Mexican Maize Research Articles

Contribution of the Zea mays insulin-like growth factor (ZmIGF) to the embryogenic competence of maize tissue cultures

Establishment of somatic embryogenic cultures is highly influenced by the plant genotype and the explant type. In maize, immature embryos generate embryogenic callus (E), whereas quiescent embryos produce non-embryogenic callus (NE). E callus shows active growth and high capacity of plant regeneration, while NE callus shows slow growth and no regeneration capacity. Active growth is needed for the establishment of embryogenic cultures; therefore, lack of this characteristic pose a handicap for plant regeneration from NE callus. To correct the slow growth on NE callus, the Zea mays insulin-like growth factor (ZmIGF), a peptide that promotes growth by activating the target of rapamycin (TOR) pathway, was used as media supplement. Additionally, since the TOR pathway is connected to the auxin pathway, ZmIGF participation in cell differentiation was considered. To this end, this research explores ZmIGF effect, beyond growth and proliferation on a Mexican maize landrace, which has shown high somatic embryogenic capacity. Expression levels of reported genes involved in the embryogenesis and differentiation processes were evaluated in maize E, NE, and NE-ZmIGF (NE-Zm) growth-activated calluses. A tendency to upregulate messenger RNA (mRNA) expression was observed for genes encoding transcription factors and auxin transport. Some genes related to epigenetic control showed downregulation. Global DNA methylation and chromatin modifications results suggest an epigenetic activation state on E callus and a repression status on NE callus. ZmIGF induced modifications at DNA methylation and chromatin over NE callus, which changed its original repression state to an active one. Overall, results suggest that the expression of genes related to auxin signaling, mainly transport and efflux carriers, are essential for accomplishing plant regeneration through somatic embryogenesis (SE).

Proximate Composition, Fatty Acid Profile and Mycotoxin Contamination in Several Varieties of Mexican Maize

In Mexico maize (Zea mays L.) is an important cereal due to excellent taste and nutritional value. Nutritional content and fatty acid profile has been reported in white maize, however, there are several genotypes natives (red, yellow, black, blue, pinto), and many improved hybrids maize of which little is known. Fumonisins and aflatoxins are mycotoxins present in 25% of the world’s cereals, mainly in tropical and subtropical regions around the world. This study presents the analysis of proximate composition (ash, protein, lipids), as well as mycotoxins (fumonisins and aflatoxins) and five different fatty acids, two of saturated fatty acids (palmitic and stearic) and three of polyunsaturated fatty acids (oleic, linoleic and linolenic), evaluated by Gas Chromatography and Flame Detector (GC-DF). Thirty varieties of maize (native and hybrid maize) were collected in states of central region. The total fumonisins were determined using the QuickTox TM extraction and quantificated by QuickScan fumonisins; the aflatoxins were analyzed by commercial ELISA kit. The highest protein level was 10.43 g/100g, 5.63 g/100g for fat, 1.62 g/100g for ash in hybrid maize. In native maize, the highest levels of protein and ash were 10.94 g/100g and 1.45 g/100g for pinto maize. The higher value for fat was 5.45 g/100g in yellow maize. The palmitic and stearic acids, in native maize were higher that hybrid maize, for linoleic acid and linoleinic fatty with a significant difference between native corn. Fumonisins and aflatoxins were contaminated in all genotypes of maize, in allow levels. This information obtained may be considered in maize breeding programs, industrialization processes and healthy diets.

Determination of total arsenic and speciation analysis in Mexican maize tortillas by hydride generation – microwave plasma atomic emission spectrometry and high performance liquid chromatography – inductively coupled plasma – mass spectrometry

Determination and speciation of As in tortillas are reported.

