The Seeds of Science: Two out of three ain’t bad for blackberries

Imagine blackberry growing becoming more streamlined – literally.

Pairwise, a company based in Durham, NC, uses proprietary plant gene editing technology to deliver breakthroughs that benefit farmers, consumers and the planet. At last year’s American Society for Horticultural Science meeting, they shared an update on developing a seedless, thornless and compact blackberry using gene editing technologies.

Their success record so far seems impressive. Their website boasts a 72% success rate in creating targeted crop improvements; 81 potential products created; 15 crops edited; and 11 million transformations performed. Pairwise’s goal is to “rapidly propel research from proof-of-concept to product development.”

The research they shared was specifically about blackberries, the fourth most economically important berry crop in the U.S. Pairwise said they’re participating in a unique public-private collaboration to accelerate blackberry resource development of berry products that benefit farmers and consumers called the Rubus Diversity Project. (The Rubus genus includes over 740 species of blackberries, raspberries and hybrids.)

Pairwise evaluated 568 Rubus species total, prioritizing the traits that would improve blackberry for growers and consumers.

The first major traits they’re looking to enhance in blackberries are seedlessness, thornlessness and compactness. “We expect these traits to create value for consumers, growers and the production channel,” the research team stated.

Field testing took place over two seasons using a high throughput phenotyping platform and image-based fruit evaluation.

How does gene editing work in plants? Using a flowchart, Pairwise put it this way: First, identify the trait to be changed; locate the gene causing the trait; identify the gene sequence edit that will affect the trait; program an editing tool to identify the gene; combine both pieces of the editing tool; introduce the tool into plant cells; identify developing plants with the desired change; and then characterize the edited lines for performance.

Seedlessness

Thanks to advances in other fruit crops, consumers have accepted other “seedless” fruits, such as watermelons, grapes and mandarins. Seedlessness is achieved by different means in other crops, but according to Pairwise, gene editing a blackberry plant to have softer seeds (or pits) is a scientific breakthrough.

In blackberry fruits, each drupelet is like a stone fruit. The endocarp (like the peach pit) is the key tissue to soften. The edited plants displayed softer endocarp and provided an eating experience similar to that of seedless grapes. Pairwise reported the edited blackberries had an 80% to 90% reduction in the amount of force required to crush the seeds when compared to unedited – a success!

Thornlessness

One of the major challenges in Rubus production is the presence of prickles on stems, petioles and leaf veins of many species. These prickles can injure workers and consumers (especially in U-pick operations), damage equipment and packaging and reduce fruit quality and shelf life.

Prickles can also complicate field management practices like harvesting, pruning, training and trellising, which are essential for maintaining high yields and fruit quality.

Pairwise’s genomic analysis narrowed the genomic region of interest and identified suspected thornless variants in both blackberry and raspberry. Editing a WOX gene did produce a thornless phenotype in some blackberries.

Work continues on the thornless trait.

Compactness

The final trait being tweaked enables flowering control and compactness in blackberries by targeting the terminal flower 1 (TFL1) gene. Wild blackberries have a biennial fruiting habit with a chilling requirement, so to satisfy growing demand, there is increased focus on breeding new blackberry selections that are well-adapted for low-chill areas.

TFL1 is a major factor associated with meristem identity and branching. Mutations in TFL1 (which lead to determinate growth habit and early flowering) have been identified or created in many domesticated crop species.

Pairwise said TFL1-edited plants “exhibited an altered growth habit four to six weeks after plugging. The primary apical meristem transitioned from a vegetative to a reproductive meristem terminating in a flower with about 10 to 15 nodes between the crown and terminal flower. At about 20 weeks, the edited plants were heavily branched with flowers and fruit developing on branches with six or more weeks of growth.”

To make sure this wasn’t a fluke, replicated greenhouse and field trials with propagated clones confirmed the observations made on the mother plants. The edited plants were more compact and had ripe fruit development earlier when compared to the unedited control plants.

Compact plants can be planted in higher densities and are expected to have increased yields per acre.

So on this front, more success!

Want to learn more about the work Pairwise is doing? Head to pairwise.com.

by Courtney Llewellyn