Bananas, disease, diversity, research and The One Show

Pat Heslop-Harrison and bananas

Our favour­ite fruit, the banana, is threatened by fungal, viral and bac­terial dis­eases. This was dis­cussed on the BBC TV pro­gramme ‘The One Show’ on 13 May, to include an inter­view with Pat Heslop-Harrison by renowned journ­al­ist, food critic and presenter Jay Rayner. The bana­nas we eat in the West are almost all of the single vari­ety called Cavendish, intro­duced to the world through the col­lec­tions based at the coun­try house Chatsworth in the 1820s, as shown in the pro­gramme. (For UK view­ers and proxy-server users, avail­able on iPlayer here until 20 May.)

Plants, just like people, are con­tinu­ously threatened by new types of dis­eases. These dis­eases change every year so plants that used to be immune to the dis­ease become sus­cept­ible or chem­ical con­trols (plant medi­cines) become inef­fect­ive. Our work in Leicester (pro­nounced ‘Lester’) is look­ing at the genetic diversity of all bana­nas and related plants (‘bird of para­dise’ flower and ginger are examples) to find those with genetic prop­er­ties that will allow bana­nas to meet these chal­lenges, and make sure we can enjoy the healthy ‘five-a-day’ fruit, the 500 mil­lion people eat­ing banana as a staple starch source keep their food, and the 30 coun­tries where banana is a major cash crop can increase their prosper­ity and sus­tain­ab­il­ity of agriculture.

Cavendish Banana Dead from Fusarium TR4 in south China

Cavendish Banana Dead from Fusarium TR4 in south China

As poin­ted out in the One Show, Cavendish banana is now being attacked by a new race of the Panama dis­ease, Fusarium Tropical Race 4 (TR4 for short). The pic­ture shows com­plete dev­ast­a­tion of a plant­a­tion in Guangzhou, China. Another race of the same dis­ease stopped pro­duc­tion of the pre­vi­ous dom­in­ant vari­ety, Gros Michel or Big Mike.

Gros Michel banana killed by Panama disease

Gros Michel banana killed by Panama disease

Many dis­eases can be con­trolled by care­ful grow­ing of the plants, start­ing with healthy plant­ing mater­ial grown in dis­ease free soil — any gardener knows about the import­ance with another veget­at­ively propag­ated crop, potato. For a bac­terial dis­ease of banana called Xanthomonas wilt, stop­ping plant-to-plant spread means dip­ping the machete used to cut the fruit bunches and dead stems into a bucket of bleach between every plant. Stopping dis­ease spread also needs care­ful crop man­age­ment and cut­ting out of dis­eased plants: in parts of South India, banana-funeral-pyres are found every mile along road­sides, burn­ing plants with banana bunchy-top virus. For another fungal dis­ease, sig­a­toka, cut­ting leaves at the first sign of infec­tion and remov­ing or pla­cing them upside down can slow spread of dis­ease. Controlling plant dis­eases also means strict con­trol of move­ment of plants — just like foot and mouth dis­ease in the UK.

Quarantine Bin - Don't Spread Diseases

Quarantine Bin — Don’t Spread Diseases

In Africa, polit­ical parties must stop using real banana leaves as their sym­bol at ral­lies or on buses, where they are driven around vil­lages; Mexicans need to stop using banana leaves as cool­ing hats or to cover boxes of fresh fruit. For banana, the recog­ni­tion of the new TR4 dis­ease and its sever­ity in the early 2000s has meant that the spread between con­tin­ents and out of South East Asia has at least been slowed. The first press stor­ies at the time — in the UK, includ­ing The Guardian and The Telegraph — cer­tainly increased levels of bio­se­c­ur­ity and care in trans­fer of plants.

Another approach to dis­ease con­trol is sprays. Like anti­bi­ot­ics in human medi­cine, plant dis­eases can become res­ist­ant to them, or the side-effects and tox­icity of the drugs are real­ised to be so great that they are with­drawn — so both the costs and lack of sus­tain­ab­il­ity means that the spray approach is not sustainable.

Aerial spraying to control banana disease

Aerial spray­ing to con­trol banana disease

Banana germplasm collection showing diverse genotypes

Banana ger­mplasm col­lec­tion show­ing diverse genotypes

Fortunately, within banana, there is a lot of genetic vari­ation, and the dif­fer­ent wild and cul­tiv­ated lines have dif­fer­ences in res­ist­ance. Our work is look­ing at diversity in banana, and hop­ing to find the genes which can be used to meet the dis­ease chal­lenges faced by the crop.

Banana plants look rather sim­ilar, and it is dif­fi­cult to meas­ure the dif­fer­ences, not least because their appear­ance is a func­tion of both the genes and the envir­on­ment — known as the gen­o­type x envir­on­ment inter­ac­tion. Growing plants to look at dis­ease responses is also dif­fi­cult — and you would cer­tainly not want to move a dis­ease from one banana grow­ing coun­try to another.

Banana germplasm maintained in sterile tissue culture

Banana ger­mplasm main­tained in sterile tis­sue culture

In fact, here in Leicester we have bana­nas — with their dis­eases — from all over the world. One plan we have is to grow plants in our con­fined green­houses where infec­tion can be meas­ured, and there is no chance of spread­ing dis­ease to plant­a­tions. Resistance tri­als are essen­tial, and we can then find the genes which give res­ist­ances, and sur­vey even more vari­et­ies by dir­ectly read­ing their DNA sequences.

