Mateo Vargas P | Universidad Sergio Arboleda (original) (raw)

Papers by Mateo Vargas P

Research paper thumbnail of Variabilidad del carbono orgánico en suelos de ladera del sureste de México

Research paper thumbnail of META: A suite of sas programs to analyze multienvironment breeding trials

Research paper thumbnail of Studying the effect of environmental variables on the genotype x environment interaction of tomato

Euphytica, 2007

Genotype · environment interaction (GEI) affects marketable fruit yield and average fruit weight ... more Genotype · environment interaction (GEI) affects marketable fruit yield and average fruit weight of both hybrid and open-pollinated (OP) tomato genotypes. Cultivars vary significantly for marketable fruit yield, with hybrid cultivars having, on average, higher yield than OP cultivars. However, information is scanty on environmental factors affecting the differential response of tomato genotypes across environments. Hence, the aim of this research was to use factorial regression (FR) and partial least squares (PLS) regression, which incorporate external environmental and genotypic covariables directly into the model for interpreting GEI. In this research, data from an FAO multi-environment trial comprising 15 tomato genotypes (7 hybrid and 8 OP) evaluated in 18 locations of Latin America and the Caribbean were analyzed using FR and PLS. Environmental factors such as days to harvest, soil pH, mean temperature (MET), potassium available in the soil, and phosphorus fertilizer accounted for a sizeable portion of GEI for marketable fruit yield, whereas trimming, irrigation, soil organic matter, and nitrogen and phosphorus fertilizers were important environmental covariables for explaining GEI of average fruit weight. Locations with relatively high minimum and mean temperatures favored the marketable fruit yield of OP heat-tolerant lines CL 5915-223 and CL 5915-93. An OP cultivar (Catalina) and a hybrid (Apla) showed average marketable fruit yield across environments, while two hybrids (Sunny and Luxor) exhibited outstanding marketable fruit yield in high yielding locations (due to lower temperatures and higher pH) but a sharp yield loss in poor environments. Two stable hybrid genotypes in high yielding environments, Narita and BHN-39, also showed high and stable yield in average and low yielding environments.

Research paper thumbnail of Mapping QTLs and QTL 3 environment interaction for CIMMYT maize drought stress program using factorial regression and partial least squares methods

Research paper thumbnail of Analysing QTL by environment interaction by factorial regression, with an application to the CIMMYT drought and low nitrogen stress programme in maize

Research paper thumbnail of Interpreting genotype x environment interaction in wheat by partial least squares regression

Crop Science, May 1, 1998

Research paper thumbnail of Interpreting treatment x environment interaction in agronomy trials

Agron J, 2001

Page 1. STATISTICS Interpreting Treatment Environment Interaction in Agronomy Trials Mateo Vargas... more Page 1. STATISTICS Interpreting Treatment Environment Interaction in Agronomy Trials Mateo Vargas, Jose Crossa,* Fred van Eeuwijk, Kenneth D. Sayre, and Matthew P. Reynolds ... multiplicative interaction (AMMI) model (Kempton, ...

Research paper thumbnail of Biplot Graphic Display: Some Concepts

Farmers participatory research trials are conducted over different regions and over years. Resour... more Farmers participatory research trials are conducted over different regions and over years. Resource Conservation Technology (RCT) options may have an interaction with regions and/or years. It is desired to identify the RCT options that are suitable over regions/years. Further, it is desired to identify the varieties most suitable for zero tillage, bed planting systems etc. Therefore, different varieties are included in farmers' participatory research trials. Generally, the variety to be used is the prerogative of the participatory farmer. The Farmers Participatory Research Trials may have different soil types or land leveling. The aim is to study the interaction between treatments and varieties/soil types/land leveling. If we consider varieties, soil types, years, regions, land leveling etc. as environments and RCT options as treatments then it amounts to studying the treatment × environment interactions. If there is no treatment × environment interaction then the best RCT option may be identified by averaging over the environments if the data is balanced or using adjusted treatment means in case of an unbalanced data. If treatment × environment interaction is present then first we have to identify whether the interaction is a cross-over (treatment ranks changes from one environment to another) or non-cross-over type where treatment difference change in magnitude but not in direction from one among environments.

