Unlocking the genetic secrets of fruit firmness: how a single mutation doubled strawberry firmness
image: Tracing the ancestry of the favorable (mutant) PG1-6A1 allele found in firm-fruited UC cultivars. The family tree illustrates a small fraction of the thousands of descendants of ‘Tioga’ and ‘Tufts’ in the pedigree records of firm-fruited progeny developed at UC, including every UC cultivar developed since 1970. Genotypes of the AX-184242253 SNP were used to predict PG1-6A1 unfavorable allele homozygotes (−/−; blue points), heterozygotes (+/−; red points), and favorable allele homozygotes (+/+; brown points), where the favorable (mutant) allele (PG1-6A2+) increases fruit firmness. Gray nodes identify individuals that were not genotyped or phenotyped, many of which are extinct.
Credit: Horticulture Research
Strawberries are notoriously soft and highly perishable, posing challenges to global production. Recent research has identified a genetic breakthrough that could help cultivate firmer strawberries with enhanced shelf-life. The study focuses on a specific gene, POLYGALACTURONASE1 (FaPG1), which influences fruit firmness by regulating cell wall degradation. Loss-of-function mutations in this gene double fruit firmness, making strawberries more resilient to damage during storage and transportation. This discovery could have major implications for breeding strategies aimed at improving fruit quality and longevity.
Strawberry firmness has long been a key trait for breeding, influencing both storage capacity and marketability. While wild-type strawberries are soft and easily bruised, the development of firm-fruited cultivars has been crucial to extending their shelf life. Despite previous research on the gene FaPG1, the genetic mechanisms behind fruit firmness variation remained poorly understood. This study delves into the molecular biology of the gene and identifies key mutations that control fruit texture. Due to these findings, further research is now required to explore the full range of genetic contributors to firmness.
The team from the University of California, Davis, and the United States Department of Agriculture has published new findings on the genetic basis of fruit firmness in strawberries. The research, published (DOI: 10.1093/hr/uhae315) in Horticulture Research in November 2024, reveals that mutations in the FaPG1 gene significantly affect the texture of strawberries, leading to firmer fruit. The study provides a valuable insight into how these genetic variations could be applied in breeding programs to produce strawberries with enhanced firmness and longer shelf life.
The research team identified a key mutation in the FaPG1 gene responsible for fruit softening in strawberries. Through genome-wide association studies (GWAS) and gene expression analysis, they found that loss-of-function mutations in FaPG1 led to a doubling of fruit firmness in strawberries. Notably, an En/Spm transposon insertion upstream of FaPG1 appears to reduce gene expression, resulting in firmer fruit. The researchers also developed highly accurate genotyping assays that allow for marker-assisted selection (MAS) of this favorable mutation, which could greatly streamline breeding efforts for firmer, more durable strawberries.
"Understanding the genetic underpinnings of fruit firmness opens up new opportunities for enhancing strawberry cultivation," said Dr. Steven J. Knapp, the study’s lead researcher from the University of California, Davis. "This mutation not only increases firmness but also provides a robust genetic marker that can be used in breeding programs. The potential for improving fruit quality and extending postharvest life is immense, and we are excited to see how these findings will impact the industry."
The identification of genetic variants associated with fruit firmness in strawberries has profound implications for the agricultural sector. By using these findings, breeders can develop new strawberry varieties that maintain quality during transportation and have extended shelf-lives, reducing food waste. The ability to use molecular markers to select for desired traits will accelerate breeding programs, making them more efficient and effective. Additionally, the research provides insights that could be applied to other soft fruits, paving the way for broader agricultural improvements in fruit quality.
###
References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae315
Funding information
This research was supported by grants to S.J.K. from the United Stated Department of Agriculture (USDA) (http://dx.doi.org/10.13039/100000199) National Institute of Food and Agriculture (NIFA) Specialty Crops Research Initiative (SCRI) (#2017-51181B6833), S.J.K., M.J.F., D.D.A.P., and M.B. from the USDA NIFA SCRI (#2022-51181-38328-0), and S.J.K., G.S.C., M.J.F., D.D.A.P., and M.B. from the California Strawberry Commission (http://dx.doi.org/10.13039/100006760).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.