Cassava varieties are popularly separated by taste as bitter or sweet cultivars. Roots of bitter cultivars have a high HCN content (over 100 mg HCN equivalent/kg fresh roots) and are consumed only after processing, as flour, starch and other products. Sweet cultivars have low HCN content and can be consumed without any kind of processing. With the purpose of studing the possibility of using bitter varieties in the breeding of sweet cassava varieties, crosses were made between the different types of varieties to verify the cyanogenic profile of the segregating progenies. Two sweet varieties (IAC 289-70, IAC 576-70) and a bitter variety (SRT-1330 Xingu) were pollinated by a sweet variety (SRT-797 Ouro do Vale). Crosses between sweet cultivars yielded progenies with 85.7% of individuals with a HCN content below 100 mg HCN equivalent/kg fresh roots, while only 31.3% of the individuals from crosses between sweet and bitter varieties were under this value. The average HCN content of the progenies was very similar to the average of parents. In all crosses most of individuals showed values between 50 and 100 mg HCN equivalent/kg fresh roots, even those derivated from the cross between sweet and bitter varieties. All crosses yielded transgressive segregants, with HCN content superior or inferior to either parent. The observed data show that the HCN content is a quantitative characteristic and that there is genetic variability allowing selections for high or low HCN content. Bitter cultivars may arise from crosses between sweet cultivars and sweet cultivars may be selected from crosses between sweet and bitter cultivars.
breeding; HCN content; sweet cassava; bitter cassava; sweet cassava breeding
