2017 年 61 巻 4 号 p. 153-158
In Madagascar, off-type plants are frequently found in rice fields for breeders’ seed (G0) and foundation seed (G1), which are under the management of official agencies of seed production.
Accordingly, line cultivation method was introduced in 2013 for the maintenance of G0 of four varieties in 2 research centers, i.e., Mailaka and FOFIFA160 at FOFIFA-Mahitsy Center, and Makalioka34 and Makalioka Malady at FOFIFA-CALA Center (Arai et al., 2015) and the occurrence of off-types in G0 and G1 was investigated for 3 consecutive years. Percentage of off-types in G0 of 4 varieties was reduced to nearly 0% between 2013-2015. Although the percentage of off-types of G1, which utilized the remnant seeds of G0 line cultivation, drastically reduced to less than 1% between 2013-2015 from the initial level of more than 10% in 2012, some varieties could not reach to under the standard upper limit of 0.1%. Accidental events caused by the natural and social conditions of research centers, such as the mixing of the varieties at nursery and flow of foreign seedlings with flooding, seemed to be factors provoking contamination. Proper and strict field management along with the adoption of line cultivation will be indispensable to maintain the purity in rice seed production in Madagascar.
