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Hydrogen peroxide is an important signal molecule in plant defense against biotic and abiotic stress. Pepper golden mosaic virus (PepGMV) is a whitefly-transmitted geminivirus causing significant yield and quality losses in pepper and other horticultural crops in Mexico. Several pesticides have been used trying to control whiteflies and thus, PepGMV disease in host crops. The present work examined the effect of exogenous application of hydrogen peroxide (H2O2) on inducing resistance to PepGMV infection in pepper plants. Experiments were carried out under greenhouse conditions aiming to evaluate phenotypical, biochemical and molecular features in these pepper plants. Hydrogen peroxide at 6, 14 and 18 mM induced tolerance to PepGMV either by absence of symptoms as well as by attenuating and/or delaying them. The protection observed was directly dependent on the concentration of H2O2 sprayed on plants. Moreover, PepGMV DNA levels were inversely proportional to the protection level. Enzymatic and gene expression profiles related with plant defense were induced in protected, in comparison to susceptible control plants. Interestingly, the levels of some phenolic compounds were also associated with plant protection. Taking together, these results suggested that exogenous foliar applications of H2O2 protect pepper plants against PepGMV infection inducing the plant host defense arsenal.

Chili pepper (Capsicum annuumL.) production is affected by wilt and root rot, the most devastating disease caused by the pathogen complex of oomycetePhytophthora capsiciLeon and the fungiFusarium oxysporumSchlecht andRhizoctonia solaniKühn, infecting roots, stems, leaves, and fruits. Fungicides are currently inefficient against this disease and have a high environmental impact. The use of elicitors is a sustainable alternative for inducing resistance to wilting and root rot. DNA fragments of an organism’s own origin (conspecific or self-DNA) have shown the ability to inhibit growth and activate defense mechanisms in some plant species. In this investigation, the effect of the fragmented DNA mixture ofPhytophthora capsiciL.,Fusarium oxysporumS., andRhizoctonia solaniK. on the protection against wilt and root rot ofCapsicum annuumL. plants was evaluated. Changes in plant performance, phenolics, and flavonoids contents, as well as gene expression involved in the production of defense metabolites after the fragmented and unfragmented DNA mixture in three concentrations (20, 60, and 100 μg mL–1) in chili peppers, were studied. The results obtained showed a decrease in plant height in 60 and 100 μg mL–1concentrations in absence of pathogens. Moreover, the treatment with fragmented DNA 100 μg mL–1showed significant increase in the content of phenolic compounds and total flavonoids as well as gene expression associated to plant defense in comparison with control plants. Interestingly, foliar application of DNA fragments of the pathogen complex to a concentration of 100 μg mL–1caused a 40% decrease in the mortality of infected plants with the pathogens at 30 days post-inoculation compared with control plants inoculated with the pathogen complex but not sprayed with DNA fragments. These results suggested a perspective for application of fragmented DNA of these pathogens at the agricultural level in crop protection strategies to cope with wilt and root rot inCapsicum.

In the recent years, there has been a great necessity to increase crop productivity of staple crops in order to provide the food that is needed by a growing world population. Nowadays, not only crop yield is important, but also the ability to keep and, if possible, increase their bioactive compounds, the content of which is beneficial effects on human health, which have been widely reported. Nevertheless, various abiotic stresses affect crop productivity. Especially if the stress is prolonged, plant growth and productivity are severely diminished. In this sense, water scarcity constitutes a crucial constraint for agricultural productivity. Drought is one of the most serious abiotic stresses that restricts plant growth, development and productivity, and affects their physiological and biochemical mechanisms. However, there is evidence that a controlled water deficit (WD) may improve fruit quality through higher concentration of flavor compounds and phytochemicals. This review presents information about how a controlled WD may be used as an abiotic stress factor of crop phytochemicals, thereby improving health benefits for all consumers.

