Jose Crossa - Academia.edu (original) (raw)
Papers by Jose Crossa
Crop Science, 2007
T he importance of sustained increases in wheat production and productivity for food security is ... more T he importance of sustained increases in wheat production and productivity for food security is well recognized in South Asia, where wheat is a major staple crop and human population is increasing. After signifi cant expansion during the initial years of the Green Revolution, the wheat production area in the region appears to have stabilized in the last decade (Evenson et al., 1999; Joshi et al., 2006) and is expected to remain at current levels in the coming decades. Adaptable and higher-yielding genotypes will
Crop Science, 2002
Harlan, 1972) to describe what he viewed as a diminishing global stock of "landraces," or traditi... more Harlan, 1972) to describe what he viewed as a diminishing global stock of "landraces," or traditional forms of Diverse and varied crop genetic resources are necessary (though cultivated crop plants still grown in parts of the develnot sufficient) for adequate food production in a rapidly changing oping world. By referring to the stock of crop germplasm world. Since the scientific community first raised public concern several decades ago, modern cultivars have been viewed as the cause of as resource economists refer to a nonrenewable natural declining diversity in the world's crop genetic resources. This paper resource, he drew attention to the economic value assotests the hypothesis of increasing genetic uniformity in modern spring ciated with rare alleles or unique gene complexes that bread wheat (Triticum aestivum L.) cultivars from 1965, a year which may be found in such landraces. marks the release of some of the first modern semidwarf cultivars Genetic erosion became synonymous with the discarrying Rht1 and Rht2 genes in the developing world. Results from placement of landraces by modern cultivars. In 1970, previously published studies are summarized. Preliminary molecular Frankel called for urgent collection expeditions to foreanalyses, and new analyses of cultivar numbers, areas, ages, and genestall "the loss of ancient patterns of diversity in the alogies are presented. An estimated 77% of the spring bread wheat Vavilovian centers," since modern cultivars contain "a area in the developing world today is sown to CIMMYT-related minimum of genetic variation" and "in many instances wheats, but this does not imply that they are genetically uniform. The hypothesis of increasing genetic uniformity is tested by assessing have a narrow genetic base" (Frankel, 1970, p. 11). Harchanges in the diversity of leading progenitors over three decades, in lan asserted that the "destruction of genetic resources terms of several dimensions of diversity. Latent dimensions include is caused primarily by the very success of modern plant genetic distance and genealogies. Apparent dimensions include perbreeding programs" (Frankel, 1972, p. 212). About a formance with respect to yield potential, maintenance and stability decade later, Hawkes warned that "the breeder, who across management (input use), and growing environments. The data means well, is destroying by his actions the genetic base are not consistent with the view that the genetic diversity of modern for a new generation of varieties" (Hawkes, 1983, p. 109). semidwarf wheat grown in the developing world has decreased over Two related economic issues motivated these exprestime. Moreover, since national programs in developing countries cross sions of concern. One relates to the pattern of cultivars CIMMYT lines with their own materials before releasing them, the sown by farmers across a crop-producing region and the genetic diversity in their cultivars is at least as great as that present diversity of the genetic mechanisms that convey their among CIMMYT lines.
The linear regression approach has been widely used for selecting high yielding and stable genoty... more The linear regression approach has been widely used for selecting high yielding and stable genotypes targeted to 5 6 7 ' Three maize genotypes out of nine showed Di that were significantly larger than a hypothetical, stable genotype. These were considered desirable, eventhough two of them had slopes significantly greater than 1.0.
