|May 2003. The banana in the photo from Pakistan shows streaking on the bracts of the flower and has deformed fingers. Can anyone identify it?
Members considered this was caused by Banana bract mosaic virus (BBMV), a disease that has been recorded in Bangladesh, India and Sri Lanka (and elsewhere). But has it been verified before in Pakistan? The severe mosaic in the bracts is a very good indication that BBMV is present. The necrosis in the pseudostem may also be a symptom of BBMV, but this is by no means definite. BBMV and severe strains of Cucumber mosaic virus can cause internal necrosis and plants can have a double infection.
It was asked whether the cultivar was Basrai? This variety, which is Dwarf Cavendish, is the most common dessert cultivar in Pakistan. In 1992, the whole Basrai industry in Sindh Province was being ravaged by Banana bunchy top virus (BBTV). Dr David Jones and Dr S. Mansoor saw total infection in some crops covering 20 hectares or more. A significant proportion of the planting material being used was infected and black aphids spread the virus to the rest. It was thought then that the only way out was to eliminate existing plantations and replace with planting material derived from virus-tested stocks. Drastic action was needed along the lines that had to be used in Australia in the 1920s. Whole areas would need to be cleared of bananas and then replanted in sequence. Buffer zones between areas would be required to prevent reinfection. The operation would have needed to have been strictly controlled by the Government and appropriate legislation introduced. There was talk in 1992 of initiating a tissue culture programme to provide the industry in Pakistan with clean stocks. This seems more necessary than ever with additional problems now being caused by CMV and BBMV.
As regards the late development of symptoms of BBTV in material taken from diseased stools, there may be several reasons. Although not documented, it could be that some suckers in an infected stool can escape infection. Could the bananas that developed symptoms after 3-4 years have been infected later from viruliferous aphids? Another possibility is that the suckers from infected stools experienced a partial recovery from symptoms (as has been described in Fiji in the Cavendish cultivar ‘Veimama’) and later symptoms return. However, it was felt that is was more likely to be the former.
It was said that black Sigatoka is now present in Pakistan. This was not the case in 1992. This is surprising, given that the disease has not been reported elsewhere in the Indian subcontinent, other than Bhutan. It was thought that the leaf spot would more likely have been caused by Mycosphaerella eumusae, which is present in India and Sri Lanka. Symptoms are very similar to black Sigatoka and yellow Sigatoka. It would be good if leaf spot specimens could be sent to Jean Carlier (CIRAD, Montpellier, France) for diagnosis.