Cassava roots are an important source of dietary and industrial carbohydrates and suffer markedly from postharvest physiological deterioration (PPD). This paper deals with metabolomics combined with chemometric tools for screening the chemical and enzymatic composition in several genotypes of cassava roots during PPD. Metabolome analyses showed increases in carotenoids, flavonoids, anthocyanins, phenolics, reactive scavenging species, and enzymes (superoxide dismutase family, hydrogen peroxide, and catalase) until 3-5days postharvest. PPD correlated negatively with phenolics and carotenoids and positively with anthocyanins and flavonoids. Chemometric tools such as principal component analysis, partial least squares discriminant analysis, and support vector machines discriminated well cassava samples and enabled a good prediction of samples. Hierarchical clustering analyses grouped samples according to their levels of PPD and chemical compositions.

This study aimed to investigate the role of ascorbate peroxidase (APX), guaiacol peroxidase (GPX), polysaccharides, and protein contents associated with the early events of postharvest physiological deterioration (PPD) in cassava roots. Increases in APX and GPX activity, as well as total protein contents occurred from 3 to 5 days of storage and were correlated with the delay of PPD. Cassava samples stained with Periodic Acid-Schiff (PAS) highlighted the presence of starch and cellulose. Degradation of starch granules during PPD was also detected. Slight metachromatic reaction with toluidine blue is indicative of increasing of acidic polysaccharides and may play an important role in PPD delay. Principal component analysis (PCA) classified samples according to their levels of enzymatic activity based on the decision tree model which showed GPX and total protein amounts to be correlated with PPD. The Oriental (ORI) cultivar was more susceptible to PPD.

Limited information is available concerning nutrient requirements of high-energy sorghums (HES) (Sorghum bicolor L., Moench). The purpose of this study was to compare a HES, an intermediate grain cultivar (IGC), and a conventional grain cultivar (CGC) for grain and biomass (stover) yield, responses to applied Nand P, and effects on nutrient partitioning and removal. Field experiments were conducted in 1983 and 1984 on Ships clay (Udic Chromustert) near College Station, TX. Nitrogen (0, 84, 168 kg N ha-•) and P (0, 15, 30 kg P ha-1 ) were factorially applied to the three cultivars. Soil nutrient availability decreased after only one year of total dry matter harvesting and was reflected in greater responses to applied N and lower tissue nutrient concentrations and removals the second year. Cultivar and N influenced grain and biomass yields, while applied P had little effect on these parameters. The CGC and IGC produced more grain, but less biomass, than HES. The CGC removed the least nutrients in biomass and the most in grain, while removals by HES components were reversed. Although HES did yield more total dry matter, total crop N and P removals were similiar for all cultivars. HES did remove greater total quantities of all other nutrients. Applied N increased concentrations and uptake of most nutrients in grain and biomass. ------------------