Maize In Mexico Research Articles

Functional transgenes in Mexican maize: benefits and risks for insect pest management in Mexico and the United States

Abstract Corn earworm (Helicoverpa zea) and fall armyworm (Spodoptera frugiperda) are major migratory pests of maize (Zea mays) in the United States and Mexico. They are primarily controlled in the United States with genetically engineered (GE) maize, while the 25-yr moratorium on cultivating GE maize in Mexico has forced growers to control these pests with insecticides, where maize productivity remains 35% below the world’s average. The United States annually exports 5% of its maize grain to Mexico, where it provides human food and animal feed. This seed is often sown by smallholder growers, leading to plantings of GE transgene-expressing maize and potential hybridization with local landraces. As a result, transgenes are now present in Mexican maize products and landraces. In this study, we examined the F1 offspring of GE maize to better understand the frequency of different transgenes expressed in maize seeds exported to Mexico. We show that exported seed contains numerous transgenes, including an estimated ~68% epsps expressing resistance to the herbicide glyphosate; ~80% pat and bar expressing resistance to the herbicide glufosinate; and ~82% Bacillus thuringiensis (Bt) genes that effectively protect maize plants from several insect pests. We tested 134 samples, including landraces from 10 Mexican states, and found that 35% expressed resistance to glyphosate and 33% to glufosinate. Many samples containing herbicide resistance also expressed 11%–100% functional Bt transgenes, which can effectively reduce the refuge area provided by Mexican maize and increase the Bt-resistant allele frequency. We discuss ways that the introgression of transgenes could provide pest management benefits to Mexican growers but, at the same time, accelerate the development of Bt-resistance in corn earworm and fall armyworm. Our cost-effective screening methods can be used to determine the introgression of functional herbicide resistance and Bt transgenes in maize.

Cytogenetics of maize in Mexico as a field of transnational exchange: The case of Takeo Ángel Kato Yamakake

Societal Impact StatementMaize is one of the most consumed grains worldwide. Its production and international trade are expected to continue increasing because of its use as animal fodder and direct human food. Although maize's history spans millennia, in the last century it underwent significant changes due to genetic engineering, particularly during the Green Revolution. Due to maize's importance for current food security and energy production, it is fundamental to understand this engineering process to assess the implications of current styles of maize production for local and global landscapes, scientific institutions, and transnational networks of agricultural science.Summary This article aims to explain how Mexican agricultural expertise contributed to the development of cytogenetics as a specialized field in the study of the diversity of maize within the framework of the Green Revolution. To this end, the article follows the work of Mexican agronomist Takeo Ángel Kato Yamakake within the activities of the Inter‐American Maize Improvement Program (IMIP), formally established in 1960. By reconstructing the debate on the genetic implications of chromosomal structure and function, this study contributes to the historiography devoted to the role played by local experts in the classification, experimentation, and conservation of maize. The article is based on sources from Mexico and the United States, an interview with Kato, and the consultation of the database “Rockefeller Fellows. Individual Mobility Awards at Rockefeller‐endowed Organizations, 1914‐1970.” Kato's trajectory provides an overview of agronomy in Mexico and shows the relevance of transnational exchange in the establishment of plant cytogenetics. Kato's academic activity features collaborations with key figures such as Edwin Wellhausen, Albert Longley, Barbara McClintock, W. Gallinat, Czeslawa Prywer, and Almiro Blumenschein. A Green Revolution era quest to unravel the origin of maize as a way of perfecting its genetic manipulation fueled the interest in establishing cytogenetics in Mexico. However, the irruption of the molecular approach made the study of the position of chromosomal knobs less of a priority. Despite this, classical cytogenetics, under Kato's leadership, remains a field that contributed to the knowledge of the vegetal genome, even when the IMIP disappeared and the logic of the Green Revolution lost its centrality.

Is Microdochium maydis Associated with Necrotic Lesions in the Tar Spot Disease Complex? A Culture-Based Survey of Maize in Mexico and the Midwestern United States.

