2018 ASHS Annual Conference
Enhancement of Florida Strawberries Using Advanced Molecular Breeding Technologies
For effective molecular marker-assisted breeding to screening large seedling populations, the method to amplify DNA directly from strawberry leaf tissue is critical. My program developed a high-throughput genotyping system through SNP-based high-resolution melting analysis (HRM). Using this method, we are capable to quickly and cheaply screen molecular markers in tens of thousands of seedlings, allowing us to “stack the deck” for desirable traits prior to field evaluation. Until 2014, no molecular markers had been applied in the UF strawberry breeding program for parent and seedling selections though markers had been utilized for identify verification of specific varieties and advanced selection. In 2015, high-throughput molecular markers for fruity aroma and PhCR were developed for the effective MAS. By screening with this DNA test, approximately half were discarded prior to establishment of the summer nursery. A total of 13,000 seedlings were retained for evaluation in the 2016-17 season; thus, the effective size of the breeding program was increased to ~25,000, counting the ~12,000 seedlings that were discarded after marker screening. In the spring of 2018, two additional markers will be added: HRM assays for fruit anthracnose resistance and day-neutrality. These markers can predict parental phenotypes/haplotypes with greater than 95% accuracy. With this high-throughput MAS, we are now able to combine many important traits for fruit quality and disease resistance together to achieve successful new cultivars.
Most of the recent varieties released from our breeding program have been susceptible to major diseases in strawberry. We have the genetic resources to develop new varieties with better resistance. But to efficiently combine disease resistance with all the other desired fruit and plant traits is quite a challenge due to the high levels of heterozygosity and the octoploid nature of the genome. Currently, my program is using advanced genetic mapping and whole genome sequencing techniques to identify genes associated with Florida-relevant diseases like angular leaf spot, crown rots, fruit anthracnose, charcoal rot and powdery mildew. We are in the process of identifying candidate genes for disease resistance and flavor using whole-genome SNP genotyping, sequencing, and transcriptome analysis. A bacterial artificial libraries are developed to facilitate gene cloning in these candidate regions. Furthermore, by using CRISPR/Cas gene-editing technology, these genes or gene variants for disease resistance can be rapidly moved into desirable breeding selections and can be further moved via conventional crossing in later generations. This technology allows for the adjustment or removal of specific genes in already established cultivars or breeding parents without otherwise altering the genetic constitution of an elite genotype. This is particularly useful for cultivated strawberries because they are genetically complex, and it would be much easier to simply adjust a single trait than reshuffle the genetic deck and hope for a plant with all traits incorporated. Importantly, we can utilize established MAS tools to track the transmission of edited genes.
The FSGA has great interest and motivation to commercialize and promote varieties with resistant to multiple pathogens for the benefit of growers. The extension efforts from my program includes participation in cooperative extension and industry organized meetings and workshops to foster scientific exchange and the translation of genomic-enabled breeding approaches. My group has actively engaged in the training of extension agents and industry workers through formal programs, personal farm visits, FSGA sponsored field days and meetings, workshops, newsletter articles and extension reports. Graduate students from my program also have the opportunity to communicate results (oral or poster presentation) to the public and stakeholders through field days, cooperative extension meetings and FSGA-organized meetings. My program also successfully established outreach program with existing strawberry advisory committee for communicating the latest research results to the industry, and receive feedback. This is an excellent way to communicate information how our team can successfully developed better strawberries for growers, markets, and consumers using molecular breeding approaches. Looking to the future, the technologies developed in my research projects should contribute to breeding efforts for many years to come, far beyond the project period, and increase the sustainability and profitability of the Florida strawberry industry through better varieties.
My program is an active participant in RosBREED, the USDA/NIFA SCRI CAP project which focuses on developing DNA tests for routine use in Rosaceae crop breeding programs. Total 22 U.S. breeding programs are involved in this multi-state project focusing on eight fruit crops. The developed high-throughput genotyping platform and markers has been applied to the multi-state breeding programs. We have participated last three years and shown the great impact on this multi-state project. Work on the genetic basis of important strawberry disease resistance traits is being done in collaboration with the RosBREED members every year. From last year, my program has been involved in the USDA/NIFA SCRI project, “Next-generation disease resistance breeding and management”. This research is for accelerating the development of disease resistant cultivars through the application of genomic technologies, and delivering cultivars with commercially viable levels of resistance to multiple pathogens through collaborative research with national wide strawberry teams of UF and University of California Davis researchers in the areas of breeding, genomics and pathology.