Location: Physiology and Pathology of Tree Fruits Research
Project Number: 2094-21220-003-018-A
Project Type: Cooperative Agreement
Start Date: Jun 1, 2025
End Date: Jan 31, 2026
Objective:
Long term goals: Improve understanding, predictability, and efficiency of Pyrus rooting for both researchers and nurseries to apply to emerging and future rootstock cultivars. Fill knowledge gaps pertaining to cultivar-specific hormone responses and sensitivities.
Grant goals: Develop tools and identify preliminary targets for future rooting, hormone-related, and molecular studies and grants for pear rootstock cultivar improvement.
Objectives:
Obj. 1. Characterize rooting efficiency across a diverse Pyrus germplasm set
Obj. 2. Compare transcriptional responses to rooting treatments among Pyrus cultivars
Obj. 3. Compare hormone responses to rooting treatments
Approach:
Objective 1: Characterize rooting efficiency across a diverse Pyrus germplasm set
Obj. 1A: Propagate plants in tissue culture and determine plantlet standardization protocol.
Sixteen diverse Pyrus accessions will be established in tissue culture for the purpose of identifying a subset that vary significantly in rooting efficiency in response to treatments.
Obj. 1B: Treat germplasm with multiple rooting treatments to determine efficiencies and stages.
Once shoot growth timelines are characterized, plants of similar stage will be subjected to multiple rooting treatments. From these experiments, we aim to find three or four cultivars that range from easy- to hard-to-root and have 1. different rooting efficiencies from one another in response to each treatment and 2. varied individual responses to the four treatments.
Objective 2: Compare transcriptional response to rooting treatments between Pyrus cultivars.
Obj. 2A: Identify root- and stem-specific genes by comparing transcriptomes across pear tissues.
To determine tissue-specific gene expression across pear tissues, comparative transcriptome sequencing will be performed.
Obj. 2B: Compare dynamic gene expression between cultivars in response to rooting treatments.
As an early step in uncovering the genes and molecular pathways underlying cultivar-specific rooting responses, transcriptomic comparisons will be made between treatments, tissues, cultivars, and over multiple timepoints.
Objective 3. Compare hormone responses to rooting treatments
Obj. 3A: Quantify hormone content in different tissue types in response to rooting treatments
To investigate spatiotemporal differences in endogenous hormone responses between cultivars, multiple approaches will be taken to quantify and visualize hormone content and localization in relevant tissues. First, in response to different rooting treatments, stem tissue hormone content will be compared between two of the cultivars used in Objective 2.
Obj. 3B: Transform the subset of germplasm with auxin and cytokinin biosensors for future analysis of hormone localization and signaling dynamics
In addition to hormone content analysis, hormone biosensors have proved very useful in assessing spatiotemporal responses in many plant species. These tools have been applied to some perennial crop species, and many pear species and cultivars have successful transformation systems in place. To visualize auxin and cytokinin responses, the subset of cultivars determined in Objective 1B will be transformed with auxin and cytokinin reporters and biosensors.