DIVERSITY AMONG FUNGICIDES RESISTANCE RICE BLAST PATHOGENMAGNAPORTHE ORYZAE STRAINS ISOLATED FROM FARMERS' FIELDS IN NIGER STATE NIGERIA

Abstract

Rice blast caused by fungus Magnaporthe oryzae is one of the major fungal diseases affecting rice (Oryza Sativa) cultivation. The resistance of this fungus to fungicide is imperative as the presence of fungicide resistant strains (biotypes) has been associated with control failure; therefore ,managing resistance is critical to disease control. This study was carried out to evaluate the genetic diversity among the strains of M oryzae in relation to their fungicide resistance found in rice fields in Niger State. The blast infested leaves, stems and panicles of rice plants were collected in November, 2015 from five farmers' field located in Gbak0, Katcha and Lavun Local Government Areas in Niger state, Nigeria. Isolation of the pathogen was carried out on Potato Dextrose Agar (PDA). A total of ten M. oryzae strains designated as MORO01- 0010 were isolated from all the samples collected and subjected to two fungicides (Mancozeb and Benomyl). 1The strains were analyzed using random amplified polymorphic DNA (RAPD) PCR. The results showed three distinct groups among the M oryzae isolates. MORO10 is genetically different from other isolates. MORO04 showed relatedness to MORO06 genome-wise than to MORO09 and MORO05. MOR004, MORO06, MOR005 and MORO09 were found to have common recent gene. MORO09 showed similarity with MORO05. MORO08 and MORO01 were genome wise related. Both group 2 (MORO04, MORO06, MORO05 and MORO09) and group 3 (MORO01 and MORO08) have the same common late accessory different from accessory of group1 (MORO10). However MORO02, MOROO3 and MOROO7 that did not show any band do not amplify with all the primers screened.The results revealed that among the three groups, only group 2 was found to contain the two isolates (MOR0O4 and MORO05) that were completely resistant to both fungicides used in this study. This information could be useful in rice breeding programs aiming at developing a lineage exclusion method in breeding for durable fungicide-blast-resistant relationship in rice cultivars.