May 10, 2011 - WHY do crocodiles have clean white teeth? ... Why do bananas bear fruits? ... from attacks by a nasty worm known by its scientific name as ...
Is it wise to inoculate bananas? Tuesday, 10th May, 2011
Dr. Opiyo Oloya
WHY do crocodiles have clean white teeth? Any good hunter will tell you that the answer lies with birds that clean up the big reptile’s teeth. In return for their cleaning services, the birds are protected by the crocodiles. Here then is a question that should wake you up. Why do bananas bear fruits? The answer, according to scientists who have studied the question lies with tiny microbes that fend off attacks from burrowing worms, weevils and other pests that usually destroy banana plants.
Sometime ago, scientists researching banana in Uganda identified Fusarium oxysporum V5w2 as a friendly microbial fungus crucial in fighting off banana-boring worms and weevils. For the purpose of this story, I have taken the letter F from the first half of the scientific name and combined it with the first three letters of the second half of the name to nickname the fungus as Foxy.
The scientists found that Foxy was especially effective in keeping young banana plants from attacks by a nasty worm known by its scientific name as Radopholus similis (just call it Rados), causing the banana tree to topple over.
Now in the age-old method in which Uganda and most African farmers removed young banana known as suckers from the old plant to plant in new fields, Foxy was always present in the soil ready to do battle with Rados.
Soon, however, scientists began producing banana seedlings by cleaning tiny pieces of banana in laboratory using a process known as banana tissue culture.
The process got rid of bad Rados, but it also got rid of the friendly Foxy. To make sure young banana plants are protected against bad Rados, Ugandan scientists began inoculating clean banana seedlings with doses of good old Foxy. The process is all natural and it is all good science. So far so good, so the scientists thought.
Now, however, a study published by a Kenyan scientist has concluded that inoculating banana with Foxy may actually be the beginning of the end of banana as we know it. Foxy, according to the study by Dr. Dennis Ochieno, is not the Good Samaritan helping young banana grow. Rather, Foxy might actually be causing more harm by making it easy for Rados to attack the tender roots of young banana.
In the study carried out in Uganda from 2006 to 2009, Ochieno noted that banana plants inoculated with Foxy “took shorter time from planting to harvest than those not treated with the microbe. Moreover, these banana plants were short, had few leaves of small size, and a shorter time to harvest.
“A considerable number of the plants in the current study became weak after inoculation while still young,” Ochieno observed in the study which formed the basis of his doctoral thesis at Wageningen University in the Netherlands. Meanwhile, young bananas that were not treated with Foxy seemed to produce heavy bunches though fewer fingers. However, scientists who supervised and are familiar with Dr. Ochieno’s conclusions urge caution. Dr. Thomas DuBois a Uganda-based banana researcher with the International Institute of Tropical Agriculture (IITA) noted that Ochieno’s own study showed that banana plants inoculated with Foxy went on to produce 36% more than those plants that were not treated.
“Look, this was just one study that needs to be taken with a grain of salt because there are flaws in the study,” he said in a phone conversation from Kampala. He however was not very specific about the flaws in the study.
A similar sentiment was echoed by Professor Arnold van Huis of Wageningen University when reached for his comments. As the lead supervisor of Ochieno’s study, Prof. van Huis pointed out that the study was sufficient for the student to get his doctorate but “the methodology was not very sound.”
But when pressed why, as a supervisor, he allowed Ochieno to graduate at all if the thesis was substandard, Prof. van Huis responded that Ochieno demonstrated that he could carry out scientific research. “But, you have to be very careful in reading the study’s conclusion which is not published in a scientific journal,” he repeated.
Both Prof. van Huis and Dr. DuBois also felt confident that enough is known about Foxy, and how it works to protect young banana from Rados. Dr. DuBois pointed out that Foxy is undergoing further tests and will need to be approved before it becomes available to
farmers in Uganda and Kenya. “We have only tested the inoculation on seven farms in total,” he said.
Nonetheless, Ochieno’s study which is published as a monograph in Kenya raises a number of very interesting questions that must be followed up. What do scientists really know about Foxy? What if Dr. Ochieno is right and Foxy is a masked attacker pretending to be banana- friendly? What if Ugandans wake up one morning and find their banana wilted? Is inoculating banana with Foxy the right thing to do or are there better ways of dealing with pests?
On the last question, Dr. Pamela Paparu who studied Foxy for almost 10 years as a graduate student at Makerere University and the University of Pretoria was confident that Foxy “does protect the banana from pest attacks”. Moreover, just like crocodiles and birds, Foxy has “co-existed with the plants over time and are beneficial to each other” she said when contacted early this week in Kampala. Still, because Ochieno’s study has raised serious questions about Foxy, authorities do need to follow up on it.