FROM MAIZE TO HAZE: AGRICULTURAL SHOCKS AND THE GROWTH OF THE MEXICAN DRUG SECTOR

Understanding how economic incentives affect illegal drug production is essential for crafting policies in response to the international drug trade. Policymakers typically face a choice between two strategies:targetingcriminalgroupsvialawenforcement, andofferingproducersincentivestoengage in alternate activities. Yet, little is known about how the returns to alternate legal activities affect drug supply. We contribute to this literature by examining how shocks to legal commodity prices affect the drug trade in Mexico. Our analysis exploits exogenous movements in the Mexican maize price stemming from weather conditions in U.S. maize-growing regions, as well as exports of other major maize producers. Using data on over 2200 municipios spanning 1990-2010, we show that lower prices differentially increased the cultivation of both marijuana and opium poppies in municipios

Poliembrionía en maices de porte normal y enano.

The Mexican Maize Institute, in Saltillo, Northern Mexico, has developed maize populations with polyembryonic traits. Polyembryony (PE) is interesting for at least two reasons: two or more embryos per seed can produce more oil and embryo protein, as well as savings in the number of seeds necessary to reach a certain population per unit area. The founding population (established in 1973) had 1.5% of PE, identified as "twin plants" by seed. Starting in 1975 different recurrent selection schemes have been applied in order to increase the PE frequency. By 1991 the selection response placed PE at 47%; then the base population was divided into two groups: brachytic and normal height. By 1996 these two populations showed a PE frequency above 60%. For the last 5 years, reproduction management of polyembryonic groups has been made through parental crosses with a mixture of pollen. Between 200 and 250 halfsib families (SHS) were selected in a given cycle in the field in each group; each SHS is represented by 50 seeds, which were individually planted and kept under greenhouse conditions. The families to be transplanted were selected from these according to their PE proportion and at least 75% germination. PE increase seems to limit seed germination to an average lower than 90% under greenhouse conditions, and lower than 60% under direct planting.

Color, phenolic composition and antioxidant activity of blue tortillas from Mexican maize races

ABSTRACTCereal products made from pigmented grains are attractive to consumers. We determined the variability in color, phenolic composition and antioxidant activity (AA) of blue tortillas made from 18 landraces belonging to three blue/purple grained Mexican maize races – Chalqueño (Chal), Elotes Cónicos (Ec) and Bolita (Bol). The color of the tortillas produced ranged from yellow-green to blue-green. Ec tortillas were the only true blue type. Total anthocyanin content (TAC) varied between 3.67 and 1.11 mg equivalents of cyanidin 3-glucoside/kg dry weight (DW). Total soluble phenolics (TSP) were between 9.42 and 5.16 mg equivalents of gallic acid/kg DW. AA was highly correlated (p < 0.01) with TAC, but not with TSP. Blue Ec tortillas had the highest AA, and Bol tortillas had the lowest AA. Color parameters, TSP and TAC allowed the appropriate grouping of blue tortillas according to the maize race they belong to and were made from.

Open Trade, Price Supports, and Regional Price Behavior in Mexican Maize Markets

We analyze wholesale maize prices in 12 Mexican markets from 1998 to 2010, a period when markets became more open to inter- and intranational trade. We ask how the influence of global and local forces on Mexican maize prices changed during this period. We also explore how the strength of global and local forces varies across maize-producing regions. In general, we expect the influence of global forces to increase and local forces to decrease as markets become more open. We find that the influence of global forces does vary over the study period and, counter to expectation, is the highest at the beginning and middle of the period rather than at the end. This result suggests that even under less open market conditions, buyers and sellers were still following global price signals. In contrast, the influence of local forces follows expectation and decreases over time. However, the estimated pattern of response is not uniform across various maize-producing regions. Taken together, our results suggest that opening agricultural markets can result in regionally distinct outcomes and counterintuitive price behavior.

Genomic variation in recently collected maize landraces from Mexico.

