Guava leaf (Psidium guajava L.) extracts are used in both traditional medicine and the pharmaceutical industry. The antioxidant compounds in P. guajava leaves can have positive effects including anti-inflammatory, anti-hyperglycemic, hepatoprotective, analgesic, anti-cancer effects, as well as protecting against cardiovascular diseases. In the present study, phenolic compounds and in vitro antioxidant capacity were measured in extracts obtained with polar and non-polar solvents from leaves of two varieties of guava, Calvillo Siglo XXI and Hidrozac. The quantity of total phenolics and total flavonoids were expressed as equivalents of gallic acid and quercetin, respectively. Hydroxyl radical, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and Oxygen Radical Absorbance Capacity using fluorescein (ORAC-FL) in vitro tests were used to assess the radical scavenging abilities of the extracts. The total phenolics were higher in the aqueous fraction of the variety Calvillo Siglo XXI, while in the Hidrozac variety total phenolics were higher in the acetone and chloroform fractions. Total flavonoids were higher in all fractions in the variety Calvillo Siglo XXI. Total phenolics showed a highly positive correlation for ORAC-FL, and a moderately positive correlation with hydroxyl radicals. Finally, total flavonoids showed a slightly positive correlation for ORAC-FL and hydroxyl radicals. Both varieties of guava leaf extract showed excellent antioxidant properties.

Fifty morphological characteristics, fruit production over 3 years (from 1999 to 2002) and the amplified fragment length polymorphism (AFLP) technique were used to analyse a set of 48 guava (Psidium guajavaL.) accessions cultivated in Mexico, in order to characterize their genetic relationships. Germplasm was collected from the Calvillo-Cañones region and planted in Huanusco, Mexico. The study included twoP. cattleianum(Sabine) and twoP. friedrichsthalianum(Berg-Niedenzu) accessions from Costa Rica as outgroups. Principal component analysis (PCA) explained less than 30% of total variation and 14 characteristics from trees (1), leaves (2) and fruits (11) were the most informative. PCA analysis separated the germplasm into three major groups of accessions based on fruit size and weight, stem diameter and leaf size. Significant differences in fruit yield were detected among accessions and years, whereP.guajavaproduced 36 kg/year/tree of fresh fruit whileP. cattleianumandP. friedrichsthalianumshowed fruit yield lower than 7 kg/year/tree. The fruit yield broad sense heritability was 0.25. The AFLP analysis produced two clusters ofPsidiumaccessions, the first includedP. cattleianumandP. friedrichsthalianum, and the secondP. guajavaaccessions. This is the first report about the use of AFLP marker methodology for the genetic characterization of Mexican native guava germplasm and the results based on phenotypic and productive characteristics suggest that germplasm was selected from open pollinated trees.

Classification and regression trees (CARTs) for data analysis, an hourly weather dataset, and a 3 year field incidence and severity dataset of winter wheat rust were integrated to forecast pathogens’ presence/absence. The field dataset of incidence and severity was collected for three production cycles. Measured records of 88 Automatic Meteorological Stations and the indirect weather dataset generated in the Weather Research and Forecasting environment interpolated to each Automatic Meteorological Station location were analysed in the Python ecosystem. The focal point of the analysis was the severity of the disease. The analysis of direct weather data revealed the association of leaf rust severity with a night temperature of <14.25°C and global radiation of <521.67 W·m–2, while the estimated dataset showed that its severity is better explained by the dew point temperature of <13.7°C and a mean temperature of <19.06°C. The direct dataset also indicated that stripe rust severity was associated with relative humidity of <88.73%, global radiation of <597.39 W·m–2 and dew point temperature of <16.09°C, whereas the estimated data revealed that pathogen severity is better explained by a model composed of a dew point temperature of <14.6°C, night temperature of <20.4°C and a maximum temperature of <27.9°C. The severity and intensity analysis indicated the pathogen's preference for non‐dry ambient conditions and the preference of stripe rust pathogen for humid and warmer temperatures than leaf rust. The weather thresholds of both pathogens, and CART analysis, unveiled that winter wheat rust can be forecasted. This constitutes the foundation of a more efficient extension programme based on the internet of things.

The influence of osmotic potential (Ψs) on in vitro growth and morphology of four isolates of Macrophomina phaseolina was studied using potato‐glucose‐agar adjusted to different osmotic potentials with KCl, NaCl and sucrose. The effect of NaCl on M. phaseolina pathogenicity in common bean was determined and then related to the pathogenicity of each isolate on seeds of 12 differential common bean cultivars. The three sources of Ψs reduced M. phaseolina growth under in vitro conditions, whereby NaCl caused the highest negative effects. The high solute concentrations reduced the synthesis of mycelial pigments and the size and shape of microsclerotia. Pathogenicity of M. phaseolina in common bean seeds was reduced by high concentrations of NaCl but no relationship was found between the tolerance to high Ψs concentrations under in vitro conditions and M. phaseolina pathogenicity in common bean seeds.

Para la obtención de altos rendimientos en frijol de temporal es necesario ajustar el manejo agronómico del cultivo al medio ambiente. La presente investigación se realizó con el objetivo de evaluar la respuesta de rendimiento de la variedad Pinto Saltillo, con hábito de crecimiento indeterminado postrado, a diferentes densidades de plantas (90 mil, 145 mil y 260 mil plantas ha-1) y distanciamiento entre surcos (0.76, 0.40 y 0.20 m). Los experimentos se realizaron en Sandovales y Pabellón, Ags. durante primavera-verano en 2010 y 2011. Se estudiaron tres métodos de siembra (una, hilera en surcos de 0.76 m, y tres y seis hileras en surcos estrechos en camas a 1.52 m). Se registraron datos sobre rendimiento y sus componentes. En ambos años, los análisis de varianza para el rendimiento y sus componentes mostraron diferencias significativas (p< 0.01) entre tratamientos. Los máximos rendimientos se obtuvieron con la siembra a tres y seis hileras, en densidades de 145 mil y 260 mil plantas ha-1, respectivamente. El rendimiento aumentó 28.6% y 41% al reducir la distancia entre surcos, del distanciamiento tradicional de 0.76 m, a 0.40 y 0.20 m, respectivamente. Se concluye que la variedad de frijol estudiada incrementa su rendimiento en alta densidad de plantas bajo condiciones de temporal en la región semiárida de México.