2012 Annual Report
1a.Objectives (from AD-416):
1. Rapid development and introduction of improved purple-fleshed sweetpotato (PFSP) varieties with higher pigment yield, better adaptation and disease resistance.
2. Develop near infrared spectroscopic (NIRS) method for high throughput screening and breeding of PFSP lines for increased anthocyanin content and varied cyanidin-peonidin ratios with specific color characteristics.
1b.Approach (from AD-416):
Advanced PFSP breeding lines from NCSU Sweetpotato Breeding Program will be evaluated for anthocyanin profiles and color characteristics. Anthocyanins will be extracted from freeze-dried samples using a Dionex ASE 200 accelerated solvent extractor. Total monomeric anthocyanin (TMA) content will be determined by pH-differential method. The extract will be acid hydrolyzed in a screw-cap vial at 100ºC for 1 hr for anthocyanin analysis. Anthocyanin and anthocyanidin compounds will be separated and identified by high pressure liquid chromatography (HPLC). Relationship between cyanidin-peonidin ratios and color values (L*, a*, b*) of the extracts will be assessed. Near-infrared (NIR) spectroscopy will be used to develop a more efficient and cost effective method for rapidly analyzing anthocyanin components. Samples will be scanned in the diffuse reflectance mode (400-2500nm) of NIR spectrometer. The mean NIR spectra of the analyzed samples will be modeled against the data generated by pH-differential and HPLC methods using partial least square regression, and the regression models will be validated by full cross-validation. Standard curves that relate the NIR spectra and quantitative measurements of anthocyanin components will be used for speeding up the breeding efforts in developing specific PFSP varieties that have exceptional agronomic and high anthocyanin traits for natural colorant markets.
This project is related to in-house objective 5 of this project: Evaluate advanced sweetpotato genotypes intended for processing applications, postharvest handling systems, and processing technologies for their potential to increase levels of beneficial phytochemicals in concert with production of high quality food products.
Freeze-dried powders from 150 clones of purple-fleshed sweetpotatoes (PFSP) generated by the breeding program were extracted with acidified methanol. The extracts were analyzed for total phenolics, total monomeric anthocyanins and peonidin/cyanidin ratio by spectrophotometric and HPLC methods. The anthocyanin and phenolic contents varied widely from < 1mg to 783 mg/100g powder and 78 mg to 3,080 mg/100g powder, respectively, and the peonidin/cyanidin ratios ranged from 0.01 to 21. These wide variations suggested a feasibility of developing high-polyphenolic PFSP varieties for natural colorants and functional foods. Near-infrared (NIR) absorbance spectra, in the range from 400 to 2500 nm, were scanned for the 150 freeze-dried samples using a FOSS XDS Near Infrared Spectrometer. Each sample was scanned twice and the spectral data averaged for modified partial least square regression analysis. Progress has been made in the development of different NIR predictive models for high throughput assessment of polyphenolic content in PFSP clones.
Progress on this project was made through communication via e-mail, phone/conference calls, on-site Cooperator/ARS meetings and discussions at professional conferences/meetings.