Abstract-The plants of rice varieties (Arco, Thaibonnet and Elio)

Effet in vitro de différent niveaux NPK sur la croissance mycélienne et la sporulation de pathogènes foliaires du riz: Helminthosporium sp. et Curvularia lunata Helminthosporium oryzae, H. sativum, H. australiensis, H. spiciferum et Curvularia lunata, including the mycelial growth and sporulation. Methodology and Results: Three organic media cultures (PDA, rice meal and malt extract) were used to test the NPK effect on mycelia growth and sporulation of the five fungal species. The sources of nitrogen, phosphorus and potassium were incorporated separately in the culture medium at increasing concentrations, 0.01M (C1), 0.025 M (C2), 0.05M (C3), 0.1M (C4) and 0.15 M (C5), before the sterilization. Two scoring criteria were considered: mycelial growth and sporulation of the fungal species. The obtained results showed that the tested Curvularia lunata and Helminthosporium spp. have variable behaviors, mycelia growth and sporulation on nutritional diets on nitrogen, phosphorus and potassium. These behaviors depend on culture medium, the dose and source of fertilizing element incorporated. Conclusion and results application. This in vitro study on the growth and sporulation has shown a great adaptation of rice foliar pathogens (Helminthosporium spp. and C. lunata) at different levels of the tested NPK. Such adaptation suggests that the nutrient intake has a greater effect on the host as in the pathogen itself. These observations will be useful to approach the in vivo effect of fertilization on rice foliar diseases.

Rice ( Oryza sativa L.) is the staple food of more than half of the world population. However, its production is facing several biotic constraints. Among serious biotic factors that harm rice crops, the Helminthosporium disease has severe adverse impacts on rice yield, generating heavy losses of up to 90%. Four Bipolaris oryzae isolates were recovered for the first time from leaf lesions in the weed species Typha latifolia , and then subjected to pathogenicity tests on several rice varieties. The results indicated that Moroccan isolates of B. oryzae altered the leaf surface of five rice varieties tested. Among four isolates, Hor4 was the most pathogenic, showing high aggressiveness on the Cererrer and Elio varieties, with disease severity of 92.59%, followed by the Hor1, Hor2, and Hor3 isolates. The Arpa variety showed higher resistance to the Hor1 isolate, with a severity index of 35.18%. Through mycelial cutting or conidial suspension, B. oryzae isolated from T. latifolia was able to produce conidia on the leaves of this weed species.