Transient expression of β-glucuronidase in recalcitrant Ugandan sweetpotato and putative transformation with two cry genes

Abstract

Sweetpotato (Ipomoea batatas Lam.) has high potential to contain hunger, malnutrition and poverty in sub-Saharan Africa (SSA), since it gives early yield with few inputs. However, productivity of the crop in Africa is very low due to various challenges, such as severe viral diseases and increasing attacks by sweetpotato weevils, Cylas puncticollis and C. brunneus. Effective resistance to weevils has not been identified in the sweetpotato gene pool. On the other hand, the weevil-resistance genes, cry7Aa1 and cry3Ca1 were assembled into a plasmid vector for use in genetic transformation of African sweetpotato cultivars. The parameters for efficient transfer of these genes and the conditions for de novo regeneration optimised in preliminary studies were used in the genetic transformation of Ugandan landrace ‘Kyebandula’ with Agrobacterium tumefaciens EHA 105 harbouring the plasmid pCIP84, which contains cry7Aa1, cry3Ca1 and nptII in its T-DNA. Fifty-four percent of the explants formed adventitious buds. With a mean of 7 buds formed per explant, 6.0% explants formed shoots with a mean of one shoot per explant for those explants that formed shoots on medium containing 50 mg L^-1 kanamycin as a selection agent. PCR analysis using primers for cry7Aa1 showed that the transformation efficiency could be as high as 2%. These data highlight the potential of genetic transformation in transferring resistance genes and pave way for enhancement of food security through production of adapted sweetpotato weevil resistant cultivars.

Key Words: Agrobacterium tumefaciens, b-glucuronidase, Ipomoea batatas