Dw6 dwarfing gene enhances shoot elongation of CCC treated plants

Abstract

Dwarf oat cultivars are often stated to be insensitive to antigibberellins. In some cases antigibberellins have, however, even enhanced stem elongation in dwarf oat. Antigibberellin chlormequat chloride (CCC) and an ethylenereleasing ethephon (ETH, Cerone) were applied to long-strawed landrace cultivar and conventional height (Virma), naked (Rhiannon) and dwarf type (Grane and Pal) oats. Field experiments were conducted at Viikki Experimental Farm, University of Helsinki, Finland and growth chamber experiments at the University of Minnesota, St Paul, USA. They were applied at early growth stages (ZGS 13) or at recommended stages (CCC at ZGS 32 and ETH at ZGS 39). Oat cultivars excluding dwarf type responded to CCC and ethephon, effect being more profound in long-strawed cultivars. Cultivars with Dw6 dwarfing gene expressed, however, enhanced stem elongation. Repeated measures on field grown dwarf cultivars indicated that stem elongation was retarded or unaffected when measured 7 to 14 days after treatment. However, at post-anthesis, stem elongation was enhanced: especially elongation of peduncle was promoted when compared to controls. This could be a consequence of GA precursor accumulation resulting in CCC induced inhibition of GA biosynthesis. Later on, when inhibition effect fades and GA synthesis resumes there are excess amounts of precursors to be used in GAsynthesis resulting higher rates of GA and concurrently enhanced stem elongation in dwarf type. In some Dw6 lines the dwarfing effect may also be turned off at later stages, resulting in higher elongation rate of the peduncle (Burrows 1986). Burrows, V.D. 1986. In: Webster, F.H. (ed.). Oats: Chemistry and technology. AACC, St. Paul, Minnesota. p. 13 46.