Inheritance of Amylase Activity and Dry Matter in the Sweet Potato Storage Root.

The sweetpotato (Ipomoea batatas L.) is the 3^rd main root crop in the world, and grows well in poor soils. The sweetpotato storage root is a major carbohydrate sink. Currently sweetpotato is mostly produced for fresh consumption. However, additional applications are needed in order to expand the market for sweetpotato. There is a great potential for sweetpotato to be an alternative feedstock for ethanol production. However, the ability to use sweetpotato for ethanol production will be largely determined by the starch content and the level of amylase activity in the roots. The starch content of the storage root has a direct correlation with the dry matter content. This study examined the inheritance of dry matter content and amylase activity in the sweetpotato storage root.  The specific objectives were to: 1) create a sweetpotato families that differ in their genetic ability to accumulate starch and vary in the degree of amylase activities; 2) determine the variation in dry matter content among sweetpotato hybrids; and 3) determine the variation in amylase activity among sweetpotato hybrids.  F1 families were created by crossing parents that contrasted for both dry matter and amylase activities. Some parents were high in dry matter content and others were high in amylase activity. Hybrid seeds were germinated and grown in the greenhouse to obtain vines for field evaluation. Hybrids were transplanted in the field in a randomized complete block design. Storage roots were harvested and analyzed for dry matter and amylase activities.  Frequency distributions of dry matter content ranged from 10% to 40% and the distribution of amylase activities among the genotypes ranged from 0.06 to 1.7 mg maltose/ml/min on a fresh weight basis. Broad sense heritability estimates were 0.22 and 0.32 for amylase activity and dry matter, respectively.