Environmental Biosafety Research, 2005
There is much discussion of the probability of transgene flow from transgenic crop varieties to l... more There is much discussion of the probability of transgene flow from transgenic crop varieties to landraces and wild relatives in centers of origin or diversity, and its genetic, ecological, and social consequences. Without costly research on the variables determining gene flow, research on transgene frequencies in landrace (or wild relative) populations can be valuable for understanding transgene flow and its effects. Minimal research requirements include (1) understanding how farmer practices and seed systems affect landrace populations, (2) sampling to optimize N e /n (effective /census population size), (3) minimizing variance at all levels sampled, and (4) using N e to calculate binomial probabilities for transgene frequencies. A key case is maize in Mexico. Two peer-reviewed papers, based on landrace samples from the Sierra Juárez region of Oaxaca, Mexico, reached seemingly conflicting conclusions: transgenes are present (
Seed Science Research, 2011
Group testing is a procedure in which groups that contain several units (plants) are analysed wit... more Group testing is a procedure in which groups that contain several units (plants) are analysed without having to inspect individual plants, with the purpose of estimating the prevalence of genetically modified plants (adventitious presence of unwanted transgenic plants, AP) in a population at a low cost, without losing precision. When pool (group) testing is used to estimate the proportion of AP (p), there are several procedures that can be used for computing the confidence interval (CI); however, they usually do not ensure precision in the estimation of p. This research proposes a formula for determining the required number of pools (g), given a pool size (k), for estimating the proportion of AP plants using the Dorfman model. The proposed formula ensures precision in the estimated proportion of AP because it guarantees that the width (W) of the CI will be equal to, or narrower than, the desired width (ω), with a probability of γ. This probability accounts for the stochastic nature of the sample variance of p. We give examples to show how to use the proposed sample-size formula. Simulated data were created and tables are presented showing the different scenarios that a researcher may encounter. The Monte Carlo method was used to study the coverage and the level of assurance achieved by the proposed sample sizes. An R program that reproduces the results in the tables and makes it easy for the researcher to create other scenarios is given in the Appendix.
Genetics, 2008
The traditional molecular selection index (MSI) employed in marker-assisted selection maximizes t... more The traditional molecular selection index (MSI) employed in marker-assisted selection maximizes the selection response by combining information on molecular markers linked to quantitative trait loci (QTL) and phenotypic values of the traits of the individuals of interest. This study proposes an MSI based on an eigenanalysis method (molecular eigen selection index method, MESIM), where the first eigenvector is used as a selection index criterion, and its elements determine the proportion of the trait's contribution to the selection index. This article develops the theoretical framework of MESIM. Simulation results show that the genotypic means and the expected selection response from MESIM for each trait are equal to or greater than those from the traditional MSI. When several traits are simultaneously selected, MESIM performs well for traits with relatively low heritability. The main advantages of MESIM over the traditional molecular selection index are that its statistical samp...
Field Crops Research, 1991
ABSTRACT
Euphytica, 2005
... Therefore, the heterotic groups defined here should not be considered as static, but could al... more ... Therefore, the heterotic groups defined here should not be considered as static, but could also evolve over time as ... Phylogenetic analysis: Models and estimation procedures ... Comparison of RFLP and morphological distances between maize Zea mays L. inbred lines: Consequen
Euphytica, 2007
Yield potential is the maximum attainable yield within the limits imposed by the production envir... more Yield potential is the maximum attainable yield within the limits imposed by the production environment. Better understanding of these constraints and the underlying causes of genotype • environment interaction will improve productivity regionally and globally.
Crop Science, 2001
on scaled or non-scaled data. When replicated data are available, SREG on scaled data (Crossa and... more on scaled or non-scaled data. When replicated data are available, SREG on scaled data (Crossa and Cornelius, SA genotype main effect plus genotype ϫ environment interaction 1997) is more desirable because it deals with any hetero-(GGE) biplot graphically displays the genotypic main effect (G) and geneity of within-site error variance. the genotype ϫ environment interaction (GE) of the multienviron-One unique merit of a GGE biplot is that it can graphment trial (MET) data and facilitates visual evaluation of both the ically show the which-won-where patterns of the data, genotypes and the environments. This paper compares the merits of two types of GGE biplots in MET data analysis. The first type is as first described in Yan et al. (2000). Briefly, markers constructed by the least squares solution of the sites regression model of the cultivars furthest from the plot origin (0,0) are (SREG 2), with the first two principal components as the primary and connected with straight lines to form a polygon such secondary effects, respectively. The second type is constructed by Manthat markers of all other cultivars are contained in the del's solution for sites regression as the primary effect and the first polygon. To each side of the polygon, a perpendicular principal component extracted from the regression residual as the line, starting from the origin of the biplot, is drawn secondary effect (SREG M؉1). Results indicate that both the SREG 2 and extended beyond the polygon so that the biplot is biplot and the SREG M؉1 biplot are equally effective in displaying the divided into several sectors and the markers of the test "which-won-where" pattern of the MET data, although the SREG 2 sites are separated into different sectors. The cultivar biplot explains slightly more GGE variation. The SREG M؉1 biplot is at the vertex for each sector is the best performer at more desirable, however, in that it always explicitly indicates the sites included in that sector, provided that the GGE is average yield and stability of the genotypes and the discriminating sufficiently approximated by PC1 and PC2. Thus, groups ability and representativeness of the test environments. of sites that share the same best performers are graphically identified.
