Cassava evaluation trials are mostly harvested at 12 months after planting, irrespective of their actual maturity date, which includes the maximum accumulation of dry matter in tuberous roots. Depending on the market needs, some producers prefer to keep their crops up to 24 months after planting and harvest sequentially when needed. Such varieties should mature early at 12 months after planting, and maintain or enhance their root dry matter rather than losing it.
A modified breeding scheme has been suggested to evaluate selected lines from 12 to 24 months after planting. In a harvest scheme such as this, many of the improved varieties lose their dry yield as starch is converted to sugar. Hence the breeding program in DR Congo started screening both early and late bulking varieties to identify those that can bulk early and keep their economically profitable dry root yield until late in the growing cycle. Six varieties and one local variety were subjected to several harvest dates ranging from 9 to 24 months after planting.
By assessing early generation populations in clonal trials, study results revealed that breeders may lose around 15% of superior clones with good dry root yield from 12 to 24 months after planting, when limiting the selection to clones selected at 12 months after planting.