Chili peppers come to the rescue of bananas

Bananas are susceptible to all sorts of diseases. One of those pests is Banana Xanthomonas wilt (BXW), caused by the bacterium Xanthomonas campestris pv. Musacearum, and it is considered one of the most devastating diseases of bananas in the Great Lakes region of Africa.

It has been identified in the 1960s in Etiopia on a close relative of the banana, the Ensete ventricosum. It has then spread rapidly and has to date been diagnosed in several Central and East African countries, such as Rwanda, Congo, Tanzania, Kenya, Burundi and Uganda. The rapid spread of the pathogen is threatening the livelihood of millions of Africans who rely on banana fruit for food security and income. The disease is very destructive and is infecting all banana varieties, including both East African Highland bananas and most exotic cultivars of the banana.

Not one banana cultivar in the affected region has shown any resistance to Banana Xanthomonas wilt. Chili peppers however, have antibacterial properties and scientists have been able to transfer two separate genes form a chili pepper to a banana.

The two genes, encoding the proteins plant ferredoxin-like amphipathic protein (pflp) and hypersensitive response-assisting protein (hrap), did induce a hypersensitive respons and systemic acquired resistance within the banana. The proteins work by quickly killing the cells that come into contact with the disease-spreading bacteria, blocking the disease from spreading any further.

The results of the study confirmed that expression of the Pflp gene in banana results in enhanced resistance to BXW: About 67% of transgenic lines evaluated were completely resistant to BXW[1].

The majority of transgenic lines (six of eight) expressing Hrap did not show any symptoms of infection after artificial inoculation of potted plants in the greenhouse, whereas control nontransgenic plants showed severe symptoms resulting in complete wilting[2].

Which is a promising step forward. Thanks to the trusty chili pepper.

Field trials in Uganda showed that the banana showed complete resistance to the wilt over three generations.

[1] Namukwaya et al: Transgenic banana expressing Pflp gene confers enhanced resistance to Xanthomonas wilt disease in Transgenic Resistance - 2012
[2] Tripathi et al: Expression of sweet pepper Hrap gene in banana enhances resistance to Xanthomonas campestris pv. Musacearum in Molecular Plant Pathology - 2010