First disease report of a root and rhizome rot of banana by ceratobasidium sp. AG-G (Rhizoctonia fragariae)
2009
Pérez, L., Instituto de Investigaciones de Sanidad Vegetal, Ciudad de La Habana (Cuba) | Martínez, E., Laboratorio Central de Cuarentena Vegetal, Ciudad de La Habana (Cuba) | González, M., Instituto de Investigaciones de Sanidad Vegetal, Ciudad de La Habana (Cuba)
It is described a root necrosis which develops in a stem and central leaf rot in Pisang awak, FHIA 21 and FHIA 23 tissue culture banana plants growing in nurseries on a substrate of sugarcane filter press and 10 por ciento of zeolite. In the border of the lower leaves of the plants appeared a mild yellowish discoloration which develops in a characteristic deep yellow-orange-reddish shade. The affected plants showed between 10 and 30 por ciento of necrotic roots with different levels of severity. Internally, could be appreciated the continuity of the infection from the roots to the developing corm that finally become completely necrotic. The affected plants invariably present a delay of the growth and die. All the isolates obtained from the affected plants belong to a Rhizoctonia specie with a light cream to gray binucleated mycelia exhibing aerial growth by hyphal aggregates. The alignement of the amplificated and sequenced ITS1-5.8S-ITS2 rDNA region analized by BLAST, showed a 93 por ciento homology (identity = 91 por ciento, E value = 0) with Ceratobasidium sp. AG-G (Rhizoctonia fragarie). This isolate form a clade in the cluster analysis performed with sequences reported in the NCBI database belonging to binucleated Ceratobasidium sp. AG-G. Healthy FHIA 23 tissue culture plants inoculated artificially with the isolate obtained from natural diseased plants to fulfil the Koch's postulates shown symptoms after 17 days, from which the fungus was re-isolated. This is the first report of R. fragarie as causal agent of root and corm rots of banana and plantains.
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