Methanolic extracts of Acaciella angustissima pods (MEA) were analyzed in order to determine some biological activities such as antioxidant, antimutagenic and antimicrobial properties by 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azinobis-3 ethylbenzothiazoline-6-sulfonic acid (ABTS), ferric reducing antioxidant power (FRAP), Kado microsuspension assay and in vitro antimicrobial assays, respectively. Moreover, a transcriptomic study of Timbe grown in greenhouse conditions was also performed using subtractive suppression hybridization methodology (SSH). MEA presented significant antioxidant activity by DPPH, ABTS and FRAP methods. The maximum concentration of MEA inhibited 80.33% and 77.39% of mutagenicity induced either by 4-nitro-O-phenylenediamine or sodium azide, respectively. MEA presented fungistatic activity against Fusarium oxysporum, Rhizoctonia solani and Phytophtora capsici. Moreover, a good in vivo protection against P. capsici was obtained in comparison to a commercial antifungal used toward this pathogen. Transcriptomic study displayed the expression of genes that have biological importance, such as protein TIC55, GATA transcription factor, maturase-like protein, and NAC domain protein. NAC domain protein might have some biotechnological or industrial application, because, NAC transcription factor plays an important role in responses to biotic and abiotic stress from some plants. Results suggest that Timbe might be useful in pharmaceutical, food and agro-industrial sectors.

Hydrogen peroxide (H2O2) is an important ROS molecule (Reactive oxygen species) that serves as a signal of oxidative stress and activation of signaling cascades as a result of the early response of the plant to biotic stress. This response can also be generated with the application of elicitors, stable molecules that induce the activation of transduction cascades and hormonal pathways, which trigger induced resistance to environmental stress. In this work, we evaluated the endogenous H2O2 production caused by salicylic acid (SA), chitosan (QN), and H2O2 elicitors in Capsicum annuum L. Hydrogen peroxide production after elicitation, catalase (CAT) and phenylalanine ammonia lyase (PAL) activities, as well as gene expression analysis of cat1, pal, and pathogenesis-related protein 1 (pr1) were determined. Our results displayed that 6.7 and 10 mM SA concentrations, and, 14 and 18 mM H2O2 concentrations, induced an endogenous H2O2 and gene expression. QN treatments induced the same responses in lesser proportion than the other two elicitors. Endogenous H2O2 production monitored during several days, showed results that could be an indicator for determining application opportunity uses in agriculture for maintaining plant alert systems against a stress.

Common bean (Phaseolus vulgaris L.) is the most important grain legume for direct human consumption; however, bean production is affected by several diseases such as Rhizoctonia root rot. Few bean cultivars have been identified that effectively resist the attack of this fungus. Herein, we used the P. vulgaris Pv-2094 landrace, which is less susceptible to Rhizoctonia root rot, for the construction of a suppressive subtractive hybridization cDNA library in order to isolate plant defense-related genes. Total RNAs obtained after 8 and 16 h from inoculated and non-inoculated roots with R. solani Kühn, were used as the source of the "tester" and the "driver" samples, respectively. A total of 136 unigenes were obtained and classified into 12 functional categories. Six unigenes were selected to analyze for differential expression by qRT-PCR, including a receptor-like kinase (PvRK20-1), an acid phosphatase associated to defense (PA), a pathogenesis related protein (PR1), an ethylene responsive factor (ERF), a polygalacturonase inhibitor protein (PGIP), and an alpha-dioxygenase (α-DOX). These genes were found to be differentially expressed in a time-dependent manner in bean roots during the interaction with R. solani. Data generated from this study will contribute to the understanding of the molecular mechanisms associated with plant defense against root rot in common bean.

An organogenic regeneration protocol in common bean (Phaseolus vulgaris L.) using embryo-axes derived from mature seeds from commercial cultivars Flor de Junio Marcela (FJM) and Flor de Mayo Anita (FMA) is reported. Embryonic axes were excised from surface sterilized seeds and established in MS medium containing different benzylaminopurine (BAP) and adenine (A) concentrations. Efficient regeneration was achieved when 5 or 10 mg/l BAP was added to the medium regardless of the A concentration, inducing the formation of differentiated cells as bud clusters. These clusters mainly formed at the internodal segment of the embryo for FJM and at the apical segment for FMA embryonic axes. Regeneration efficiency varied considerably between the two cultivars where FJM showed higher bud cluster formation (90%) and full plant regeneration (83%), whereas FMA showed 18% bud cluster formation, and 50% full plant regeneration. The division and transfer of FMA and FJM bud clusters to induction media every 15 days resulted in the formation of three to five new bud clusters each transfer. A single 5 mm cluster formed up to 15 shoots from which 1–2 plants were regenerated. Genetic variation analysis by amplified fragment length polymorphism (AFLP) showed no variation between regenerated plants.

