of irrigation and other inputs. At appropriate world prices, the annual benefits from improved yield stability alone are about US$143 million for wheat and about US$149 million for maize.


Statistics Prices Varieties Maize Agricultural development Agricultural research CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA

Adoption and impacts of improved winter and spring wheat varieties in Turkey

Ahmed Mazid Mesut KESER Alexey Morgounov MUSTAFA KAN (2009)

Wheat is one of the most important agricultural commodities in Turkey, and the country ranks among the top ten producers in the world. It is a staple and strategic crop, and an essential food in the Turkish diet, consumed mostly as bread, but also as bulgur, yufka (flat bread) and cookies. Total annual wheat production is estimated at 17.7 million tonnes, valued at approximately US$5 billion in 2006/07 (FAO, 2009). Value addition via processing make the wheat industry one of the major sectors in the economy. Wheat production increased in the late 1970s, enabling the country to become a wheat exporter, though production declined in the 1980s. With its research infrastructure and a core of well-trained scientists, Turkey has also made a significant contribution to international efforts to improve winter wheat production. In 1986, the government of Turkey and CIMMYT, joined by ICARDA in 1990, established the International Winter Wheat Improvement Program (IWWIP). Several improved wheat varieties have since been jointly developed, disseminated and grown by producers both in Turkey and elsewhere in the world. Other varieties were also introduced into the country, particularly with the implementation of new agricultural policies in the 1980s, and both private companies and public agencies introduced new varieties at an accelerated rate. However, there has been no systematic monitoring of the adoption of these vari-eties, and economic impacts on producers were not evaluated. Key socio-econom-ic research questions remain unanswered, especially whether these improved vari-eties have effectively contributed to achieving their intended impacts.



Genetic diversity and population structure analysis based on the high density SNP markers in Ethiopian durum wheat (Triticum turgidum ssp. durum)

Bekele Abeyo (2020)

Background: Ethiopia has been considered as a center of diversity and the second possible center of domestication of durum wheat. Genetic diversity and population structure analysis in the existing Ethiopian durum wheat germplasm have enormous importance in enhancing breeding effort and for sustainable conservation. Hence, 192 Ethiopian durum wheat accessions comprising 167 landraces collected from major wheat-growing areas of the country and 25 improved varieties released from Debre Zeit and Sinana Agricultural Research Centers, Ethiopia in different years (1994–2010) were assembled for the current study. Results: The panel was genotyped with a High-density 90 K wheat SNP array by Illumina and generated 15,338 polymorphic SNPs that were used to analyze the genetic diversity and to estimate the population structure. Varied values of genetic diversity indices were scored across chromosomes and genomes. Genome-wide mean values of Nei’s gene diversity (0.246) and polymorphism information content (0.203) were recorded signifying the presence of high genetic diversity within this collection. Minor allele frequency of the genome varied with a range of 0.005 to 0.5 scoring a mean value of 0.175. Improved varieties clustered separately to landraces in population structure analysis resulted from STRUCTURE, PCA and neighbor joining tree. Landraces clustering was irrespective of their geographical origin signifying the presence of higher admixture that could arise due to the existence of historical exchanges of seeds through informal seed system involving regional and countrywide farming communities in Ethiopia. Conclusions: Sustainable utilization and conservation of this rich Ethiopian durum wheat genetic resource is an irreplaceable means to cope up from the recurrent climate changes and biotic stresses happening widely and thereby able to keep meeting the demand of durum productivity for the ever-growing human population.



Genética de la resistencia a roya amarilla causada por Puccinia striiformis f sp tritici e identificación de genes en trigos de primavera.


Tesis (Doctorado en Ciencias, especialista en Fitopatología).- Colegio de Postgraduados, 2017.

