Evaluation de l'effet combiné de deux souches de Mycorhize (Gigaspora Margarita et Acaulospora Tuberculata) sur l'évolution du Mildiou du taro [Colocasia Esculenta(L) Schott] causé par Phytophthora Colocasiae Racib

Abstract

Taro (Colocasia esculenta L. Schott) is a tuber plant from South-East Asia origin. It is cultivated for its edible tubers and leaves. The main cause of the decline in production is attributed to Phytophthora colocasiae Racib., causal agent of the Taro Leaf Blight (TLB). Several studies have shown the importance of mycorrhizae in protecting plants against pathogens. Thus, to assess the combined effect of two strains of mycorrhizae (Gigaspora margarita and Acaulospora tuberculata) on the development of Taro Leaf Blight, three taro cultivars (Ekwanfré, Macoumba and Banlah) were cultivated. Morphological and histological parameters were taken every 30 days until the 90th. Morphological analysis showed that mycorrhizal Macoumba and Banlah cultivars have achieved greater heights is respectively 31.9 ± 0.2 cm and 26.5 ± 0.4 cm in D90 against 17.3 ± 0.3 cm and 24.5 ± 0.3 cm in the control. Other morphological parameters are more pronounced in the absence of mycorrhizae although the differences are not significant. The small amount of significant results do not allow us interesting assertions about the growth and development of mycorrhizal seedlings. Histological analysis showed the maximum frequency of mycorrhization obtained is 64% in Macoumba at D30, 63% in Ekwanfré at D60 and 52% in Banlah at D60. After these 90 days, the seedlings were infected and the impact of mildew evaluated for 12 days. It is highest in the control of 78.57% in Ekwanfré, 130% and 145% in Macoumba respectively for D3, D6 and D9 against 15.38%, 18.18% and 9.09% in the same days at the same cultivars respectively. Biochemical analysis showed that mycorrhizal seedlings are richer in protein reserve is 4.31 ± 0.24 g.g-1 of WFM, 2.99 ± 00 g.g-1of WFM and 4.29 ± 0.46 g.g-1 of WFM respectively at Ekwanfré, Macoumba and Banlah and in the presence of infection, non-mycorrhizal seedlings get richer in anti-stress proteins or enzymatic proteins of 3.16 ± 0.26 g.g-1 of WFM, 3.62 ± 0.01 g.g-1 of WFM and 3.35 ± 0.04 g.g-1 of WFM respectively at Ekwanfré, Macoumba and Banlah. As for AsP and Pox, levels decreased in the presence of mycorrhizae in all cultivars. All these results allow us to assign a role to the mycorrhizae, the AsP and Pox in the fight against infections in plants.