Tar spot, caused byPhyllachora maydis, is an emerging disease of corn in the United States. Stromata ofP. maydisare sometimes surrounded by necrotic lesions known as fisheyes and were previously reported to be caused by the fungus Microdochiummaydis. The association ofM. maydiswith fisheye lesions has not been well documented outside of initial descriptions from the early 1980s. The objective of this work was to assess and identify Microdochium-like fungi associated with necrotic lesions surrounding P. maydis stromata using a culture-based method. In 2018, corn leaf samples with fisheye lesions associated with tar spot stromata were collected from 31 production fields across Mexico, Illinois, and Wisconsin. Cultures of pure isolates collected from Mexico believed to be M. maydis were included in the study. A total of 101 Microdochium/Fusarium-like isolates were obtained from the necrotic lesions, and 91% were identified asFusariumspp., based on initial ITS sequence data.Multi-gene (ITS, TEF1-α, RPB1, and RPB2)phylogenies were constructed for a subset of 55 isolates;Microdochium,Cryptostroma, andFusariumreference sequences were obtained from GenBank. All the necrotic lesion isolates clustered withinFusariumlineages and were phylogenetically distinct from the Microdochiumclade. All Fusarium isolates from Mexico belonged to theF. incarnatum-equisetispecies complex, whereas >85% of the U.S. isolates grouped within theF. sambucinumspecies complex. Our study suggests that initial reports of M. maydis were misidentifications of resident Fusarium spp. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Large scale sampling of Mexican maize landraces for the presence of transgenes.

The presence and levels of transgenic maize in Mexico and the effect this could have on local landraces or closely related species such as teosinte has been the subject of several previous reports, some showing contrasting results. Cultural, social and political factors all affect maize cultivation in Mexico and although since 1998 there has been a moratorium on the commercial cultivation of transgenic maize, Mexico imports maize, mainly from the USA where transgenic cultivars are widely grown. Additionally extensive migration between rural areas in Mexico and the USA and customs of seed exchange between farmers may also play an unintentional role in the establishment of transgenic seed. A comprehensive study of all Mexican maize landraces throughout the country is not feasible, however this report presents data based on analysis of 3204 maize accessions obtained from the central region of Mexico (where permits have never been authorized for cultivation of transgenic maize) and the northern region (where for a short period authorization for experimental plots was granted). The results of the study confirm that transgenes are present in all the geographical areas sampled and were more common in germplasm obtained in the northern region. However, there was no evidence that regions where field trials had been authorized showed higher levels of transgene presence or that the morphology of seed lots harboring transgenic material was significantly modified in favor of expected transgenic phenotypes.

Occurrence and Distribution of Physiological Races of Exserohilum turcicum in Maize Growing Regions of Mexico.

Turcicum leaf blight (TLB), is a common foliar disease of maize in Mexico that is caused by the fungal pathogen Exserohilum turcicum. The most effective management strategy against TLB is monogenic race-specific resistance. Among the 140 E. turcicum isolates from symptomatic leaves collected from maize fields in Mexico, 100 were obtained from tropical (Veracruz) and temperate areas (Estado de México) between 2010 and 2019, and 40 isolates were obtained from tropical (Sinaloa, Tamaulipas, Veracruz, and Chiapas), subtropical (Nayarit, Jalisco and Guanajuato) and temperate areas (Estado de Mexico, Hidalgo, and Puebla) collected in 2019. All the isolates caused TLB symptoms on the positive control (ht4) showing that they were all pathogenic. Six physiological races of E. turcicum (2, 3, 23, 3N, 23N, and 123N) were identified based on resistant or susceptible responses displayed by five maize differential genotypes (A619Ht1, A619Ht2, A619Ht3, B68HtN, and A619ht4). The most common was race 23 accounting for 68% of the isolates, followed by races 23N, 123N, 3, 2, and 3N at 15%, 8%, 6%, 2%, and 1%, respectively. Race 123N was able to infect the greatest number of maize differential genotypes used in the study. Race 123N was detected in Sinaloa and Estado de México. Race 3 was detected in Nayarit and Jalisco. Race 2 was detected in Jalisco, Estado de México and Veracruz, and race 3N was detected in Tamaulipas. Race 23 was equally dominant in the tropical, subtropical, and temperate regions, while race 123N was more common in the tropical environment and race 23N was more common in the tropical and temperate environments. There was no evidence for shifts in the races between 2010 and 2019.

