Getting the sequence right
By Gabrielle Stannus
The age of waiting for random plant mutations to occur in your nursery could be over. Advances in selective plant breeding are increasingly being made using genetic analysis technology. Not to be confused with genetic modification, where genes can be introduced into a plant or rearranged within it, genetic analysis involves the reading of existing genes within a plant to identify key markers. These markers, or specific patterns of genes, indicate whether or not a desired trait is present in a plant, such as novel flower colour or disease resistance.
Chris Beytes, editor of GrowerTalks in the USA, says that a new impatiens currently in development is said to be highly resistant to Impatiens Downy Mildew (IDM). Ball Horticultural Company and KeyGene recently announced their claim to have completed the genome sequence and assembly of Impatiens walleriana. These two companies are now working with PanAmerican Seed, an American plant breeding company, to produce impatiens with high resistance to IDM.
Chris explains that PanAmerican’s breeder still breeds the old-fashioned way, i.e. by selecting parent plants and crossing them. However, seeds are collected from these crosses, germinated, and then sent to KeyGene for genetic analysis. KeyGene checks these young seedlings for the markers for IDM resistance, and are able to tell the breeder which ones contain the trait and which ones do not. All this can take place within a few weeks of sowing, instead of having to wait months to grow the plants to maturity. Plants without the IDM-resistant trait are then discarded, whilst the breeder can focus their attention on growing those seedlings conferred with that trait.
Genetic analysis technology is helping in the selection of plants with other desirable traits, e.g. novel flower colour. In the Netherlands, a consortium of three leading Dutch organizations, BaseClear, Generade, and Dümmen Orange announced late last year that they had sequenced the Tulipa gesneriana genome 1 . Chris says that this consortium hope that by having this sequence and finding markers that they will greatly speed up the tulip breeding process, which currently takes up to fifteen years.
Using genetic analysis technology can potentially save time and therefore money. Rather than waiting years to develop a new plant cultivar, breeders can select and identify the plant offspring possessing the trait that is desired without growing hundreds, if not thousands, of those plants. Speeding up this process also saves on greenhouse and/or land space, not to mention energy and water consumption.
Which plant would you sequence?
Digby Growns, Senior Plant Breeder at Kings Park & Botanic Garden in Western Australia says that genome sequencing is still an emerging technology in Australian plant breeding.
“We (Kings Park) aren’t using marker assisted breeding at present, mainly due to the expense in undertaking genome sequences and then the time needed for identifying markers. However it is likely due to new technology developments and the associated reduction in cost that we will be using this technology in the next few years” says Digby.
When asked which plant genome he would sequence if had the chance, Digby says “That’s a bit like asking what my favourite rock ‘n’ roll band is!” Tossing up between members of the Chamelaucium (Wax-flowers) and Grevillea genera, Digby suggests that selective breeding of members of both genera would provide benefits to the nursery industry.
Selective breeding of these plants may result in improved returns for growers and retailers. Digby argues that Chamelaucium spp. are of huge interest to ornamental horticulture given the close relationship they share with the Verticordia (Featherflowers) and Darwinia (Mountain Bells) genera. Digby says that Chamelaucium is Australia’s number one cut flower export and is grown worldwide as a cut flower and landscape plant, so any advances in breeding have the potential for excellent economic benefits. Likewise, opportunities abound with Grevilleas, Australia’s top selling genus for ornamental plants, given their climatic range.
The future in Australia?
Genetic analysis is not normally the work of a grower, and definitely not a retailer. However, small breeding companies in Australia might be able to take advantage of this technology in the near future as the cost of gene sequencing is coming down rapidly. But as Chris suggests, having the sequence is only the first part.
“You need to know what traits you are looking for in your breeding, and identify markers for those traits. Then it’s still old-fashioned breeding to get your new variety. So can a backyard Aussie breeder take advantage of modern genetic technology? Depends on how well they did in science class, I guess!” says Chris.
As this technology will soon become more accessible in Australia, now is a great time for plant growers to start working with breeders and geneticists to identify desirable traits for plants they want to develop.
Ball Horticultural Company: https://www.ballhort.com/
PanAmerican Seed: www.panamseed.com
Tulipa gesneriana genome: https://na.dummenorange.com/site/en/news/detail/dutch-consortium-unravels-first-tulip-genome/en-111-278
GrowerTalks Magazine: https://www.growertalks.com