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Es un cultivo anual de ambientes templados y semicálidos con suelos arcillosos y arenosos. Existen poblaciones silvestres en México que en tiempos precolombinos permitieron seleccionar plantas con fruto más grande que no dispersara la semilla. Las variedades domesticadas, comparadas con las silvestres, tienen semillas de mayor tamaño, inflorescencia más compacta, cálices cerrados, flor más larga, dominancia apical, uniformidad en los periodos de floración y maduración. La chía contiene entre 9 y 23% de proteína, 26-41% de carbohidratos y de 30 a 33% de aceite, 40% de fibra dietética y calcio y un alto contenido de antioxidantes. Ha adquirido gran importancia porque se considera un alimento funcional. Existe consenso sobre la importancia del estudio y conservación de los recursos fitogenéticos. El objetivo de esta investigación fue caracterizar la diversidad morfológica de 31 genotipos de chía con base en las variaciones identificadas entre poblaciones silvestres y domesticadas. Se observó que la presencia de antocianinas es característica de plantas silvestres, así como la presencia de cáliz abierto, que está relacionado con la dispersión de las semillas; estas fueron más pequeñas y oscuras y sus cálices fueron cortos y se abrieron al madurar. El tamaño de la semilla y el peso de mil semillas están altamente correlacionado con el rendimiento por planta. Las plantas domesticadas presentaron cáliz cerrado, sin coloración por antocianinas, reducción de la pubescencia en la mayor parte de la planta, inflorescencia más grande, mayor número de floretes, mayor peso de semilla, mayor rendimiento. Se caracterizaron y agruparon poblaciones domesticadas, semidomesticadas y silvestres. Las silvestres presentan cáliz abierto. Las semidomesticadas son semejantes a las cultivadas pero presentan cáliz abierto. Las domesticadas tuvieron dominancia apical, mayor tamaño de espiga y cáliz cerrado.

Premise Domestication usually involves local adaptation to environmental conditions. Cucurbita species are a promising model for studying these processes. Cucurbita moschata is the third major crop in the genus because of its economic value and because it displays high landrace diversity, but research about its genetic diversity, population structure, and phylogeography is limited. We aimed at understanding how geography and elevation shape the distribution of genetic diversity in C. moschata landraces in Mexico. Methods We sampled fruits from 24 localities throughout Mexico. We assessed 11 nuclear microsatellite loci, one mtDNA region, and three cpDNA regions but found no variation in cpDNA. We explored genetic structure with cluster analysis, and phylogeographic relationships with haplotype network analysis. Results Mitochondrial genetic diversity was high, and nuclear genetic differentiation among localities was intermediate compared to other domesticated Cucurbita. We found high levels of inbreeding. We recovered two mitochondrial lineages: highland (associated with the Trans-Mexican Volcanic Belt) and lowland. Nuclear microsatellites show that localities from the Yucatan Peninsula constitute a well-differentiated group. Conclusions Mexico is an area of high diversity for C. moschata, and these landraces represent important plant genetic resources. In Mexico this species is characterized by divergence processes linked to an elevational gradient, which could be related to adaptation and may be of value for applications in agriculture. The Isthmus of Tehuantepec may be a partial barrier to gene flow. Morphological variation, agricultural management, and cultural differences may be related to this pattern of genetic structure, but further studies are needed.

