Project Number: 2094-21220-003-010-I
Project Type: Interagency Reimbursable Agreement
Start Date: Apr 1, 2023
End Date: Mar 31, 2025
Long-term objective: To develop the tools, protocols, and data necessary to better understand hormone responses and improve predictability of pear rooting across cultivars. Obj 1. Characterize rooting efficiency across a diverse germplasm set. 1a. Establish and propagate plants in tissue culture. 1b. Determine plantlet standardization protocol. 1c. Treat germplasm with multiple rooting treatments to determine efficiencies Obj 2. Compare transcriptional response to rooting treatments. 2a. Identify root- and stem-specific genes by comparing transcriptomes across pear tissues. 2b. Determine a subset of germplasm comprising hard-to-root and easier-to-root cultivars. 2c. Compare dynamic gene expression in response to different rooting treatments between cultivars. Obj 3. Compare hormone responses to rooting treatments. 3a. Quantify and analyze hormone content in different tissue types in response to rooting treatments. 3b. Transform the subset of germplasm with auxin and cytokinin biosensors for future analysis of hormone localization and signaling dynamics.
Most fruit trees in the U.S. are propagated as clones and grafted onto rootstocks. Our national pear industry has a high demand for rootstock cultivars that can offer dwarfing and disease resistance, as well as material that is virus free, all of which is becoming increasingly important as climate change progresses and disease and resource use become more pressing issues. However, when new cultivars are developed to meet these needs and the industry needs to produce these plants, they run up against another big issue: pears are well known for being difficult to root. While protocols have been published for rooting pears, these are largely focused on few specific cultivars, and we know that pear cultivars vary widely in their responses to different rooting treatments. The proposed work aims to understand the changes in gene expression (using transcriptomics) and hormone localization and signaling (using quantification and sensors) across cultivars in response to rooting treatments, with the goal of improving predictability. By establishing protocols and tools to compare gene expression and hormone responses between hard-to-root and easier-to-root cultivars, this work seeks to identify genes, molecular pathways, and patterns associated with successful rooting, as well as lay the groundwork for understanding other hormone-related phenotypes and processes in pears. The proposed work addresses priorities within the Physiology of Agricultural Plants program area through improvement to plant production and propagation and improvement of a fundamental step in producing and releasing new varieties that may be developed for combating climate challenges.