The pathotypes of 17 isolates of Colletotrichum lindemuthianum from the central region of Mexico were characterized to determine the genetic relationship among isolates from this region and other regions of Mexico, and to evaluate the resistance present in the elite germ plasm collection of Phaseolus vulgaris at INIFAP. Eight pathotypes were identified, including pathotype 292, which is reported for the first time in Mexico. The lack of isolates infecting cultivar TU carrying the Co-5 resistance gene suggests that this cultivar is a useful source of resistance. Six pathotypes produced susceptible reactions on only differential cultivars of Middle American origin, one pathotype on a single cultivar of Andean origin, and one pathotype on cultivars of both Middle American and Andean origin. Comparison of amplified fragment length polymorphism (AFLP) genotypes of 21 isolates confirmed suggestions that populations of C. lindemuthianum are comprised of asexually reproducing clonal lineages. Analysis of five different pathotypes of C. lindemuthianum on 21 elite genotypes of P. vulgaris identified four genotypes from different races of P. vulgaris resistant to all five pathotypes. This information will allow breeders and farmers to select the resistant genotypes most suited to their needs.

Macrophomina phaseolina infects a wide range of plant species. In the case of Phaseolus vulgaris (the common bean), the fungus causes charcoal rot which can lead to severe losses especially under arid conditions. In order to combat the disease, it is necessary to have information on the population structure of the pathogen in terms of pathogenesis on different species which may be grown simultaneously or successively within a region. Previous reports have demonstrated the heterogeneity of the pathogen both in terms of morphological characteristics and molecular genotype; however no systematic attempt has been made to compare pathogenesis of different isolates in relation to genotype, species of origin or geographical location. With this aim 84 isolates of M. phaseolina from different plant species in different geographical regions of Mexico were analysed by inoculation on a set of P. vulgaris cultivars differing in reaction to the fungus and by determination of their amplified fragment length polymorphism (AFLP) genotype. Forty three distinct pathotypes were identified, only two of which were found in more than one species. All 84 isolates had distinct AFLP genotypes and cluster analysis showed a tendency of the isolates to form groups related to geographical origin or species of origin.

Chili pepper blight observed on pepper farms from north Aguascalientes was monitored for the presence ofPhytophthora capsiciduring 2008–2010. Initially, ELISA tests were directed to plant samples from greenhouses and rustic nurseries, showing an 86% of positive samples. Later, samples of wilted plants from the farms during the first survey were tested with ELISA. The subsequent survey on soil samples included mycelia isolation and PCR amplification of a 560 bp fragment of ITS-specific DNA sequence ofP. capsici. Data was analyzed according to four geographical areas defined by coordinates to ease the dispersal assessment. In general, one-third of the samples from surveyed fields containedP. capsici, inferring that this may be the pathogen responsible of the observed wilt. Nevertheless, only five sites from a total of 92 were consistently negative toP. capsici. The presence of this pathogen was detected through ELISA and confirmed through PCR. The other two-thirds of the negative samples may be attributable toFusariumandRhizoctonia, both isolated instead ofPhytophthorain these areas. Due to these striking results, this information would be of interest for local plant protection committees and farmers to avoid further dispersal of pathogens to new lands.

Trypsin inhibitors (TI), tannins, and lectins appear to have a role in preventing chronic diseases in humans. The genetic variability of these traits in common bean needs to be ascertained in order to increase levels through breeding. The variability of TI, tannin, and lectins was determined in five bean cultivars grown at five locations in Mexico. TI and tannins contents in colored beans that belong to the Jalisco race were higher (11.1-11.9 trypsin units inhibited (TUI)/mg and 29.0-38.1 mg catechin equivalent (CE)/g, respectively) than cultivars of the Durango race (7.9-8.3 TUI/mg and 16.8-19.9 CE/mg, respectively). Bayo Victoria, a Durango race cultivar, had three times more lectins than levels reported for soybean. Cultivar influenced TI and tannins contents (p < 0.001), whereas site affected lectins (p < 0.001). An increase in levels of TI and tannins could be enhanced through breeding.