The banana plant (Musa spp. L) is a widely produced crop, with an average world production of fruit around 62.7 million MT per year in 2006. India, Brazil, China, Ecuador, and the Philippines were among the top banana producers.
The banana is an economically significant commodity, with the banana plant able to yield various products apart from fruit, such as fiber, banana peel for fuel, and food wrap from leaves. Various fruit varieties are present and commercially distinct: Cavendish for export; Lakatan and Latundan for local markets; and Cardaba for the banana chip industry. Cavendish bananas are also used for manufacture of feeds, flour, vinegar, and banana catsup. Banana cultivation generates jobs for some ten million people in 25 tropical countries and constitutes the living of small-scale farmers.
The banana is common in tropical regions of Southeast Asia, where it originated. The fruit contains on the average 75% water, 21% carbohydrate, and about 1% each of fat, protein, fiber, and ash. They are valuable sources of vitamin A, vitamin C, vitamin B6, phosphorus, calcium, and potassium. Aside from their trade value, bananas serve as staple food for an estimated 400 million people in tropical countries. Only 10%-15% of bananas are exported; about 85% are consumed locally by producing countries.
The herbaceous, tree-like crop is from the order Zingiberales, family Musaceae, section Eumusa, and genus Musa. Bananas are grown in more than 120 countries, with the term usually referring to the soft and sweet fruit which is yellow and fully ripe when eaten.
All cultivated bananas are triploid, sterile hybrids derived from the cross between Musa acuminata and Musa balbisiana. New plants arise only through vegetative propagation of suckers, leading to low genetic variability. Thus Musa species are in danger of being wiped out from outbreaks of disease such as black Sigatoka, anthracnose, and Panama disease, which often affect the fruit yield of the plant. In fact, devastation by Fusarium wilt or Panama disease caused the replacement of Gros Michel banana crops by Cavendish species worldwide.
The market practice for bananas involves fresh fruit traders and middle men buying produce from farms, and consignees distributing sales to wholesalers and retailers. There is no seasonality for bananas, and the fruits can be harvested any time of the year in topical countries. Thus bananas in plantations and small farms can be observed at any stage of vegetative growth and maturity. The advantage of this is a continuous supplement of nutritious food, and a regular source of income. However, this poses a danger since the plant is endlessly exposed to adverse environmental factors, pests, and pathogens.
Diseases are among the most important factors in banana production worldwide. They remain a primary focus of breeding programs, where biotechnological efforts exist to improve the banana crop.
The most economically important disease affecting bananas not only in the Philippines but in most banana-producing countries is black Sigatoka, a disease noted commonly by characteristic black spots and necrotic yellowing of banana leaves. The disease itself is caused by Mycosphaerella fijiensis, a fungus known to attack the banana and no other crop.
Black Sigatoka is considered the most damaging and costly disease of bananas and plantains since 27% of total production costs is due to its control, to which around 50% lower yield of fruit may occur when control measures fail. It affects the leaves of plants, destroying leaves rapidly when uncontrolled. The result is a reduction in surface area for photosynthesis, which decreases growth and fruit yield. However, black Sigatoka's most harmful impact is the premature ripening of fruit, which can occur while the bananas are in transport or storage. The reduction of time for fruit maturity was found to be significantly higher in leaves stricken with the disease, and when crude extracts of M. fijiensis were injected on the banana fruit. Host resistance studies led to the discovery and identification of phytotoxins produced by the pathogen, none of which was associated specifically with early ripening. It was therefore hypothesized that a physiologically active substance was translocated and induced at certain levels of disease severity.
Also known as black leaf streak or BLS, black Sigatoka was first described in Fiji in 1963 and is similar in symptoms to yellow Sigatoka caused by Mycosphaerella musicola. It was already widespread in the Pacific even before its discovery. The pathogen, Mycosphaerella fijiensis, later spread to other banana-growing areas in Latin America as well as to other banana-growing regions in the world. In 2009, only Argentina, Paraguay, and the French Antilles were free of the disease. In banana-producing regions such as Asia and Central America, M. fijiensis eventually replaced M. musicola, which grows at higher altitudes and lower temperatures. BLS is more virulent and even affects a wider range of genotypes, including plantains, desserts, and ABB cooking bananas not affected by yellow Sigatoka. Gasparotto (2005) reported that aside from bananas, M. fijiensis also infects leaves of Heliconia psittacorum found in Brazil.
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