Twenty-nine DNA regions of plastid origin have been previously identified in the mitochondrial genome of Cucurbita pepo (pumpkin; Cucurbitaceae). Four of these regions harbor homolog sequences of rbcL, matK, rpl20-rps12 and trnL-trnF, which are widely used as molecular markers for phylogenetic and phylogeographic studies. We extracted the mitochondrial copies of these regions based on the mitochondrial genome of C. pepo and, along with published sequences for these plastome markers from 13 Cucurbita taxa, we performed phylogenetic molecular analyses to identify inter-organellar transfer events in the Cucurbita phylogeny and changes in their nucleotide substitution rates. Phylogenetic reconstruction and tree selection tests suggest that rpl20 and rbcL mitochondrial paralogs arose before Cucurbita diversification whereas the mitochondrial matK and trnL-trnF paralogs emerged most probably later, in the mesophytic Cucurbita clade. Nucleotide substitution rates increased one order of magnitude in all the mitochondrial paralogs compared to their original plastid sequences. Additionally, mitochondrial trnL-trnF sequences obtained by PCR from nine Cucurbita taxa revealed higher nucleotide diversity in the mitochondrial than in the plastid copies, likely related to the higher nucleotide substitution rates in the mitochondrial region and loss of functional constraints in its tRNA genes.

Los mejoradores de maíz (Zea mays L.) prefieren las fuentes de germoplasma tradicionales, desaprovechando poblaciones de teocintle (Zea spp) que pueden ampliar la variación genética en sus programas de mejoramiento. Uno de los problemas en el uso de especies silvestres, es su bajo rendimiento económico, debido a que no han estado sujetas al proceso de selección a que han sido sometidas las especies cultivadas. Sin embargo, constituye un reto el poder valorar la utilidad del teocintle en los programas de mejoramiento genético. El presente trabajo tuvo como objetivo principal evaluar en seis líneas élite de maíz recobradas, los cambios en el rendimiento económico y sus componentes en función de la fuente de teocintle y el nivel de retrocruzamiento utilizado. Las líneas se evaluaron en Celaya Gto. (1996 y 1997) y Tlajomulco, Jal. (1996). Se utilizó el diseño experimental bloques completos al azar, con tres repeticiones y un arreglo de tratamientos en parcelas subdivididas, que incluyó como parcela principal las seis líneas de maíz, como subparcelas las seis fuentes de teocintle y como sub-subparcelas los cuatro niveles de retrocruzamiento. Los resultados indicaron que las líneas modificadas con germoplasma de teocintle se pueden aprovechar en la formación de poblaciones para programas de selección recurrente con amplia base genética o bien, combinar las líneas modificadas en RC2 y RC3 de manera que sintetizaran la diversidad total de las líneas y de las fuentes de teocintle. Si se quiere recuperar las líneas para programas de hibridación, sería a partir de la RC3 con la fuente de teocintle que confiera alelos favorables para rendimiento de grano y el menor número de alelos desfavorables para otros caracteres agronómicos.

Gene flow among crops and their wild relatives is an active study area in evolutionary biology and horticulture, because genetic exchange between them may impact their evolutionary trajectories and increase the genetic variation of the cultivated lineages. Mexico is a center of diversity for the genus Cucurbita that includes pumpkins, squash and gourds. Gene flow between domesticated and wild species has been reported as common in Cucurbita; but gene flow among populations of C. pepo ssp. pepo from Mexico and its wild relative has not been studied. We used 2,061 SNPs, derived from tunable genotyping by sequencing (tGBS) to estimate gene flow among 14 Mexican traditional landraces of C. pepo ssp. pepo, also including individuals from five improved cultivars of C. pepo ssp. pepo and C. pepo ssp. ovifera var. ovifera, and individuals of their wild relative C. pepo ssp. fraterna. We found moderate to high levels of genetic diversity, and low to moderate genetic differentiation. In the test of introgression between lineages, we found that all possible arrangements for ancestral and derived sites between the lineages showed similar frequencies; thus, incomplete lineage sorting, but also gene flow, might be taking place in C. pepo. Overall, our results suggest that gene flow between these subspecies and cultigens, incomplete lineage sorting and the retention of ancestral characters shaped the evolutionary trajectory of C. pepo in its area of origin and diversification. In addition, we found evidence of the use of Mexican landraces as genetic material for the improvement of commercial cultivars. The landraces of Mexico are an important source of genetic diversity for C. pepo, which has been preserved both by management practices of small farmers and by the natural gene flow that exists between the different crop fields of the region.

