SURVEY OF RICE DISEASES IN THREE REGIONS IN MADAGASCAR
2013
Mamiharisoa Razanakoto, Léa | De Clerck, Caroline | Zalmine, Francia | Rabemanantsoa, Christian | El Jaziri, Mondher | Jijakli, Haissam
Rice (Oryza sativa) is the most cultivated crop and the staple food in Madagascar. However, the country has never achieved food self-sufficiency and continues to import rice abroad. Rice diseases are one of the factors limiting rice production and causing significant yield reductions. Our study aims to identify the rice pathogens present in three region of Madagascar: two of these regions (Analamanga and Vakinankaratra) are located in upland region when the last (Atsinanana) is located in coastal regions. Fifty five (55) rice samples were collected and cultured on standard media. A survey questionnaire was also conducted with the farmers in order to collect information about the context in which the diseases appeared. Micro-organisms isolated were identified by morphological characteristics for fungi, gram stain and anaerobic growth test for bacteria. In addition, molecular DNA characterization was performed by PCR using universal primers for both fungi and bacteria. The amplicons obtained were sequenced and analyzed by BLAST. In Analamanga and Vakinankaratra, Alternaria sp. and Xanthomonas oryzae pv. oryzae were pre-dominant. In the Atsinanana region, however, Curvularia lunata and Pseudomonas fuscovaginae were the most present. The weather in upland regions is indeed warm and humid in summer, dry and cold in winter which favours Xanthomonas oryzae pv. oryzae and Alternaria sp.growth. Moreover, irrigation is practiced in those regions which can explain the spread of the diseases. The weather in coastal region is warm and humid all year long which tend to favor weed development all year, serving as alternative hosts for Pseudomonas fuscovaginae and Curvularia lunata in interseason.
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