Research paper thumbnail of Antinociceptive effects of azepexole (BHT 933) in mice

Pain, 1989

Subcutaneous (s.c.) administration of azepexole (BHT 933) at doses between 4 and 40 mg/kg produce... more Subcutaneous (s.c.) administration of azepexole (BHT 933) at doses between 4 and 40 mg/kg produced dose-dependent antinociceptive effects in mice as assessed by tail-immersion, tail-pinch and acetic acid writhing tests. The ED16s were 5.6 +/- 0.4, 6.7 +/- 1.2 and 2.96 +/- 0.2 mg/kg respectively. Similarly, morphine produced analgesia in the same tests with ED16s of 0.87 +/- 0.03, 0.47 +/- 0.1 and 0.45 +/- 0.01 mg/kg respectively. In all instances naloxone (0.1 mg/kg s.c.) shifted the dose-response curves to morphine to the right in a parallel manner. Naloxone (0.1 and 1 mg/kg s.c.) partially antagonized the effect of azepexole in the tail-immersion and tail-pinch tests but significantly decreased the slope of the dose-response curve suggesting that a competitive interaction at the level of the opioid receptors did not occur. Naloxone had no effect on the antinociceptive action of azepexole in the acetic acid writhing test.

Research paper thumbnail of An eco-physiological - statistical framework for th e analysis of GxE and QTLxE as occurring in abiotic stress trials, wi th applications to the CIMMYT drought stress programs in tropical maize and bread wheat

Research paper thumbnail of Genetic Gains in Grain Yield Through Genomic Selection in Eight Bi-parental Maize Populations under Drought Stress

Research paper thumbnail of Identification of quantitative trait loci for cold-tolerance of photosynthesis in maize (Zea mays L.)

Journal of Experimental Botany, 2002

The effects of low growth temperature (15 ∞C) on the photosynthetic apparatus of maize were inves... more The effects of low growth temperature (15 ∞C) on the photosynthetic apparatus of maize were investigated in a set of 233 recombinant inbred lines by means of chlorophyll fluorescence, gas exchange measure- ments and analysis of photosynthetic pigments. A quantitative trait loci (QTL) analysis of five traits related to the functioning of the photosynthetic apparatus revealed a total of eight

Research paper thumbnail of Analysis and Interpretation of Interactions in Agricultural Research

Agronomy Journal, 2014

When reporting on well-conducted research, a characteristic of a complete and proper manuscript i... more When reporting on well-conducted research, a characteristic of a complete and proper manuscript is one that includes analyses and interpretations of all interactions. Our purpose is to show how to analyze and interpret interactions in agronomy and breeding research by means of three data sets comprising random and fixed effects. Experiment 1 tested wheat (Triticum aestivum L.) at two N and four P fertilizer rates in two soil types. For this data set, we used a fixed-effect linear model with the highest order (three-way) interaction considered first and then worked down through the lower order interactions and main effects to illustrate the importance of interactions in data analysis. Experiment 2 evaluated maize (Zea mays L.) hybrids under four rates of N for 3 yr. For this data set, we used a linear mixed model and partitioned the four N rates into orthogonal polynomials. Experiment 3 evaluated genotypes in six environments where the objective was to show how to study genotype × environment interactions. Researchers must analyze all interactions, determine if they are due to changes in rank (crossover) or only to changes in scale, and then judge whether reporting on significant main effects or interactions would best explain the biological responses in their experiments. In an experiment with more than one factor, complete and correct analysis of interactions is essential for reporting and interpreting the research properly.