La domesticación de plantas y animales permite estudiar diferentes procesos evolutivos, como la selección, adaptación y especiación. En este artículo se describen avances recientes en el estudio de las calabazas, las cuales constituyen el género Cucurbita (Cucurbitaceae) siendo un grupo de plantas herbáceas americanas que incluyen entre 12 y 15 especies. Cucurbita ha tenido seis eventos de domesticación, de los cuales cuatro sucedieron en México. Este es un género relativamente reciente, que surgió en Norte América hace 16 millones de años y sus especies cultivadas mantienen una alta variación genética; Cucurbita pepo es la especie que presenta mayor variación genética,variación asociada a dos domesticaciones independientes, una en el norte de México, y otra en el Sureste de los Estados Unidos. En otra especie, Cucurbita argyrosperma, sus poblaciones de la Península de Yucatán, representan una poza genética diferenciada del resto de la especie. El estudio del genoma de C. argyrosperma y taxa cercanos ha revelado las regiones de su genoma asociadas a la domesticación. Las poblaciones de las especies de este género representan una fuente de importantes recursos genéticos frente al cambio climático y constituyen un buen sistema para el estudio de la domesticación y de diferentes procesos evolutivos.

In the present investigation, the morphological variability of 11 populations of wild piquin chili (Capsicum annuum var. glabriusculum) of the Mountain range Gorda and Semidesert of Queretaro (Municipalities of Arroyo Seco, Jalpan of Serra, Toliman and Cadereyta de Montes) and Guanajuato (Municipality of Xichu). The characterization was carried out under greenhouse conditions at the Technological Institute of Roque (ITR) located in Celaya, Guanajuato, Mexico. The 44 characters were recorded in seedling, plant, flowering, fruit maturity and seed. The principal component analysis (CP) showed that the first three components explained 56.6% of the total morphological variability. The CP1 was explained by the characteristics of weight (0.326), width (0.301) and fruit length (0.271), leaf density (0.277) and seed diameter (0.297). In CP2, the variables that contributed most to the expression of the variation were width (0.329) and leaf pubescence (0.317) and finally, in CP3, the shape of the fruit (0.344) and color of the anthers (-0.308) were the most important characters. On the other hand, the cluster analysis generated four groups, group I included the G3 (Rosa of Castilla), G2 (Palmitas The Tanque), G1 (The Tanque) populations, all of the Mountain range Gorda in Guanajuato. Group II was made up of population Q7 (The Patol, Queretaro). Group III was formed by population Q5 (Presa Jalpan, Queretaro) and finally, group IV was integrated by six populations, Q4 (San Antonio Tancoyol), Q8 (Higuerillas stream), Q6 (Higuerillas The Shote), Q2 (The Refugio solar-huerta), Q3 (Tancoyol Road to Tancoyol) and Q1 (The Chilar Refuge), all of the State of Queretaro. The morphological diversity found in this species tells us that this native plant should be conserved and that it can be easily integrated into a program of sustainable use of the flora of the region.

Salvia hispanica (chia) constituted an important crop for pre-Columbian civilizations and is considered a superfood for its rich content of essential fatty acids and proteins. In this study, we performed the first comprehensive comparative transcriptome analysis between seeds from cultivated varieties and from accessions collected from native wild populations in Mexico. From the 69,873 annotated transcripts assembled de novo, enriched functional categories and pathways revealed that the lipid metabolism was one of the most activated processes. Expression changes were detected among wild and cultivated groups and among growth conditions in transcripts responsible for triacylglycerol and fatty acid synthesis and degradation. We also quantified storage protein fractions that revealed variation concerning nutraceutical proteins such as albumin and glutelin. Genetic diversity estimated with 23,641 single nucleotide polymorphisms (SNPs) revealed that most of the variation remains in the wild populations, and that a wild-type cultivated variety is genetically related to wild accessions. Additionally, we reported 202 simple sequence repeat (SSRs) markers useful for population genetic studies. Overall, we provided transcript variation that can be used for breeding programs to further develop chia varieties with enhanced nutraceutical traits and tools to explore the genetic diversity and history of this rediscovered plant.