Crop Science, 2010
... of Global Grain Yield Data Eduardo Hernandez-Segundo,* Flavio Capettini, Richard Trethowan, M... more ... of Global Grain Yield Data Eduardo Hernandez-Segundo,* Flavio Capettini, Richard Trethowan, Maarten van Ginkel, Apolinar Mejia, Aquiles Carballo, Jose Crossa, Mateo Vargas, and Artemio Balbuena-Melgarejo ... Balagne (Le Clos Landry) France 46°22′ N 1°8′ E X ...
Crop Science, 2002
The International Maize and Wheat Improvement Center (CIMMYT) currently holds about 17 000 sample... more The International Maize and Wheat Improvement Center (CIMMYT) currently holds about 17 000 samples of maize (Zea mays L.) and teosinte (Z. mays, several subspecies), a wild relative of maize. Seven CIMMYT populations and 57 inbreds were characterized by simple ...
Crop Science, 1998
ABSTRACT
Crop Science, 1998
RefDoc Bienvenue - Welcome. Refdoc est un service / is powered by. ...
Crop Science, 1992
ABSTRACT Knowledge about the combining ability and heterotic patterns among CIMMYT's maize (... more ABSTRACT Knowledge about the combining ability and heterotic patterns among CIMMYT's maize (Zea mays L.) germplasm is essential for hybrid development work at CIMMYT, as well as at other national research programs using CIMMYT germplasm. This study was ...
Applied Soil Ecology, 2006
Densely populated and intensively cropped, the subtropical highlands of the world have severe agr... more Densely populated and intensively cropped, the subtropical highlands of the world have severe agricultural sustainability problems resulting from soil erosion and fertility decline. In 1991, the International Maize and Wheat Improvement Center (CIMMYT) initiated a long-term field experiment with zero tillage under rainfed conditions at its semi-arid highland experiment station in Mexico (2240 m asl; 19.318N, 98.508W; Cumulic Phaeozem) to evaluate the effects of tillage, residue management, and rotation on maize and wheat production. Long-term effects on root rot and nematode populations-and their possible detrimental effects on yield-were monitored from 1998 to 2003 to evaluate the sustainability of the cropping system. In general, wheat showed less root rot incidence than maize. Crop residue retention reduced the numbers of the nematode Pratylenchus thornei in both crops, as did zero tillage compared with conventional tillage. Conventional tillage with continuous maize and residue removal, the common farmer practice in this region, reduced yield and dramatically increased P. thornei. Zero tillage with residue removal resulted in low values for yield, root rot, and nematode populations, especially under maize monoculture. Under zero tillage and residue retention, root rot incidence in maize was moderate, parasitic nematode numbers were low, and yield was highest compared to alternative practices. In wheat, the highest yields were observed under zero tillage and residue retention, with intermediate root rot incidence. Zero tillage with rotation and residue retention enhanced water availability, soil structure, and nutrient availability more than conventional tillage. Microbial life diversity increased under zero tillage and residue retention, which may useful for biological control and integrated pest management.
