In Vitro Conservation of Mexican Garlic Varieties by Minimal Growth.

Garlic (Allium sativum L.) is one of the 30 crops that are essential for world food; therefore, its conservation should be considered a priority. There are two main plant conservation strategies: in situ and ex situ conservation. Both strategies are important; nevertheless, ex situ field conservation is affected by biotic and abiotic factors. A complementary strategy to preserve garlic germplasm in the medium term is through in vitro culture by minimal growth. The aim of this study was to evaluate the in vitro conservation of three Mexican garlic varieties by minimal growth. Garlic plants obtained from in vitro garlic bulbs were preserved in six culture media at 25, 18, and 5 °C. A randomized design was used and an analysis of the variance of the survival, contamination, and shoot height of the explants was performed at 30, 60, 90, 180, 270, and 365 days of culture. The results showed that the in vitro conservation of Pebeco, Tacátzcuaro Especial, and Huerteño garlic varieties was optimally obtained for one year at 5 °C in a basal Murashige and Skoog (MS) culture medium with 68.46 g L-1 sucrose and 36.43 g L-1 sorbitol. Thus, the achieved protocol can be adapted to other varieties of garlic for medium-term storage in germplasm banks.

Contact Mode Atomic Force Microscopy as a Rapid Technique for Morphological Observation and Bacterial Cell Damage Analysis.

Electron microscopy is one of the tools required to characterize cellular structures. However, the procedure is complicated and expensive due to the sample preparation for observation. Atomic force microscopy (AFM) is a very useful characterization technique due to its high resolution in three dimensions and because of the absence of any requirement for vacuum and sample conductivity. AFM can image a wide variety of samples with different topographies and different types of materials. AFM provides high-resolution 3D topography information from the angstrom level to the micron scale. Unlike traditional microscopy, AFM uses a probe to generate an image of the surface topography of a sample. In this protocol, the use of this type of microscopy is suggested for the morphological and cell damage characterization of bacteria fixed on a support. Strains of Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), and Pseudomonas hunanensis (isolated from garlic bulb samples) were used. In this work, bacterial cells were grown in specific culture media. To observe cell damage, Staphylococcus aureus and Escherichia coli were incubated with different concentrations of nanoparticles (NPs). A drop of bacterial suspension was fixed on a glass support, and images were taken with AFM at different scales. The images obtained showed the morphological characteristics of the bacteria. Further, employing AFM, it was possible to observe the damage to the cellular structure caused by the effect of NPs. Based on the images obtained, contact AFM can be used to characterize the morphology of bacterial cells fixed on a support. AFM is also a suitable tool for the investigation of the effects of NPs on bacteria. Compared to electron microscopy, AFM is an inexpensive and easy-to-use technique.