Patterns of genomic divergence between hybridizing taxa can be heterogeneous along the genome. Both differential introgression and local adaptation may contribute to this pattern. Here, we analysed two teosinte subspecies, Zea mays ssp. parviglumis and ssp. mexicana, to test whether their divergence has occurred in the face of gene flow and to infer which environmental variables have been important drivers of their ecological differentiation. We generated 9,780 DArTseqTM SNPs for 47 populations, and used an additional data set containing 33,454 MaizeSNP50 SNPs for 49 populations. With these data, we inferred features of demographic history and performed genome wide scans to determine the number of outlier SNPs associated with climate and soil variables. The two data sets indicate that divergence has occurred or been maintained despite continuous gene flow and/or secondary contact. Most of the significant SNP associations were to temperature and to phosphorus concentration in the soil. A large proportion of these candidate SNPs were located in regions of high differentiation that had been identified previously as putative inversions. We therefore propose that genomic differentiation in teosintes has occurred by a process of adaptive divergence, with putative inversions contributing to reduced gene flow between locally adapted populations.

Local adaptation across species range is widespread. Yet, much has to be discovered on its environmental drivers, the underlying functional traits and their molecular determinants. Because elevation gradients display continuous environmental changes at a short geographical scale, they provide an exceptional opportunity to investigate these questions. Here, we used two common gardens to phenotype 1664 plants from 11 populations of annual teosintes. These populations were sampled across two elevation gradients in Mexico. Our results point to a syndrome of adaptation to altitude with the production of offspring that flowered earlier, produced less tillers, and larger, longer and heavier grains with increasing elevation. We genotyped these plants for 178 outlier single nucleotide polymorphisms (SNPs), which had been chosen because they displayed excess of allele differentiation and/or correlation with environmental variables in six populations with contrasted altitudes. A high proportion of outlier SNPs associated with the phenotypic variation of at least one trait. We tested phenotypic pairwise correlations between traits, and found that the higher the correlation, the greater the number of common associated SNPs. In addition, allele frequencies at 87 of the outlier SNPs correlated with an environmental component best summarized by altitudinal variation on a broad sample of 28 populations. Chromosomal inversions were enriched for both phenotypically-associated and environmentally-correlated SNPs. Altogether, our results are consistent with the set-up of an altitudinal syndrome promoted by local adaptation of teosinte populations in the face of gene flow. We showed that pleiotropy is pervasive and potentially has constrained the evolution of traits. Finally, we recovered variants underlying phenotypic variation at adaptive traits. Because elevation mimics climate change through space, these variants may be relevant for future maize breeding.Author summaryAcross their native range, species encounter a diversity of habitats promoting local adaptation of geographically distributed populations. While local adaptation is widespread, much has yet to be discovered about the conditions of its emergence, the targeted traits, their molecular determinants and the underlying ecological drivers. Here we employed a reverse ecology approach, combining phenotypes and genotypes, to mine the determinants of local adaptation of teosinte populations distributed along two steep altitudinal gradients in Mexico. Evaluation of 11 populations in two common gardens located at mid-elevation pointed to the set-up of an altitudinal syndrome, in spite of gene flow. We scanned genomes to identify loci with allele frequencies shifts along elevation. Interestingly, variation at these loci was commonly associated to variation of phenotypes. Because elevation mimics climate change through space, these variants may be relevant for future maize breeding.

