To improve the disease resistance of adapted rice genotypes, fourteen rice genotypes selected from previous field screening and four controls (two resistant and two susceptible) were screened in greenhouse trials against ten Beninese and four East African pathogenic isolates at rice seedling and tillering stages. Results show that across isolates, no significant difference was observed between disease severity on tested genotypes at both growth stages while a significant difference at P ?0.05 was observed between disease severity on tested genotypes and susceptible controls. In fact, among tested genotypes, twelve previously resistant under field conditions were also resistant under greenhouse conditions, and more resistant ones were OU244, ARICA 5, IRAT 104, and PiN°4. In addition, among all tested genotypes that were resistant, two (OU244 and RIL249 MORO) with R genes, Piz and Pi5t, were particularly promising. Besides, at the seedling stage and across isolates, genotype OU244 and IRBLZ-Fu harboring the same R
-gene Piz displayed resistance and susceptibility reactions and the same results were observed between genotypes RIL249 MORO and IRBL5-M harboring the same R gene Pi5t but only with Beninese isolates. Also, an incompatibility reaction was observed between susceptible controls and some Beninese isolates. In conclusion, screening for resistance at the rice tillering stage appears a suitable protocol for the reliable selection of rice breeding material for improved rice production in Africa. Also, results lead to first selecting rice genotype OU244 as the most stable and promising that could be used for rice improvement against rice blast in Africa; and to further initiate identification of R gene (s) involved in the resistance of the tested genotypes and avirulence (Avr) genes in the isolates used in the current study.
Key words: Magnaporthe Oryza, disease severity (DS), area under disease progress curve (AUDPC); seedling; tillering.
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