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Shining a light on nematodes


Work by PARC scientists aimed at finding out how parasite causes problems with blueberry roots. By Judie Steeves


I


f it’s underground, it’s out of sight, so what’s occurring in the root zone of plants is a mystery to those growing them.


But, scientists at the Pacific Agri- food Research Centre at Agassiz are uncovering those secrets buried beneath the soil, in an attempt to learn more about the effects of nematodes on plant health and vigour.


Their work began as a result of complaints in 2006 from blueberry growers about a lack of vigour in the blueberry plants in some farmers’ fields.


Research scientist and


nematologist Tom Forge of PARC sampled the fields for plant parasitic nematodes and found 60 percent infested with the stubby root nematode, Paratrichodorus renifer. It was the first discovery in North America and very little was known about this species, Forge said. It was also the first link to an economically- important crop: highbush blueberries.


Initially, Forge conducted


experiments in pots on the Chippewa variety of blueberry, due to an error in shipping, even though it’s not a variety grown commercially in the Fraser Valley.


Those experiments showed the nematode liked growing on blueberries. In fact, within six months there were 70 times the population density of nematodes. In that experimental plot, the blueberries grown that were inoculated with the nematodes ended up with a reduction of 30 to 40


percent in their plant mass. During the experiment yield data was gathered, along with crown volume, and biomass was measured. This year, Forge has set up micro- plot experiments using more standard varieties of blueberry plants, Duke and Bluecrop, and in some of the large pots, he has set up minirhizotrons, clear tubes inserted into the soil which can accommodate a digital image capture device to photograph the fine roots, without causing them damage.


This allows scientists to “watch” the roots at regular intervals and compare the amount of root growth, by comparing images on the computer.


A co-op student from Simon Fraser University, Russell Warwick, is working with Forge on this experiment, analyzing the images so the impact of nematodes on root growth can be measured.


He notes that some root groups are expected to be static, while over time


12 British Columbia Berry Grower • Summer 2011


Tom Forge inspecting minirhizotrons in blueberry micro-plots.


JUDIE STEEVES


others will change significantly. Some nematodes can be very specific—even to the variety of the plants they infest—while others are not so particular. Whether this one is fussy about the variety of blueberry it is attracted to will be one of the questions they hope to answer during this experiment.


Forge explains that this spring half the pots will be inoculated with nematodes they have grown in the greenhouse and then the growth of all the plants will be followed. Once it has been proven this is worth pursuing and it is determined that these nematodes are harming the health of these commercial varieties of blueberries, they’ll look at getting a nematicide approved for use on blueberries, perhaps the same one currently used on raspberries to control nematodes.


Other control strategies, including cultural ones, will be investigated, to see what helps to control them, he said.


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