Morphological characterization of the causal agent of mango red rust in two production basins (Noun and Lékié) in Cameroon

Abstract

ABSTRACT Objective: In Cameroon, mango fruit is of vital importance as it is essential for food, health, nutritional and economic security of many villages and small cities. Unfortunately, its yield is reduced by numerous diseases such as red rust, for which there is no appropriate control method yet. The aim of this study was to contribute to the control of mango red rust through morphological characterization of the causal agent in two production basins. Methodology and Results: The state of the disease and its symptoms were assessed at the two study sites (Noun and Lékié). The pathogen was characterized morphologically, the incidence and severity assessed and finally a pathogenicity test was carried out on the laboratory. The results show that the incidence was 100% in both sites, while the severity ranged from 58.23 % to 10.75% in Noun and Lekié respectively. The development of red rust on mango was therefore significantly different at the two sites Typical rust symptoms are characterized by rusty brown-orange spots of circular shape, with leaves showing an average of 65 lesions with an average diameter of 2.32 mm in Noun, while in Lekié there was an average of 87 lesions with an average diameter of 2.43 mm. Microscopic observation showed that the sporangiophores were single or grouped, septate (with an average of 6 partitions). At the Noun site, observation showed an average of 4 sporangiophores per thallus with an average size of 325 µm/19.3 µm and each sporangiophores produced an average of 3 sporangia with an average size of 32.15 µm/22.15 µm. For Lekié, microscopic observations showed an average of 3 sporangiophores per thallus with an average size of 253.55µm/16.05µm and each sporangiophore produced an average of 3 sporangia with an average size of 20443 Kone et al., J. Appl. Biosci. Vol: 193, 2024 Morphological characterization of the causal agent of mango red rust in two production basins (Noun and Lékié) in Cameroon 26.45µm/15.35µm. The pathogenicity test carried out showed no characteristic symptoms of red rust on the leaves inoculated with the algal suspensions. Conclusion and application of results: The symptomatological study, microscopic observation and study of the micro-morphological characteristics of the strains associated with the red rust symptoms enabled us to identify the Cephaleurus virescens species (which is the highest among the different species of the Cephaleurus genus) as responsible for the disease in the two study sites. Key words: Algae; Cephaleurus virescens; Red rust; sporangium; sporangiophore.