The present dataset comprises 36,931 SNPs genotyped in 46 maize landraces native to Mexico as well as the teosinte subspecies Zea maiz ssp. parviglumis and ssp. mexicana. These landraces were collected directly from farmers mostly between 2006 and 2010. We accompany these data with a short description of the variation within each landrace, as well as maps, principal component analyses and neighbor joining trees showing the distribution of the genetic diversity relative to landrace, geographical features and maize biogeography. High levels of genetic variation were detected for the maize landraces (HE = 0.234 to 0.318 (mean 0.311), while slightly lower levels were detected in Zea m. mexicana and Zea m. parviglumis (HE = 0.262 and 0.234, respectively). The distribution of genetic variation was better explained by environmental variables given by the interaction of altitude and latitude than by landrace identity. This dataset is a follow up product of the Global Native Maize Project, an initiative to update the data on Mexican maize landraces and their wild relatives, and to generate information that is necessary for implementing the Mexican Biosafety Law.

Finding potential high-yield areas for Mexican maize under current and climate change conditions

SUMMARYAnalyses of the geographic patterns of wild species abundance have been carried out in studies ranging from those interested in hot-spots for biodiversity and conservation to basic ecological analyses. Based on the methodological approaches used, the present study searched for areas of higher yield among native races of maize in Mexico, its centre of origin and diversification. Ecological theory suggests that population fitness, and thus abundance, is maximal at the centroid of the multi-dimensional ecological niche of a particular species, and decreases progressively as distance from it increases. In the present study, yield was used instead of abundance, assuming it to be higher under optimal environmental conditions. It was assessed whether nine Mexican maize races exhibited higher yields in areas that are ecologically closer to their niche centroid (NC), or a niche optimum (NO) that did not always coincide with the geometric centroid. Environmental and geographical clusters for each race were also created to identify additional NOs in widely distributed races. All races showed significant correlations between yield and distance, both to the NC or NOs, but in only six of them was the chosen model better than the null model. Three races and two sub-groups were selected for projection under climate change conditions: Celaya (R2= 0·288), Celaya 3 (R2= 0·774), Vandeño (R2= 0·277) and Vandeño 2 (R2= 0·466) and Tepecintle (R2= 0·537). The Celaya race improved with environmental clustering, while Vandeño improved under geographical clustering. Finally, Tepecintle was projected at a race level. Projections under climate change suggested some potential areas for high yields in the future. It was concluded that the approach used in the present paper, considering the distance to NC/NO as a predictor of maize landrace yield, may contribute important information to agro-ecological projects.

Strategies for White and Yellow Maize Cultivar Improvement Research and Technology Transfer in Mexico

The Mexican federal government recently implemented a program to increase Mexico's maize (Zea mays L.) production through development and diffusion of technological packages incorporating improved seed cultivars. The initiative is known as MasAgro, Modernización Sustentable de la Agricultura Tradicional (i.e., Program of Sustainable Modernization of Traditional Agriculture). Mexico's diverse maize production sector requires research and technology transfer of white and yellow maize produced under rainfed and irrigated conditions by both traditional and commercially oriented farmers. A spatial and intertemporal Mexican maize sector model was formulated to assess three strategies for targeted cultivar development and optimized spatial distribution of maize production to improve Mexico's food security. Information by state and production season for average years 2008 to 2010 was used to obtain the model solution. Information and data for the model came from secondary sources, primarily Mexican government institutions. Research results provide guidance for Mexico's agricultural research and technology transfer efforts. Mexico's potential maize production was estimated, and strategies that consider distribution logistics and domestic maize consumption were compared. Results indicate that Mexico's potential maize production is 29.34 million Mg, or 95.1% of the average annual Mexican maize consumption between 2008 and 2010. The three maize sector planning strategies evaluated had higher social welfare values than the actual maize sector conditions in the baseline period 2008 to 2010. Thus, there are significant opportunities for agricultural research and technology transfer to improve Mexico's well‐being using integrated maize sector planning that includes targeted cultivar development and customized technology transfer for different regions, crop water conditions, and farmers.

Independent Molecular Basis of Convergent Highland Adaptation in Maize.

