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Author: J. Kumari
Publisher:
ISBN:
Category :
Languages : en
Pages : 73
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Author: J. Kumari
Publisher:
ISBN:
Category :
Languages : en
Pages : 73
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Author: Dan Makumbi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Maize is susceptible to biotic and abiotic stresses. The most important abiotic stresses in Africa are drought and low soil fertility. Aflatoxin contamination is a potential problem in areas facing drought and low soil fertility. Three studies were conducted to evaluate maize germplasm for tolerance to stress. In the first study, fifteen maize inbred lines crossed in a diallel were evaluated under drought, low N stress, and well-watered conditions at six locations in three countries to estimate general (GCA) and specific combining ability (SCA), investigate genotype x environment interaction, and estimate genetic diversity and its relationship with grain yield and heterosis. GCA effects were not significant for grain yield across environments. Lines with good GCA effect for grain yield were P501 and CML258 across stresses. Lines CML339, CML341, and SPLC7-F had good GCA effects for anthesis silking interval across stresses. Additive genetic effects were more important for grain yield under drought and well-watered conditions. Heterosis estimates were highest in stress environments. Clustering based on genetic distance calculated using marker data from AFLP, RFLP, and SSRs grouped lines according to origin. Genetic distance was positively correlated with grain yield and specific combining ability. In the second study, synthetic hybrids were evaluated at seven locations in three countries to estimate GCA and SCA effects under low N stress and optimal conditions and investigate genotype x environment interaction. GCA effects were significant for all traits across low N stress and optimal conditions. The highest yielding synthetic hybrids involved synthetics developed from stress tolerant lines. Synthetics 99SADVIA-# and SYNA00F2 had good GCA for grain yield across low N stress conditions. Heterosis was highly correlated with grain yield. Optimal environments explained more variation than stress environments. The third study evaluated the agronomic performance and aflatoxin accumulation of single and three-way cross white maize hybrids at five locations in Texas. Inbreds CML343, Tx601W, and Tx110 showed positive GCA effects for grain yield. Significant GCA effects for reduced aflatoxin concentration were observed in lines CML269, CML270, and CML78 across locations. Differences in performance between single and three-way crosses hybrids were dependent mostly on the inbred lines.
Author: R. L. Paliwal
Publisher: Fao
ISBN:
Category : Business & Economics
Languages : en
Pages : 384
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Book Description
Maize is an important crop and the demand for as both food and animal feed is expected to grow by 235 million tonnes between now and 2030. In many countries it will be difficult to increase the area under cultivation, so gains will have to come from increased productivity and intensification of the cropping system. This book looks at all aspects of tropical maize production from physiology, growing environments, pest and diseases, plant breeding and crop management and it is a substantial information resource necessary for the development of the crop.
Author: Bullo Tulu
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659147401
Category :
Languages : de
Pages : 100
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Book Description
Information on the combining ability of elite germplasm is essential to maximize their use for variety development. In the current study, sixty-six F1 crosses resulted from diallel crosses of 12 QPM inbred lines and two standard checks BHQP-542 and Melkassa-6Q were evaluated using alpha-lattice design with two replications during the 2009 cropping season at Mechara Agricultural Research Center. The objectives of the study were to determine general(GCA) and specific (SCA) combining ability for yield and yield related traits; estimate correlation among yield and yield related traits and find direct and indirect effects of yield related traits on grain yield. Analysis of variance showed that mean squares due to entries were significant to highly significant for most traits studied, indicating mean squares due to entries, crosses and crosses versus checks were non significant for stand count after thinning, leaf rolling, number of kernels per ear, plant aspect, shelling percentage, number of ears per plant and disease score. Entry and cross mean squares were non significant for stand count at harvest and ear aspect.
