Location: Crops Pathology and Genetics Research
Project Number: 2032-22000-017-021-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Jul 1, 2021
End Date: Aug 19, 2022
Objective:
1. Traditional and in vitro propagation of a genetically diverse collection of Juglans species including creation and characterization of an enhanced mapping population from Juglans microcarpa x J. regia crosses.
2. Identification and characterization of genetic loci which mediate disease resistance and utilization of molecular markers for rapid screening/identification of resistant genotypes.
3. Outreach and development of new, and existing, field trials examining performance of elite rootstock germplasm.
Approach:
1. Using the technologies previously described, we will continue to produce seedling and in vitro clonal propagants from our collections that will be made available for disease resistance screening. Similar to last year (i.e. yr1 of project), as each new disease resistant genotype is identified, it will be propagated under in vitro/greenhouse conditions. These genotypes will then be rescreened in the greenhouse to confirm its resistance phenotype, and if validated, then will be moved into field trials.
2. Investigate: a) pyramiding resistance to all three pathogens aided by marker assisted selection (MAS), (b) strategically select SNP markers in the QTL intervals for crown gall, Phytophthora and nematode resistances to fine-map the traits, identify close-linked markers and towards cloning the gene(s). To accomplish this objective we rely on our high thru- put validated phenotyping systems.
3. continue evaluation of our four ongoing June bud rootstock trials (one trial each in Glenn, Lake, Sutter, and Tulare counties). All four of the elite selections, as well as commercial standards of Paradox seedling and VX211 and RX1 clonal rootstocks were grafted to scions of J. regia ‘Chandler’. We will continue to assess tree growth (i.e., annual rootstock and tree trunk circumference measurements, percent of photosynthetically active radiation intercepted by tree canopy at some sites), disease incidence, and rootstock suckering. Crown gall incidence will be visually assessed annually, and roots from trees that decline or die are examined to determine whether they are infected with Phytophthora spp. or lesion nematode. Tree performance data from all orchard trials is subjected to analyses of variance and regression analyses, as appropriate. In early 2021, we draft and submit a manuscript of publication in a refereed journal.
