Fruit trees in commercial orchards are increasingly planted in high densities to maximize quality, enable mechanization, conserve resources, and increase profitability. A hundred years ago a traditional apple orchard may have had one to two hundred free standing trees per acre, while now planting over a thousand tree per acre trained to elaborate trellis systems is common practice. To maintain such high-density plantings, a significant amount of labor is needed along with growth regulator treatments and, in some cases, specialized dwarfing rootstocks. Still, not all fruit trees are easily amenable to growing in these systems. One of the focuses of my research program is to determine what controls fruit tree shoot architecture at the molecular and genetic level. The ultimate goal of this project is to identify methods that will reduce the labor required to manage high-density 2-dimensional plantings. In the process, we are generating fundamental knowledge about how plants grow the way they do, particularly in connection to the regulation of branch, or lateral shoot, angle. The main genes we are studying are TILLAR ANGLE CONTROL 1 (TAC1), LAZY1, and WEEP, which are present in vascular plants. TAC1 promotes the formation of wide branch angles, while the related gene LAZY1 promotes narrow branch angles. WEEP on the other hand regulates branch tip orientations. Peach trees with a non-functional WEEP allele exhibit a weeping branch phenotype. Genetic studies have linked the roles of these three genes together, and molecular and physiological studies suggest they have roles in regulating shoot growth in response to light and gravity. For this talk, I will present current and developing knowledge about their molecular mechanisms in connection to the regulation of lateral shoot orientations in plants.

Host: Cora MacAlister