Bacillus is one of the main rhizobacteria to have been used as a study model for understanding many processes. However, their impact on photosynthetic metabolism has been poorly studied. The aim of this study was to evaluate the physiological parameters of pepper (Capsicum chinense Jacq.) plants inoculated with Bacillus spp. strains. Pepper seeds were inoculated with Bacillus cereus (K46 strain) and Bacillus spp. (M9 strain; a mixture of B. subtilis and B. amyloliquefaciens), chlorophyll fluorescence and gas exchange were evaluated. The ANOVA (P ≤ 0.05) showed that the maximum photochemical quantum yield of photosystem II (PSII) (F v /F m ) in plants inoculated with the M9 strain (0.784) increased with respect to other treatments (K46: 0.744 and Control: 0.739). Inoculated plants with M9 and K46 strains exhibited an increase of both photochemical quenching (qP) (by 27% and 24%, respectively) and CO 2 assimilation rate (photosynthesis) (by 20% and 16%, respectively), when compared with non-inoculated plants. Furthermore, plants inoculated with M9 and K46 showed decreased transpiration (61% and 57%, respectively) with respect to controls. Likewise, both electron transport rate of PSII (ETR) and PSII operating efficiency (Φ PSII ) increased in inoculated plants. However, only plants inoculated with the M9 strain showed enhancements on all growth characteristics. Our results therefore show that inoculating plants with M9 strain positively influenced the performance of the photosynthetic mechanism in pepper plants to increase chlorophyll fluorescence and gas exchange parameters. Promotion of photosynthetic capacity in pepper was due to increased ETR in the thylakoid membranes, which was promoted by the bacteria. M9 strain could even be used in sustainable agriculture programs.

The effect of two temperature regimes (daytime, 29 Ϯ 2ЊC, night-time, 24 Ϯ 3ЊC; and daytime, 23 Ϯ 1ЊC, night-time, 18 Ϯ 2ЊC) on the symptoms caused by tomato spotted wilt virus (TSWV), and the accumulation of TSWV virions, was compared in Datura stramonium, Nicotiana tabacum cv. White Burley and Physalis ixocarpa. Tobacco plants were more severely affected by TSWV at the high temperature regime, but the incidence (percent of plants with symptoms) was 100% for both regimes. In P. ixocarpa and D. stramonium the higher temperature caused an increase in both incidence and rate of development of symptoms. At high temperature, all three species showed both local and systemic symptoms; however, at low temperature only P. ixocarpa consistently developed systemic symptoms. In general, virus accumulation in the inoculated leaves (presumably the combined effect of virus replication and local movement) of all plants was higher at the lower temperature. Long distance movement in tobacco, leading to virion accumulation in other plant organs, was favoured by high temperature; but there was relatively little effect in P. ixocarpa and D. stramonium.

ABSTRACT. DNA isolation from some fungal organisms of agronomic importance is difficult because they have cell walls or capsules that are relatively unsusceptible to lysis. We have developed a fast DNA isolation protocol for Fusarium oxysporum, which causes fusarium wilt disease in more than 100 plant species, and for Pyrenochaeta terrestris, which causes pink root in onions. This protocol was based on the sodium dodecyl sulfate/ phe nol method, without β-mercaptoethanol and without maceration in liquid nitrogen; it uses phenol/chloroform extraction to remove proteins and co-precipitated polysaccharides. The A 260/280 absorbance ratios of isolated DNA were around 1.9, suggesting that the DNA fraction was pure and may be used for further analysis. Additionally, the A 260/230 values were higher than 1.8, suggesting negligible contamination by polysaccharides. The DNA isolated by this protocol is of sufficient quality for molecular applications; this tech nique could be applied to other organisms that have similar substances that hinder DNA extraction.

Tomato crops are among the most important vegetables cultivated worldwide, Mexico being one of the major producing countries. Large quantity of this crop is found in states belonging to the arid northwest of the country; the adaptation of these regions to vegetable production has been significant with the support of agricultural technology due to the use of protective structures for plants, such as greenhouses and shaded mesh. However, pests and diseases are a major biotic factor that significantly reduces production. There are more than 200 diseases associated with the nightshade of various etiologies. The process of identifying the cause of a disease in plants is called diagnosis. The diagnosis of plant diseases has been described as an art and a science; it requires scientific knowledge of plant pathology and related disciplines. Effective disease control requires making the best possible decisions to reduce the risk of serious production losses. Control strategies based on prevention of disease and methods that slow the spread of such diseases. Therefore, proper management of diseases affecting the tomato crop, knowledge and understanding of the diagnosis and its infectious cycle is vital and to establish effective control measures.

ABSTRACT. Extraction of high-quality genomic DNA for PCR amplification from filamentous fungi is difficult because of the complex cell wall and the high concentrations of polysaccharides and other secondary metabolites that bind to or co-precipitate with nucleic acids. We developed a modified sodium dodecyl sulfate/phenol protocol, without maceration in liquid nitrogen and without a final ethanol precipitation step. The A 260/280 absorbance ratios of isolated DNA were approximately 1.7-1.9, demonstrating that the DNA fraction is pure and can be used for analysis. Additionally, the A 260/230 values were higher than 1.6, demonstrating negligible contamination by polysaccharides. The DNA isolated by this protocol is of sufficient quality for molecular applications; this technique could be applied to other organisms that have similar substances that hinder DNA extraction. The main advantages of the method are that the mycelium is directly recovered from culture medium and it does not require the use of expensive and specialized equipment.