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United States Department of Agriculture

Agricultural Research Service

Research Project: REDUCING SOYBEAN YIELD LOSSES THROUGH GENETIC IMPROVEMENT

Location: Crop Genetics Research Unit

Title: First report of alternaria leaf spot of banana caused by Alternaria alternata in the United States

Authors
item Parkunan, Venkatesan -
item Li, Shuxian
item Fonsah, Esendugue -
item Ji, Pingsheng -

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 2, 2013
Publication Date: July 26, 2013
Citation: Parkunan, V., Li, S., Fonsah, E.G., Ji, P. 2013. First report of alternaria leaf spot of banana caused by Alternaria alternata in the United States. Plant Disease. 97(8):1116.

Interpretive Summary: Banana is the most frequently consumed fresh fruit in the United State. In spring and summer 2012, seven of the cultivars (Veinte Cohol, Novaria, Cacambou, Chinese Cavendish, Raja Puri, Blue Torres Island, and African Red) grown in the field at Tifton, Georgia showed tiny oval shaped, light brown to dark brown spots around the midrib on the leaves. Cultivars Kandarian, Ice Cream, Praying Hands, Saba, Belle, and Dwarf Namwah did not show any spots. The disease is caused by the fungus Alternaria alternata. In greenhouse tests, all plants inoculated with the fungus showed disease symptoms, while non-inoculated plants were healthy without symptoms. This is the first report of Alternaria leaf spot caused by A. alternata in field grown banana in the United States. Discovery of the disease in banana cultivars provides useful information about the occurrence of the disease and those cultivars appeared to be resistant to the disease may be more suitable for production.

Technical Abstract: Research efforts were initiated in 2003 to identify and introduce banana (Musa spp.) cultivars suitable for production in Georgia. In spring and summer 2012, seven of the cultivars (Veinte Cohol, Novaria, Cacambou, Chinese Cavendish, Raja Puri, Blue Torres Island, and African Red) grown in the field at Tifton, GA showed tiny oval shaped, light brown to dark brown spots around the midrib on the leaves. Disease incidences on the seven cultivars ranged from 10 to 63% with an average of 35% when a total of 52 plants were evaluated. Cultivars Kandarian, Ice Cream, Praying Hands, Saba, Belle, and Dwarf Namwah did not show any spots. Culture morphology of the pathogen isolated from disease samples was examined, and the genomic DNA was extracted from single spore cultures. The internal transcribed spacer (ITS1-5.8S-ITS2) regions of rDNA (562 bp) were amplified and sequenced with primers ITS1 and ITS4. MegaBLAST analysis of the sequence showed that it was 100% identical to two Alternaria alternata isolates, one from tea leaves in India and the other from banana in China. Pathogenicity assay was conducted in greenhouse. All plants inoculated with the fungus showed disease symptoms, while non-inoculated plants were healthy without symptoms. The fungus was re-isolated from the inoculated plants, and the identity was confirmed by morphological characteristics and ITS sequencing. This is the first report of Alternaria leaf spot caused by A. alternata in field grown banana in the United States. Discovery of the disease in banana cultivars provides useful information about the occurrence of the disease and those cultivars appeared to be resistant to the disease may be more suitable for production.

Last Modified: 9/2/2014
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