This article proposes a study of the effect of various doses of fungicides in presence and in absence of Pyricularia oryzae or of Helminthosporium oryzae, on the germination of seeds, on the length of coleoptiles, roots, the lesions on coléoptiles and on duration of protection of the plants of rice, against both pathogens. Accordingly, the fungicides protection of seeds against appearances inferred by both pathogens depends on the pathogen, and the dose of the fungicide used. Besides, among tested fungicides, only tricyclazole, mancozebe and the carboxine +Thiram association are able to provoke an increase of the germination of seeds, length of coleoptiles and roots as well as a decrease of the lesions on coleoptiles for both pathogens without damaging seeds. Indeed, Tricyclazole and Carboxine + Thirame association, brought respectively to 1 g / kg and 1 ml / kg of grains, reduces to 100%(fully) the development of the necrosed hurts caused on the coleoptile by P. oryzae. Mancozébe at 2 g / kg of grains got 87 % of reduction of the disease. However, a better germination of grains and a good development of the coleoptile and the roots require 2 g / kg of Tricyclazole, 3 g / kg of Mancozebe and 3 ml / kg of the combination Carboxine + Thirame. Mancozebe at 3 g / kg protects better the coleoptile against the lesions caused by H. oryzae (94.4 %), followed by Tricyclazole at 3 g / kg (80.5 %) and Carboxine + Thirame at 3 ml / kg (72.2 %). These doses also increase the percentage of germination of grains, the length of roots and coleoptiles. The treatment of grains using 1 and 2 grammes of Tricyclazole per kilogramme of grains strongly protected the seedlings of rice for four weeks, compared to the treatment based on P. oryzae (respectively 81.3 and 89.33 % at 4th week). This fungicide, brought to 3 g / kg of grains, continues to protect plants even five weeks after the treatment (77.78 %). Concerning the helminthosporiose, Tricyclazole applied to 3 g / kg of grains reduced the disease to 77.8 % and 70.7 % respectively three and four weeks after treatment. When the tricyclazole is mixed with Mancozebe (1.5g+1.5g) the reduction reaches 100% during the 6th week for P. oryzae and 84.29% for H. oryzae.