Whole-genome duplications are an important source of evolutionary novelties that change the mode and tempo at which genetic elements evolve within a genome. The Cucurbita genus experienced a whole-genome duplication around 30 million years ago, although the evolutionary dynamics of the coding and noncoding genes in this genus have not yet been scrutinized. Here, we analyzed the genomes of four Cucurbita species, including a newly assembled genome of Cucurbita argyrosperma, and compared the gene contents of these species with those of five other members of the Cucurbitaceae family to assess the evolutionary dynamics of protein-coding and long intergenic noncoding RNA (lincRNA) genes after the genome duplication. We report that Cucurbita genomes have a higher protein-coding gene birth–death rate compared with the genomes of the other members of the Cucurbitaceae family. C. argyrosperma gene families associated with pollination and transmembrane transport had significantly faster evolutionary rates. lincRNA families showed high levels of gene turnover throughout the phylogeny, and 67.7% of the lincRNA families in Cucurbita showed evidence of birth from the neofunctionalization of previously existing protein-coding genes. Collectively, our results suggest that the whole-genome duplication in Cucurbita resulted in faster rates of gene family evolution through the neofunctionalization of duplicated genes.

Knowledge of the role of geographical and ecological events associated to the divergence process of wild progenitors is important to understand the process of domestication. We analysed the temporal, spatial and ecological patterns of the diversification of Cucurbita, an American genus of worldwide economic importance. We conducted a phylogenetic analysis based on six chloroplast regions (5907 bp) to estimate diversification rates and dates of divergence between taxa. This is the first phylogenetic study to include C. radicans, a wild species that is endemic to the Trans Mexican Volcanic Belt. We performed analysis of ancestral area reconstruction and paleoreconstructions of species distribution models to understand shifts in wild species ranges. We used principal component analysis (PCA) and multivariate analysis of variance (MANOVA) to evaluate the environmental differentiation among taxa within each clade. The phylogenetic analyses showed good support for at least six independent domestication events in Cucurbita. The genus Cucurbita showed a time of divergence of 11.24 Ma (6.88–17 Ma 95% HDP), and the dates of divergence between taxa within each group ranged from 0.35 to 6.58 Ma, being the divergence between C. lundelliana and C. okeechobeensis subsp. martinezii the most recent. The diversification rate of the genus was constant through time. The diversification of most wild taxa occurred during the Pleistocene, and its date of divergence is concordant with the dates of divergence reported for specialized bees of the genera Xenoglossa and Peponapis, suggesting a process of coevolution between Cucurbita and their main pollinators that should be further investigated. Tests of environmental differentiation together with ancestral area reconstruction and species distribution models past projections suggest that divergence was promoted by the onset of geographic barriers and secondary range contraction and by expansion related to glacial-interglacial cycles.

Analyses of genetic variation allow understanding the origin, diversification and genetic resources of cultivated plants. Domesticated taxa and their wild relatives are ideal systems for studying genetic processes of plant domestication and their joint is important to evaluate the distribution of their genetic resources. Such is the case of the domesticated subspecies C. argyrosperma ssp. argyrosperma, known in Mexico as calabaza pipiana, and its wild relative C. argyrosperma ssp. sororia. The main aim of this study was to use molecular data (microsatellites) to assess the levels of genetic variation and genetic differentiation within and among populations of domesticated argyrosperma across its distribution in Mexico in comparison to its wild relative, sororia, and to identify environmental suitability in previously proposed centers of domestication. We analyzed nine unlinked nuclear microsatellite loci to assess levels of diversity and distribution of genetic variation within and among populations in 440 individuals from 19 populations of cultivated landraces of argyrosperma and from six wild populations of sororia, in order to conduct a first systematic analysis of their genetic resources. We also used species distribution models (SDMs) for sororia to identify changes in this wild subspecies’ distribution from the Holocene (∼6,000 years ago) to the present, and to assess the presence of suitable environmental conditions in previously proposed domestication sites. Genetic variation was similar among subspecies (HE = 0.428 in sororia, and HE = 0.410 in argyrosperma). Nine argyrosperma populations showed significant levels of inbreeding. Both subspecies are well differentiated, and genetic differentiation (FST) among populations within each subspecies ranged from 0.152 to 0.652. Within argyrosperma we found three genetic groups (Northern Mexico, Yucatan Peninsula, including Michoacan and Veracruz, and Pacific coast plus Durango). We detected low levels of gene flow among populations at a regional scale (

