Genetic by environment interaction on fresh root yield, dry matter content and total carotene concentration of yellow-fleshed cassava genotypes in five major cassava growing agroecological zones in Nigeria

Eighteen yellow-fleshed cassava genotypes and two released white-fleshed clones (check) were evaluated in five locations representing the major cassava growing agroecological zones of Nigeria to access their performance for fresh root yield, dry matter content, total carotene content and genotypes by environment interaction effects. The aim of the study was to identify stable cassava genotypes that combine high root yield, and high dry matter with high beta carotene content in storage root. The study was conducted in two cropping seasons (2008/2009 and 2009/2010) at Ikenne (humid forest), Ibadan (forest-savanna transition), Ubiaja (sub-humid forest), Mokwa (sub-humid southern-Guinea savanna) and Zaria (moist northern-Guinea savanna). At all locations, the trials were conducted in a randomised complete block design (RCBD) with four replications. The combined analysis of variance showed that fresh root yield (t ha-1), dry matter content (%) and total carotene content (μg g-1 fresh weight) was significantly affected (P < 0.001) by Genotype (G), Environment E, and G × E interaction. For fresh root yield, the best genotype was IITA TMS I050024 followed by IITA TMS I050998 and IITA TMS I050286. For dry matter content of the storage roots, the genotype IITA TMS 1051570 had the highest score followed by IITA TMS 1051740 and IITA IMS I050998. For total carotene content, the best genotypes across the 10 environments in decreasing order of carotene content were IITA TMS I051601, IITA TMS I050311, IITA TMS I050998 and IITA TMS I050099. When combining fresh root yield and dry matter content (dry yield), the genotypes IITA TMS I050998 and IITA TMS I051740 ranked highest. The Environment effect accounted for most of the variation of the total sum of squares (SS) for fresh root yield (55.0%), dry matter content (42.3%) and dry yield (57.9%). The genotype accounted for most of the SS for total carotene content (67.9%)

Physical losses could partially explain modest carotenoid retention in dried food products from biofortified cassava

Gari, a fermented and dried semolina made from cassava, is one of the most common foods in West Africa. Recently introduced biofortified yellow cassava containing provitamin A carotenoids could help tackle vitamin A deficiency prevalent in those areas. However there are concerns because of the low retention of carotenoids during gari processing compared to other processes (e.g. boiling). The aim of the study was to assess the levels of true retention in trans–β-carotene during gari processing and investigate the causes of low retention. Influence of processing step, processor (3 commercial processors) and variety (TMS 01/ 1371; 01/1368 and 01/1412) were assessed. It was shown that low true retention (46% on average) during gari processing may be explained by not only chemical losses (i.e. due to roasting temperature) but also by physical losses (i.e. due to leaching of carotenoids in discarded liquids): true retention in the liquid lost from grating negatively correlated with true retention retained in the mash (R = -0.914). Moreover, true retention followed the same pattern as lost water at the different processing steps (i.e. for the commercial processors). Variety had a significant influence on true retention, carotenoid content, and trans-cis isomerisation but the processor type had little effect. It is the first time that the importance of physical carotenoid losses was demonstrated during processing of biofortified crops