Quantification of starch physicochemical characteristics in a cassava segregating population

Abstract

Culinary cassava (Manihot esculenta L.) qualities that make a variety popular are a function of starch physico- chemical properties. Hence, in response to inferior root qualities in some released cassava varieties in Uganda compared to the local germplasm, a study was undertaken to examine: (i) starch physicochemical characteristics in both introduced and local varieties; and (ii) the variation in the starch properties of their F1 progenies. The local varieties included Bao, Nyaraboke, Kakwale, and Bamunanika; and the introduced genotypes SE/95/00036, NASE 10, NASE 12, TME 5, and TME 14. Of the generated 7000 F1 seedlings, 1077 seedlings were selected, cloned (6-8 plants per genotype) and established in a single-row trial. Root samples were collected per clone and examined for starch physicochemical properties. Considerable variations were observed in the F1 families com- pared to the parental lines with weak correlations in most starch properties (r < 0.25). Amylose content ranged from 10 to 25%, with the amylose: amylopectin ratio between 1:3 and 1:9. Among the F1 families, solubility and swelling power ranged from 1-15g100g-1 and 40-140g100 g-1 starch at 60o C, respectively. In the parents, it ranged between 1.3-8.6 and 50-67g100g-1 starch at 60o C, respectively. Fresh root starch yield ranged from 18 to 34%, with dry matter content varying from 19-47% in both the F1 families and the parents. Ash and lipid content varied among the F1 families and parents with ranges 0.05-0.29% for ash and 0.1-0.32% for lipids. In both the parents and the F1 families, the reducing sugar and protein content ranged between 0.7-1.7 and 0.23-0.43%, respectively. These findings demonstrate: (i) existence of considerable genetic variations in starch physicochemi- cal properties in both local and introduced cassava genotypes and their progenies, and (ii) potential utilisation of cassava starches for various applications based on the inherent differences in physicochemical characteristics.