The central abundance hypothesis predicts that local adaptation is a function of the distance to the centre of a species' geographic range. To test this hypothesis, we gathered genomic diversity data from 49 populations, 646 individuals and 33,464 SNPs of two wild relatives of maize, the teosintes Zea mays ssp. parviglumis and Zea. mays. ssp. mexicana. We examined the association between the distance to their climatic and geographic centroids and the enrichment of SNPs bearing signals of adaptation. We identified candidate adaptive SNPs in each population by combining neutrality tests and cline analyses. By applying linear regression models, we found that the number of candidate SNPs is positively associated with niche suitability, while genetic diversity is reduced at the limits of the geographic distribution. Our results suggest that overall, populations located at the limit of the species' niches are adapting locally. We argue that local adaptation to this limit could initiate ecological speciation processes and facilitate adaptation to global change.

International audience; It is still an open question as to whether genome size (GS) variation is shaped by natural selection. One approach to address this question is a population-level survey that assesses both the variation in GS and the relationship of GS to ecological variants. We assessed GS in Zea mays, a species that includes the cultivated crop, maize, and its closest wild relatives, the teosintes. We measured GS in five plants of each of 22 maize landraces and 21 teosinte populations from Mexico sampled from parallel altitudinal gradients. GS was significantly smaller in landraces than in teosintes, but the largest component of GS variation was among landraces and among populations. In maize, GS correlated negatively with altitude; more generally, the best GS predictors were linked to geography. By contrast, GS variation in teosintes was best explained by temperature and precipitation. Overall, our results further document the size flexibility of the Zea genome, but also point to a drastic shift in patterns of GS variation since domestication. We argue that such patterns may reflect the indirect action of selection on GS, through a multiplicity of phenotypes and life-history traits.

The application of modern biotechnology for improvement of chili pepper productivity requires an efficient in vitro plant regeneration protocol. In this study, a reliable protocol was developed for the in vitro regeneration of four types of chili, Capsicum annuum var. annuum (Jalapeno and Serrano), C. annuum var. glabriusculum/aviculare (Piquin), and C. chinense (Habanero) by direct organogenesis using three different explants (cotyledon, hypocotyls, and embryo) and three induction media. All evaluated culture media promoted the formation of adventitious shoots. When embryos or hypocotyls were used as explants, morphologically normal adventitious shoots developed, while culturing cotyledons resulted in nonelongating rosette-shaped shoots. The highest in vitro regeneration efficiency (14.6 shoots per explant) was achieved when Habanero chili hypocotyls were grown on Murashige and Skoog medium containing 1.7 μM indole-3-acetic acid and 22.2 μM N6-benzyladenine. This regeneration rate is higher than that obtained in previous reports. Regenerated plants were ready to be transferred to the greenhouse 13 wk after the explant culture. An evaluation carried out under greenhouse conditions showed differences in agronomic performance between in vitro regenerated plants and plants developed from seeds with the magnitude of the differences depending on the genotype being studied.

