Location: Crops Pathology and Genetics Research
Project Number: 2032-22000-017-065-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Jan 1, 2024
End Date: Dec 31, 2026
Objective:
Objective 1 - Completed resistance data for Agrobacterium, Phytophthora, and phytopathogenic nematodes for commercial standard and experimental rootstock genotypes.
Objective 2 - Data on graft compatibility and almond tree growth and yield for experimental rootstock genotypes.
Objective 3 - Three rootstock candidates propagated with scions for testing in regional rootstock trials.
Approach:
Approximately 40 standard and experimental rootstocks for almond will be evaluated for resistance to Agrobacterium crown gall (CG), Phytophthora crown and root rot (PHY), and root lesion and root knot nematodes (NEM) in replicated trials. The evaluations of CG resistance will based on incidence and severity of galls formed after wound inoculations of crown and root tissues in a greenhouse assay, whereas the evaluations of PHY resistance will be based on incidence and severity of crown rot resulting from soil infestation with Phytophthora cactorum and P. niederhauserii and soil flooding in field plantings, and NEM resistance assessments will be based on reproduction levels of root lesion and root knot nematodes after soil infestation with the pathogens with under field conditions. Selections of the standard and experimental rootstocks that were planted for nematode resistance evaluations in 2020-2023 will also be monitored to determine their graft compatibility, tree growth, and almond kernel yields with Nonpareil and Monterey scions. Tree growth and graft compatibility will be monitored annually according to tree survival and increases in trunk cross sectional area. Kernel yields will be monitored for both scion varieties in the third and fourth growing seasons after planting. Kernel turnout percentages and weights will be determined for each replicate plot using a research huller/sheller at UC Davis. The investigators will use all available data on rooting and budding success (available from previous years of this project), pathogen resistance, tree growth, and yields to identify at least three rootstocks for entry into regional rootstock trials organized and managed by UC Farm Advisors. In preparation, the investigators will enter the prospective rootstocks into testing at Foundation Plant Services at UC Davis to determine whether the selections require treatment for removal of virus infection(s). The selected stocks will be propagated with scions of Nonpareil and/or other scions targeted for regional trials. Twenty-five to 50 trees will be propagated per selected rootstock, and the investigators will facilitate entry of the rootstocks into trials as appropriate.