Convergent evolution is the independent evolution of similar traits in different species or lineages of the same species; this often is a result of adaptation to similar environments, a process referred to as convergent adaptation. We investigate here the molecular basis of convergent adaptation in maize to highland climates in Mesoamerica and South America, using genome-wide SNP data. Taking advantage of archaeological data on the arrival of maize to the highlands, we infer demographic models for both populations, identifying evidence of a strong bottleneck and rapid expansion in South America. We use these models to then identify loci showing an excess of differentiation as a means of identifying putative targets of natural selection and compare our results to expectations from recently developed theory on convergent adaptation. Consistent with predictions across a wide parameter space, we see limited evidence for convergent evolution at the nucleotide level in spite of strong similarities in overall phenotypes. Instead, we show that selection appears to have predominantly acted on standing genetic variation and that introgression from wild teosinte populations appears to have played a role in highland adaptation in Mexican maize.

Maize Pests in Mexico and Challenges for the Adoption of Integrated Pest Management Programs

Mexico is the fifth largest maize producer and the area of origin and domestication of this crop. Mexico's 6.8 million hectare annual production of maize represents 30% of its total domestic agricultural production and 6.6% of the country's arable land. However, Mexico's average yield of 3.17 tons per hectare is 38% below the world's average. Although maize is a major crop globally, it is typically not grown under modern or comprehensive integrated pest management (IPM) programs aimed at minimizing economic damage and lowering environmental and health risks. Pest management in commercial maize in Mexico continues to rely primarily on chemical control using conventional synthetic insecticides. Approximately 3,000 tons of active ingredient per year are used to combat the single most important pest, the fall armyworm ( Spodoptera frugiperda Smith), followed by the corn earworm ( Helicoverpa zea Boddie) and the black cutworm ( Agrotis ipsilon (Hufnagel)). Mexican farmers have successfully adopted IPM programs for many crops, but IPM is not common in maize crops. Although different components and elements have been identified, most of the information on maize pests and IPM in Mexico has been published in technical bulletins of a reduced regional scope or in difficult-to-access reports, generally describing laboratory screenings, preliminary field evaluations, or listing technical recommendations but rarely including products and practices that growers actually use. This report provides up-to-date information on the common pests in the main maize-growing areas of Mexico from experts in the field. Updated information on maize pest population dynamics and control has been gathered from agricultural professionals directly involved in maize crop protection. This critical information, not readably available for Mexican production systems, is intended to help researchers, government officials, and industry specialists in making decisions regarding time and resource allocations in the design and implementation of IPM techniques, practices, and programs for Mexican maize.

Selling Maize in Mexico: The Persistence of Peasant Farming in an Era of Global Markets

ABSTRACTThe last decade of the twentieth century was heralded as the ‘end of agrarian reform’ in Mexico and the initiation of a new era of market‐led agricultural policy and practice. The impact of neoliberalism and the North American Free Trade Agreement on smallholder maize production has been widely conceived as negative, associated with ecological degradation, rural emigration and cultural erosion. Yet, some twenty years later, all evidence suggests that smallholder maize production is continuing in Mexico, albeit in evolving structures and forms. This article uses a farm‐level survey implemented in three Mexican states to assess the current condition of maize farming in Mexico. The authors revisit past categorizations of Mexican farmers and apply similar approaches to explore what maize‐producing households are doing with their maize, and what current patterns of production imply for future Mexican maize policy. They find evidence of greater persistence and adaptability in Mexican maize farming than is often presented. On the basis of their analysis, they advocate for a reconsideration of the underlying assumptions of public policy, highlighting the heterogeneity of the maize landscape and the unrealized and generally unrecognized potential this heterogeneity represents.