As an economic crop, pepper satisfies people's spicy taste and has medicinal uses worldwide. To gain a better understanding of Capsicum evolution, domestication, and specialization, we present here the genome sequence of the cultivated pepper Zunla-1 (C. annuum L.) and its wild progenitor Chiltepin (C. annuum var. glabriusculum). We estimate that the pepper genome expanded similar to 0.3 Mya (with respect to the genome of other Solanaceae) by a rapid amplification of retrotransposons elements, resulting in a genome comprised of similar to 81% repetitive sequences. Approximately 79% of 3.48-Gb scaffolds containing 34,476 protein-coding genes were anchored to chromosomes by a high-density genetic map. Comparison of cultivated and wild pepper genomes with 20 resequencing accessions revealed molecular footprints of artificial selection, providing us with a list of candidate domestication genes. We also found that dosage compensation effect of tandem duplication genes probably contributed to the pungent diversification in pepper. The Capsicum reference genome provides crucial information for the study of not only the evolution of the pepper genome but also, the Solanaceae family, and it will facilitate the establishment of more effective pepper breeding programs.

Cultivated squash (Cucurbita argyrosperma ssp. argyrosperma and C. moschata) are important in the Mexican traditional agroecosystem. They are typically cultivated within maize fields where adjacent populations of a wild, close relative, C. argyrosperma ssp. sororia, occur. Consequently, there are ample opportunities for gene flow between domesticated and free-living Cucurbita populations. We used allozymes to examine genetic variation and gene flow among these three Cucurbita taxa in the state of Jalisco in Western Mexico. Twelve polymorphic allozyme loci were used to calculate genetic diversity for 16 populations of Cucurbita. We found high levels of genetic variation: polymorphism of 0.96, mean allelic diversity of 2.08, average expected heterozygosity 0.407, and little differentiation among conspecific populations (D = 0.081; F S T = 0.087; N e m = 5.22). These findings indicate that Cucurbita possess a high pollen dispersal potential, a somewhat surprising result considering they have specialist pollinators. Unweighted pair group method with arithmetic means (UPGMA) analysis of allozymes suggests the existence of at least two distinct groups of populations, one consisting of both subspecies of C. argyrosperma and another consisting of C. moschata.

Con el objetivo de evaluar el rendimiento de grano y la estabilidad de genotipos de sorgo (Sorghum bicolor L. Moench), se sembraron 44 híbridos en 16 ambientes, durante los años 2001 y 2002 en los Estados de Tamaulipas, Nuevo León y Coahuila, México. La interacción genotipo-ambiente se estimó con el modelo de regresión de Finlay y Wilkinson y con el de efectos principales aditivos e interacciones multiplicativas (AMMI). El modelo AMMI resultó más efectivo para caracterizar el comportamiento de los genotipos que el análisis de Finlay y Wilkinson. Los cuatro primeros componentes principales (ACP) del modelo AMMI fueron significativos (P < 0.01), y explicaron 28, 19, 10 y 9 % de la suma de cuadrados de la interacción. En total, el modelo AMMI retuvo 75 % de la suma de cuadrados total, mientras que el residual sólo representó 4 %, lo que sugiere que el modelo AMMI fue efectivo para explicar el comportamiento de los genotipos. En este estudio los híbridos de sorgo más estables fueron ʻ RB-119x435ʼ , ʻ Magnumʼ , ʻ RB106x25CEAʼ , ʻ RB-118x430REAʼ , ʻ RB-119x430CEAʼ , ʻ Asgrow Coralʼ y ʻ WAC-690ʼ . No se observó asociación entre los híbridos más productivos y los mejores ambientes de producción.

La calabaza pipiana (Cucurbita argyrosperma Huber) carece de un registro formal de su diversidad morfológica en México. Con este antecedente, y la importancia de conservar y conocer los recursos genéticos vegetales de esta especie, se realizó esta investigación con el propósito de caracterizar 32 accesiones de calabaza pipiana del banco de germoplasma del Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Campo Experimental Bajío, durante el ciclo primavera verano 2006. Las plántulas de las poblaciones descritas se distribuyeron en el terreno bajo un diseño de bloques completos al azar, y el manejo agronómico se realizó conforme a las técnicas de la calabaza en el Bajío Guanajuatense de México. Durante el ciclo de cultivo y en post-cosecha se emplearon descriptores que incluyen variables cualitativas (37) y cuantitativas (13) para su caracterización. El soporte estadístico comprendió análisis de componentes principales y de conglomerados jerárquicos. Las variables cualitativas distribución del color terciario, intensidad de moteado, color de margen y testa de la semilla, y forma de borde de hoja, fueron las que mostraron mayor variación en las accesiones caracterizadas y permitieron la formación de siete grupos con las 32 accesiones. Mientras tanto, las variables cuantitativas peso de 100 semillas con testa y sin testa, peso de fruto y días a floración contribuyeron en mayor medida a la distinción de las accesiones y la formación de cinco grupos. Características de interés antropocéntrico, como peso de 100 semillas con y sin testa, mostraron la mayor diversidad del germoplasma de calabaza pipiana estudiado.