Field crops …, 2007
Seven hundred twenty-nine lines of diverse wheat germplasm lines were evaluated in eight location... more Seven hundred twenty-nine lines of diverse wheat germplasm lines were evaluated in eight locations of three countries (India, Nepal and Bangladesh) of South Asia for 5 years (1999-2000 to 2003-2004) through Eastern Gangetic Plains Screening Nursery (EGPSN) organized by CIMMYT South Asia, Nepal, for agronomic performance and tolerance to spot blotch of wheat. Each year, the number of lines represented a new set of 150 lines that included six common checks and a different local check at each of the eight locations. One hundred and five lines, 21 in each year, advanced from EGPSN were also tested for 5 years (2000-2001 to 2004-2005) in five locations of South Asia through Eastern Gangetic Plains Yield Trials (EGPYT) to verify spot blotch tolerance and superior yield performance of the selected germplasm. Many lines yielded significantly more than the best check and possessed high levels of spot blotch resistance under warm humid environments of South Asia. The most promising 25 lines have been listed as sources of strong resistance, with 9 lines better yielding than the best resistant check PBW 343 in fewer days to maturity. Most of these superior lines represented elite CIMMYT germplasm and around half were derived from Kauz and Veery. The line EGPYT 67, Kauz//Kauz/Star/3/Prinia/4/Milan/Kauz, was the best for spot blotch resistance, yield, days to maturity, and 1000 grain weight (TKW). The next two lines in the order of merit were EGPYT 84 (Mrng/Buc//Blo/Pvn/3/Pjb 81) and EGPYT 69 (Chirya3/Pastor). The results demonstrate that additional spot blotch resistant wheat genotypes with high grain yield and TKW, and early maturity, have become available as a result of the regional and international collaboration in South Asia.
ABSTRACTZinc (Zn) deficiency is a major risk factor for human health, affecting about 30% of the ... more ABSTRACTZinc (Zn) deficiency is a major risk factor for human health, affecting about 30% of the world’s population. To study the potential of genomic selection (GS) for maize with increased Zn concentration, an association panel and two doubled haploid (DH) populations were evaluated in three environments. Three genomic prediction models, M (M1: Environment + Line, M2: Environment + Line + Genomic, and M3: Environment + Line + Genomic + Genomic x Environment) incorporating main effects (lines and genomic) and the interaction between genomic and environment (G x E) were assessed to estimate the prediction ability (rMP) for each model. Two distinct cross-validation (CV) schemes simulating two genomic prediction breeding scenarios were used. CV1 predicts the performance of newly developed lines, whereas CV2 predicts the performance of lines tested in sparse multi-location trials. Predictions for Zn in CV1 ranged from −0.01 to 0.56 for DH1, 0.04 to 0.50 for DH2 and −0.001 to 0.47 for t...
Scientific reports, Jan 21, 2018
The value of exotic wheat genetic resources for accelerating grain yield gains is largely unprove... more The value of exotic wheat genetic resources for accelerating grain yield gains is largely unproven and unrealized. We used next-generation sequencing, together with multi-environment phenotyping, to study the contribution of exotic genomes to 984 three-way-cross-derived (exotic/elite1//elite2) pre-breeding lines (PBLs). Genomic characterization of these lines with haplotype map-based and SNP marker approaches revealed exotic specific imprints of 16.1 to 25.1%, which compares to theoretical expectation of 25%. A rare and favorable haplotype (GT) with 0.4% frequency in gene bank identified on chromosome 6D minimized grain yield (GY) loss under heat stress without GY penalty under irrigated conditions. More specifically, the 'T' allele of the haplotype GT originated in Aegilops tauschii and was absent in all elite lines used in study. In silico analysis of the SNP showed hits with a candidate gene coding for isoflavone reductase IRL-like protein in Ae. tauschii. Rare haplotypes...
G3 (Bethesda, Md.), Feb 9, 2017
Developing genomic selection (GS) models is an important step in applying GS to accelerate the ra... more Developing genomic selection (GS) models is an important step in applying GS to accelerate the rate of genetic gain in grain yield in plant breeding. In this study, seven genomic prediction models under two cross-validation (CV) scenarios were tested on 287 advanced elite spring wheat lines phenotyped for grain yield (GY), thousand-grain weight (GW), grain number (GN), and thermal time for flowering (TTF) in 18 international environments (year-location combinations) in major wheat-producing countries in 2010 and 2011. Prediction models with genomic and pedigree information included main effects and interaction with environments. Two random CV schemes were applied to predict a subset of lines that were not observed in any of the 18 environments (CV1), and a subset of lines that were not observed in a set of the environments, but were observed in other environments (CV2). Genomic prediction models, including genotype × environment (G×E) interaction, had the highest average prediction ...
