Production
Research
Rotating with resistant wheat helps tomatoes
May 16, 2013 – In a study published online in Crop Science, scientists describe a nematode-resistant wheat. But while the wheat carries the resistance to the pest, the benefits are actually seen in the crop that is grown after it. Root-knot nematodes cause crop losses around the world, and they can be difficult to control. In order to reproduce, nematodes need to infect a living plant root. Once they are present in soil, they can survive winter in a fallow field and infect plants during the next growing season. Trap crops – unsuitable hosts that “trick” the nematodes into starting their life cycle but then prevent them from reproducing – are often a better option than leaving the field fallow. “Once nematodes commit to being a parasite, they have to complete their life cycle,” explains Valerie Williamson, lead author of the study and professor at University of California – Davis. “If they don’t reproduce, the population dies out.” Trap crops can reduce the number of parasites in the soil and lessen the effects of the pests on the next crop in the rotation. But crops resistant to nematodes can be hard to find due to the pest’s wide range of hosts, and trap crops are often plants that are less valuable to farmers. In the present study, researchers found a resistant strain of wheat that can reduce nematode numbers in soil and protect the next rotation of tomato plants. The researchers were surprised to find the resistant wheat. They had tried a number of different rotation crops before turning to wheat. Wheat breeder and senior co-author Jorge Dubcovsky then gave Williamson a strain of wheat called Lassik. Lassik is similar to wheat that is commonly grown, but it has a slight difference. A small segment of genes from another wheat strain relocated, through breeding, into Lassik. This relocated segment has no effect on yield or behavior of the crop, but Williamson and her co-authors found that it did have a benefit – it made the wheat resistant to nematodes. “Dubcovsky gave us this strain because it had other resistance genes in it,” says Williamson. “It turned out, to our surprise, that it also had nematode resistance.” Once they realized the Lassik wheat was more resistant to nematodes than the wheat normally grown, the research team validated the source of the resistance by comparing pairs of strains with and without the relocated segment. Then to determine if rotating the resistant wheat with tomato plants would help protect the tomatoes, the authors grew Lassik wheat and used some of the soil to plant tomato seedlings. The wheat had the effect they were hoping for – the tomatoes grown in soil from the resistant wheat plots were less damaged by nematodes. “If farmers use a wheat that does not have the resistant genes, more nematodes survive, and they’ll be there when they plant tomatoes,” explains Williamson. “But if they plant the resistant wheat, there won’t be as many nematodes in the soil.” The results from the study offer a promising option for reducing nematode damage. The next step is to verify the findings on a larger scale. Williamson and her team grew plants both in greenhouses and in small microplots. They are now anticipating that agronomists will try the rotation on a field scale. “We wanted to get the results out there so that people who work in the field, farm advisers for example, can see if it works in practice as well as it did in a controlled experiment.” View the abstract at: http://dx.doi.org/doi:10.2135/cropsci2012.12.0681.
Profiles
NASGA delegates tour NS strawberry nursery grower
Jeff Allen received a mid-August visit from some of his customers. The 65 delegates of the North America Strawberry Growers Association stopped by the G.W. Allen Nursery in Centreville in the Annapolis Valley on the first day of their two-day visit to Nova Scotia. The Allen Nursery produces certified nursery growing stock from its southern and northern strawberry and raspberry fields. The NASGA delegates – from 12 U.S. states and six Canadian provinces – toured Allen’s nursery packing house, which has 6,000 feet of refrigerated storage and his northern variety screen house. Allen, who took over the nursery nine years ago from his father, Gilbert Allen, told his visitors it is hand-intensive work and off-shore workers are essential. Jamaican workers do most of the harvesting, sorting, packaging and shipping of the certified nursery stock grown under the regulations of the Nova Scotia Strawberry Nursing Stock Program. Allen explained there is a three-year production cycle for strawberry nursery stock, with the acquisition in the first year of newly bred lead stocks from the Atlantic Food and Horticulture Research Centre, followed by the foundation year for the growing nursery plants, and in the third year, harvesting of the certified strawberries for growers in Florida, the northern U.S. states and Canadian provinces. Southern plants harvested throughout September to meet the demand from Florida growers are shipped in October.“It is a challenge to get the plants to Florida growers when they want them,” said Allen. After harvest, the the Florida-bound plants are hand-sorted on a table in the packing house. The pickers and sorter on the table remove the mother plants, small plants and vines, and discard them. The Florida plants are then packed and wrapped in plastic in a box so they will not dehydrate during the trip. The plants are cooled to 2 C and will be shipped within two days, Allen said. Northern plants are harvested in November and are then placed in cold storage at 2 C for later shipping. Allen has found that the refrigerated plants grow better for producers. Before refrigeration, the pickers and sorters remove the leaves of the northern plants, place them in bundles of 25 plants and pack them in plastic or wood boxes, 500 plants to a box. “We find we have to have an air flow around them at all times,” once they are in storage, Allen explained. “We try to harvest as many plants as we can in the fall but they have to be dormant before we are able to harvest 100 per cent.” Once the plant is dormant, it is less susceptible to stress, he said. “Most years, we can get 50 to 70 per cent off in the fall.” Any unharvested plants are mulched well in November and harvested next spring, he said. Florida berries are short-day varieties, while northern strawberries are long-day plants. Florida cultivars are also either developed in that state or California, said Allen. He added that nursery strawberries should be planted in light soil, so when they are lifted, their roots will come clear of the soil. His plantlets come from his own farm or other certified nurseries. “As a nurseryman, we have to decide three years ahead what to plant,” Allen said. In 2012, he needed only 50 per cent of the southern cultivar, Treasure, so he ploughed down the rest on its eight-acre plot, noting that he will not grow any more than two acres of any given northern variety. In 2012, Allen grew three southern varieties on 60 acres, planting Treasure about April 20 for harvesting between Sept. 20 and 25. Southern varieties he has grown over the years include Festival, Radiance, Winter Star, Camino Real and Treasure.Allen practises a three-year crop rotation, followed by fall rye that he ploughs down as a green manure. Allen harvests two to three acres of nursery plants every day and then spends five weeks packing for Florida growers, followed by another six weeks for northern producers. Following their visit to the G.W. Allen Nursery, NASGA delegates stopped at the strawberry nursery of Charles Keddy near Kentville, N.S., for supper. Keddy is a past-president of NASGA.