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New branch-rooted alfalfa cultivar hits the market

AAC Trueman is more resilient in extreme weather and can withstand extended periods of dryness, wetness or flooding

Agriculture and Agri-Food Canada plant breeder Dr. Yousef Papadopoulos holding a sample of AAC Trueman alfalfa to show its branching root and unique rhizomatous growth habit systems.

It’s been 30 years in the making, but a new branch-rooted alfalfa cultivar that is tolerant to both drought and excessive moisture is now available in Canada. It’s an important advancement given the increased occurrence of extreme weather events including heavy rains, flooding and drought.

The licensing right for this new variety was awarded in 2017 to the Ontario seed company Quality Seeds Ltd., which can supply seed across Canada. While limited seed may be available for the 2019 growing season, adequate supplies should be available for the spring of 2020.

AAC Trueman

Bred by Agriculture and Agri-Food Canada (AAFC) plant breeder Yousef Papadopoulos at the Nappan Research Station in Nova Scotia, CRS-1001 received national registration in September 2018. Its official name is AAC Trueman, chosen to pay tribute to Brian Trueman, a retired farm manager at Nappan Research Farm, for his contribution of 30-plus years to conducting forage and other crop and livestock research trials in Nova Scotia.

“This cultivar is late flowering and winter hardy, which will help farmers grow a stronger, higher quality of hay, silage and forage for animal grazing,” says Papadopoulos. “It is a more resilient alfalfa in extreme weather conditions that can withstand extended periods of dryness, wetness or flooding.”

In addition to having deep roots that help it tolerate droughts, this new cultivar has a unique rhizomatous — below-ground stems originating from the main crown — growth habit. This gives it the ability to develop into new plants that spread and fill in space to produce a dense forage stand. This in turn helps the crop survive in wet conditions.

A new plant starts growing from the rhizomatous (below-ground stems) of AAC Trueman, a new branch-rooted alfalfa cultivar that is tolerant to both drought and excess moisture. photo: AAFC

“One of the major factors impacting plant death, and ultimately loss of alfalfa-based forage stands, is the susceptibility of plants to frequent flooding especially during fall, mid-winter and high water tables in the spring,” says Papadopoulos.

Breeding for soil class

When Papadopoulos started his current job at Nappan in 1987, livestock producers needed to expand into regions not commonly cropped in the past. They were interested in planting alfalfa and alfalfa-based mixtures because they can produce greater yields and better herbage quality than other legume species.

“However, alfalfa breeding efforts in North America are targeted primarily for prime agricultural land on Class 1 and 2 soils,” says Papadopoulos. “These lands are predominantly used for cropping systems other than for livestock-related production. The majority of available land for livestock-related production is on Class 3 and 4.”

In the spring of 1988, Papadopoulos began the research that would lead to the development and commercialization of AAC Trueman. The initial trials were designed to investigate the frequency of flooding periods during the growing season at the Nappan Research Farm and to evaluate the tolerance to flooding in available cultivars and germplasm.

“One of the factors related to superior winter hardiness in alfalfa in Canada is the plant’s tolerance to waterlogging,” explains Papadopoulos. “We designed a practical approach to evaluate and select plants for tolerance to prolonged periods of waterlogging conditions.”

They conducted the first trials on formed-dikeland field conditions that provided three water table levels in the fall and the spring. The base had the highest water table and the one near the highest point had the lowest water table. This allowed them to assess the growth and performance of alfalfa cultivars with diverse below-soil-surface-plant morphology at the different levels.

“Even though the evaluated germplasm did not contain sufficient flooding tolerance, a few had plants showing some tolerance,” Papadopoulos recalls. One cultivar, Rhizoma, had the highest persistence.

The next step of the research on flooding tolerance was mainly focused on developing breeding methodology to improve tolerance to extreme flooding periods during the life of alfalfa stands; determining selection gain for tolerance to fall and spring waterlogging following few selection cycles, and developing novel flooding germplasm and ultimately release new and improved cultivars.

This was done in 1994 by establishing a space-planted nursery composed of 1,125 Rhizoma plants in a field characterized as being marginal for establishing and growing alfalfa due to the oxygen-deficient conditions during a wet spring and fall.

During the 1995 and 1996 growing seasons, the first growth of each plant was harvested to estimate herbage yield. All subsequent regrowth was mob-grazed to simulate a rotational grazing system. The researchers then intercrossed 50 plants that produced superior first-cut dry matter yield and showed superior vigour prior to grazing to produce seeds of the cultivar that has become AAC Trueman.

“The path to novel perennial forage cultivar development is a complex task and long-term in nature,” says Papadopoulos.

Variety trials over the years at four diverse locations in Eastern Canada compared AAC Trueman to AC Caribou, a commonly grown alfalfa cultivar. Under flooding trials, it had a 50 per cent survival rate compared to an AC Caribou’s eight per cent survival rate. As for yield, in the third production year, AAC Trueman yielded 110 per cent.

“This hardiness benefits farmers economically in the long run while also providing better quality hay, silage and forage for animal grazing,” says Papadopoulos.

Recommended species combos

Papadopoulos says producers who do plant AAC Trueman should follow the best management practices recommended for growing alfalfa in their regions. It’s also important to grow AAC Trueman with grasses to optimize results.

A study co-funded by the Canadian Cattlemen’s Association and completed in 2014 saw researchers at the Nappan

Research Farm assess the long-term agronomic performance and associated forage quality of AAC Trueman with all possible binary combinations of six grass species under a rotational grazing system. This included three commercially available cultivars from each grass species.

“The ultimate objective is to identify mixtures that enhance forage yield and nutritional quality throughout the grazing season but particularly during all regrowth periods following the initial grazing,” explains Papadopoulos.

The results of the study identified the following superior cultivars having high regrowth herbage yield: Express timothy, Ginger Kentucky bluegrass, Kokanee tall fescue, Nordic orchardgrass, Mimer meadow fescue and AC Knowles meadow brome.

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