Las royas del trigo causadas por los hongos del género Puccinia, son enfermedades de importancia a nivel mundial. La estrategia que más ha apoyado el control de dichos hongos es el mejoramiento genético. En la actualidad existen genotipos que han mostrado resistencia en diferentes años y ambientes por lo cual, el objetivo del presente trabajo fue determinar el tipo de resistencia e identificar loci de carácter cuantitativo (QTLs) que le confieren resistencia a roya amarilla (RA) y de la hoja (RH) en la variedad de trigo harinero Huites F95 y estimar el número de genes y el tipo de resistencia que poseen los genotipos Glenlea, Romero 73 y Bonza 63 a roya amarilla. La caracterización fenotípica en Huite F95 para roya amarilla y roya de la hoja se realizó en cuatro ambientes durante el 2013, 2014 y 2015; mientras que para los genotipos Bonza 63, Romero 73 y Glenlea solo en un ambiente en 2015. Se crearon epidemias artificiales utilizando una mezcla de diferentes razas del hongo causante de la roya amarilla y de la hoja. Las proporciones fenotípicas, de resistentes y susceptibles observadas se compararon con las proporciones esperadas con una prueba de X2. Para la población Avocet-YrA/Huites F95 se construyeron mapas de ligamiento con 12,966 marcadores y utilizando mapeo por intervalo compuesto (ICIM) se realizó el análisis de QTL con el programa QTL IciMapping 4.0. Los análisis genéticos mostraron que Huites F95 posee una resistencia del tipo cuantitativa y que la resistencia a RH está determinada por 2 a 3 genes y para RA de 4 a 5 genes de resistencia en planta adulta. El análisis de QTL indicó que Huites F95 posee tres loci de efecto pleiotropico que le confieren resistencia a RH y RA localizados en los cromosomas 1AL, 1BL y 5AL. Adicionalmente se mapearon tres QTLs para RH en 2AS, 5A y 6BL y tres para RA en 3B, 4BS y 6BS. Los QTLs en 1AL, 5AL y 6BL son reportados como nuevos; por otra parte, se determinó que de 4 a 5 genes de efectos aditivos controlan la resistencia de la variedad Glenlea y de 2 a 3 genes en las variedades, Romero 73 y Bonza 63; los cuatro genotipos evaluados no poseen resistencia de plántula; sin embargo, pueden ser progenitores valiosos en los programas de mejoramiento, para lograr una resistencia durable a roya amarilla principalmente. _______________ GENETICS OF THE RESISTANCE TO YELLOW RUST CAUSED BY Puccinia striiformis f.sp. tritici AND IDENTIFICATION OF RESISTANCE GENES IN SPRING WHEAT. ABSTRACT: Rust diseases of wheat caused by fungi of the genus Puccinia, are diseases of global importance. The strategy that has most supported control of these fungi is the breeding. Currently, there are genotypes that have shown resistance in different years and environments for which this work aimed to determine the type of resistance and identify the quantitative traits loci (QTLs) which confers resistance to yellow rust (YR) and leaf (LR) in the bread wheat variety Huites F95 and estimate the number of genes and the type of resistance that Glenlea, Romero 73 and Bonza 63 genotypes possess to yellow rust. In Huites F95 phenotypic characterization for leaf rust and yellow rust was conducted in four environments during 2013, 2014 and 2015; whereas for Bonza 63, Romero 73 and Glenlea genotypes in just one environment in 2015. Artificial epidemics using a mixture of different rust races were created. The phenotypic observed ratios of resistant and susceptible were compared with the expected ratios with an X2 test. For the Avocet-YrA/Huites F95 population, linkage maps were constructed with 12,966 markers and using composite interval mapping QTL analysis was performed with the IciMapping (ICIM) 4.0 program. Genetic analyses showed that Huites F95 has a resistance of quantitative type and that the LR resistance is determined by 2-3 genes and for YR of 4-5 genes for adult plant resistance. QTL analysis indicated that Huites F95 has three loci of pleiotropic effect which confer rust resistance to LR and YR and localized on chromosomes 1AL, 1BL and 5AL. In addition they mapped three QTLs for LR on 2AS, 5A and 6BL and three for YR in 3B, 4BS, and 6BS. The QTLs 1AL 5AL, 6BL are new or not previously reported. On the other hand, it was determined that 4 to 5 genes of additive effects control the resistance in Glenlea; whereas, 2 to 3 resistance genes in Romero 73 and Bonza 63. The four genotypes evaluated do not possess seedling resistance genes; however, they might be valuable parents in breeding programs, to achieve a durable resistance to yellow rust mainly.

Doctoral thesis