Abstract
The cassava breeding scheme currently used is long, because initial stages concentrate mainly on improving yield, with root quality selection following later. To shorten the scheme, yield and root quality should be selected simultaneously, starting at the seedling nursery. In this study, a nursery comprising of eight cassava families and 1885 seedlings developed from parents adapted to three major agro-ecologies, were evaluated for yield related traits in Colombia. Percentage dry matter content (DMC) and harvest index produced similar ranking of the parents. Tuber yield, weight, and number showed potential of increasing yield through conventional breeding. A selection index including fresh root yield, percentage DMC, root weight and roots per plant, with heavier weights being assigned to root weight and roots per plant, should be used.
Highlights
In cassava improvement, the breeder’s primary concern is to increase the root yield of varieties that are resistant to major diseases and pests (Mahungu 1987, Fukuda et al 2002, Ceballos et al 2004)
Genotypes with high general combining ability (GCA) for percentage dry matter content (DMC) or yield identified through studies by Jaramillo et al (2005); were crossed following standard procedures described by Kawano (1980)
The average commercial sized storage roots (ComRt) was 2.17, with clone GM 901263 having the highest number of 15 roots
Summary
The breeder’s primary concern is to increase the root yield of varieties that are resistant to major diseases and pests (Mahungu 1987, Fukuda et al 2002, Ceballos et al 2004). Root yield is usually assessed visually as the number, size and shape of roots. Selection for root quality is normally carried out at advanced stages of yield trials when clones being evaluated are reduced in number (Mahungu 1987). Root quality and yield related characteristics often considered are cyanogenic glycosides content, percentage dry matter content (DMC) and harvest index (HI). Percentage DMC determination is very useful because of its association with other root quality characteristics and its economic relevance (Mahungu 1987, Weçolovis et al 2003, Lenis et al 2006). Harvest index is used because it is highly correlated with root yield and has a high heritability (Kawano et al 1998)
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