Optimising DNA isolation for medicinal plants

AbstractIn African traditional health care systems medicinal plants have long been known to contain pharmacologically active compounds. This has led to an excessively high demand of these plant products resulting in the extinction of some plant species. With the application of molecular techniques in plant diversity conservation becoming increasingly popular, the isolation of PCR amplifiable genomic DNA becomes an important pre-requisite. However, medicinal plants are known to contain high levels of polyphenols and polysaccharides posing a major challenge in the isolation of high quality DNA. The objective of our research was to optimize a cetyl-trimethyl ammonium bromide (CTAB)-based protocol for the extraction of genomic DNA from a range of medicinal plant species, namely Sclerocarya birrea (tree), Barleria greenii (shrub), Aloe polyphylla and Huernia hystrix (both succulent plants). The quantity of DNA (µg/g) isolated using the modified CTAB protocol was higher for the lower plant tissue amounts (0.1 and 0.2 g) per 500 µl of extraction buffer. The spectral quality of DNA as measured by the A260/A280 ratio ranged from 1.76 to 2.14 for S. birrea, B. greenii and A. polyphylla and 1.39 to 1.74 for H. hystrix. The DNA purity was further confirmed by restriction endonuclease digestion and PCR gel electrophoresis using operon arbitrary decamer primers (OPB-05, OPB-06 and OPG-07). The results show that the optimization of the amount of plant tissue per extraction buffer volume is a critical factor in genomic DNA isolation. In all cases the isolated DNA yielded high quantities from small amounts of plant tissue, and had good spectral qualities amenable to restriction endonuclease digestion and PCR amplification

Evaluation and selection of taro [Colocasia esculentra (L.) Schott] accessions under dryland conditions in South Africa

Published online: 08 Oct 2018Taro [Colocasia esculenta (L.) Schott] is an important underutilised staple food crop in South Africa, with a lot of potential to address food insecurity among poor rural households. Development of high yielding stable taro cultivars is one of the most important goals of plant breeders. Twenty-nine taro accessions collected from major taro producing regions of the country were evaluated for growth performance, yield potential and stability under dryland conditions at two sites (Umbumbulu and Roodeplaat) in 2013, 2014 and 2015 cropping seasons. The experiment was laid in a randomised complete block design replicated three times. Growth and yield traits were measured. Analysis of variance and correlation analysis was done on all measured traits. The genotype by environment interaction was analysed using additive main effects and multiplicative interaction (AMMI). As a result, significant variation was observed for most of the traits except number of leaves and leaf width as well as number of suckers, while all the traits showed significant variation for location by year interaction. Number of corms showed significant variation for location by year by genotype interaction among all the traits evaluated. Genotype effect was highly significant (p < .01) on plant height, corm length, number of corms and significant (p < .05) on yield. The significant difference between genotypes for these traits proves that there was a genetic variability and there is a scope for selection. The correlation study also reveals that majority of the characters were positively correlated with each other. Total yield was positively and highly significantly (p < .01) correlated with all the measured traits. AMMI was effective in identifying stable genotypes. The top ranking cultivars per environment may be considered for cultivation under the specific environment, the stable cultivars may be considered for cultivation across all the taro growing regions