Banana streak virus Identified for the First Time in Peru in Cavendish Banana (Musa AAA).

In October of 2005, a field survey was done in the province of Piura in northern Peru to determine the cause of a disease known locally as "mosaico" that was affecting organic Cavendish banana (Musa AAA) grown for the export market. Disease symptoms consisted of pronounced chlorotic and necrotic lesions on leaves of affected plants. Twenty-four farms were visited, and at each location, 10 randomly selected plants at flowering stage were evaluated for disease incidence and severity. Plants showing virus-like symptoms were observed in 18 of the 24 locations (75%). Fifty-two banana leaf samples, 27 from plants showing virus-like symptoms and 25 from asymptomatic plants, were tested for the presence of Banana streak virus (BSV), Cucumber mosaic virus (CMV), and Banana mild mosaic virus (BanMMV) by immunosorbent electron microscopy (ISEM) using partially purified leaf tissue extracts (2).The same extracts were also tested by immunocapture PCR (IC-PCR) for presence of BSV and specific BSV isolates (BSV-OL, BSV-GF, BSV-IM, and BSV-CAV) using badnavirus-specific degenerate primers and BSV isolate-specific primers, respectively (1). Seventeen of 27 leaf samples showing virus-like symptoms (63%) tested positive for BSV by ISEM and IC-PCR using badnavirus, but not isolate-specific, primers. The symptoms on the 10 samples that tested negative were not typical of BSV infection. One asymptomatic leaf sample (4%) also tested positive for BSV. To validate the PCR results, the nucleotide sequence of the amplicon from a plant showing the most prevalent foliar symptom type was determined. This sequence (GenBank Accession No. DQ674317) had ≤86% homology to the corresponding ORF III polyprotein region of BSV and other badnaviruses. Neither CMV nor BanMMV was detected in any of the 52 samples tested. From these results, it was concluded that "mosaico" disease of organic Cavendish bananas in northern Peru is associated frequently with BSV infection and that there is a high incidence of BSV infection in this area. To our knowledge, this is the first report of BSV occurrence in Peru. It was both surprising and interesting that neither BSV-OL nor BSV-GF, the two BSV isolates found most commonly in banana (Musa AAA) and plantain (Musa AAB) in South and Central America (B. E. L. Lockhart, unpublished), was detected in Cavendish banana in northern Peru. Failure to detect BSV-OL and BSV-GF suggests that field infection may be due to vertical transmission by clonal propagation rather than to horizontal transmission from local plantain and that control of "mosaico" disease could therefore be achieved by use of virus-free planting material. References: (1) A. D. W. Geering et al. Phytopathology 90:921, 2000. (2) B. E. L. Lockhart et al. Phytopathology 82:921, 1992.

First Outbreak of Banana Streak Badnavirus Infection in Commercial Export Bananas in Costa Rica.

Banana streak badnavirus (BSV) is the most widely occurring virus in banana and plantain (1) but has not been reported to be a significant problem in commercial export bananas. In early 1999, the first severe outbreak of BSV infection in commercial export bananas (Musa AAA cv. Grand Nain) was recorded at Siquirres on the Atlantic coast of Costa Rica. Disease incidence in the plantation was 60% and symptoms included foliar chlorotic streaks, stunting of plants, splitting and internal necrosis of pseudostems and fruits, cigar leaf necrosis, and bunch emergence through the pseudostem. Diseased plants within a 0.8 ha area were eliminated to prevent possible further spread of the disease. The presence of BSV in diseased plants was confirmed by enzyme-linked immunosorbent assay and immunosorbent electron microscopy (1). Cucumber mosaic virus and Banana mild mosaic virus, which also occur in banana and plantain in Latin America (2), were not detected in the plants tested. Other recent accounts of BSV occurrence in commercial banana plantations in South America (our unpublished results) suggest that BSV occurrence in export bananas may be more significant than previously thought. References: (1) F. Gauhl et al. Int. J. Pest Management 45:167, 1991. (2) D. R. Jones, ed. 1999. Diseases of Banana, Abacá and Enset. CABI Publishing, Wallingford, U.K.

First Report of Banana Streak Badnavirus in Plantain Landraces in Southern Cameroon, Central Africa.

Banana streak badnavirus (BSV) has been reported from Musa spp. in many parts of West Africa, including Benin, Côte d'Ivoire, Ghana, and Nigeria (1). Symptoms of BSV infection in Musa spp. are sometimes similar to and confused with those caused by cucumber mosaic virus (CMV). BSV is prevalent in areas of southern Nigeria bordering Cameroon, and the disease may also be present in other Central African countries. In June 1996, six leaf samples with viruslike yellow/chlorotic streak symptoms were collected from plantain in the four villages, Awae, M'Balmayo, Nkolfep, and Nkolfoulou, within a 60-km radius of Yaoundé, Cameroon's capital. The samples were indexed for BSV and CMV by both triple antibody sandwich indirect enzyme-linked immunosorbent assay (TAS-ELISA) and immunosorbent electron microscopy (ISEM) to ascertain the presence of these two viruses. The TAS-ELISA was performed with rabbit polyclonal antiserum (obtained from B. E. L. Lockhart, University of Minnesota) for trapping and mouse polyclonal antiserum (obtained from G. Thottappilly, IITA) for detection. Out of the six samples, one tested strongly positive (>×2 A405 of the healthy control) and four were weakly positive (<×2 but >×1.5 A405 of the healthy control) for BSV by TAS-ELISA. However, all six samples contained BSV particles when examined by ISEM with rabbit polyclonal antiserum (from B. E. L. Lockhart) for trapping. None of the samples tested positive for CMV. These results confirm that BSV is present in Cameroon and that BSV is likely to be the causal agent of the symptoms. Reference: (1) C. Pasberg-Gauhl et al. Plant Dis. 80:224, 1996.