![General and Specific Combining Ability of Eight Maize Inbred Lines [Part I]; II. Comparative Performance of Single, Double and Synthetic Hybrids PDF](https://books.google.com/books/content/images/frontcover/0nPOAAAAMAAJ?fife=w80-h100)
Author: Devender Kumar Nanda
Publisher:
ISBN:
Category : Corn
Languages : en
Pages : 238
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Author: Audrey Darrigues
Publisher:
ISBN:
Category :
Languages : en
Pages : 172
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Because maize is a major feed crop in many parts of the world, it is important to optimize its nutritional value. However, maize protein is nutritionally limited by deficiencies in Lysine, Methionine, and Tryptophan. If the levels of the limiting amino acids could be improved through conventional breeding methods, it would reduce the cost of feed in meat production. The first part of this study consists of completing the first cycle of recurrent selection to test the potential of selection for Methionine and Tryptophan levels and to test the nutritional quality of the improved populations. After one cycle of recurrent selection, two maize populations, BS11 and BS31, were evaluated for their Methionine and Tryptophan levels. The progenies of the half-sib families categorized with high levels of Methionine in the starting populations had significantly higher Methionine levels than the progenies of those with low levels of Methionine. The response to selection for Tryptophan levels was negligible. The nutritional quality of the improved BS11 populations for Methionine was tested with a rat feeding trial. While the rats fed on the Low Methionine diet consumed significantly more feed than the rats fed on the High Methionine diet, there was no difference in either weight gain or feed efficiency. The second part of this study presents the variability for Methionine and Tryptophan levels in commercial maize germplasm and the genetic effects associated with those traits. Seventy-six inbred lines representing nine different genetic groups were evaluated. There was substantial variability within and among the genetic groups. Two diallel mating schemes were completed with parents selected for low or high Methionine or Tryptophan levels. The analysis of the diallel crosses revealed the following genetic effects: general combining ability, specific combining ability, and reciprocal effects. For the Methionine diallel, there were strong effects for general combining ability and specific combining ability. The reciprocal effects were expressed in the maternal direction. Given the success of recurrent selection, the variability for Methionine and Tryptophan levels, and the genetic effects associated with those traits, we conclude that the limiting amino acids of maize can be improved through conventional breeding methods.
Author: Mohamed Barre Ahmed
Publisher:
ISBN:
Category : Corn
Languages : en
Pages : 624
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Author: Arnel R. Hallauer
Publisher: Springer Science & Business Media
ISBN: 1441907661
Category : Science
Languages : en
Pages : 669
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Book Description
Maize is used in an endless list of products that are directly or indirectly related to human nutrition and food security. Maize is grown in producer farms, farmers depend on genetically improved cultivars, and maize breeders develop improved maize cultivars for farmers. Nikolai I. Vavilov defined plant breeding as plant evolution directed by man. Among crops, maize is one of the most successful examples for breeder-directed evolution. Maize is a cross-pollinated species with unique and separate male and female organs allowing techniques from both self and cross-pollinated crops to be utilized. As a consequence, a diverse set of breeding methods can be utilized for the development of various maize cultivar types for all economic conditions (e.g., improved populations, inbred lines, and their hybrids for different types of markets). Maize breeding is the science of maize cultivar development. Public investment in maize breeding from 1865 to 1996 was $3 billion (Crosbie et al., 2004) and the return on investment was $260 billion as a consequence of applied maize breeding, even without full understanding of the genetic basis of heterosis. The principles of quantitative genetics have been successfully applied by maize breeders worldwide to adapt and improve germplasm sources of cultivars for very simple traits (e.g. maize flowering) and very complex ones (e.g., grain yield). For instance, genomic efforts have isolated early-maturing genes and QTL for potential MAS but very simple and low cost phenotypic efforts have caused significant and fast genetic progress across genotypes moving elite tropical and late temperate maize northward with minimal investment. Quantitative genetics has allowed the integration of pre-breeding with cultivar development by characterizing populations genetically, adapting them to places never thought of (e.g., tropical to short-seasons), improving them by all sorts of intra- and inter-population recurrent selection methods, extracting lines with more probability of success, and exploiting inbreeding and heterosis. Quantitative genetics in maize breeding has improved the odds of developing outstanding maize cultivars from genetically broad based improved populations such as B73. The inbred-hybrid concept in maize was a public sector invention 100 years ago and it is still considered one of the greatest achievements in plant breeding. Maize hybrids grown by farmers today are still produced following this methodology and there is still no limit to genetic improvement when most genes are targeted in the breeding process. Heterotic effects are unique for each hybrid and exotic genetic materials (e.g., tropical, early maturing) carry useful alleles for complex traits not present in the B73 genome just sequenced while increasing the genetic diversity of U.S. hybrids. Breeding programs based on classical quantitative genetics and selection methods will be the basis for proving theoretical approaches on breeding plans based on molecular markers. Mating designs still offer large sample sizes when compared to QTL approaches and there is still a need to successful integration of these methods. There is a need to increase the genetic diversity of maize hybrids available in the market (e.g., there is a need to increase the number of early maturing testers in the northern U.S.). Public programs can still develop new and genetically diverse products not available in industry. However, public U.S. maize breeding programs have either