From Maize to Haze: Agricultural Shocks and the Growth of the Mexican Drug Sector

We examine how commodity price shocks experienced by rural producers affect the drug trade in Mexico. Our analysis exploits exogenous movements in the Mexican maize price stemming from weather conditions in U.S. maize-growing regions, as well as export flows of other major maize producers. Using data on over 2,200 municipios spanning 1990-2010, we show that lower prices differentially increased the cultivation of both marijuana and opium poppies in municipios more climatically suited to growing maize. This increase was accompanied by differentially lower rural wages, suggesting that households planted more drug crops in response to the decreased income generating potential of maize farming. We also found impacts on downstream drug-trade outcomes, including the operations of drug cartels and killings perpetrated by these criminal groups. Our findings demonstrate that maize price changes contributed to the burgeoning drug trade in Mexico, and point to the violent consequences of an expanding drug sector.

Environmental and social factors account for Mexican maize richness and distribution: A data mining approach

Food security is a key topic for human welfare worldwide. In this context, the agrobiodiversity in centers of origin and diversification (COD) for the world's staple crops will be critical for feeding the world under changing environmental and social conditions. Maize is one of the most widely cultivated cereal and is the staple food for African and Latin-American countries, including its COD: Mexico, harboring more than 60% of the world's diversity for this crop. In this study we implemented a data mining approach that allowed us to evaluate spatial relationships of environmental (altitude, climate, slope and soil) and social factors (education and ethnic groups) with the spatial distribution of Mexican races, as well as the areas that can potentially harbor the highest number of races (PRA). In contrast to commonly used species distribution approaches, the data mining method implemented here allowed the integration of contrasting types of variables and their spatial relationships with the focal entity. Our results indicate that altitude, which is related with climate, was the factor with highest predictive power for most races. However, different factors showed different degrees of association with the spatial distribution of particular races. In any case, the performance of the model increased when using all evaluated factors. In our example study case, the highly vulnerable race Palomero Tolqueño was mainly influenced by climate, implying that climate change might threaten its preservation by reducing the areas with favorable conditions for its cultivation. Importantly, however, for this and other eleven races analyzed in detail, is that the ethnic group was the factor with the greatest predictive power. This finding further reinforces the key importance of in situ conservation by supporting local indigenous communities who are in charge of preserving, adapting to changing challenges and cultivating local races.

Mexican maize production: Evolving organizational and spatial structures since 1980

Maize has long been one of the most important crops produced in Mexico. The importance of maize stems not only from its role in national economic output, but also because of its strong connections to Mexican culture and, especially, the key role it plays in supporting rural livelihoods. The past 15 years have witnessed dramatic institutional and economic changes that are impacting maize production. Some are well known, such as increasing market integration under NAFTA, while others are less well known, such as the changes in irrigated land use. After an overview of the key changes that impact maize consumption and production since 1980, we provide a detailed description of changes both to the structure of production and to the spatial organization of this production. We close with a discussion of the interplay of changes to production and consumption and the associated changes in livelihood risk, food security, and political security.

Recombinant protein detection and its content in total protein, lipids and toxic antinutritional substances in Mexican maize

The engineering genetic technology has developed Bt maize events which contain recombinant protein that will be safe for the consumer. The aflatoxins are contaminants present in maize capable of producing cancer and decreasing the immune response in human, additionally contained polyphenols compounds considered non nutritive. The objective of this study was to identify the presence of recombinant protein in hybrid and local varieties of corn and evaluate the content of aflatoxins and tannins. 25 samples of white grain maize for human consumption were collected, 12 were for hybrid maize and 13 local varieties, from the states of Hidalgo, Mexico and Morelos. Samples were analyzed for Cry1Ab/Cry1Ac, using lateral flow strip method, crude protein and lipids by standard methods. Aflatoxins were assessed by comercial Elisa kit and tannins by spectroscopy method. The data were grouped in a completely random model and an analysis of variance was performed. The results indicated that 44.5% of hybrid corn was positive by Bt-Cry1Ab/1Ac proteins, containing 9.02% ± 2.5 lipids and 11.33% ± 2.2 crude protein, 189 ± 0.92 mg/g of tannins and 6.36 ± 3.3 μg·g-1 aflatoxins. The local maize samples (55.5%) were negative to Bt-Cry1Ab/ Cry1Ac, which protein content was of 8.68% ± 0.90, 6.14% lipids ± 2.3, 273 ± 0.40 mg/100g tannin and 7.15 ± 3.3 μg·g-1 of aflatoxins. In conclusion, we observed an improvement of nutrient composition in hybrid maize with Bt proteins, and decrease in tannins content comparing with some local varieties without Bt proteins. The effectiveness of Bt maize expressing the Cry1Ab/ Cry1Ac in reducing aflatoxin contamination was not observed, therefore, additive affects of aflatoxins contamination in maize Bt-Cry need to be further investigated in cancer disease development.