ARBUSCULAR MYCORRHIZAL FUNGI INFLUENCE ON GROWTH OF CREOLE MAIZE AND LARVAL DEVELOPMENT OF Spodoptera frugiperda (Lepidoptera:Noctuidae)

<p><strong>Background</strong>: The fall armyworm <em>Spodoptera frugiperda </em>is one of the main pests of maize in Mexico. Its control and management have been performed mainly with pesticides. One of the alternatives is to incorporate arbuscular mycorrhizal fungi (AMF) because of the benefits they provide to plants improving their growth and promoting their defense system against this pest. <strong>Objective</strong>: Evaluate the effect of AMF in creole maize growth in reducing leaf damage and development of <em>Spodoptera frugiperda </em>larvae<em>. </em><strong>Methodology</strong>: In greenhouse conditions, creole maize plants were inoculated with 80 spores of <em>Funneliformis mosseae</em>, <em>Rhizophagus intraradices </em>and without AMF. Height and stem diameter were determined in mycorrhized plants at 15, 30, and 45 days after plant inoculation. After 45 days, plants were infested with three third-instar larvae of <em>S. frugiperda</em> and left to feed for 12 days; fresh weight and cephalic capsule width and size were measured. Once larvae were removed, leaf damage was determined in plants by means of a visual scale, leaf area and mycorrhizal colonization. <strong>Results</strong>: Root colonization of maize plants by AMF had a significant effect (Tukey’s <em>p </em>≤ 0.05) in creole maize growth expressed in plant height at 30 days and at 45 days in stem diameter only in plants inoculated with <em>F. mosseae </em>(Tukey’s <em>p </em>≤ 0.05). Leaf damage by the fall armyworm was similar between inoculated and uninoculated with AMF. Larvae that consumed plant leaves inoculated with <em>R. intraradices </em>showed greater fresh weight compared to those inoculated with <em>F. mosseae</em>. Moreover, width of the cephalic capsule and size were similar between larvae fed with plants inoculated with and without AMF. <strong>Implications</strong>: The results provide new perspectives and considerations to incorporate AMF in management of fall armyworm in creole maize. <strong>Conclusion</strong>: These results show that AMF partially promote plant growth of creole maize; leaf damage is similar between plants with and without AMF. Insect weight increased depending on AMF species, which influenced their development.</p>

Association mapping of resistance to tar spot complex in maize

AbstractTar spot complex (TSC) is a major fungal disease of maize in Mexico and several Central and South American countries. The causal agents of the disease are Phyllachora maydis and Monographella maydis. Yield losses of up to 58% associated with this disease have been reported previously. The majority of commercial maize germplasm in the United States is considered highly susceptible to TSC. In order to accelerate the disease resistance improvement process, genes for resistance to TSC and molecular markers linked to these genes, need to be identified and characterized. Here, we used an association mapping technique to detect quantitative trait loci (QTLs) for TSC resistance using genome‐wide association study (GWAS)‐based genotyping‐by‐sequencing (GBS) and Diversity Arrays Technology Sequencing (DArTseq) single‐nucleotide polymorphisms. An association mapping panel of 228 CIMMYT maize lines was used for the GWAS. One major QTL explaining 27.66% of the phenotypic variance and four minor QTLs explaining 10.18%, 12.72%, 10.14% and 13.38% of the phenotypic variance, respectively, were identified by the GBS‐based association mapping. Two QTLs were identified by DArTseq‐based association mapping explaining 1.07% and 18.29% of the phenotypic variance, respectively. These QTLs are expected to facilitate subsequent maize improvement using marker‐assisted selection.

