Asparagus bred to beat fungus

Last updated 10:45 02/08/2013
NASTY FUNGUS: Phytophthora becomes a problem in the wet and cool conditions of spring.

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Canterbury plant breeder Peter Falloon has developed the world's first asparagus cultivar to have resistance to phytophthora, a fungus that eats the plants' roots and can devastate crops.

"It is exciting and the nice thing is it's done in New Zealand, so the growers here can take advantage of it," he said.

"One of the main drivers in food crops is reduced chemical application and this is a major aim of the asparagus industry in New Zealand. So this gives it a jump on the rest of the world.

"We can back some of our clean, green claims with the fact that this is one more chemical that we're not using."

Phytophthora becomes a problem in the wet and cool conditions of a typical New Zealand spring.

"It has an optimum temperature of about 12 degrees Celsius. That is when it is most active and when the plant is most susceptible, when it's saturated. It has little spores that swim around - they look a bit like a sperm actually - in free water in the soil."

The disease could be controlled by a fungicide that was usually applied as a preventive.

"In a dry spring, it wouldn't be such an issue and growers may opt to not use a fungicide. So you have to make a judgment call whether it is going to be a dry spring or a wet spring.

"Invariably, when you say it's going to be a dry spring, a couple of weeks later you get a dump of about 75 millimetres of rain and the place is awash. So it's a bit of a tricky management thing for growers," Falloon said.

The scientist started working on phytophthora in 1981, when he did his PhD in California.

"They had two wet El-Nino years and we were recording yield reductions of 50 per cent and crop failures of more than 80 per cent, where plants were dying because of the disease."

Most of the damage to plants happened out of sight under the soil, meaning its effects were sometimes underestimated, he said.

"It nibbles at the roots and at the crown, out of sight, out of mind. A lot of growers don't really know this is going on.

"You see about 10 per cent of the actual loss, so you think, 'It's not too bad. I won't put anything on to control it.'

"But consequently your plant gets weaker. You lose a plant here, a plant there and you do that every year, and suddenly your stand becomes weak and rundown."

Finding a cultivar that was resistant, as well as attractive and tasty, had taken more than 30 years.

"We had to screen varieties from all around the world and we got the odd surviving plant, like one in a thousand.

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"So we did millions of seedlings and eventually we got enough plants with good resistance. Then you have to cross in good horticultural characteristics like spear shape, colour and yield.

"If it doesn't look any good in the market or it tastes bad, it's all a bit academic really," he said.

The new cultivar ticked all the boxes. "It's got yields better than the best non-resistant varieties around now.

"It also lasts longer, which is important for asparagus growers.

"The biggest cost for a grower is the cost of establishing a crop. If he has to do it only every 15 or 20 years instead of every 10 or 12 years, he's much better off."

A little of the new cultivar would be available for home gardeners, but commercial producers would have to wait until there was sufficient seed. "We produced only about 1 kilogram of seed this year, which will be enough to plant a hectare. Next year we'll have 20 times that."

- The Press

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