Line Cultivation Method for Rehabilitation of Breeder's Seedof Rice in Madagascar

摘要

Off-types or alien plants are frequently found in the certified seed (R) fields of seed production farmers in Madagascar. The contamination is also observed to a lesser extent in the fields for breeder's seed (GO) and foundation seed (Gl) which are under the management of official agencies of seed production. Contamination discourages considerably the motivation of seed production farmers due to the need to remove off-types and to the decrease of the working efficiency at harvest.To maintain a high purity of GO in Madagascar, the line cultivation method which is utilized for the maintenance of Gl in Japan was introduced. Thirty plants which represent the probable characteristics of the variety were uprooted in GO fields at harvest time. With the analysis of morphological traits such as plant height, number of panicles and seed characteristics, the number of plants was reduced to twenty, which were treated as pedigree lines for the line cultivation in the following season for theselection of the next GO. Effects of the selection through line cultivation were evaluated including the variation of morphological traits, heading duration and percentage of off-types. Coefficient of variation (CV) of some of the morphological traits apparently decreased, heading duration based on the days from the beginning to the end of the panicle appearance was considerably shortened, and the percentage of off-types was reduced to 0.8% from 12.0%. These results indicate the effectiveness of the adoption of the line cultivation method for the purification of GO.