BULLETIN - Heliconia Society International

THE BULLETIN / JANUARY 2010 2005 PAGE 99the roots of the plant, colonizes and grows within the vascularsystem and eventually chokes off the flow of waterand nutrients to the plant. The growing fungus produces amycotoxin, fusaric acid, which is then carried in the transpirationstream and causes the yellowing of the olderleaves initially which then spreads to the youngerleaves. Eventually the leaves collapse near the stem andthe plant dies usually before producing fruit (Ploetz, 2000).The fungus that causes Panama disease can live for manyyears in the soil and is easily spread by the use of rhizomesor “suckers” which are commonly used as plantingmaterial for starting new plantations. The pathogen canalso be spread by irrigation water and infected soil on thetools and shoes of workers (Ploetz, 2000).In addition to Panama disease, the banana is alsoinvolved in a fight against several other diseases. Two ofthe most damaging are Black Sigatoka Disease or BlackLeaf Streak Disease (BLSD) and Banana Bunchy Top Diseasecaused by the Banana Bunchy Top Virus (BBTV).BLSD is caused by the fungus Mycosphaerella fijiensisMorelet and attacks the leaves of the banana plant (Bakryet al., 2009; Heslop-Harrison & Schwarzacher, 2007). Thedisease can cause significant reductions in yield and isonly partially controlled by the regular aerial application offungicides. It is estimated that 15-20% of the productioncosts associated with bananas is due to the need to applyfungicides to treat BLSD. Hybrid bananas that possessresistance to BLSD have been produced in bananabreeding programs. Banana Bunchy Top Disease causedby the virus BBTV is another serious disease of bananasthat is transmitted by aphids (Heslop-Harrison &Schwarzacher, 2007). However, this has a more restrictedworld-wide distribution.Fears about Panama Disease and Market ImpactPanama disease was responsible for causing a numberof problems for the banana industry in China in recentmonths. Due to reports that were published in the media inChina during the spring of 2007, the general populationbecame afraid to eat bananas. The reports of the disease inthe banana plantations led to rumors that Panama diseasewas dangerous to people. This resulted in reduced purchasingof the fruit by the general population. As a resultof the reduced demand, there was heavy overproduction offruit, which resulted in much lower prices and a huge economicloss for the banana industry in China (Koeppel,2008).Author Dan Koeppel described the situation in hisbook “Banana: The Fate of the Fruit That Changed theWorld”, published in early 2008. “The blight became bignews in China during the middle of the year, when a newspaperarticle described the malady as 'banana cancer'.Within days, scores of consumers and farmers were avoidingthe fruit, fearing it would make them sick. Within amonth, banana sales across China had plummeted”(Koeppel, 2008). When asked about thepotential danger of eating fruit from plants grown insoils infested with the Panama disease pathogen, Dr.Alice C.L. Churchill, from Cornell University and Chairof the ProMusa Crop Protection Working Group, madethe following statement for this article: "Fortunately,consumer fears of contracting a disease from bananasharvested from F. oxysporum f. sp. cubensecontaminatedareas are unfounded since the fungus is nota human pathogen. Like most plant pathogens, thefungus that causes Panama disease is specific for itsplant host, in this case susceptible banana and somealternative plant hosts, primarily infecting the roots ofplants grown in contaminated soil. Although the roots,pseudostem, and leaves of infected banana plants willeventually show disease symptoms caused by fungaldamage to the plant vascular system, the fungus is notknown to infect or contaminate the fruits of the plantbut, instead, significantly weakens and eventually killsthe plant, reducing fruit yield during disease progression.Therefore, consumption of fruit from Panama diseaseaffectedplants poses no direct risk to consumers."In addition to attacking bananas, different formsof F. oxysporum attack a number of important plantsgrown for food production around the world includingtomatoes, potatoes, peppers, eggplants, asparagus, gingerand melons (Nelson, 1990).Possible SolutionsThere are few effective methods for the managementand control of Panama disease. Chemical treatmentsare of little use for the effective, long term removalof F. oxysporum f. sp. cubense from the soil(Bakry et al., 2009). Varieties of bananas susceptible toPanama disease Tropical Race 4 can be grown in noninfectedsoil if disease-free plants from tissue culture areused as planting material and the pathogen is not introducedinto the area by some other means. Even thoughdisease-free plants can be provided for establishing bananaplantations, it is very difficult to prevent the plantsfrom contracting Panama disease after they are placed inthe fields (Ploetz, 2000).Employing banana cultivars that possess resistanceto the fungus is at present the best method availablefor the production of bananas in soils infested withthe pathogen. Several Fusarium-resistant cultivars ofthe Cavendish group have been developed by the TaiwanBanana Research Institute as a result of intensive selectionfor disease-resistant somaclonal variants (Hwang &Ko, 2004). When plants are produced using tissueculture, differences are sometimes observed in theplants. These differences are referred to as somaclonalvariation. These somaclonal variations can be a negative