A tweak to help potatoes withstand late blight disease

Not anymore. A crop of potatoes bioengineered to resist late blight makes her harvest. And she’s getting hope: the sleepless nights that have made growing potatoes less attractive are lifting. 

She is not alone. Thousands of potato farmers in Nigeria face the annual threat of late blight, a disease considered the biggest problem to potatoes. 

The disease, caused by water mould, strikes potatoes in the humid regions where temperatures get up to 29oC. Infected plants can rot within two short weeks, wiping out an entire crop. Late blight in potato caused the Ireland’s Great Famine in the mid-19th Century and destroyed more than half the tomato crop in the US in 1946. 

Some 1.5 million metric tonnes of potatoes are produced on the Plateau alone and account for 92% of Nigeria’s yearly output, according to the National Root Crop Research Institute (NRCRI). 

Plateau potato farmers regularly face loss to late blight, capable of wiping out 85% of crops on record. An outbreak in 2014 damaged nearly 500 hectares of potato farms—the equivalent of just over 700 football fields. Yields have been seen to reduce to 4.3tonnes per hectare—almost half of it all attributed to late blight. 

Blight in the wild 

Breeding plant varieties resistant to diseases is considered the most economic and environmentally sustainable control of plant disease. For potato late blight, the answer was to transfer known resistance to water mould in wild potatoes into the varieties of potatoes farmers prefer to grow. 

More than 4,000 varieties of potatoes abound. Two wild potato varieties known to have resistance to late blight were selected—Solanum venturii, native to northern Argentina, and Solanum bulbocastanum, (aka ornamental nightshade) native to Mexico and parts of the US southwest. The nightshade has been the star of genetically engineering resistance into cultivated potatoes around the world. 

In Nigeria, NRCRI has been part of the Future Global Biotech Partnership project to tackle the menace of late blight by developing and releasing blight-resistant potatoes. It is a collaboration anchored by Michigan State University with Nigeria, Kenya, Indonesia and Bangladesh taking part. 

Collaborating institutions include University of Minnesota, University of Idaho, International Potato Centre (CIP), African Agricultural Technology Foundation (AATF), Bangladesh Agricultural Research Institute (BARI), Indonesian Centre for Agricultural Biotechnology and Genetic Research and Development (ICABIOGRAD), Kenya Agricultural and Livestock Research Organization (KALRO) and National Root Crops Research Institute in Nigeria. 

In Nigeria, NRCRI field trials are at its Potato Research Station at Kuru, where it collaborates with Plateau State University Bokkos and Cocoa Research Institute of Nigeria (CRIN). 

‘The difference between biotech potatoes and the conventional varieties is in their resistance to late blight – a devastating disease of potato,” says Charles Amadi, principal investigator for the project. 

“Biotech potatoes are completely resistant to Late blight while the conventional varieties from which they were developed are susceptible. 

Gunshot to the genes 

The latest outcome is the 3R biotech potato from the International Potato Centre. Genes for resistance were taken from unmodified DNA fragments of both wild potatoes and transferred into potatoes that farmers prefer to grow—diamant, desiree, tigoni, Victoria and shangi.  

All five are susceptible to late blight and any resistance in them tends to breakdown in time, depending on how severe the disease becomes over time or on in changes in the pathogen that causes late blight. 

“In the field, under severe blight attack, the foliage of the conventional varieties is completely destroyed by late blight while those of biotech potatoes are not affected,” says Amadi. 

“The effect is that while tuber yield of conventional varieties is drastically reduced, those of the biotech potatoes remain high.” 

Efficacy and safety in using 3R potatoes have been shown in Uganda before being scaled out in Nigeria. It is expected the project will begin releasing them for wider use in two years. 

The trials are confined fields, the equivalent of clinical trials in animals—the first at Kuru, then at two locations at Bokos and Kusuka “until after the environmental release of the materials as required by regulation,” Amadi explains. 

Nigeria is not new to crops being developed and distributed. Cowpea and cotton have seen some bioengineering recently, just ahead of the biotech potato. And three varieties of potato—Jelly, Rumba and Marabel—have been released and registered between 2014 and 2016 at the Nigerian Seed Portal Initiative. 

Resistance to late plight potentially allows desiree yield to reach an estimated 29 tonnes per hectare and 45 tonnes per hectare for Victoria—a wide departure from the national average of 4.3 tonnes per hectare. 

Labour of love 

Isaiah Buwah, who has farmed potatoes for the last 40 years, is among farmers who witnessed the harvest of the first batch of biotech potatoes last year. In the 40 years he has grown potatoes in Bokos, Plateau, his fellow growers have given up on potatoes. Last June, just as they anticipated a good harvest, late blight struck. 

Buwah is staying on because of biotech potatoes. 

“What I am seeing is salvation coming to potato farmers on the Plateau. I am happy it is happening in my lifetime,” he says. 

“We have seriously suffered from the impact of late blight to the extent that some of our colleagues suffered seriously because of the massive destruction and losses we have encountered yearly. Those of us still growing potatoes have done so as a labour of love.” 

Kpenpiya Deshi is a potato breeder in the department of plant science and biotechnology.  

“As a breeder, I know firsthand what farmers are going through. It has been tough,” she says. 

The “brown field” day when researchers from NRCRI and CIP showcase differences between biotech potatoes and conventional potatoes rekindles hope against late blight. 

“The happiness is not only for farmers but also for us breeders, who have been toiling day and night to find solutions to the blight crisis,” says Deshi. 

Until now, farmers must battle late blight with fungicides or risk losing their harvest. That is one hassle farmers must deal with. 

“The fungicide comes with instructions on usage, but we hardly follow this,” Buwah explains. 

“Because when you see your crop flourishing and you don’t want late blight to rob you of it, you keep applying the fungicide till harvest and this could have health implications on the consumption of the crop.” 

Reducing need for fungicide frees the crop to spur greater yields. That’s higher productivity and more profit. Higher yield estimates from previous trials outside the country are encouraging—but nothing is being rushed. 

“The plan is to register and release the biotech potatoes to farmers after the required regulatory evaluations have been carried out.,” says Amadi. 

“Two years is certainly too optimistic to do all the needful. We are looking at four to five years.” 

Given, the number of crops that have gone through breeding programmes and are already in cultivation, Nigerians remain sceptical in general about the “GM” word—the recondite and arcane world of genetic modification. In the case of biotech potatoes, the modification involved taking genes that conferred resistance in wild potatoes and transferring them into varieties of potatoes grown on the Plateau. That might be first step in dealing with the challenge of acceptance. 

“Because of the dire need for late blight resistant varieties, and the safety of biotech potatoes for human consumption, we do not anticipate any major challenges in acceptance by farmers and the consuming public,” says Amadi.