The inheritance of β-amylase null in storage roots of sweet potato,Ipomoea batatas (L.) Lam.

Several sweet potato genotypes were found to lack completely or to have only traces ofβ-amylase in their storage roots. Such genotypes do not increase in sweetness during cooking because, without a sufficient amount ofβ-amylase, the normal hydrolysis of starch to maltose does not occur in the cooking process. In order to study the inheritance of this biochemical variant in the genotype, 41 families were generated. The following conclusions were drawn from analyzing these families. (1) This trait is controlled by one recessive allele (designatedβ-amy) (2) It is inherited in a hexasomic or tetradisomic manner, but not disomically or tetrasomically. This conclusion supports previous cytological data that sweet potato is an autohexaploid or has two identical genomes plus one genome which is somewhat different. (3) Theβ-amy allele appears to exist at a high frequency in cultivated germplasm. (4) Breeding sweet potato for lowβ-amylase activity is relatively easy. New types of sweet potato without normalβ-amylase activity have great potential for processing and as a staple food.