Induced Mutation for Developing Mutant Rice Lines Tolerant to the Parasitic Weed Striga Asiatica (L.) Kuntze

Full text: The parasitic weed Striga asiatica causes damage on rainfed rice culture and may reduce production from 75-100% in Madagascar. The lack of resistant variety is one of the main problems for rice production. This work aimed at screening rice mutant lines tolerant to Striga asiatica. Two rainfed Striga sensitive rice varieties B22 and F154 were used. After radiosensitivity test, 1000 rice seeds per variety were irradiated at 100, 200Gy for F154, and 300Gy for B22, then planted one per hole in the field to develop M₁ then M₂ generation. 200 rice seeds of each 500 M₂ genotypes per dose of irradiation per variety were planted in the field with artificial infestation of S. asiatica seeds. 5 rice seeds per pot of all selected genotypes from M₄ to M₆ were planted in the greenhouse under severe artificial infestation. Plant survival rate, infection rate per plant, number of Striga plant per pot, were considered for the tolerance evaluation then plant fertility rate, number of fertile panicle per plant, 100 seeds grain weight were assessed for agronomic traits. As a result, of this experiment 10 lines were selected as tolerant to S. asiatica from F154 and 12 lines from B22. The survival rate of the two parents was significantly lower (9.74a and 11.83a) than those of mutant lines (52.36b and 74.36b); the Striga plants emergence per pot were significantly higher for the parents (13.96c and 14.89c) as compared to the mutants (0.12a to 1.5b); the infection rate for the parents (7.37b and 7.86b) was higher compared to the mutants (2.27a to 2.74a); the fertility rate per plant for the two parents was lower (20.98%b and 22.29%b) but much higher for the mutants (72.19%b and 78.35%b); the average panicle number per plant for the parents was significantly lower (0,5a and 1a) than those of mutants (1,5b to 2,4bc) and the 100 grain weight of the parents are significantly lower (2.35a to 2.56a) than those of the mutants (3.19b to 3.23b). The culture of those mutant lines may increase rice production and contribute to enhancing food security in Madagascar. (author)