Stingless blackberries (Lubus subgenus Lubus) canes are highly favored by growers due to concerns regarding food and worker safety, as well as the potential damage to fruit caused by the mechanical injuries associated with stings.

Blackberries represent a specialized crop that is capturing a larger portion of the fresh berry market.

The rising demand coupled with increasing production costs has created a need for cultivars adaptable to various environmental and management practices.

Stings pose a challenge in blackberry production systems, presenting food safety issues and causing mechanical damage to the fruit, thereby reducing its shelf life.

The primary aim of a fresh market blackberry breeding program is to introduce thornless cultivars. These terms are often used interchangeably in existing literature.

Stinging differentiates plant-based differentiation from thorns and spines due to the formation of cortical and epidermal cells.

“Blackberry breeders lacked the genetic information required to ascertain whether certain plants were devoid of what is technically called nausea, commonly referred to as thorns,” stated Dr. Margaret Worthington, a researcher with the Arkansas Agricultural Experimental Bureau.

“All fresh market blackberry varieties are Tetraploid, meaning they possess four copies of all chromosomes as opposed to the two copies found in humans.”

“The greater the number of copies, the more challenging it becomes to conduct genetic analyses.”

“Previously, the locus and positioning of genes on chromosomes linked to spine traits were unknown.”

The team’s findings introduced the first diagnostic markers related to any traits developed and documented in blackberries.

“These markers are the first publicly available tools developed for both fresh market and processed blackberries,” expressed Dr. Ellen Thompson, Global Rubus Breeding and Development Director at Hortifrut Genetics.

“Markers expedite the breeding process, saving time and resources, and facilitate faster decision-making before seedlings are introduced into the field.”

The authors utilized genome-wide association studies to pinpoint the loci responsible for the spineless traits.

They gathered DNA samples from a total of 374 blackberry varieties.

These samples underwent genotyping, which is a highly accurate method that scans and identifies genetic codes impacting stinging characteristics.

If these variants, known as single nucleotide polymorphisms (SNPs), show significant correlations with certain traits, it implies that genes in that area might influence those traits.

These SNPs, or markers, highlight regions associated with the characteristic in question.

“Genetic markers are currently being implemented in blackberries and raspberries, but the technology is more mature for row crops like rice and soybeans,” noted Dr. Worthington.

“Genetic markers are widely utilized in row crops to select for disease resistance, growth or flowering periods, and other desirable traits.”

Another significant discovery from this study indicates that the absence of genetic mutations around chromosome RA04 leads to linkage disequilibrium blocks, or regions where genetic markers are more likely to be inherited together than by chance.

For the genes that are spineless within this block, these traits are often inherited from parent to offspring along with various other genes, including those linked to high acidity, lack of cold resistance, and less desirable traits like canes that require support to remain upright.

“The focus on selecting for spineless plants has inadvertently resulted in the loss of genetic variation surrounding the locus,” Dr. Worthington commented.

“Crossbreeding with thorny plants can help restore this variation.”

The team’s paper has been published in the journal G3: Genes, Genomes, Genetics.

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Carmen A. Johns et al. Genetic control of exhalation in tetraploid blackberries. G3: Genes, genomes, genetics Published online on March 20th, 2025. doi:10.1093/g3journal/jkaf065