Crop Science, 2007
T he importance of sustained increases in wheat production and productivity for food security is ... more T he importance of sustained increases in wheat production and productivity for food security is well recognized in South Asia, where wheat is a major staple crop and human population is increasing. After signifi cant expansion during the initial years of the Green Revolution, the wheat production area in the region appears to have stabilized in the last decade (Evenson et al., 1999; Joshi et al., 2006) and is expected to remain at current levels in the coming decades. Adaptable and higher-yielding genotypes will
Crop Science, 2002
Harlan, 1972) to describe what he viewed as a diminishing global stock of "landraces," or traditi... more Harlan, 1972) to describe what he viewed as a diminishing global stock of "landraces," or traditional forms of Diverse and varied crop genetic resources are necessary (though cultivated crop plants still grown in parts of the develnot sufficient) for adequate food production in a rapidly changing oping world. By referring to the stock of crop germplasm world. Since the scientific community first raised public concern several decades ago, modern cultivars have been viewed as the cause of as resource economists refer to a nonrenewable natural declining diversity in the world's crop genetic resources. This paper resource, he drew attention to the economic value assotests the hypothesis of increasing genetic uniformity in modern spring ciated with rare alleles or unique gene complexes that bread wheat (Triticum aestivum L.) cultivars from 1965, a year which may be found in such landraces. marks the release of some of the first modern semidwarf cultivars Genetic erosion became synonymous with the discarrying Rht1 and Rht2 genes in the developing world. Results from placement of landraces by modern cultivars. In 1970, previously published studies are summarized. Preliminary molecular Frankel called for urgent collection expeditions to foreanalyses, and new analyses of cultivar numbers, areas, ages, and genestall "the loss of ancient patterns of diversity in the alogies are presented. An estimated 77% of the spring bread wheat Vavilovian centers," since modern cultivars contain "a area in the developing world today is sown to CIMMYT-related minimum of genetic variation" and "in many instances wheats, but this does not imply that they are genetically uniform. The hypothesis of increasing genetic uniformity is tested by assessing have a narrow genetic base" (Frankel, 1970, p. 11). Harchanges in the diversity of leading progenitors over three decades, in lan asserted that the "destruction of genetic resources terms of several dimensions of diversity. Latent dimensions include is caused primarily by the very success of modern plant genetic distance and genealogies. Apparent dimensions include perbreeding programs" (Frankel, 1972, p. 212). About a formance with respect to yield potential, maintenance and stability decade later, Hawkes warned that "the breeder, who across management (input use), and growing environments. The data means well, is destroying by his actions the genetic base are not consistent with the view that the genetic diversity of modern for a new generation of varieties" (Hawkes, 1983, p. 109). semidwarf wheat grown in the developing world has decreased over Two related economic issues motivated these exprestime. Moreover, since national programs in developing countries cross sions of concern. One relates to the pattern of cultivars CIMMYT lines with their own materials before releasing them, the sown by farmers across a crop-producing region and the genetic diversity in their cultivars is at least as great as that present diversity of the genetic mechanisms that convey their among CIMMYT lines.
The linear regression approach has been widely used for selecting high yielding and stable genoty... more The linear regression approach has been widely used for selecting high yielding and stable genotypes targeted to 5 6 7 ' Three maize genotypes out of nine showed Di that were significantly larger than a hypothetical, stable genotype. These were considered desirable, eventhough two of them had slopes significantly greater than 1.0.
