Promoting the sweet potato in Africa

Good to see the March edition of Hortinews magazine focusing on the sweetpotato in Africa. ((Thanks to CIP for pointing to it.)) I found it a little difficult to navigate the feature online, although you can also just download the whole issue as a pdf, so let me link directly to two stories on orange-fleshed sweetpotatoes (OFSP):

Now, a lot of effort has gone into developing and disseminating OFSP in parts of Africa, and their potential importance in addressing vitamin A deficiency is not disputed. However, not everything has gone totally smoothly. As an IDS report, coincidentally also just out, points out:

Donor-funded initiatives have played a central role in developing all stages of the OFSP value chain, with a particular focus on breeding new varieties that appeal to the preferences of both producers and consumers. Development projects have also supported the dissemination of planting materials and funded public awareness campaigns. However, information collected for this case study suggests that, so far, interventions have not achieved widespread uptake of OFSP. Only a small minority of farming households in intervention districts grow OFSP. ((All emphases added.)) Commercial farmers who supplied OFSP planting materials to project distribution systems have found that, after project funding ended, the local market was not viable, and have ceased production. Meanwhile, awareness of and demand for the crop among consumers have been very limited; one survey conducted in an intervention district found that only 2 per cent of households consumed OFSP. Traders and food processors report that there is little demand, and dealing with the crop is not profitable. This state is perhaps unsurprising given that the introduction of OFSP is still relatively recent, that project efforts have been relatively scattered and uncoordinated, and that there has been little focus on commercially viable value chains. Yet the challenges encountered in Tanzania provide important lessons for other agriculture-nutrition initiatives.

But no need to panic, all is not lost. It’s still relatively early days yet, and the report also makes some sensible recommendations to turbo-charge adoption:

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I think it would have been useful, as well as fair, for Hortinews to point out what still needs to be done, as well as what has been achieved. But maybe that doesn’t sell glossy magazines.

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Saving the banana. Again

Australian banana farming changed forever last month. That’s because TR4 was detected on two farms in north Queensland, representing probably the greatest ever threat to the A$ 400 million industry.

Tropical race 4 (TR4) is the name given to the fungal strains of Fusarium oxysporum f. sp. cubense (Foc) that cause Fusarium wilt (popularly known as Panama disease) in Cavendish cultivars grown in tropical conditions.

Remember that Cavendish dominates the international banana trade. The spread of TR4 is seriously bad news, as recognized even by FAO.

Following the Australian report, someone asked on the ProMusa mailing list ((Which is well worth subscribing too, BTW.)) whether the wild species might be a source of resistance. While admitting that he wasn’t fully up to date on developments, and pointing to some very recent literature, ((Li WM, Dita M, Wu W, Hu GB, Xie JH, Ge XJ (2015) Resistance sources to Fusarium oxysporum f. sp. cubense tropical race 4 in banana wild relatives. Plant Pathology.)) Australian expert Dr David Jones had this to say:

As far as I am aware, wild Musa species have not been included in tropical race 4 screening trials except in the Northern Territory of Australia and then it was limited to six accessions of M. acuminata subspecies malaccensis. Of these six accessions, three were resistant and three susceptible. M. a. malaccensis grows wild in areas of Malaysia and Indonesia where it is believed Foc TR4 evolved.

More wild M. acuminata subspecies, other Musa species and pollen-producing, banana cultivars need to be screened as part of the global programme that is being developed to combat TR4. Germplasm with resistance could then be incorporated into conventional breeding projects. Others may have more information on proposed or active screening trials not available to me.

On the local front here in Australia, TR4 has been detected on another farm in North Queensland. The big worry is that it is on the Atherton Tableland in a completely different banana-growing district some 180 km by road from the Tully Valley, the scene of the first outbreak. The prognosis is not as good as it was, but we will have to wait and see what happens next.

Those involved with genetic engineering now have a golden opportunity to push their breeding techniques as the only way to save the global banana industry based on TR4 susceptible cultivars, notably Cavendish, even though no gene ready for insertion is guaranteed to work. If by some lucky chance a banana could be developed that has resistance, I have grave doubts about whether discerning consumers would be willing to eat the fruit. I think the big export fruit companies know this.

It has also often been said by proponents of GM bananas that there is no possibility of genes engineered into GM bananas ‘escaping’ into the environment because commercial cultivars are propagated asexually. I am wondering what would happen if GM bananas were grown in countries with wild bananas present in the adjacent bush, like Malaysia, Indonesia, PNG etc.? Isn’t there a risk that if pollen were released from GM plants it could fertilise nearby wild species?

So anyway, the wild might be a source of resistance, but so also are the Eastern African Highland bananas and plantains, apparently. Some will ask whether the Cavendish is worth saving at all, whether by biotechnological or conventional means, whether using wild or domesticated sources. But that’s another story.

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