No abstract

M. Barra, E. Salazar, M. Beltrán, and B. Sagredo. 2012. Simple and robust DNA extraction method for the large-scale analysis of genotypes containing high polyphenolic content, such as landraces of Solanum tuberosum and Zea mays. Cien Inv. Agr. 39(3): 593-601. The extraction of high-quality DNA is essential for studies conducted at the molecular level in species with an abundance of contaminants in their tissues, such as some landraces of potato and maize, in which it is difficult to extract good-quality genomic DNA. Compounds such as polyphenols interfere with the amplification of DNA during polymerase chain reaction (PCR), which makes it difficult to conduct PCR-based studies of molecular markers. This article describes a simple and robust protocol for DNA isolation that was applied to potato and maize landraces and resulted in a high DNA concentration with excellent purity and quality. This method is based on the method of Krizman et al. (2006) with some modifications and was tested on potato leaves and young maize leaves. The protocol was compared with one commercial DNA extraction kit and three methods that were previously described for plant DNA extraction: Keb-Llanes et al. (2002), for plants with high polyphenolic content; Fulton et al. (1995), which was developed for Solanaceae and other herbaceous plants; and the original Krizman et al. (2006) cetyltrimethylammonium bromide (CTAB)-activated charcoal method . The method proposed is suitable for isolating DNA from potato and maize genotypes with high polyphenol contents, yielding high-quality DNA that can be utilized for molecular techniques that involve PCR, cutting with restriction enzymes and other applications. The method is short, similar to a commercial kit, but cheaper. The amount of DNA extracted from maize using our method is superior compared with other published methods tested in this article.

The potato is susceptible to water stress at all stages of development. We examined four clones of tetraploid potato, Cardinal, Desirée, Clone 37 FB, and Mije, from the germplasm bank of the National Institute of Agricultural Research (INIA) in Chile. Water stress was applied by suspending irrigation at the beginning of tuberization. Stomatal conductance, and tuber and plant fresh and dry weight were used to categorize water stress tolerance. Cardinal had a high susceptibility to water stress. Desirée was less susceptible than Cardinal and had some characteristics of tolerance. Mije had moderate tolerance and Clone 37 FB had high tolerance. Differential gene expression in leaves from plants with and without water stress were examined using transcriptome sequencing. Water stress-susceptible Cardinal had the fewest differentially expressed genes at 101, compared to Desirée at 1867, Clone 37 FB at 1179, and Mije at 1010. Water stress tolerance was associated with upregulation of the expression of transcription factor genes and genes involved in osmolyte and polyamine biosynthesis. Increased expression of genes encoding late embryogenesis abundant (LEA) and dehydrin proteins along with decreased expression of genes involved in nitrate assimilation and amino acid metabolism were found for clones showing water stress tolerance. The results also show that a water deficit was associated with reduced biotic stress responses. Additionally, heat shock protein genes were differentially expressed in all clones except for highly susceptible Cardinal. Together, the gene expression study demonstrates variation in the molecular pathways and biological processes in response to water stress contributing to tolerance and susceptibility.