been discontinued or are eroding because of decreasing state and federal funding toward basic science. Future significant genetic gains in maize are dependent on the incorporation of useful and unique genetic diversity not available in industry (e.g., NDSU EarlyGEM lines). The integration of pre-breeding methods with cultivar development should enhance future breeding efforts to maintain active public breeding programs not only adapting and improving genetically broad-based germplasm but also developing unique products and training the next generation of maize breeders producing research dissertations directly linked to breeding programs. This is especially important in areas where commercial hybrids are not locally bred. More than ever public and private institutions are encouraged to cooperate in order to share breeding rights, research goals, winter nurseries, managed stress environments, and latest technology for the benefit of producing the best possible hybrids for farmers with the least cost. We have the opportunity to link both classical and modern technology for the benefit of breeding in close cooperation with industry without the need for investing in academic labs and time (e.g., industry labs take a week vs months/years in academic labs for the same work). This volume, as part of the Handbook of Plant Breeding series, aims to increase awareness of the relative value and impact of maize breeding for food, feed, and fuel security. Without breeding programs continuously developing improved germplasm, no technology can develop improved cultivars. Quantitative Genetics in Maize Breeding presents principles and data that can be applied to maximize genetic improvement of germplasm and develop superior genotypes in different crops. The topics included should be of interest of graduate students and breeders conducting research not only on breeding and selection methods but also developing pure lines and hybrid cultivars in crop species. This volume is a unique and permanent contribution to breeders, geneticists, students, policy makers, and land-grant institutions still promoting quality research in applied plant breeding as opposed to promoting grant monies and indirect costs at any short-term cost. The book is dedicated to those who envision the development of the next generation of cultivars with less need of water and inputs, with better nutrition; and with higher percentages of exotic germplasm as well as those that pursue independent research goals before searching for funding. Scientists are encouraged to use all possible breeding methodologies available (e.g., transgenics, classical breeding, MAS, and all possible combinations could be used with specific sound long and short-term goals on mind) once germplasm is chosen making wise decisions with proven and scientifically sound technologies for assisting current breeding efforts depending on the particular trait under selection. Arnel R. Hallauer is C. F. Curtiss Distinguished Professor in Agriculture (Emeritus) at Iowa State University (ISU). Dr. Hallauer has led maize-breeding research for mid-season maturity at ISU since 1958. His work has had a worldwide impact on plant-breeding programs, industry, and students and was named a member of the National Academy of Sciences. Hallauer is a native of Kansas, USA. José B. Miranda Filho is full-professor in the Department of Genetics, Escola Superior de Agricultura Luiz de Queiroz - University of São Paulo located at Piracicaba, Brazil. His research interests have emphasized development of quantitative genetic theory and its application to maize breeding. Miranda Filho is native of Pirassununga, São Paulo, Brazil. M.J. Carena is professor of plant sciences at North Dakota State University (NDSU). Dr. Carena has led maize-breeding research for short-season maturity at NDSU since 1999. This program is currently one the of the few public U.S. programs left integrating pre-breeding with cultivar development and training in applied maize breeding. He teaches Quantitative Genetics and Crop Breeding Techniques at NDSU. Carena is a native of Buenos Aires, Argentina. http://www.ag.ndsu.nodak.edu/plantsci/faculty/Carena.htm
Author: G. O. Edmeades
Publisher: CIMMYT
ISBN: 9789686923933
Category : Corn
Languages : en
Pages : 580
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Book Description
Incidence and intensity of drought and low N stresss in the tropics; Case studies strategies for crop production under drought and low n stresses in the tropics; Stress physology and identification of secondary traits; Physiology of low nitrogen stress; Breeding for tolerance to drought and low n stresses; General breeding strategies for stress tolerance; Progress in breeding drought tolerance; Progress in breeding low nitrogen tolerance; Experimental design and software.
Author: Schuyler Smith
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The Texas maize breeding program at Texas A&M University has been unique among breeding programs for the incorporation of a wealth of germplasm from a wide range of origins into inbred lines. The Texas program, situated in a subtropical environment, has found beneficial traits beyond what is seen in the temperate material commonly used in the far more productive Midwestern region of the United States from maize of tropical origin. To date, no molecular studies had been conducted to make any quantitative differentiations between the genetic diversity in the germplasm developed in the Texas program or compared to the germplasm commonly used in breeding programs from the Midwest. In this study a molecular characterization of genetic diversity was performed. A unique set of 266 lines were selected and genotyped using 766 single nucleotide polymorphism markers and was combined with data published in a similar study focusing on ex-PVP lines released by private companies. The two data sets combined to have 380 genotypes with 635 markers. It was determined from the results of the genotyping that there were five subpopulations of material as determined by population structure. A principal coordinate analysis showed only 18% of the variation could be explained by the first two principal components. This suggested that the array markers, designed to cluster the Midwestern heterotic groups did not discriminate this exotic material well and/or that the heterotic pools were not well supported. We conclude that the Texas program material shows dissimilar genetic results when compared to Midwest temperate material and has the ability to act as a source of unique genetics for other maize breeding program. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155199