The final part of the puzzle to ensure the future of banana is using the diversity. Almost all bana­nas that are eaten have three genetic par­ents, not just two which most spe­cies and wild bana­nas have. This is part of the reason it makes fruits without seed — in human terms, like a pla­centa without a baby. We need new cross­ing and ways to use the genes to bring the res­ist­ances into banana, another part of the pro­jects here in Leicester with both the­or­et­ical and prac­tical aspects.

The wild fertile seeded banana 'Jungle Kela'

The wild fer­tile seeded banana ‘Jungle Kela’

Banana DNA polymorphisms seen in a fluorescent separation assay

Banana DNA poly­morph­isms seen in a fluor­es­cent sep­ar­a­tion assay

So over­all, I am very optim­istic about the future of banana as a fruit in the UK, and as a staple food in the trop­ics, and as a source of much-needed and sus­tain­able income. But the future vari­et­ies will be dif­fer­ent from those we eat now, and hope­fully the genetic improve­ments will increase sus­tain­ab­il­ity of pro­duc­tion through­out the world, while deliv­er­ing the nutri­tion required by a pop­u­la­tion increas­ing to 9 billion.

Many types of banana on sale in Kerala, South India

Many types of banana on sale in Kerala, South India

For those look­ing for more inform­a­tion, sev­eral other AoBBlog​.com posts have writ­ten about bananas:

Two papers in Annals of Botany, freely avail­able (although writ­ten with a tech­nical approach and formal writ­ing style), also give much inform­a­tion about banana research: Did back­cross­ing con­trib­ute to the ori­gin of hybrid edible bana­nas? by Edmond De Langhe, Eva Hribová, Sebastien Carpentier, Jaroslav Dolezel and Rony Swennen (http://​dx​.doi​.org/​1​0​.​1​0​9​3​/​a​o​b​/​m​c​q​187 )

and my own: Heslop-Harrison JS, Schwarzacher T. 2007. Domestication, gen­om­ics and the future for banana. Annals of Botany 100(5):1073–1084. (http://​dx​.doi​.org/​1​0​.​1​0​9​3​/​a​o​b​/​m​c​m​191 )

Several power­point talks of mine are on the web, access­ible through my labs homepage at http://​www​.mol​cyt​.com For any University Students suf­fer­ing from Death-by-Powerpoint, there is a non-powerpoint talk on Prezi.

Editor Pat Heslop-Harrison. ORCID 0000-0002-3105-2167

Pat Heslop-Harrison is Professor of Molecular Cytogenetics and Cell Biology at the University of Leicester. He is also Chief Editor of Annals of Botany.

9 Responses

  1. Newton Alexander says:

    Prof. Pat: fas­cin­at­ing! I’m in Grenada. We have roughly about 8 var­it­ies of bana­nas in G/da. The main types are the export­able ones (we don’t export any­more) — no par­tic­u­lar name; plantains, some gros michel, which some farm­ers hang on to for sen­ti­mental reas­ons; blog­goes — gen­er­ally eaten green and now riddled with Moko/Panama desease and another very pop­u­lar type, gen­er­ally eaten ripe, called rock figs. your article/blog is inter­est­ing to in that we get no tech­nical help/advice from the local min. of ag. the pre­dom­in­ant type, the once export­able one, suf­fers hor­rendously from what we call Leaf Spot. The main char­ac­ter­istic is that the leaves whither and die, leav­ing the plant with no means of absorb­ing mois­ture, res­ult­ing in pre­ma­ture destruc­tion of the fruit.
    In G/da, most fam­il­ies farm a small plot of land and rely heav­ily on the cul­tiv­a­tion of the vari­ous vari­et­ies of the bana­nas for food and in some cases a little cash. I farm two one-acre plots. For me, farm­ing keeps me occu­pied (I’m a few days away from 70), it provides food and the occa­sional dol­lar.
    I’ll be extremely grate­ful for any advice with you may be able to give other what’s already in your blog.

    • Newton, Thanks for the fas­cin­at­ing per­spect­ive and insight into the chal­lenges you are facing in grow­ing banana. I really value these com­ments — the account of vari­et­ies you grow, the real dis­ease prob­lems, and how you grow and use bana­nas. They help give my lab’s research extra dir­ec­tion to address some of the long stand­ing and increas­ing dif­fi­culties with grow­ing crops such as banana. I expect the leaf spot is the black sig­a­toka leaf spot, which is one of the very destruct­ive dis­eases. I am con­tact­ing some col­leagues who have more exper­i­ence in the Caribbean and I hope they will be able to add some com­ments soon. Pat.

  2. More news on the spread and need for research on this dev­ast­at­ing Fusarium research comes from the Philippines on 7 October 2011

    Panama dis­ease has become a major threat to bana­nas in the Philippines
    [MANILA] Scientists in the Philippines are urging their gov­ern­ment to set up a national research centre to develop vari­et­ies of banana res­ist­ant to a dis­ease now threat­en­ing plant­a­tions across South-East Asia. The move fol­lows appeals from grow­ers who are facing the uncon­trol­lable spread of Panama dis­ease, caused by a destruct­ive fungus that has wiped out banana vari­et­ies in the past.

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