Research paper thumbnail of Drought stress and tropical maize: QTL-by-environment interactions and stability of QTLs across environments for yield components and secondary traits

Theoretical and Applied Genetics, 2009

A recombinant inbred line (RIL) population was evaluated in seven field experiments representing ... more A recombinant inbred line (RIL) population was evaluated in seven field experiments representing four environments: water stress at flowering (WS) and wellwatered (WW) conditions in Mexico and Zimbabwe. The QTLs were identified for each trait in each individual experiment (single-experiment analysis) as well as per environment, per water regime across locations and across all experiments (joint analyses). For the six target traits (male flowering, anthesis-to-silking interval, grain yield, kernel number, 100-kernel fresh weight and plant height) 81, 57, 51 and 34 QTLs were identified in the four stepwise analyses, respectively. Despite high values of heritability, the phenotypic variance explained by QTLs was reduced, indicating epistatic interactions. About 80, 60 and 6% of the QTLs did not present significant QTL-by-environment interactions (QTL 9 E) in the joint analyses per environment, per water regime and across all experiments. The expression of QTLs was quite stable across years at a given location and across locations under the same water regime. However, the stability of QTLs decreased drastically when data were combined across water regimes, reflecting a different genetic basis of the target traits in the drought and well-watered trials. Several clusters of QTLs for different traits were identified by the joint analyses of the WW (chromosomes 1 and 8) and WS (chromosomes 1, 3 and 5) treatments and across water regimes (chromosome 1). Those regions are clear targets for future markerassisted breeding, and our results confirm that the best approach to breeding for drought tolerance includes selection under water stress.

Research paper thumbnail of Mapping QTLs and QTL × environment interaction for CIMMYT maize drought stress program using factorial regression and partial least squares methods

Theoretical and Applied Genetics, 2006

The study of QTL x environment interaction (QEI) is important for understanding genotype x enviro... more The study of QTL x environment interaction (QEI) is important for understanding genotype x environment interaction (GEI) in many quantitative traits. For modeling GEI and QEI, factorial regression (FR) models form a powerful class of models. In FR models, covariables (contrasts) defined on the levels of the genotypic and/or environmental factor(s) are used to describe main effects and interactions. In FR models for QTL expression, considerable numbers of genotypic covariables can occur as for each putative QTL an additional covariable needs to be introduced. For large numbers of genotypic and/or environmental covariables, least square estimation breaks down and partial least squares (PLS) estimation procedures become an attractive alternative. In this paper we develop methodology for analyzing QEI by FR for estimating effects and locations of QTLs and QEI and interpreting QEI in terms of environmental variables. A randomization test for the main effects of QTLs and QEI is presented. A population of F2 derived F3 families was evaluated in eight environments differing in drought stress and soil nitrogen content and the traits yield and anthesis silking interval (ASI) were measured. For grain yield, chromosomes 1 and 10 showed significant QEI, whereas in chromosomes 3 and 8 only main effect QTLs were observed. For ASI, QTL main effects were observed on chromosomes 1, 2, 6, 8, and 10, whereas QEI was observed only on chromosome 8. The assessment of the QEI at chromosome 1 for grain yield showed that the QTL main effect explained 35.8% of the QTL + QEI variability, while QEI explained 64.2%. Minimum temperature during flowering time explained 77.6% of the QEI. The QEI analysis at chromosome 10 showed that the QTL main effect explained 59.8% of the QTL + QEI variability, while QEI explained 40.2%. Maximum temperature during flowering time explained 23.8% of the QEI. Results of this study show the possibilities of using FR for mapping QTL and for dissecting QEI in terms of environmental variables. PLS regression is efficient in accounting for background noise produced by other QTLs.

Research paper thumbnail of PAPER PRESENTED AT INTERNATIONAL WORKSHOP ON INCREASING WHEAT YIELD POTENTIAL, CIMMYT, OBREGON, MEXICO, 20–24 MARCH 2006 Association of source/sink traits with yield, biomass and radiation use efficiency among random sister lines from three wheat crosses in a high-yield environment

The Journal of Agricultural Science, 2007

For many years yield improvement reported in wheat was associated with increased dry matter parti... more For many years yield improvement reported in wheat was associated with increased dry matter partitioning to grain, but more recently increases in above-ground biomass have indicated a different mechanism for achieving yield potential. The most likely way of increasing crop biomass is by improving radiation use efficiency (RUE); however there is evidence that sink strength is still a critical yield limiting factor in wheat, suggesting that improving the balance between source and sink (source/sink (SS)) is currently the most promising approach for increasing yield, biomass, and RUE. Experiments were designed to establish a more definitive link of SS traits with yield, biomass and RUE in high-yield environments using progeny deriving from parents contrasting in some of those traits. The SS traits formed three main groups relating to (i) phenological pattern of the crop, (ii) assimilation capacity up until shortly after anthesis, and (iii) partitioning of assimilates to reproductive st...

