Sampling strategies for proper quantification of carotenoid content in cassava breeding
Rapid-cycling recurrent selection has been implemented to produce cassava varieties that deliver provitamin A carotenoids to human populations that are affected by vitamin A deficiency. Rapid-cycling 

	selection relies on quantification in just one plant per genotype. This study was conducted to assess the 

	reliability of single-plant evaluations and the effect of age of the plant on carotenoid content in cassava 

	roots. Variation in aliquot quantifications from the same root was negligible indicating a reliable 

	experimental procedure. A large source of variation for carotenoids was due to differences among 

	genotypes. Root-to-root variation from the same plant in some cases was surprisingly high and 

	accounted for an average of 25% of the total variation. Plant-to-plant variation was not as high and 

	accounted for 20% of the total variance. Carotenoid content was shown to vary depending on the age of 

	the plant. Single-plant evaluations for carotenoid content in cassava, which is a requirement for rapidcycling recurrent selection is acceptable considering that it reduces in half the time required for 

	evaluation and selection. However, it is suggested that 2 to 3 roots per plant be combined together in a 

	sample to represent each genotype at a standard plant age.  

	 

	Key words: Plant age, environmental influence, rapid cycling, genetic gains, -carotene, repeatability