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Bract mosaic


Bract mosaic is a viral disease caused by the Banana bract mosaic virus (BBrMV) and transmitted by aphids. Its common name comes from the characteristic mosaic symptoms on the flower bracts. Infection can result in growth defects, reduced suckering and misshapen fruit. Severe incidences can lead to fruit rejection and consequently to economic losses.

Distribution

Bract mosaic was first noted in the Philippines in 1979[1]. In 1966, a disease with the same symptoms, but unkown etiology, had been reported as Kokkan disease in Kerala, India[2]. The causal agent of Kokkan disease was later confirmed to be BBrMV[3]. The disease has also been reported in Sri Lanka, Vietnam and Western Samoa[4].

Symptoms

Mosaic patterns on the bracts of the inflorescence are diagnostic. Green or red streaks or spindle-shaped lesions can appear on leaf petioles and sometimes on the midrid of new leaves (not to be confused with nitrogen deficiency). Chlorotic streaks on the leaf blade can also indicate infection. Sometimes the only symptom is on the leaf sheaths. Peeling back the dead outer leaf sheaths will reveal spindle-like streaks on the exposed pseudostem. Chlorotic streaks may also appear on bunch stems.

Transmission

The virus can be transmitted in a nonpersistent manner (i.e. retained by the vector for a short period) by at least three species of aphid, Pentalonia nigronervous, Aphis gossypi and Rhopalosiphum maidis. The virus can also be transmitted by infected planting material.

References

1. Magnaye, L. and Espino, R.R.C. 1990. Banana bract mosaic, a new disease of banana. I. Symptomatology. Philipp. Agric. 73:55-59.
2. Samraj, J., Menon, M.R., Christudas, S.P., Satyarajan, P.K. 1966. Kokkan a new disease of banana (Musa paradisiaca Linn.). Agric Res J Keral 4:116.
3. Rodoni, B.C., Ahlawat, Y.S., Varma, A., Dale, J. and Harding, R. 1997. Identification and Characterization of Banana Bract Mosaic Virus in India. Plant Disease 81(6): 669-672.