Location: National Clonal Germplasm RepositoryTitle: Perpetual flowering in strawberry species
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2017
Publication Date: 11/21/2017
Citation: Cai, W., Zurn, J.D., Bassil, N.V., Hummer, K.E. 2017. Perpetual flowering in strawberry species. HortScience. 52(11):1496-1500. https://doi.org/10.21273/HORTSCI12025-17.
Interpretive Summary: Studies have revealed genetic control of flowering patterns for seasonal flowering (SF) and perpetual flowering (PF) in the common garden strawberry, as compared to the alpine strawberry. There are about 22 species of strawberries in the world. There are many subspecies and hybrids. Identification of flowering traits and patterns for these taxa could broaden the available strawberry parents for breeding programs who want to have multiple strawberry crops within one year. The objective of this project was to compare flowering of many diverse strawberry species from the USDA-ARS National Clonal Germplasm Repository (NCGR) in Corvallis, Oregon. This facility contains a national strawberry genebank.The strawberry collection was observed for flowering on a monthly basis for 962 different strawberries from the first of May (week 16) through October (week 39) in 2015 and 2016. The flowering stems were removed each month after the data was collected. Plants that flowered only once in July or earlier and were considered "seasonal"; those with flowers in August, September, and/or October, were considered PF. A special non-parametric statistical test was applied to compare sample pairs. The most predominantly PF taxa were alpine strawberries. The majority of the strawberries bloomed seasonally (SF). Fifteen strawberries were PF. Some species from China tended to have SF clones. Some American species had both SF and PF clones. Some South American and North American beach strawberries showed that they could have repeat flowering, which was a new finding. Western American strawberries with two sets of chromosomes were different than their European diploid alpine relatives. About one third of the total clones examined for all taxa demonstrated PF. Many genes have been identified as controlling the flowering phases in the common garden and alpine strawberries. More studies are needed to determine which genes control flowering in these other strawberry species. .
Technical Abstract: Studies have revealed genetic control of flowering patterns for seasonal flowering (SF) and perpetual flowering (PF) genotypes in the common garden strawberry, with associated links to gene homeologs in diploid alpine strawberry, F. vesca L. Within the genus Fragaria, 22 species and multiple subspecies and numerous species hybrids have been globally described. Identification of flowering traits and patterns for these taxa could broaden the genepool of available PF parents for breeding programs. The objective of this project was to screen diverse strawberry genetic resources housed at the USDA-ARS National Clonal Germplasm Repository (NCGR) in Corvallis, Oregon for flowering habit and identify PF clones. Flower presence was recorded monthly for 962 clones of 36 taxa from the first of May (week 16) through October (week 39) in 2015 and 2016. Complete flower trusses were removed each month after the data was collected. Plants flowering earlier than July 31 were SF; those with flowers in August, September, and/or October, were PF. Due to unequal sample genotype replicates, pairwise comparisons between taxa were examined using a Pearson’s Chi-squared test with N-1 correction. The most predominantly PF taxa were F. vesca subsp. vesca f. semperflorens and f. alba, F. vesca subsp. americana, and F. virginiana subsp. glauca. These taxa were similar to each other but highly significantly different (a = 0.01) than the majority of taxa in which the SF trait was predominant. Fifteen clones which demonstrated the strongest PF phenotype were identified. The china group tended to have SF clones, high ploidy vesca group members tended to have both SF and PF clones, and low ploidy vesca were mostly PF with the exceptions: clones of F. vesca subsp. californica and F. vesca subsp. bracteata, which were mixed. Fragaria iinumae clones were predominantly SF. About 38% of the total clones examined for all taxa demonstrated PF. Multiple genetic controls have been observed for flowering phases in the common garden and alpine strawberries. The additional taxa of this study could be examined for similarity of genetic controls.