Effects of chemical growth retardants on growth and development of sweetpotato (Ipomoea batatas (L.) Lam.) in vitro

Plant growth retardants were evaluated for their ability to reduce the growth rate of sweetpotato (Ipomoea batatas (L.) Lam.) in vitro. Nodal sections of cv. Jewel were cultured for 30 days on medium containing NDA, ancymidol, phosfon, TIBA, difenzoquat, chlormequat, ACC, mepiquat chloride, or daminozide at 0, 10(-4), 10(-5), 10(-6), 10(-7), or 10(-8) M. Difenzoquat, NDA, phosfon, and TIBA, at 10(-4) M, were lethal to axillary bud explants. A low concentration (10(-8) M) of chlorflurenol or NDA stimulated shoot elongation. The effective concentration range for most growth retardants was 10(-5) to 10(-6) M. Small (2- to 4-mm diameter) storage root-like swellings were observed on roots in cultures containing TIBA or ancymidol. The growth-inhibiting effects of ancymidol and NDA were transitory and did not persist through a 180-day culture period. Shoots cultured on medium containing 10(-5) M phosfon, TIBA, or difenzoquat were significantly shorter than control plants after a 180-day culture period. Culture on medium containing TIBA, NDA, ancymidol, or ACC resulted in abnormal leaf and stem development. Plants derived from nodal explants cultured on medium containing either phosfon or chlormequat were near normal in appearance but with some plants exhibiting interveinal chlorosis and reduced root system development.