This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000 Azospirilla are free-living rhizobacteria that are able to promote plant growth and increase yields in many crops of agronomic importance. It is assumed that the bacteria affect plant growth mainly by the production of plant growth promoting substances, which leads to an improvement in root development and an increase in the rate of water and mineral uptake. In the present review, we discuss the physiological responses of the plant roots to inoculation with Azospirillum , and report on field and greenhouse experiments carried out with these bacteria during 1994–2001 in Belgium, Uruguay, Mexico and Israel.

The Sechium edule Perla Negra cultivar is a recently-obtained biological material whose progenitors are S. edule var. nigrum minor and S. edule var. amarus silvestrys, the latter of which has been reported to have antiproliferative activity against the HeLa P-388 and L-929 cancer cell lines. The present study aimed to determine if the methanolic extract of the fruit of the Perla Negra cultivar had the same biological activity. The methanolic extract was phytochemically characterized by thin layer chromatography (TLC) and column chromatography (CC), identifying the terpenes and flavonoids. The compounds identified via high performance liquid chromatography (HPLC) were Cucurbitacins B, D, E, and I for the terpene fractions, and Rutin, Phlorizidin, Myricetin, Quercetin, Naringenin, Phloretin, Apigenin, and Galangin for the flavonoid fractions). Biological activity was evaluated with different concentrations of the methanolic extract in the HeLa cell line and normal lymphocytes. The methanolic extract inhibited the proliferation of HeLa cells (IC₅₀ 1.85 µg·mL⁻¹), but the lymphocytes were affected by the extract (IC₅₀ 30.04 µg·mL⁻¹). Some fractions, and the pool of all of them, showed inhibition higher than 80% at a concentration of 2.11 µg·mL⁻¹. Therefore, the biological effect shown by the methanolic extract of the Perla Negra has some specificity in inhibiting tumor cells and not normal cells; an unusual feature among molecules investigated as potential biomedical agents.

The African citrus psyllid, Trioza erytreae (Del Guercio) (Hemiptera: Triozidae), is a vector of Candidatus Liberibacter africanus (CLaf), a pathogen that causes huanglongbing (HLB) in Africa. Trioza erytreae has invaded areas of Asia and Europe and has threatened citrus production due to its biological habits and the transmission of CLaf. Mexico is a country where citrus production has a vital role from the economic and social point of view. Therefore, ecological niche modeling (ENM) was used to determine if Mexico has the environmental availability that will allow T. erytreae invasion. We analyzed whether or not the distribution of Casimiroa edulis La Llave (Rutaceae) in the country could be a factor that enables the dispersal of T. eytreae. The environmental connectivity between five points of entry into the country (two ports and three airports) was explored to determine possible routes of dispersal of T. erytrae. The results showed that Mexico has wide availability for the invasion of the African citrus psyllid, which coincides with essential citrus areas of the country and with the distribution of C. edulis. Of the entry points studied, the Port of Veracruz showed nearby areas with environmental connectivity. Preventive monitoring measures for T. erytreae in Mexico should focus on Veracruz state because it has an entry point, ideal environmental availability, citrus areas, and specimens of C. edulis.

Los cultivos absorben en promedio de 20 a 40% del fertilizante aplicado, el porcentaje restante se pierde del sistema agrícola por diversos mecanismos, ocasionando cuantiosas pérdidas económicas y contaminación ambiental. Entre los beneficios del uso de microorganismos en la agricultura está su capacidad para mejorar la asimilación de nutrimentos. Se realizó un experimento en campo cuyo objetivo fue evaluar el efecto de la inoculación de biofertilizantes bacterianos y fúngicos sobre la eficiencia de asimilación del fertilizante nitrogenado en el cultivo de trigo. El diseño experimental fue de bloques completos al azar con cuatro repeticiones y nueve tratamientos de biofertilización empleando la técnica de dilución isotópica de 15N para determinar el N en la planta derivado del fertilizante y el porcentaje de utilización del fertilizante N. La fertilización química produjo los mayores rendimientos de grano y asegura su calidad. La inoculación del trigo con HVA incrementó significativamente el rendimiento de grano hasta en 1 291 kg ha-1, la cantidad de N en la planta proveniente del fertilizante hasta en 15 kg y la eficiencia de utilización del fertilizante nitrogenado hasta en 11% en comparación con el testigo sin inocular. Hubo diferencias significativas en la interacción planta-microorganismo en la producción de biomasa y asimilación de N.