Potatoes in Canada

Features Agronomy Traits and Genetics
Breeding out tuber defects

Many things can disrupt normal tuber growth, leading to reduced yields and reduced profits.

Uncontrollable environmental factors, such as temperature extremes, can contribute to malformed tubers and a defect called hollow heart, and global climate change is expected to bring more temperature extremes and drought in the future. However, cultivation practices also matter, and things like inadequate, excess or uneven levels of soil nutrients can disrupt normal tuber development and cause undesirable physiological disorders.

“If farmers do their best to ensure uniform and adequate soil moisture and fertility throughout tuber initiation and growth, losses from many physiological disorders can be avoided or minimized,” says Dr. Benoit Bizimungu, an Agriculture and Agri-Food Canada (AAFC) research scientist and potato breeder in Fredericton. “Of course, most farms are not irrigated, and even if all care is taken and irrigation is used, things like high or low temperatures can cause defects. Furthermore, the causes of some defect disorders are not well known.”

Malformation of the tuber actually occurs after environmental stresses have temporarily slowed or halted tuber growth. “The resumption of growth after this stress can result in non-uniform secondary growth,” Bizimungu explains. The defect known as hollow heart is also associated with fluctuating growing conditions, but also by soil nutritional imbalances, or conditions that favour rapid tuber enlargement. Although the incidence of hollow heart is influenced strongly by the environment, Bizimungu says there is also a genetic component to its expression. “Under conditions promoting its development, some cultivars exhibit more severe expression than others,” he notes. “The two standard potato varieties (Russet Burbank for frozen French fries, and Atlantic for chip processing) are both susceptible to environmental stresses leading to hollow heart and other tuber defects.”

Because not all the unfavourable conditions that contribute to growth disorders can be controlled, it’s fortunate that genetic improvement can play a role in reducing the prevalence of defects and thereby avoiding or minimizing losses. Of course, no cultivar is completely resistant to every disorder, but some are less susceptible than others. Tubers used for seed, fresh market, or processing may be affected differently by environmental stresses, Bizimungu explains, and certain disorders are not as important in some of these end uses as they are in others (consumers and processors prefer uniform potatoes, for example).

Breeding efforts
As part of the national potato breeding program, Bizimungu and his team have carried out evaluation and selection of breeding clones for resistance to stress-induced defect disorders over the last six years. Selection for each generation was narrowed down by the team from approximately 100,000 original lines planted in the first year of selection. After planting under rain-fed production in Eastern Canada at the Benton Ridge breeding substation in New Brunswick, and under irrigated conditions at the Vauxhall research substation in southern Alberta, the number of clones was narrowed down to about 50. Superior selections were then chosen for adaptation evaluation, in collaboration with industry, at eight test sites across seven provinces.

The list of outstanding selections nearing completion or in advanced industry tests includes French fry clones CV99222-2, AR2010-01 and AR2010-02, chip clones AR2010-03, AR2013-02 and AR2014-02, and dual French fry/fresh clone CV01236-3. They have all shown much better fry colour than Russet Burbank or Atlantic. All of them have also shown greater marketable yields due to fewer defects than both Russet Burbank and Atlantic by four to 21 per cent in experimental plots. Bizimungu’s preliminary data shows that CV99222-2 and CV01236-3 outperformed Russet Burbank in western Canadian trials conducted under irrigation in Manitoba, Saskatchewan and Alberta. These clones also appear to do well in rain-fed conditions in New Brunswick. Clones AR2013-02 and AR2014-02 also appear to have a wide geographic adaptation, Bizimungu notes, and outperformed Atlantic in most national test sites in terms of marketable yield.

“The national trials aim to check performance of these selections showing the potential to offer improved yields and processing quality under different conditions and different local environmental stresses,” Bizimungu says, “in order to choose the most promising ones for release to industry for further testing. Upon successful completion of industry testing, their registration as cultivars will follow.”

Industry can visit AAFC’s Accelerated Release program website to access trial data, with locations and performance, to decide which selection to request for further testing, with the option to license.

 

March 16, 2015  By Treena Hein



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