Non-proline-accumulating rice mutants resistant to hydroxy-L-proline

Summary Three rice (Oryza sativa L.) mutants resistant to hydroxy-L-proline (Hyp), HYP 101, HYP 202 and HYP 203, were selected from an ethylene imine mutagenized M₂ population of the original variety, Nipponbare, and their biochemical and genetical characteristics were investigated. The sensitivity of the mutants to Hyp could be clearly differentiated from that of the original variety when seeds were germinated and cultured with 10^–410^–3 M Hyp for 10 days. A difference in Hyp sensitivity was also observed among the HYP mutant lines, HYP 101 being the most resistant line. When free amino acids in seeds and 15-day-old seedlings were analyzed, the composition of the amino acids in the mutants was somewhat different from that found in the original variety. However, free proline accumulation was not detected in either the HYP mutants or the original variety. In each mutant line, HYP resistance was transmitted with a single recessive nuclear gene (hpr). These results suggest that the mechanism of Hyp resistance controlled by the recessive gene do not involve free proline accumulation.Abbreviations Hyp hydroxy-L-proline - T-Pro thioproline