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There is great interest in Mexico in reducing imports of grain and becoming self-sufficient in cereal production. Identifying high-yielding and stable maize (Zea mays L.) hybrids from different research institutions could contribute to increasing maize production in the highlands of Mexico. In this study, 16 early white maize hybrids were evaluated at 37 highland sites in several Mexican states with the objective of identifying high-yielding and stable hybrids, as well as high-yielding sites. Using the site regression model, it was possible to identify some outstanding hybrids (CHLHW09035, CHLHW02517 and HIBRIDO 2010) with acceptable grain yield production that were also stable across most of the 37 sites. Hybrids ST-010 and ASPROS-823 were less stable but produced acceptable yields. Sites with higher stability included Site 26 (Amealco, Queretaro), Site 7 (Epitacio Huerta, Michoacan), Site 37 (Tlachaloya, State of Mexico), Site 34 (Ciudad Hidalgo, Michoacan) and Site 29 (Metepec, State of Mexico). Other sites with satisfactory stability included Site 20 (Jilotepec, State of Mexico), Site 5 (Quecholac, Puebla), Site 6 (Huejotzingo, Puebla), Site 13 (Ajacuba, Hidalgo) and Site 19 (Santo Domingo, Oaxaca). [ABSTRACT FROM AUTHOR]

Disease outbreaks attributed to leaf scald of sugarcane caused by Xanthomonas albilineans were recently reported in southern Mexico. In this study, the distribution of leaf scald was investigated in the main sugarcane producing-states in Mexico. The disease was found in eight of 14 sugarcane-growing states and in 12 of 31 fields. In contaminated fields, incidence of leaf scald based on symptomatic plants ranged from 3 to 15%. The causal agent was identified by phylogenetic reconstruction using a single concatenated sequence of four genes (16S rRNA, fus A, leu S, and rpi A). Twelve X. albilineans isolates from different locations in Mexico produced disease symptoms after inoculation into stalks of susceptible variety Mex 69–290. Microscopic examination of infected stalks revealed structural changes within vascular and non-vascular tissues. These alterations reflected acute disease development and highlighted the importance of selecting varieties resistant to X. albilineans in breeding programs in Mexico. • In three decades X. albilineans spread from 2 to 8 sugarcane producing states in Mexico. • The aggressive isolate CPO 12.120 can be used for X. albilineans resistance screening. • By microscopy infected stalks showed damage inside vascular and non-vascular tissues. [ABSTRACT FROM AUTHOR]

Vitamin A deficiency remains prevalent on a global scale, including in regions where maize constitutes a high percentage of human diets. One solution for alleviating this deficiency has been to increase grain concentrations of provitamin A carotenoids in maize (Zea mays ssp. mays L.)—an example of biofortification. The International Maize and Wheat Improvement Center (CIMMYT) developed a Carotenoid Association Mapping panel of 380 inbred lines adapted to tropical and subtropical environments that have varying grain concentrations of provitamin A and other health-beneficial carotenoids. Several major genes have been identified for these traits, 2 of which have particularly been leveraged in marker-assisted selection. This project assesses the predictive ability of several genomic prediction strategies for maize grain carotenoid traits within and between 4 environments in Mexico. Ridge Regression-Best Linear Unbiased Prediction, Elastic Net, and Reproducing Kernel Hilbert Spaces had high predictive abilities for all tested traits (β-carotene, β-cryptoxanthin, provitamin A, lutein, and zeaxanthin) and outperformed Least Absolute Shrinkage and Selection Operator. Furthermore, predictive abilities were higher when using genome-wide markers rather than only the markers proximal to 2 or 13 genes. These findings suggest that genomic prediction models using genome-wide markers (and assuming equal variance of marker effects) are worthwhile for these traits even though key genes have already been identified, especially if breeding for additional grain carotenoid traits alongside β-carotene. Predictive ability was maintained for all traits except lutein in between-environment prediction. The TASSEL (Trait Analysis by aSSociation, Evolution, and Linkage) Genomic Selection plugin performed as well as other more computationally intensive methods for within-environment prediction. The findings observed herein indicate the utility of genomic prediction methods for these traits and could inform their resource-efficient implementation in biofortification breeding programs. [ABSTRACT FROM AUTHOR]

Hyperspectral reflectance phenotyping and genomic selection are two emerging technologies that have the potential to increase plant breeding efficiency by improving prediction accuracy for grain yield. Hyperspectral cameras quantify canopy reflectance across a wide range of wavelengths that are associated with numerous biophysical and biochemical processes in plants. Genomic selection models utilize genome-wide marker or pedigree information to predict the genetic values of breeding lines. In this study, we propose a multi-kernel GBLUP approach to genomic selection that uses genomic marker-, pedigree-, and hyperspectral reflectance-derived relationship matrices to model the genetic main effects and genotype · environment (G X E) interactions across environments within a bread wheat (Triticum aestivum L.) breeding program. We utilized an airplane equipped with a hyperspectral camera to phenotype five differentially managed treatments of the yield trials conducted by the Bread Wheat Improvement Program of the International Maize and Wheat Improvement Center (CIMMYT) at Ciudad Obregón, México over four breeding cycles. We observed that single-kernel models using hyperspectral reflectance-derived relationship matrices performed similarly or superior to marker- and pedigree-based genomic selection models when predicting within and across environments. Multi-kernel models combining marker/pedigree information with hyperspectral reflectance phentoypes had the highest prediction accuracies; however, improvements in accuracy over marker- and pedigree-based models were marginal when correcting for days to heading. Our results demonstrate the potential of using hyperspectral imaging to predict grain yield within a multi-environment context and also support further studies on the integration of hyperspectral reflectance phenotyping into breeding programs. [ABSTRACT FROM AUTHOR]

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 Ne/n (effective/census population size), (3) minimizing variance at all levels sampled, and (4) using Ne 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 (Quist and Chapela, 2001, Nature 414: 541-543; 2002, Nature 416: 602) or "detectable transgenes" are absent (Ortiz-García et al., 2005, Proc. Natl. Acad. Sci. USA 102: 12338-12343 and 18242). We analyzed these papers using information on Oaxacan maize seed systems and estimates of Ne. We conclude that if Quist and Chapela's results showing presence are accepted, Ortiz-García et al.'s conclusions of no evidence of transgenes at detectable levels or for their introgression into maize landraces in the Sierra de Juárez of Oaxaca are not scientifically justified. This is because their samples are not representative, and their statistical analysis is inconclusive due to using n instead of Ne. Using estimates of Ne based on Ortiz-García et al.'s n, we estimate that transgenes could be present in maize landraces in the Sierra Juárez region at frequencies of approximately 1-4%, and are more likely to be present in the 90% of Oaxacan landrace area that is not mountainous. Thus, we have no scientific evidence of maize transgene presence or absence in recent years in Mexico, Oaxaca State, or the Sierra Juárez region.