Environmental Biosafety Research, 2005
There is much discussion of the probability of transgene flow from transgenic crop varieties to l... more There is much discussion of the probability of transgene flow from transgenic crop varieties to landraces and wild relatives in centers of origin or diversity, and its genetic, ecological, and social consequences. Without costly research on the variables determining gene flow, research on transgene frequencies in landrace (or wild relative) populations can be valuable for understanding transgene flow and its effects. Minimal research requirements include (1) understanding how farmer practices and seed systems affect landrace populations, (2) sampling to optimize N e /n (effective /census population size), (3) minimizing variance at all levels sampled, and (4) using N e to calculate binomial probabilities for transgene frequencies. A key case is maize in Mexico. Two peer-reviewed papers, based on landrace samples from the Sierra Juárez region of Oaxaca, Mexico, reached seemingly conflicting conclusions: transgenes are present (
Seed Science Research, 2011
Group testing is a procedure in which groups that contain several units (plants) are analysed wit... more Group testing is a procedure in which groups that contain several units (plants) are analysed without having to inspect individual plants, with the purpose of estimating the prevalence of genetically modified plants (adventitious presence of unwanted transgenic plants, AP) in a population at a low cost, without losing precision. When pool (group) testing is used to estimate the proportion of AP (p), there are several procedures that can be used for computing the confidence interval (CI); however, they usually do not ensure precision in the estimation of p. This research proposes a formula for determining the required number of pools (g), given a pool size (k), for estimating the proportion of AP plants using the Dorfman model. The proposed formula ensures precision in the estimated proportion of AP because it guarantees that the width (W) of the CI will be equal to, or narrower than, the desired width (ω), with a probability of γ. This probability accounts for the stochastic nature of the sample variance of p. We give examples to show how to use the proposed sample-size formula. Simulated data were created and tables are presented showing the different scenarios that a researcher may encounter. The Monte Carlo method was used to study the coverage and the level of assurance achieved by the proposed sample sizes. An R program that reproduces the results in the tables and makes it easy for the researcher to create other scenarios is given in the Appendix.
Genetics, 2008
The traditional molecular selection index (MSI) employed in marker-assisted selection maximizes t... more The traditional molecular selection index (MSI) employed in marker-assisted selection maximizes the selection response by combining information on molecular markers linked to quantitative trait loci (QTL) and phenotypic values of the traits of the individuals of interest. This study proposes an MSI based on an eigenanalysis method (molecular eigen selection index method, MESIM), where the first eigenvector is used as a selection index criterion, and its elements determine the proportion of the trait's contribution to the selection index. This article develops the theoretical framework of MESIM. Simulation results show that the genotypic means and the expected selection response from MESIM for each trait are equal to or greater than those from the traditional MSI. When several traits are simultaneously selected, MESIM performs well for traits with relatively low heritability. The main advantages of MESIM over the traditional molecular selection index are that its statistical samp...
Field Crops Research, 1991
ABSTRACT
Euphytica, 2005
... Therefore, the heterotic groups defined here should not be considered as static, but could al... more ... Therefore, the heterotic groups defined here should not be considered as static, but could also evolve over time as ... Phylogenetic analysis: Models and estimation procedures ... Comparison of RFLP and morphological distances between maize Zea mays L. inbred lines: Consequen
Euphytica, 2007
Yield potential is the maximum attainable yield within the limits imposed by the production envir... more Yield potential is the maximum attainable yield within the limits imposed by the production environment. Better understanding of these constraints and the underlying causes of genotype • environment interaction will improve productivity regionally and globally.
Crop Science, 2001
on scaled or non-scaled data. When replicated data are available, SREG on scaled data (Crossa and... more on scaled or non-scaled data. When replicated data are available, SREG on scaled data (Crossa and Cornelius, SA genotype main effect plus genotype ϫ environment interaction 1997) is more desirable because it deals with any hetero-(GGE) biplot graphically displays the genotypic main effect (G) and geneity of within-site error variance. the genotype ϫ environment interaction (GE) of the multienviron-One unique merit of a GGE biplot is that it can graphment trial (MET) data and facilitates visual evaluation of both the ically show the which-won-where patterns of the data, genotypes and the environments. This paper compares the merits of two types of GGE biplots in MET data analysis. The first type is as first described in Yan et al. (2000). Briefly, markers constructed by the least squares solution of the sites regression model of the cultivars furthest from the plot origin (0,0) are (SREG 2), with the first two principal components as the primary and connected with straight lines to form a polygon such secondary effects, respectively. The second type is constructed by Manthat markers of all other cultivars are contained in the del's solution for sites regression as the primary effect and the first polygon. To each side of the polygon, a perpendicular principal component extracted from the regression residual as the line, starting from the origin of the biplot, is drawn secondary effect (SREG M؉1). Results indicate that both the SREG 2 and extended beyond the polygon so that the biplot is biplot and the SREG M؉1 biplot are equally effective in displaying the divided into several sectors and the markers of the test "which-won-where" pattern of the MET data, although the SREG 2 sites are separated into different sectors. The cultivar biplot explains slightly more GGE variation. The SREG M؉1 biplot is at the vertex for each sector is the best performer at more desirable, however, in that it always explicitly indicates the sites included in that sector, provided that the GGE is average yield and stability of the genotypes and the discriminating sufficiently approximated by PC1 and PC2. Thus, groups ability and representativeness of the test environments. of sites that share the same best performers are graphically identified.
