Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

INTERACTION OF DRY AFTER RIPENING AND INCUBATION TEMPERATURE IN RED RICE

GIANINETTI A.*, COHN M.A.**

* Experimental Institute for Cereal Research, 29017 Fiorenzuola, Piacenza, Italy

** Dept. Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803 USA

To study the effects of incubation temperature on dormancy and germination of red rice (Oryza sativa) seeds following different times of afterripening, a two-step incubation experiment was performed. Fully dormant seeds were dry afterripened at 30 °C for 1, 2, 3, 4, 6, 8 and 10 weeks and then were wet incubated for two weeks at 1, 5, 15, 20, 25, 30 and 35°C. All the seeds that did not germinate during this initial incubation step were transferred to a second incubation step at 30 °C (optimum temperature for germination) for two additional weeks. As an effect of dry afterripening, germination percentages obtained at the end of the first incubation step increased faster at temperatures near the optimum for germination, so that the ‘temperature window’ for germination initially opened at high (optimum) temperatures and only subsequently at low temperatures (15 °C). During the first incubation step, cold stratification (1 °C) had a consistent promotive effect on the subsequent germination at 30°C, particularly after a short period of dry afterripening (1-2 weeks at 30 °C). On the contrary, intermediate temperature (15 °C) had a dormancy-inducing effect. For each incubation temperature tested during the first step, afterripening times to 50 % germination, obtained either at the end of first or second incubation steps, were utilized as relative dormancy indices to monitor effects of incubation temperature. Comparison of the plots obtained for these indices either at the end of first or second steps suggested that temperature acts independently on germination and dormancy and that the final germination percentage is a result of the balance of these two opposite processes.