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En el norte de Tamaulipas, México se cultivan entre 30 mil y 100 mil hectáreas con maíz (Zea mays L.) cada año. La superficie varía debido a la incidencia de factores bióticos (plagas de insectos, hongos toxígenos) y abióticos (alta temperatura, salinidad del suelo, sequía), así como la disponibilidad de agua para riego. Por tal razón, alternativas culturales, genéticas, biológicas y químicas para el manejo del cultivo se deben evaluar constantemente para maximizar el rendimiento y la calidad de grano. En este trabajo, se evaluó el comportamiento agronómico y la interacción genotipo x ambiente de ocho híbridos de maíz sembrados en cuatro fechas de siembra y tres años de cultivo con base el análisis de la interacción de efectos principales aditivos y multiplicativos (AMMI) y el modelo genotipo, genotipo x ambiente (GGA) Biplot; así como en el análisis de sendero secuencial (ASS). El análisis AMMI para rendimiento de grano indicó diferencias significativas (p≤ 0.01) entre híbridos y ambientes de prueba. El análisis de componentes principales indicó que los dos primeros componentes (CP) contribuyeron con 76% de la varianza total (PC1= 20 y PC2= 56%); el análisis GGE biplot indicó que DK-697 fue el híbrido con mayor rendimiento y mayor estabilidad. El gráfico biplot mostró que los vectores estuvieron más alejados del centro para el año 2006A, 2006B, 2006C y 2007A (mayores interacción y capacidad de discriminación de genotipos), mientras que los vectores más cercanos fueron 2008B y 2008C (menor interacción). Entre híbridos, los más alejados del origen (menos estables) fueron H-437 y G-8222; el más cercano al origen y más estable fue DK-697. El análisis ASS detectó colinealidad moderada para todas las características evaluadas, con efectos fuertes del número de mazorcas sanas (Valor de Inflación de la Varianza o VIF= -1.41) y peso de mazorca (VIF= -1.19). Las variables con mayor asociación al rendimiento de grano fueron peso de mazorca, altura de planta, relación de altura de planta/mazorca y número de mazorcas sanas que explicaron 86% de la variación.

The aim of this study was to evaluate the genetic diversity of Jatropha curcas in Chiapas, Mexico using AFLP markers. The AFLP technique allowed us to estimate the genetic relationships in the germplasm of J. curcas and to detect a high level of polymorphism. Analysis of the frequency and distribution of polymorphic fragments allowed us to detect the highest number of rare fragments in one single accession (e.g., accession number 1 from Tuxtla Chico). Besides being an accession that exhibits traits of agronomic importance (such as the presence of 100% pistillated flowers), this diversity of rare fragments may allow for development of markers for identification of this accession and/or development of markers linked to this trait. In addition, very divergent collections have been detected from regions where high average oil content and other characters associated with productivity have been found. Moreover, the analysis of genetic relationships, Analysis of Molecular Variance (AMOVA) and the diversity index (DI = 60%) confirm a broad gene pool in the J. curcas germplasm from Chiapas, Mexico. The high diversity found within the accessions showed non-random mating between groups and/or regions of accessions of J. curcas, which complicates the selection of representative collections.

Sampling of agricultural soils from the Mexican northeastern region was performed to detect Trichoderma spp., genetically characterize it, and assess its potential use as a biologic control agent against Macrophomina phaseolina. M. phaseolina is a phytopathogen that attacks over 500 species of cultivated plants and causes heavy losses in the regional sorghum crop. Sampling was performed immediately after sorghum or corn harvest in an area that was approximately 170 km from the Mexico-USA border. Sixteen isolates were obtained in total. Using colony morphology and sequencing the internal transcribed spacers (ITS) 1 and 4 of 18S rDNA, 14 strains were identified as Trichoderma harzianum, T. koningiopsis and T. virens. Subsequently, their antagonistic activity against M. phaseolina was evaluated in vitro, and 11 isolates showed antagonism by competition and stopped M. phaseolina growth. In 4 of these isolates, the antibiosis phenomenon was observed through the formation of an intermediate band without growth between colonies. One strain, HTE808, was identified as Trichoderma koningiopsis and grew rapidly; when it came into contact with the M. phaseolina colony, it continued to grow and sporulated until it covered the entire petri dish. Microscopic examination confirmed that it has a high level of hyperparasitism and is thus considered to have high potential for use in the control of this phytopathogen.

Seed germination involves complex processes where plant growth-promoting substances are released into the growth medium, mainly involving pathways that start in tryptophan (TRP) and end in the formation of indole-3-acetic acid (IAA). Among them, four are known as TRP-dependent and a fifth as TRP-independent. Some compounds were observed during germination of bean seeds that involved at least three IAA synthesis pathways and that kynurenine (KYN) is the first detected metabolite which is found in greater concentration. It was followed by tryptamine (TAM), TRP and IAA. The results of Trichoderma harzianum inoculation in greenhouse tests showed variability in Flor de Mayo beans seedlings in response to physiological level and production parameters. The effect of Trichoderma in Flor de Mayo common bean showed that strain 802 had a significant effect on the development of the height of bean seedlings, and that the 812 strain showed significant effect on the development of root bean seedlings. Increased growth of stem and root caused byTrichoderma strains in Flor de Mayo beans involves beneficial effects of inoculation on plant growth and development parameters and can be taken as they were a measure of survival and development of seedlings. Key words: Biofertilizers, indole-3-acetamide, tryptophan,indole-3- acetic acid, kynurenine.