Crop Science, 2010
... of Global Grain Yield Data Eduardo Hernandez-Segundo,* Flavio Capettini, Richard Trethowan, M... more ... of Global Grain Yield Data Eduardo Hernandez-Segundo,* Flavio Capettini, Richard Trethowan, Maarten van Ginkel, Apolinar Mejia, Aquiles Carballo, Jose Crossa, Mateo Vargas, and Artemio Balbuena-Melgarejo ... Balagne (Le Clos Landry) France 46°22′ N 1°8′ E X ...
Crop Science, 2002
The International Maize and Wheat Improvement Center (CIMMYT) currently holds about 17 000 sample... more The International Maize and Wheat Improvement Center (CIMMYT) currently holds about 17 000 samples of maize (Zea mays L.) and teosinte (Z. mays, several subspecies), a wild relative of maize. Seven CIMMYT populations and 57 inbreds were characterized by simple ...
Crop Science, 1998
ABSTRACT
Crop Science, 1998
RefDoc Bienvenue - Welcome. Refdoc est un service / is powered by. ...
Crop Science, 1992
ABSTRACT Knowledge about the combining ability and heterotic patterns among CIMMYT's maize (... more ABSTRACT Knowledge about the combining ability and heterotic patterns among CIMMYT's maize (Zea mays L.) germplasm is essential for hybrid development work at CIMMYT, as well as at other national research programs using CIMMYT germplasm. This study was ...
Applied Soil Ecology, 2006
Densely populated and intensively cropped, the subtropical highlands of the world have severe agr... more Densely populated and intensively cropped, the subtropical highlands of the world have severe agricultural sustainability problems resulting from soil erosion and fertility decline. In 1991, the International Maize and Wheat Improvement Center (CIMMYT) initiated a long-term field experiment with zero tillage under rainfed conditions at its semi-arid highland experiment station in Mexico (2240 m asl; 19.318N, 98.508W; Cumulic Phaeozem) to evaluate the effects of tillage, residue management, and rotation on maize and wheat production. Long-term effects on root rot and nematode populations-and their possible detrimental effects on yield-were monitored from 1998 to 2003 to evaluate the sustainability of the cropping system. In general, wheat showed less root rot incidence than maize. Crop residue retention reduced the numbers of the nematode Pratylenchus thornei in both crops, as did zero tillage compared with conventional tillage. Conventional tillage with continuous maize and residue removal, the common farmer practice in this region, reduced yield and dramatically increased P. thornei. Zero tillage with residue removal resulted in low values for yield, root rot, and nematode populations, especially under maize monoculture. Under zero tillage and residue retention, root rot incidence in maize was moderate, parasitic nematode numbers were low, and yield was highest compared to alternative practices. In wheat, the highest yields were observed under zero tillage and residue retention, with intermediate root rot incidence. Zero tillage with rotation and residue retention enhanced water availability, soil structure, and nutrient availability more than conventional tillage. Microbial life diversity increased under zero tillage and residue retention, which may useful for biological control and integrated pest management.