The importance of the territorial perspective for the protection of native maize in Mexico

The importance of the territorial perspective for the protection of native maize in Mexico

Nixtamal techniques for different maize races prepared as tortillas and tostadas by women of Chiapas, Mexico

Nixtamalization, which means cooking maize in alkaline water, is the central technique for the culinary use of maize in Mexico and Central America. Without this procedure, relying on maize as the basic starch staple is inadequate because of nutriment deficiencies. Mexico has more than 50 principal racial types of maize, and these differ in grain qualities that can require the adjustment of the nixtamalization process. Properties such as hardness and grain composition influence nixtamalization because they are related to the absorption of water that occurs during cooking and steeping. Some maize preparations, like tortillas and tostadas, can also require the adjustment of nixtamalization to obtain a high-quality foodstuff. We studied how women in three regions of the state of Chiapas, which differ in the prevalent maize race available, prepare their nixtamal and whether they make changes according to the type of food they prepare. Interviews of 30 women follow the measure of relevant variables when the women prepared nixtamal. We found that nixtamalization is adjusted for different grain hardnesses and for environmental conditions. Variations were found in the cooking time of the nixtamal, in the amount of time the nixtamal was steeped, and in a special process of double boiling of the nixtamal performed by some women for tostadas. Women that specialize in production for the market have developed variations preferred by consumers. As practiced by women in Chiapas, nixtamalization is a flexible technique that is adjusted for maize type and for food preparations.

EVALUATION OF MEXICAN NATIVE AND HYBRID MAIZE (ZEA MAYS) SILAGES FOR SUSTAINABLE MILK PRODUCTION

<p><strong>Background</strong>. Maize cultivation and dairy cattle represent two of the main economic activities in Mexico. <strong>Objective</strong>. Determine the forage yield (ton / ha) and forage quality of the maize silage produced in Mexico and estimate potential milk production. <strong>Methodology</strong>. For this purpose, 13 studies carried out in Mexico, were analyzed according to study area (north vs. center of Mexico) and variety (native vs. hybrid). For inclusion in the final database, the studies should have been including agronomic and chemical variables such as: dry matter yield (DMY) (ton / ha), plant density (number of plants / ha), dry matter content (DM), crude protein (CP), neutral detergent fiber (NDF), ash or organic matter (OM), dry matter digestibility (DMD), neutral detergent fiber digestibility (NDFD), starch and fat content. The data were analyzed using a completely randomized statistical design. <strong>Results</strong>. The forage DMY (dry matter yield) / ha, and the milk production (ton DM / ha) were higher (P <0.0001) for the central region with respect to the northern region. Regarding to the milk production (kg milk/ ha) the native silages produced more (P <0.05) than the hybrids. A positive correlation was observed for the content of NEL (net energy of lactation) (MJ / kg DM) and kg milk / ton DM. <strong>Implications</strong>. The native maize of Mexico thus has the potential to provide greater production of milk / ha and kg Milk/ per ton DM with respect to hybrid maize, due to the higher digestibility of the NDF that causes the higher NEl.<strong> Conclusions.</strong> The use of native maize in Mexico is a viable alternative for use as a silage in feed for dairy cows, with higher milk production per hectare and per ton of dry matter compared to hybrid maize.</p>

Perspectives on native maize conservation in Mexico: a public programme analysis

SummaryIn any conservation programme, a variety of actors participate and interact in its different phases. They commonly have different perspectives and priorities regarding conservation, and diversity in the ensuing perspectives constitutes a barrier to effective conservation. In this paper, we analyse the different perspectives around thePrograma de Conservación de Maíz Criollo(Programme for the Conservation of Native Maize in Mexico; PROMAC) in order to understand the possible causes that resulted in the programme not fulfilling its objectives. We used Q methodology and semi-structured interviews with farmers from a natural protected area to analyse the perspectives of the key actors who conceptualized, designed and implemented the programme and of the target population. Our research identified two different perspectives: (1) native maize can only be conserved with the support of community processes; and (2) the government, and not farmers, is responsible for the conservation of native maize. For farmers, native maize is key to their subsistence livelihoods, and they participated in the programme because of government monetary incentives. These differences contributed to dissimilar interpretations throughout the programme’s implementation phase, which, in turn, likely contributed to PROMAC failing to meet its objectives.