Research paper thumbnail of PAPER PRESENTED AT INTERNATIONAL WORKSHOP ON INCREASING WHEAT YIELD POTENTIAL, CIMMYT, OBREGON, MEXICO, 20–24 MARCH 2006 Reduced nitrogen and improved farm income for irrigated spring wheat in the Yaqui Valley, Mexico, using sensor based nitrogen management

The Journal of Agricultural Science, 2007

Wheat nitrogen-use efficiency in the Yaqui Valley has been estimated at about 0·31. The nitrogen ... more Wheat nitrogen-use efficiency in the Yaqui Valley has been estimated at about 0·31. The nitrogen that is not recovered by the crop has important environmental costs that have regional and global consequences. In addition, these nitrogen losses represent an important reduction in farm income. The objective of the present work was to validate a technology that includes the use of N-rich strips together with the GreenSeeker™ sensor and a crop algorithm in farmers' fields with the ultimate goal of improving nitrogen-use efficiency through site-specific nitrogen management in irrigated spring wheat. During the wheat crop cycle 2002/03 and 2003/04, 13 validation experiments of c. 1 ha each were established in farmers' fields in the Yaqui Valley. After the validation phase, during the wheat crop cycle 2005/06, eight technology transfer trials were established in farmers' fields; these had on an average an area of 10 ha each. Both the validation and technology transfer trials co...

Research paper thumbnail of Quantitative trait loci for yield and correlated traits under high and low soil nitrogen conditions in tropical maize

Molecular Breeding, 2007

Abstract The first objective of this study was to map and characterize quantitative trait loci (Q... more Abstract The first objective of this study was to map and characterize quantitative trait loci (QTL) for grain yield (GY) and for secondary traits under varying nitrogen (N) supply. To achieve this objective, a segregating F2:3 popula-tion previously developed for QTL mapping ...

Research paper thumbnail of Dissecting Maize Productivity: Ideotypes Associated with Grain Yield under Drought Stress and Well-watered Conditions

Journal of Integrative Plant Biology, 2012

To increase maize (Zea mays L.) yields in drought-prone environments and offset predicted maize y... more To increase maize (Zea mays L.) yields in drought-prone environments and offset predicted maize yield losses under future climates, the development of improved breeding pipelines using a multi-disciplinary approach is essential. Elucidating key growth processes will provide opportunities to improve drought breeding progress through the identification of key phenotypic traits, ideotypes, and donors. In this study, we tested a large set of tropical and subtropical maize inbreds and single cross hybrids under reproductive stage drought stress and well-watered conditions. Patterns of biomass production, senescence, and plant water status were measured throughout the crop cycle. Under drought stress, early biomass production prior to anthesis was important for inbred yield, while delayed senescence was important for hybrid yield. Under well-watered conditions, the ability to maintain a high biomass throughout the growing cycle was crucial for inbred yield, while a stay-green pattern was important for hybrid yield. While new quantitative phenotyping tools such as spectral reflectance (Normalized Difference Vegetation Index, NDVI) allowed for the characterization of growth and senescence patterns as well as yield, qualitative measurements of canopy senescence were also found to be associated with grain yield.

Research paper thumbnail of Stability and Quality of Minimally Processed Orange Slices

Journal of Food Processing and Preservation, 2008

Osmotic dehydration of orange slices (cv. Valencia Late), by applying a vacuum pulse at mild temp... more Osmotic dehydration of orange slices (cv. Valencia Late), by applying a vacuum pulse at mild temperature (30C), and by using different concentrations and two kinds of osmotic agents (sucrose and glucose), was studied in order to obtain stable minimally processed orange slices. Optimal processing conditions were established by modeling process kinetics from compositional changes of the fruit liquid phase related with the product stability, and taking into account the two slice fractions (pulp and peel).

