Genetic Regulation of Flowering in Kiwifruit

Kiwifruit (Actinidia spp.) are dioecious woody perennial vines with a reproductive cycle different from those of model plants. Kiwifruit flowers develop over two growing seasons. Floral evocation occurs in the first year, when lateral dome-shaped meristems are established in latent shoot buds. Flower differentiation occurs in the second growing season, after the winter dormancy period. Flower development depends on winter chilling, which is suboptimal in many growing regions and is becoming increasingly inadequate with climate change. Understanding the genetic control of kiwifruit flowering becomes essential in establishing new methods to manipulate flowering and develop cultivars less dependent on winter chilling. However, the molecular mechanisms regulating flower initiation, differentiation and sex determination in kiwifruit are largely unknown. Our aim is to identify and characterize kiwifruit flowering genes. Candidate genes with homology to flowering genes of model species Arabidopsis thaliana were identified in the EST databases. Phylogenetic study and expression profiling were used to prioritize candidates. Candidates were cloned into binary vectors and transformed into wild-type or appropriate mutant Arabidopsis for flowering time and floral phenotype assessment. We have identified genes that will be utilized as genetic markers for bud and flower development and candidates that are expected to affect kiwifruit growth, phase change, and time and efficiency of flowering.