Maize genetic diversity in traditionally cultivated polycultures in an isolated rural community in Mexico: implications for management and sustainability

ABSTRACTBackground: Maize in Mexico exhibits great genetic diversity, maintained by traditional practices of indigenous and non-indigenous communities, the same practices that have led to crop diversification over centuries. As one of the main staple crops worldwide, safeguarding the genetic diversity of maize is paramount to food security.Aims: This study evaluated the genetic diversity and population structure of traditionally cultured maize landraces in a rural seasonal agricultural community in Veracruz, Mexico, in order to learn how traditional practices shape these landraces, and propose strategies for their preservation.Methods: We analysed 118 individual maize samples belonging to five morphotypes (white, yellow, black, red and mottled) with eight microsatellite markers.Results: We encountered high genetic diversity, according to expected heterozygosity (He = 0.61). However, inbreeding coefficient and gene flow values suggested the existence of assortative mating, which causes low genetic differentiation. Population structure analysis identified three genetic pools, independent of grain colour. These findings suggest that all morphotypes belong to the same population, which is sub-structured due to assortative mating and gene flow related to local agronomic management.Conclusions: Current management practices in this community could lead to genetic erosion. In order to preserve diversity, wider regional seed exchange and selection for morphological diversity could be implemented.

Population genetics of lepidopteran (noctuidae) collected on transgenic and non-transgenic maize in Mexico

Allele frequency of the resistance of the gene Onb3GalT5 to Cry proteins was analyzed in insect populations (Helicoverpa zea and Heliothis virescens), collected from maize transgenic and non-transgenic plants. The genetic parameters estimated in these populations were allele and genotype frequency, genetic balance and Wright statistics (Fis, Fit and Fst). Statistical analyses were performed using the package Genepop (4.0.10). Results showed that from the DNA of H. virescens, collected on non-transgenic maize, a higher number of bands were amplified in a range from 250 bp to 600 bp. In contrast, the bands amplified from insects collected on transgenic maize were in the range of 250 bp-500 bp, being the 400 bp band in both cases the most frequent, while in the DNA of Helicoverpa zea, collected on transgenic maize, three bands (350 bp, 400 bp and 450 bp) were amplified, and in H. zea, collected on non-transgenic maize, only two bands (350 bp and 400 bp) were observed. Genetic diversity in insect populations was higher than within these same populations.

Aflatoxin B1 in nixtamalized maize in Mexico; occurrence and accompanying risk assessment.

Maize is a staple food in Mexico that might contain Aflatoxin B1 (AFB1). Nonetheless, data on the exposure and risk assessment of AFB1 from maize for the Mexican population are limited. The aim of the present study was to analyse the occurrence of AFB1 in Mexican nixtamalized maize samples, and to assess the accompanying exposure and risk. Four out of 88 samples contained AFB1 at levels above the limit of detection (1 ng/g). AFB1 occurrence values obtained in this study and additional occurrence values from literature were combined with available literature data for mean and P95 consumption of maize based products. For a 70 kg body weight person, lower bound and upper bound exposure assessments resulted in estimated daily intakes (EDI) of 0.7-8.5 ng/kg bw/day, based on a mean maize consumption. Based on the P95 maize consumption these EDI values amounted to 3.3-11.7 ng/kg bw/day. The corresponding Margin of Exposure (MOE) values amounted to 257-20 for the mean and 50-15 for the P95 consumers. The estimated increased cancer risks were 9-320 and 43-439 cases/106 individuals/lifetime of 75 years for the mean and P95 consumers, respectively. Altogether, the assessment reveals the need for continued risk management of AFB1 in Mexico.

Pythium arrhenomanes causal agent of root rot on yellow maize in Mexico

Here we show that Pythium arrhenomanes is a causal agent of root rot on maize. The pathogen was isolated from diseased root tissue collected from a conventional maize crop in Michoacan, during 2015. For taxonomic identification, the obtained isolate was used for morphological characteristics and molecular analysis (ITS and COXII genes). Pathogenicity tests confirmed that P. arrhenomanes causes root rot on maize plants.

