Pedro Osuna-Ávila

Alginate modifies the physiological impact of CeO2 nanoparticles in corn seedlings cultivated in soil.

Alginates are naturally occurring components of organic matter in natural soil whose effects on nanoparticle (NP) toxicity to plants is not well understood. In the present study, corn plants were grown for one month in soil spiked with 400 mg/kg CeO2 NPs with various alginate concentrations. After one month of growth in the NPs impacted soil, plants were harvested and analyzed for Ce and mineral element concentrations. Chlorophyll concentration and heat shock protein 70, used as biomarkers for oxidative stress, were also evaluated. Results showed that, compared to CeO2 NPs treatment, alginate at 10, 50, and 100 mg/kg increased Ce concentration in roots by approximately 46%, 38%, and 29% and by 115%, 45%, and 56% in shoots, respectively. CeO2 NPs without alginate increased Mn accumulation in roots by 34% compared to control. CeO2 NPs with low and medium alginate increased Mn by ca. 92% respect to NPs without alginate and by ca. 155% respect to control. CeO2 NPs without/with alginate significantly increased accumulation of Fe and Al in roots. In addition, alginate at 50 mg/kg increased Zn accumulation in roots by 52% compared to control. In shoots, K increased at all NP treatments but the accumulation of other elements was not affected. Alginate enlarged the impact of CeO2 NPs to corn plants by reducing chlorophyll a content and triggering overexpression of heat shock protein 70.

An initial assessment of genetic diversity for Phytophthora capsici in northern and central Mexico

Phytophthora capsici causes significant damage to vegetable production in Mexico, but very little is known about the population structure or how populations survive and spread. The objective of the present study was to evaluate the genetic diversity of P. capsici isolates recovered from 1998–2014 in central and northern Mexico. Isolates (n = 81) were genotyped for 33 polymorphic single nucleotide polymorphism (SNP) loci using a targeted sequencing approach. There were a total of 72 unique genotypes and both the A1 and A2 mating types were common in both regions. Genetic analyses suggest clonal reproduction may play a more prominent role in the north, but the large proportion of unique genotypes and the finding of both mating types throughout both regions suggests outcrossing and sexual recombination likely play an important role in the overall epidemiology. Further studies with finer scale sampling at single locations over multiple years will be valuable.

Mango nurseries as sources of Fusarium mexicanum, cause of mango malformation disease in central western Mexico

Malformation is the most important disease of mango in Mexico. It affects floral and vegetative shoots, and reduces fruit production. Although several species of Fusarium cause the disease worldwide, F. mexicanum is most important in Mexico. To better understand epidemiology of disease in Mexico, we studied mango nurseries as a source of infected planting material. In 2011, 2012 and 2014, 20 mango nurseries in the states of Colima (1 nursery), Jalisco (1 nursery), Guerrero (6 nurseries) and Michoacan (12 nurseries) were examined for floral and vegetative symptoms of the disease. Although malformed plants were not observed in Colima, Guerrero and Jalisco, malformed mango seedlings and grafted plants were observed in 10 commercial nurseries in Michoacan in 2011 and 2012. Thirty-three isolates from a total of 197 symptomatic plants were identified as F. mexicanum, based on morphological and genetic criteria. Analyses of partial sequences of the EF-1α and β-tubulin genes and mating type indicated that isolates of F. mexicanum from mango nurseries are mostly a single clonal population, identical to F. mexicanum isolates previously described from mango orchards in Michoacan. Thus, mango nurseries in Michoacan could be a significant source of inoculum when new mango orchards are established in the state. Efforts should be made to produce and utilize pathogen-free planting material during orchard establishment.

Traditional and Molecular Studies of the Plant Pathogen Phytophthora capsici: A Review

Phytophthora capsici is responsible for large worldwide economic losses and is considered one of the limiting factors in the production of many crops [1]. More than 50 vegetable species have been identified as hosts of this plant pathogen [1,2]. Recently, two leguminous species, Phaseolus vulgaris [3], and Phaseolus lunatus [4], have been identified as hosts of this oomycete. Losses of up to 100% of the crop con occur in fields due to the incidence of this pathogen [5].