Field crops …, 2007
Seven hundred twenty-nine lines of diverse wheat germplasm lines were evaluated in eight location... more Seven hundred twenty-nine lines of diverse wheat germplasm lines were evaluated in eight locations of three countries (India, Nepal and Bangladesh) of South Asia for 5 years (1999-2000 to 2003-2004) through Eastern Gangetic Plains Screening Nursery (EGPSN) organized by CIMMYT South Asia, Nepal, for agronomic performance and tolerance to spot blotch of wheat. Each year, the number of lines represented a new set of 150 lines that included six common checks and a different local check at each of the eight locations. One hundred and five lines, 21 in each year, advanced from EGPSN were also tested for 5 years (2000-2001 to 2004-2005) in five locations of South Asia through Eastern Gangetic Plains Yield Trials (EGPYT) to verify spot blotch tolerance and superior yield performance of the selected germplasm. Many lines yielded significantly more than the best check and possessed high levels of spot blotch resistance under warm humid environments of South Asia. The most promising 25 lines have been listed as sources of strong resistance, with 9 lines better yielding than the best resistant check PBW 343 in fewer days to maturity. Most of these superior lines represented elite CIMMYT germplasm and around half were derived from Kauz and Veery. The line EGPYT 67, Kauz//Kauz/Star/3/Prinia/4/Milan/Kauz, was the best for spot blotch resistance, yield, days to maturity, and 1000 grain weight (TKW). The next two lines in the order of merit were EGPYT 84 (Mrng/Buc//Blo/Pvn/3/Pjb 81) and EGPYT 69 (Chirya3/Pastor). The results demonstrate that additional spot blotch resistant wheat genotypes with high grain yield and TKW, and early maturity, have become available as a result of the regional and international collaboration in South Asia.
ABSTRACTZinc (Zn) deficiency is a major risk factor for human health, affecting about 30% of the ... more ABSTRACTZinc (Zn) deficiency is a major risk factor for human health, affecting about 30% of the world’s population. To study the potential of genomic selection (GS) for maize with increased Zn concentration, an association panel and two doubled haploid (DH) populations were evaluated in three environments. Three genomic prediction models, M (M1: Environment + Line, M2: Environment + Line + Genomic, and M3: Environment + Line + Genomic + Genomic x Environment) incorporating main effects (lines and genomic) and the interaction between genomic and environment (G x E) were assessed to estimate the prediction ability (rMP) for each model. Two distinct cross-validation (CV) schemes simulating two genomic prediction breeding scenarios were used. CV1 predicts the performance of newly developed lines, whereas CV2 predicts the performance of lines tested in sparse multi-location trials. Predictions for Zn in CV1 ranged from −0.01 to 0.56 for DH1, 0.04 to 0.50 for DH2 and −0.001 to 0.47 for t...
Scientific reports, Jan 21, 2018
The value of exotic wheat genetic resources for accelerating grain yield gains is largely unprove... more The value of exotic wheat genetic resources for accelerating grain yield gains is largely unproven and unrealized. We used next-generation sequencing, together with multi-environment phenotyping, to study the contribution of exotic genomes to 984 three-way-cross-derived (exotic/elite1//elite2) pre-breeding lines (PBLs). Genomic characterization of these lines with haplotype map-based and SNP marker approaches revealed exotic specific imprints of 16.1 to 25.1%, which compares to theoretical expectation of 25%. A rare and favorable haplotype (GT) with 0.4% frequency in gene bank identified on chromosome 6D minimized grain yield (GY) loss under heat stress without GY penalty under irrigated conditions. More specifically, the 'T' allele of the haplotype GT originated in Aegilops tauschii and was absent in all elite lines used in study. In silico analysis of the SNP showed hits with a candidate gene coding for isoflavone reductase IRL-like protein in Ae. tauschii. Rare haplotypes...
G3 (Bethesda, Md.), Feb 9, 2017
Developing genomic selection (GS) models is an important step in applying GS to accelerate the ra... more Developing genomic selection (GS) models is an important step in applying GS to accelerate the rate of genetic gain in grain yield in plant breeding. In this study, seven genomic prediction models under two cross-validation (CV) scenarios were tested on 287 advanced elite spring wheat lines phenotyped for grain yield (GY), thousand-grain weight (GW), grain number (GN), and thermal time for flowering (TTF) in 18 international environments (year-location combinations) in major wheat-producing countries in 2010 and 2011. Prediction models with genomic and pedigree information included main effects and interaction with environments. Two random CV schemes were applied to predict a subset of lines that were not observed in any of the 18 environments (CV1), and a subset of lines that were not observed in a set of the environments, but were observed in other environments (CV2). Genomic prediction models, including genotype × environment (G×E) interaction, had the highest average prediction ...