Research paper thumbnail of Variabilidad del carbono orgánico en suelos de ladera del sureste de México

Research paper thumbnail of META: A suite of sas programs to analyze multienvironment breeding trials

Research paper thumbnail of Studying the effect of environmental variables on the genotype x environment interaction of tomato

Euphytica, 2007

Genotype · environment interaction (GEI) affects marketable fruit yield and average fruit weight ... more Genotype · environment interaction (GEI) affects marketable fruit yield and average fruit weight of both hybrid and open-pollinated (OP) tomato genotypes. Cultivars vary significantly for marketable fruit yield, with hybrid cultivars having, on average, higher yield than OP cultivars. However, information is scanty on environmental factors affecting the differential response of tomato genotypes across environments. Hence, the aim of this research was to use factorial regression (FR) and partial least squares (PLS) regression, which incorporate external environmental and genotypic covariables directly into the model for interpreting GEI. In this research, data from an FAO multi-environment trial comprising 15 tomato genotypes (7 hybrid and 8 OP) evaluated in 18 locations of Latin America and the Caribbean were analyzed using FR and PLS. Environmental factors such as days to harvest, soil pH, mean temperature (MET), potassium available in the soil, and phosphorus fertilizer accounted for a sizeable portion of GEI for marketable fruit yield, whereas trimming, irrigation, soil organic matter, and nitrogen and phosphorus fertilizers were important environmental covariables for explaining GEI of average fruit weight. Locations with relatively high minimum and mean temperatures favored the marketable fruit yield of OP heat-tolerant lines CL 5915-223 and CL 5915-93. An OP cultivar (Catalina) and a hybrid (Apla) showed average marketable fruit yield across environments, while two hybrids (Sunny and Luxor) exhibited outstanding marketable fruit yield in high yielding locations (due to lower temperatures and higher pH) but a sharp yield loss in poor environments. Two stable hybrid genotypes in high yielding environments, Narita and BHN-39, also showed high and stable yield in average and low yielding environments.

Research paper thumbnail of Mapping QTLs and QTL 3 environment interaction for CIMMYT maize drought stress program using factorial regression and partial least squares methods

Research paper thumbnail of Analysing QTL by environment interaction by factorial regression, with an application to the CIMMYT drought and low nitrogen stress programme in maize

Research paper thumbnail of Interpreting genotype x environment interaction in wheat by partial least squares regression

Crop Science, May 1, 1998

Research paper thumbnail of Interpreting treatment x environment interaction in agronomy trials

Agron J, 2001

Page 1. STATISTICS Interpreting Treatment Environment Interaction in Agronomy Trials Mateo Vargas... more Page 1. STATISTICS Interpreting Treatment Environment Interaction in Agronomy Trials Mateo Vargas, Jose Crossa,* Fred van Eeuwijk, Kenneth D. Sayre, and Matthew P. Reynolds ... multiplicative interaction (AMMI) model (Kempton, ...

Research paper thumbnail of Biplot Graphic Display: Some Concepts

Farmers participatory research trials are conducted over different regions and over years. Resour... more Farmers participatory research trials are conducted over different regions and over years. Resource Conservation Technology (RCT) options may have an interaction with regions and/or years. It is desired to identify the RCT options that are suitable over regions/years. Further, it is desired to identify the varieties most suitable for zero tillage, bed planting systems etc. Therefore, different varieties are included in farmers' participatory research trials. Generally, the variety to be used is the prerogative of the participatory farmer. The Farmers Participatory Research Trials may have different soil types or land leveling. The aim is to study the interaction between treatments and varieties/soil types/land leveling. If we consider varieties, soil types, years, regions, land leveling etc. as environments and RCT options as treatments then it amounts to studying the treatment × environment interactions. If there is no treatment × environment interaction then the best RCT option may be identified by averaging over the environments if the data is balanced or using adjusted treatment means in case of an unbalanced data. If treatment × environment interaction is present then first we have to identify whether the interaction is a cross-over (treatment ranks changes from one environment to another) or non-cross-over type where treatment difference change in magnitude but not in direction from one among environments.

