This study was carried out to find out how dependent are two local rice varieties (Magitolngar and Tox-728-1) to inoculation with selected endogenous arbuscular mycorrhizal fungi (AMF) in a field where they were isolated. The multi-indigenous endomycorrhiza spores previously isolated and identified were the active ingredient in the production of bioinoculants used for this purpose. Spores massively multiplied from the rhizosphere of each rice variety in each of the four locally collected soils substrates were harvested to constitute 08 AMF inoculants (Kema = T1; Lama = T2; Latox = T3; Ndjatox = T4; Koloma = T5; Kolotox = T6; Ndjama = T7; Ketox = T8). These inoculants were field tested on the two rice varieties at Kelo, under a complete randomized block design, comprising 10 treatments (8 inoculants, 01 positive control = T9, 01 negative control = T10), each of which was repeated thrice. The analysis of data indicates that AMF-inoculated plants were taller, developed more tillers/plant, and produced more rice grains/panicle than non-AMFinoculated plants for both studied rice varieties. The rice variety Madjitolngar yielded more grains (7.5 t/ha) than the Tox-728-1 variety (5.8 t/ha). Moreover, inoculants Koloma (T1), Latox (T3) and Kolotox (T6) on the one hand, Koloma (T1) and Ketox (T8) on the other hand, were best suited for the improvement of growth and yield of the rice varieties Madjitolngar and Tox-728-1 respectively, tested under field conditions at Kelo. In this study, the two rice varieties have shown a dependency to endomycorrhizal symbiosis at Kelo, and therefore, an industrial-scale production of efficient endomycorrhal inoculants is necessary to sustainably boost the productivity of this important crop in Chad.

In Chad, rice is grown for its starchy seeds or caryopses, but is also for consumption in the form of seeds pasta with soup. However, little or no work has been conducted in Chad to assess the composition of endomycorrhiza community inhabiting the plant rice rhizospheres. Hence, the main objective of this study was to investigate on native endomycorrhiza that are efficient to establish a symbiotic relationship with two rice varieties in the Sahelian zone in Chad. Two rice varieties were grown in a pot experiment on composite soils samples from Laï, Kelo, Kolobo and N’Djamena for 3 months. Parameters such as mycorrhizal frequency, intensity, specific density and richness were determined following to the standard methods. After spore extraction, species description and characterization were obtained through the informations provided by the International Vesicular Mycorrhizal fungi collection (INVAM): http://invam.caf.wv.edu/fungi/taxonomy/species ID.htm. The highest specific endomycorrhizal density (97.3%) and richness (11%) were registered respectively at kelo, Laï and Kolobo. The endomycorrhizal frequency and intensity were respectively between 4.33-7.33% and 0.8-2.9% for the two rice varieties. Eleven endomycorrhiza species belonging to six genera were identified from different soil samples. These include Septoglomus (S. constrictum, S. deserticola); Rhizophagus (R. aggregatus, R. fasciculatus, R. intraradices); Acaulospora (A. lacunosa, A. rugosa, A. trappei); Claroideoglomus lamellosum; Glomus pansihalos and Diversispora epigae. S. constrictum was the most dominant and frequent species found in all the soil sampling sites, while R. aggregatus was the less frequently encountered specimen. The lowest macorrhizal richness and frequency obtained is a proof that cultivation of rice dependent on endomycorrhiza in this zone. The multi-native endomycorhiza spores identified are the active principle to be included in the bioinoculants production in order to increase and improve the production of rice in the south of Chad.

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