A core collection of the common bean (Phaseolus vulgaris L.), representing genetic diversity in the entire Mexican holding, is kept at the INIFAP (Instituto Nacional de Investigaciones Forestales, Agricolas y Pecuarias, Mexico) Germplasm Bank. After evaluation, the genetic structure of this collection (200 accessions) was compared with that of landraces from the states of Oaxaca, Chiapas and Veracruz (10 genotypes from each), as well as a further 10 cultivars, by means of four amplified fragment length polymorphisms (AFLP) +3/+3 primer combinations and seven simple sequence repeats (SSR) loci, in order to define genetic diversity, variability and mutual relationships. Data underwent cluster (UPGMA) and molecular variance (AMOVA) analyses. AFLP analysis produced 530 bands (88.5% polymorphic) while SSR primers amplified 174 alleles, all polymorphic (8.2 alleles per locus). AFLP indicated that the highest genetic diversity was to be found in ten commercial-seed classes from two major groups of accessions from Central Mexico and Chiapas, which seems to be an important center of diversity in the south. A third group included genotypes from Nueva Granada, Mesoamerica, Jalisco and Durango races. Here, SSR analysis indicated a reduced number of shared haplotypes among accessions, whereas the highest genetic components of AMOVA variation were found within accessions. Genetic diversity observed in the common-bean core collection represents an important sample of the total Phaseolus genetic variability at the main Germplasm Bank of INIFAP. Molecular marker strategies could contribute to a better understanding of the genetic structure of the core collection as well as to its improvement and validation.

Mexico imports large quantities of soybeans in order to satisfy its internal demand for vegetable oil and protein for human and animal consumption. A new soybean cultivar was developed for the southern region of the state of Tamaulipas, Mexico and other similar tropical areas. Huasteca 300, the new cultivar is resistant to the most important diseases and pests present in the region and shows low sensitivity to short photoperiod. Average from multiple trials, the yield of Huasteca 300 was 23% higher than that of cultivar Huasteca 200 with similar oil and protein content and quality. Huasteca 300 is adapted to tropical lowland regions with humid and subhumid climate with annual rainfall average from 800 to 1 000 mm, and average temperatura from 25 to 27 °C.

El análisis de la diversidad genética del germoplasma de soya es importante para la identifi cación de los genotipos mejor adaptados a las condiciones agroclimáticas de una región. En esta investigación se caracterizaron 108 genotipos de soya: nueve variedades introducidas de soya, cinco mexicanas y 94 líneas experimentales con 18 parámetros morfoagronómicos y marcadores moleculares AFLP con el objetivo de determinar las relaciones genéticas y la diversidad genética en el germoplasma. En 2004 se evaluaron 82 genotipos por sus características morfoagronómicas en el Campo Experimental Sur de Tamaulipas. El color de las vainas y de la pubescencia de las vainas, número de vainas con un grano y con dos granos, y peso de la semilla fueron las variables con mayor valor descriptivo de acuerdo con el análisis de componentes principales. Con base en estas características, el germoplasma de soya se dividió en tres grupos. En el grupo I se incluyó el germoplasma con vainas y pubescencia de vainas grises, valores intermedios en vainas con una y dos semillas, y bajo peso de semilla y rendimiento. En el grupo II, el que mostró color de la pubescencia y de vaina café y alto rendimiento, y en el grupo III el que presentó valores intermedios en todas las características mencionadas. El dendrograma obtenido con datos AFLP presentó tres grupos principales de genotipos, con disimilitud genética de 7.25 a 8.25%. El grupo I incluyó líneas derivadas de los progenitores Júpiter y Santa Rosa, así como variedades mexicanas y extranjeras; el grupo II incluyó variedades introducidas, líneas experimentales derivadas de Júpiter y variedades mexicanas; el grupo III sólo incluyó líneas experimentales. Las variedades introducidas Júpiter y Santa Rosa generaron 38 y 37% de la variabilidad genética total, respectivamente. El análisis de componentes principales de datos AFLP no separó las variedades introducidas de las mexicanas, aunque las líneas experimentales derivadas de Santa Rosa y Júpiter fueron diferentes a estos progenitores. El análisis de varianza molecular indicó reducida diversidad genética en el germoplasma de soya. Los resultados indicaron que no existe estrecha asociación entre los patrones de variabilidad genética y morfoagronómica en soya, y que es necesario ampliar la base genética del germoplasma de soya en México