Improving total carotenoids content (TCC) in cassava roots is an important strategy to reduce vitamin A deficiency in human populations that rely on cassava as a source of energy in their diets. The high heritability for TCC in the roots allowed the International Center for Tropical Agriculture to implement a rapid cycling recurrent selection approach that reduced the standard length of each cycle from the ordinary 8 yr to 3. Data from successive evaluation nurseries suggested that gains have been made through time. However, no comparison of different cycles of selection has been made when representatives of each cycle were grown together. This study compares 4 to 5 clones representative of cycles of selection from 2004 to 2009. Results demonstrated significant gains for TCC as well as for total β‐carotene (TBC) expressed both in a fresh and dry weight basis. Although dry matter content (DMC) was not a selection criterion during the selection process, it increased with the successive cycles of selection. This suggests that indeed, simultaneous gains for TCC, TBC, and DMC are feasible. This finding is relevant for the important ongoing efforts at the International Institute of Tropical Agriculture and African National Programs to release biofortified cassava clones in Africa with adequate levels of dry matter content.

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Past research developed reliable equations to base selections for high b-carotene on nearinfrared spectroscopy (NIR) predictions (100 genotypes d −1

The CGIAR Harvest Plus Challenge Program began in the mid-2000s to support the genetic improvement of nutritional quality in various crops, including the carotenoids content of cassava roots. Successful conventional breeding requires a large number of segregating progenies. However, only a few samples can be quantified by high performance liquid chromatography each day for total carotenoids (TCC) and b-carotene (TBC) contents, limiting the gains from breeding. This study describes the usefulness of near infrared (NIR) spectroscopy and the efficiency of a large database coupled to a LOCAL regression algorithm to reach accurate TCC/TBC predictions on fresh cassava roots. The cassava database (6026 samples) was built over six years. TCC values ranged from 0.11 μg g -1 to 29.0 μg g -1 , whereas TBC ranged from negligible values up to 20.1 μg g -1 . All values were measured and expressed on a fresh weight basis. Between 2009 and 2014 increases in TCC and TBC were 86% and 122%, respectively. A comparison of calibrations using partial least squares (PLS) regression and LOCAL regression was done. The standard error of prediction were 1.82 μg g -1 for TCC and 1.28 μg g -1 for TBC using PLS model and 1.38 μg g -1 and 1.02 μg g -1 , respectively, using LOCAL regression. The specificity of the data, with increasing content of the constituent of interest year after year, clearly showed the limitation of the classical partial least squares regression approach. The LOCAL regression algorithm takes advantage of large databases; this study highlighted the efficiency of this concept. NIR spectroscopy coupled to LOCAL regression led to efficient models for breeding programmes aiming at increasing carotenoids content in fresh cassava roots. NIR spectroscopy can also be used to predict other important constituents such as dry matter content and cyanogenic glucosides.

Consumers, traders and processors consider post-harvest physiological deterioration (PPD) an important constraint. In Experiment 1, PPD was assessed three consecutive years in roots from five genotypes through seven storage days. PPD, scopoletin and dry matter content (DMC) was recorded during storage. Year, genotype, duration of storage and their interactions were significant. PPD was associated with duration of storage period, DMC and scopoletin contents. Ambient moisture and temperature during storage influenced PPD. In Experiment 2, roots from seven clones were harvested 10 months after planting from 30 consecutive biweekly plantings. PPD was assessed 0, 2 and 7 days after harvest. In 13 harvests, roots from plants pruned six days earlier were also evaluated. Results indicated large seasonal variation across genotypes. Pruning reduced PPD and DMC. Complex and contrasting relationships among the variables analysed were found. There is no uniform model explaining the relationship between PPD and the independent variables considered.

Cassava cyanogenic, carotenoid and protein content found across seven‐ecogeographic subpopulation has the potential to increase the crop’s nutritional and food safety value through breeding.

Ten and thirty cassava genotypes producing wildtype and amylose‐free (waxy) starch respectively, are grown at low (LA) and intermediate (IA) altitudes (<213 and >900 m above sea level (m.a.s.l.) respectively). The functional properties of the starch from these materials are analyzed. The relative importance of environment, clones (within starch type) and genotype‐by‐environment interaction (GxE) is assessed through an analysis of variance. GxE effects are non‐significant, whereas environment and clones (within starch type) are highly significant in most of the cases (particularly for waxy starches). Results confirm that waxy cassava starches consistently show higher peak viscosity (PV) compared with wildtypes. Peak viscosity is statistically higher in plants grown in IA compared with those from the same genotypes grown in LA, both for waxy and wildtype genotypes. In a second experiment, a single waxy genotype is grown in five locations ranging from 934 to 1485 m.a.s.l. PV is highest in the location with higher altitude. The second highest PV is measured in starches from the second highest location at 1071 m. Both experiments clearly indicate that PV is positively correlated with altitude above sea level where cassava is grown. Altitude above sea level influenced starch granule size: the higher the altitude the larger the average granule size. Waxy starch granules tend to be larger than those from wildtype genotypes.

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