Optimizing sweet potato [Ipomoea batatas (L.) Lam.] root and plantlet formation by selection of proper embryo developmental stage and size, and gel type for fluidized sowing.

Potassium starch polyacrylamide, potassium acrylate, a copolymer of potassium acrylate and acrylamide, and hydroxyethylcellulose carrier gels were tested to find a fluid drilling material suited for synthetic seeding of sweet potato (Ipomoea batatas (L.) Lam.) somatic embryos. Somatic embryo developmental stage and size, and maturation (incubation) time were also evaluated to improve plantlet formation. All embryos suspended in the fluidized hydroxyethylcellulose gel were viable after six days and 7% developed into plantlets after two weeks. Up to 97% of the somatic embryos suspended in acrylate and/or acrylamide gels died within six days. Root development was at least 10% and plantlet development at least 30% greater when embryos were subcultured on basal medium for 16 instead of 25 days prior to placement and suspension in hydroxyethylcellulose gel. Up to 25% more plantlets were obtained from embryos at the elongated torpedo stage than those at the cotyledonary or torpedo stages of development. When suspended in hydroxyethylcellulose gel embryo length had no effect on the percentage of plantlets obtained.