Screening cassava for time of maturity to respond to various market needs: Case study in African sub-tropical zones

Cassava evaluation trials are mostly harvested at 12 months after planting (MAP) 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 MAP and harvest sequentially when needed. Such varieties should mature early at 12 MAP 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 MAP. 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 MAP.

In general, the best harvests occurred at 15 MAP. Variety Zizila continued to increase its dry root yield from 15 t ha^-1 at 15 MAP to 20 t ha^-1 at 24 MAP. However, the varieties Butamu and Disanka both with dry yields of 15 t ha^-1 at 15 MAP reduced their dry root yields to 5 t ha^-1 at 24 MAP, thus limiting themselves to early maturing varieties.

By assessing early generation populations in the clonal trials, study results revealed that breeders may lose around 15% of superior clones with good dry root yield from 12 to 24 MAP when limiting the selection at 12 MAP. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.