Research paper thumbnail of Antinociceptive effects of azepexole (BHT 933) in mice

Pain, 1989

Subcutaneous (s.c.) administration of azepexole (BHT 933) at doses between 4 and 40 mg/kg produce... more Subcutaneous (s.c.) administration of azepexole (BHT 933) at doses between 4 and 40 mg/kg produced dose-dependent antinociceptive effects in mice as assessed by tail-immersion, tail-pinch and acetic acid writhing tests. The ED16s were 5.6 +/- 0.4, 6.7 +/- 1.2 and 2.96 +/- 0.2 mg/kg respectively. Similarly, morphine produced analgesia in the same tests with ED16s of 0.87 +/- 0.03, 0.47 +/- 0.1 and 0.45 +/- 0.01 mg/kg respectively. In all instances naloxone (0.1 mg/kg s.c.) shifted the dose-response curves to morphine to the right in a parallel manner. Naloxone (0.1 and 1 mg/kg s.c.) partially antagonized the effect of azepexole in the tail-immersion and tail-pinch tests but significantly decreased the slope of the dose-response curve suggesting that a competitive interaction at the level of the opioid receptors did not occur. Naloxone had no effect on the antinociceptive action of azepexole in the acetic acid writhing test.

Research paper thumbnail of An eco-physiological - statistical framework for th e analysis of GxE and QTLxE as occurring in abiotic stress trials, wi th applications to the CIMMYT drought stress programs in tropical maize and bread wheat

Research paper thumbnail of Genetic Gains in Grain Yield Through Genomic Selection in Eight Bi-parental Maize Populations under Drought Stress

Research paper thumbnail of Identification of quantitative trait loci for cold-tolerance of photosynthesis in maize (Zea mays L.)

Journal of Experimental Botany, 2002

The effects of low growth temperature (15 ∞C) on the photosynthetic apparatus of maize were inves... more The effects of low growth temperature (15 ∞C) on the photosynthetic apparatus of maize were investigated in a set of 233 recombinant inbred lines by means of chlorophyll fluorescence, gas exchange measure- ments and analysis of photosynthetic pigments. A quantitative trait loci (QTL) analysis of five traits related to the functioning of the photosynthetic apparatus revealed a total of eight

Research paper thumbnail of Analysis and Interpretation of Interactions in Agricultural Research

Agronomy Journal, 2014

When reporting on well-conducted research, a characteristic of a complete and proper manuscript i... more When reporting on well-conducted research, a characteristic of a complete and proper manuscript is one that includes analyses and interpretations of all interactions. Our purpose is to show how to analyze and interpret interactions in agronomy and breeding research by means of three data sets comprising random and fixed effects. Experiment 1 tested wheat (Triticum aestivum L.) at two N and four P fertilizer rates in two soil types. For this data set, we used a fixed-effect linear model with the highest order (three-way) interaction considered first and then worked down through the lower order interactions and main effects to illustrate the importance of interactions in data analysis. Experiment 2 evaluated maize (Zea mays L.) hybrids under four rates of N for 3 yr. For this data set, we used a linear mixed model and partitioned the four N rates into orthogonal polynomials. Experiment 3 evaluated genotypes in six environments where the objective was to show how to study genotype × environment interactions. Researchers must analyze all interactions, determine if they are due to changes in rank (crossover) or only to changes in scale, and then judge whether reporting on significant main effects or interactions would best explain the biological responses in their experiments. In an experiment with more than one factor, complete and correct analysis of interactions is essential for reporting and interpreting the research properly.