Transportability of non‐target arthropod field data for the use in environmental risk assessment of genetically modified maize in Northern Mexico

AbstractIn country, non‐target arthropod (NTA) field evaluations are required to comply with the regulatory process for cultivation of genetically modified (GM) maize in Mexico. Two sets of field trials, Experimental Phase and Pilot Phase, were conducted to identify any potential harm of insect‐protected and glyphosate‐tolerant maize (MON‐89Ø34‐3 × MON‐88Ø17‐3 and MON‐89Ø34‐3 × MON‐ØØ6Ø3‐6) and glyphosate‐tolerant maize (MON‐ØØ6Ø3‐6) to local NTAs compared to conventional maize. NTA abundance data were collected at 32 sites, providing high geographic and environmental diversity within maize production areas from four ecological regions (ecoregions) in northern Mexico. The most abundant herbivorous taxa collected included field crickets, corn flea beetles, rootworm beetles, cornsilk flies, aphids, leafhoppers, plant bugs and thrips while the most abundant beneficial taxa captured were soil mites, spiders, predatory ground beetles, rove beetles, springtails (Collembola), predatory earwigs, ladybird beetles, syrphid flies, tachinid flies, minute pirate bugs, parasitic wasps and lacewings. Across the taxa analysed, no statistically significant differences in abundance were detected between GM maize and the conventional maize control for 69 of the 74 comparisons (93.2%) indicating that the single or stacked insect‐protected and herbicide‐tolerant GM traits generally exert no marked adverse effects on the arthropod populations compared with conventional maize. The distribution of taxa observed in this study provides evidence that irrespective of variations in overall biodiversity of a given ecoregion, important herbivore, predatory and parasitic arthropod taxa within the commercial maize agroecosystem are highly similar indicating that relevant data generated in one ecoregion can be transportable for the risk assessment of the same or similar GM crop in another ecoregion.

Over a Decade of Scholarship on the Politics and Policy of Science and Technology

Over a Decade of Scholarship on the Politics and Policy of Science and Technology

Híbrido de maíz H-568: nueva opción para áreas de alta productividad del trópico bajo de México


 
 
 En México el maíz (Zea mays L.), es el cultivo de mayor importancia por su superficie sembrada y el rol que juega dentro de la dieta alimentaria del mexicano, ya que su consumo alcanza 200 kg por persona al año y en tortilla se calcula en promedio una ingesta diaria de 225 g. Por ello el Programa de Mejoramiento Genético del INIFAP con sede en Iguala, Guerrero, continúa el proceso de generar nuevos materiales de maíz para las diferentes condiciones de producción en el trópico bajo de México, para la montaña se conservan y mejoran los criollos regionales, en las áreas intermedias con variedades e híbridos varietalesy las áreas de alta productividad con híbridos convencionales.
 
 

The Role of Scientific Excellence in the Changing Meaning of Maize in Mexico

AbstractMaking policy is giving a meaning to objects. This perspective on policy making gained importance in the 1990s with the emergence of discursive approaches. In this article, we use the concepts of Hajer's discourse coalition approach to shed light on the evolving meaning of maize in Mexican society. Specifically, we trace a parallel between the evolution of biotechnology policy and discourses on maize over a 25‐year period. The article argues that until recently, the protection against biotechnological manipulations enjoyed by maize has been bolstered by a discourse granting the plant a special status in the country's history. However, the emergence of a new discourse grounded on the practice of scientific excellence is now challenging the old perspectives, and also finding support among government officials. As a result, the Mexican policies granting maize special protection is changing, and this policy change will likely trigger changes in the symbolic meaning of maize.

Subsidies for Price Risk in Grains: The Case of Maize in Mexico

Across the globe, grain farmers face considerable volatility in international prices for their harvests, now considered commodities. Several years ago, the Mexican government implemented subsidy programs to protect farmers and firms from the risks entailed in price volatility. In this article, I analyze the characteristics and limitations of these programs as well as effects on maize producers and feed enterprises in the state of Puebla, Mexico. Among the findings is the fact that while these programs offer important advantages to the participants, the buyer-seller contracts are often breached as a result of climatic disasters, differences in relative prices (international versus open market), and changes in international exchange rates. The program resources are also concentrated in the hands of a few producers and firms, as well as geographically. I reflect on the need to reorient agricultural policy in Mexico, directing the resources devoted to the government hedging strategy to less regressive programs, such as direct income support for the producer.