Arbuscular mycorrhizal root colonization and soil P availability are positively related to agrodiversity in Mexican maize polycultures

In Los Tuxtlas, Mexico, the local Popoluca people maintain the traditional management of their maize agroecosystems. However, it is not known whether the loss of agrodiversity over recent decades has affected mycorrhizal populations, nutrient availability, and crop productivity. This study utilized linear mixed effect models to analyze the relationship between agrodiversity (three, six, and greater than or equal to eight cultivated species) and (a) arbuscular mycorrhizal fungi (AMF) inoculum potential, measured as the most probable number (MPN) of propagules and colonization level, (b) nutrient availability, and (c) aboveground maize productivity. We also investigated the relationship between soil nutrient content and inoculum potential. Soil samples were taken before planting, and during flowering, in the 2009 maize cycle. We found that AMF colonization level of maize roots and P availability increased with planted species richness, but that this effect only occurred at the flowering sampling date. Plots with a higher MPN of propagules presented increased C and NO3− contents and lower C/N ratio than those with lower MPN of propagules, regardless of agrodiversity. Soils that produced the highest maize root colonization level also featured high P availability and N content. We conclude that decreased agrodiversity in these traditional systems does not significantly affect the soil MPN of propagules, but may have a negative impact on the ability of the mycorrhizal community to colonize maize roots, as well as reducing the availability of P, which is often the most limiting nutrient in tropical soils.

Handbook of maize: its biology

Handbook of maize: its biology

Impact pathways of trade liberalization on rural livelihoods: A case study of smallholder maize farmers in Mexico

Research assessing the impacts of trade liberalization on poor rural populations can be divided intotwo categories: more quantitative research, assessing relationships between specific, measurable variables (such as changes in the macroeconomic environment and their impact on farmers’ income levels); and more qualitative research, which takes trade policy as a context and provides broad, descriptive data about dynamic livelihood strategies. In this paper, we outline a framework that could be used to integrate these two approaches by unravelling the macro-micro linkages between national policies and responses at a household level. Using the Mexican maize sector as an illustration, we trace the pathways through which trade liberalization (including the North American Free Trade Agreement) has interacted with changes in government institutions, and thereby impacted on farmers’ livelihood strategies. We identify three pathways through which trade policy affects households and individuals: via enterprises, distribution channels, and government, and we link these to a five-category typology of smallholders’ strategies for escaping rural poverty: intensification, diversification, expansion, increased off-farm income and exit from agriculture. Based on a case-study from Chiapas, Mexico, we report on farmers’ responses to post-liberalization agricultural policies. Data suggest that farmers have intensified maize production, sought more off-farm employment or have exited agriculture altogether. The potential for smallholders to escape poverty by diversifying farms or expanding their land-holdings or herd-size has been largely unrealized. We provide a conceptual framework for linking the impacts of liberalization to farmers’ livelihood strategies and suggest that this framework is useful in the context of agricultural modernisation initiatives that seek to increase agricultural productionand productivity.CITE AS:Hellin, J., Groenewald, S., Keleman, A. (2012). Impact pathways of trade liberalization on rural livelihoods: A case study of smallholder maize farmers in Mexico. Iberoamerican Journal of Development Studies, 1 (1): 58-82