Research paper thumbnail of Drought stress and tropical maize: QTL-by-environment interactions and stability of QTLs across environments for yield components and secondary traits

Theoretical and Applied Genetics, 2009

A recombinant inbred line (RIL) population was evaluated in seven field experiments representing ... more A recombinant inbred line (RIL) population was evaluated in seven field experiments representing four environments: water stress at flowering (WS) and wellwatered (WW) conditions in Mexico and Zimbabwe. The QTLs were identified for each trait in each individual experiment (single-experiment analysis) as well as per environment, per water regime across locations and across all experiments (joint analyses). For the six target traits (male flowering, anthesis-to-silking interval, grain yield, kernel number, 100-kernel fresh weight and plant height) 81, 57, 51 and 34 QTLs were identified in the four stepwise analyses, respectively. Despite high values of heritability, the phenotypic variance explained by QTLs was reduced, indicating epistatic interactions. About 80, 60 and 6% of the QTLs did not present significant QTL-by-environment interactions (QTL 9 E) in the joint analyses per environment, per water regime and across all experiments. The expression of QTLs was quite stable across years at a given location and across locations under the same water regime. However, the stability of QTLs decreased drastically when data were combined across water regimes, reflecting a different genetic basis of the target traits in the drought and well-watered trials. Several clusters of QTLs for different traits were identified by the joint analyses of the WW (chromosomes 1 and 8) and WS (chromosomes 1, 3 and 5) treatments and across water regimes (chromosome 1). Those regions are clear targets for future markerassisted breeding, and our results confirm that the best approach to breeding for drought tolerance includes selection under water stress.

Research paper thumbnail of Mapping QTLs and QTL × environment interaction for CIMMYT maize drought stress program using factorial regression and partial least squares methods

Theoretical and Applied Genetics, 2006

The study of QTL x environment interaction (QEI) is important for understanding genotype x enviro... more The study of QTL x environment interaction (QEI) is important for understanding genotype x environment interaction (GEI) in many quantitative traits. For modeling GEI and QEI, factorial regression (FR) models form a powerful class of models. In FR models, covariables (contrasts) defined on the levels of the genotypic and/or environmental factor(s) are used to describe main effects and interactions. In FR models for QTL expression, considerable numbers of genotypic covariables can occur as for each putative QTL an additional covariable needs to be introduced. For large numbers of genotypic and/or environmental covariables, least square estimation breaks down and partial least squares (PLS) estimation procedures become an attractive alternative. In this paper we develop methodology for analyzing QEI by FR for estimating effects and locations of QTLs and QEI and interpreting QEI in terms of environmental variables. A randomization test for the main effects of QTLs and QEI is presented. A population of F2 derived F3 families was evaluated in eight environments differing in drought stress and soil nitrogen content and the traits yield and anthesis silking interval (ASI) were measured. For grain yield, chromosomes 1 and 10 showed significant QEI, whereas in chromosomes 3 and 8 only main effect QTLs were observed. For ASI, QTL main effects were observed on chromosomes 1, 2, 6, 8, and 10, whereas QEI was observed only on chromosome 8. The assessment of the QEI at chromosome 1 for grain yield showed that the QTL main effect explained 35.8% of the QTL + QEI variability, while QEI explained 64.2%. Minimum temperature during flowering time explained 77.6% of the QEI. The QEI analysis at chromosome 10 showed that the QTL main effect explained 59.8% of the QTL + QEI variability, while QEI explained 40.2%. Maximum temperature during flowering time explained 23.8% of the QEI. Results of this study show the possibilities of using FR for mapping QTL and for dissecting QEI in terms of environmental variables. PLS regression is efficient in accounting for background noise produced by other QTLs.

Research paper thumbnail of PAPER PRESENTED AT INTERNATIONAL WORKSHOP ON INCREASING WHEAT YIELD POTENTIAL, CIMMYT, OBREGON, MEXICO, 20–24 MARCH 2006 Association of source/sink traits with yield, biomass and radiation use efficiency among random sister lines from three wheat crosses in a high-yield environment

The Journal of Agricultural Science, 2007

For many years yield improvement reported in wheat was associated with increased dry matter parti... more For many years yield improvement reported in wheat was associated with increased dry matter partitioning to grain, but more recently increases in above-ground biomass have indicated a different mechanism for achieving yield potential. The most likely way of increasing crop biomass is by improving radiation use efficiency (RUE); however there is evidence that sink strength is still a critical yield limiting factor in wheat, suggesting that improving the balance between source and sink (source/sink (SS)) is currently the most promising approach for increasing yield, biomass, and RUE. Experiments were designed to establish a more definitive link of SS traits with yield, biomass and RUE in high-yield environments using progeny deriving from parents contrasting in some of those traits. The SS traits formed three main groups relating to (i) phenological pattern of the crop, (ii) assimilation capacity up until shortly after anthesis, and (iii) partitioning of assimilates to reproductive st...

