2019 ASHS Annual Conference

The cultivated strawberry, Fragaria xananassa, is a valuable perennial crop with a recently published genome sequence. Molecular research has focused on fruit development, primarily with respect to ripening and fruit quality, or resistance to disease, however, little is known about the molecular physiology of plant growth and development. F. xananassa is octoploid, so one of the diploid progenitors, the woodland strawberry F. vesca, was developed as a model system for strawberry. A high quality PacBio genome sequence of F. vesca is published, several inbred lines of this small plant are available, and F. vesca is transformable with Agrobacterium. Chemically induced mutants of F. vesca have been described, and CRISPR technology has been successfully applied this plant. To increase the utility of F. vesca, EMS treatment of imbibed seed was used to induce mutations in the runnering inbred line, Hawaii 4F7-3 (PI664444), the line used for sequencing. Resulting M2 seedlings and plants were scored for plant size and architecture, leaf color, texture and shape, flowering and flower morphology, ability to produce fruit, and fruit shape and size. Plants with mutations affecting runnering and crown architecture, fruit shape, and sexual reproductive development have been further analyzed. H4EMS703 is non-runnering, however the sequences of FveGa20ox4 and FveRGA1 DELLA, two genes reported as regulating runnering, are wild-type. Gene expression and bulked segregant analysis are underway with this mutant. The fruit of H4EMS065 appear long and slender. Morphological analysis indicates that H4EMS065 fruit are not longer than wild-type, but are significantly more slender. The genetics of this mutation, and that of H4EMS068, which has severely short inflorescences are being investigated. In preliminary experiments, both mutations appear result from a single recessive mutation. Six mutants exhibiting various degrees of decreased, or even no fruit production (the fertilized pistil called an achene) are being characterized for pollen development as well as the ability to form fruit when fertilized with wild-type pollen.