Persea americana var. drymifolia (aguacate criollo) en forma silvestre se encuentra en bosques con un precario estado de conservación. Se estudió la química foliar de poblaciones de este aguacate ubicadas en el Banco de Germoplasma del Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias en Celaya, Guanajuato, uno de los bancos más representativos para esta variedad en México. Se tomaron hojas maduras de 291 árboles correspondientes a 35 accesiones de siete estados del país. Se determinó el perfil químico foliar por cromatografía de gases acoplada a espectrometría de masas. Se cuantificó la concentración de 33 compuestos, de los cuales se identificaron 28. Los más abundantes fueron estragol y cariofileno; cada uno representó más de 10 % de la concentración total de la muestra. La variación química de los árboles clasificada con análisis de conglomerados, mostró grupos y subgrupos con 40 a 60 % de similitud. Los subgrupos químicos que contienen a la mayoría de los árboles a 40 % de similitud se diferenciaron entre sí principalmente por estragol, sabineno y β-cubebeno. Estragol, cariofileno, pcimeno, β-felandreno y chavicol-metil-éter fueron los componentes característicos en otros subgrupos a una escala de similitud de 60 %. Ningún subgrupo se asoció con una distribución geográfica particular. Se encontró mayor variación entre estados que dentro de ellos, para la mayoría de los compuestos químicos.

Existen poblaciones de teocintle (Zea spp.) que pueden ser recursos genéticos importantes para que, mediante retrocruzamiento, generar diversidad en los programas de mejoramiento genético del maíz (Zea mays L.) y para incrementar el rendimiento de grano y mejorar algunas características agronómicas. El objetivo de este estudio fue evaluar, en seis líneas élite de maíz recobradas, los cambios en rendimiento de grano y características agronómicas en función de la fuente de teocintle y el nivel de retrocruzamiento. Las líneas originales y sus retrocruzamientos se evaluaron en ensayos uniformes en Celaya, Guanajuato (1996, 1997) y Tlajomulco, Jalisco (1996), en México. Se utilizó un diseño experimental de bloques completos al azar, con un arreglo de tratamientos en parcelas subdivididas; la parcela grande se conformó con las seis líneas de maíz; como subparcelas, las seis fuentes de teocintle, y como sub-subparcelas, los cuatro niveles de retrocruzamiento. El método de retrocruzamiento fue efectivo para transferir genes de teocintle a líneas élite de maíz cultivado, los cuales pueden aprovecharse en el mejoramiento genético del maíz. La transferencia de germoplasma de teocintle incrementó el rendimiento de grano, el vigor de las plantas y la precocidad de las líneas élite de maíz. Las fuentes provenientes de Zea mays ssp. parviglumis Iltis & Doebley incrementaron más el rendimiento de grano de las líneas, mientras que las de Zea mays ssp. mexicana (Schrader) Iltis, confirieron mayor precocidad. La mejor dosis de teocintle en las líneas modificadas fue 6.25 %, porque logró conjugar mayor rendimiento de grano, mayor vigor de la planta y más precocidad; aunque los porcentajes de acame de la raíz y del tallo fueron similares a los de las líneas originales.