Research paper thumbnail of PAPER PRESENTED AT INTERNATIONAL WORKSHOP ON INCREASING WHEAT YIELD POTENTIAL, CIMMYT, OBREGON, MEXICO, 20–24 MARCH 2006 Reduced nitrogen and improved farm income for irrigated spring wheat in the Yaqui Valley, Mexico, using sensor based nitrogen management

The Journal of Agricultural Science, 2007

Wheat nitrogen-use efficiency in the Yaqui Valley has been estimated at about 0·31. The nitrogen ... more Wheat nitrogen-use efficiency in the Yaqui Valley has been estimated at about 0·31. The nitrogen that is not recovered by the crop has important environmental costs that have regional and global consequences. In addition, these nitrogen losses represent an important reduction in farm income. The objective of the present work was to validate a technology that includes the use of N-rich strips together with the GreenSeeker™ sensor and a crop algorithm in farmers' fields with the ultimate goal of improving nitrogen-use efficiency through site-specific nitrogen management in irrigated spring wheat. During the wheat crop cycle 2002/03 and 2003/04, 13 validation experiments of c. 1 ha each were established in farmers' fields in the Yaqui Valley. After the validation phase, during the wheat crop cycle 2005/06, eight technology transfer trials were established in farmers' fields; these had on an average an area of 10 ha each. Both the validation and technology transfer trials co...

Research paper thumbnail of Quantitative trait loci for yield and correlated traits under high and low soil nitrogen conditions in tropical maize

Molecular Breeding, 2007

Abstract The first objective of this study was to map and characterize quantitative trait loci (Q... more Abstract The first objective of this study was to map and characterize quantitative trait loci (QTL) for grain yield (GY) and for secondary traits under varying nitrogen (N) supply. To achieve this objective, a segregating F2:3 popula-tion previously developed for QTL mapping ...

Research paper thumbnail of Dissecting Maize Productivity: Ideotypes Associated with Grain Yield under Drought Stress and Well-watered Conditions

Journal of Integrative Plant Biology, 2012

To increase maize (Zea mays L.) yields in drought-prone environments and offset predicted maize y... more To increase maize (Zea mays L.) yields in drought-prone environments and offset predicted maize yield losses under future climates, the development of improved breeding pipelines using a multi-disciplinary approach is essential. Elucidating key growth processes will provide opportunities to improve drought breeding progress through the identification of key phenotypic traits, ideotypes, and donors. In this study, we tested a large set of tropical and subtropical maize inbreds and single cross hybrids under reproductive stage drought stress and well-watered conditions. Patterns of biomass production, senescence, and plant water status were measured throughout the crop cycle. Under drought stress, early biomass production prior to anthesis was important for inbred yield, while delayed senescence was important for hybrid yield. Under well-watered conditions, the ability to maintain a high biomass throughout the growing cycle was crucial for inbred yield, while a stay-green pattern was important for hybrid yield. While new quantitative phenotyping tools such as spectral reflectance (Normalized Difference Vegetation Index, NDVI) allowed for the characterization of growth and senescence patterns as well as yield, qualitative measurements of canopy senescence were also found to be associated with grain yield.

Research paper thumbnail of Stability and Quality of Minimally Processed Orange Slices

Journal of Food Processing and Preservation, 2008

Osmotic dehydration of orange slices (cv. Valencia Late), by applying a vacuum pulse at mild temp... more Osmotic dehydration of orange slices (cv. Valencia Late), by applying a vacuum pulse at mild temperature (30C), and by using different concentrations and two kinds of osmotic agents (sucrose and glucose), was studied in order to obtain stable minimally processed orange slices. Optimal processing conditions were established by modeling process kinetics from compositional changes of the fruit liquid phase related with the product stability, and taking into account the two slice fractions (pulp and peel).