Submitted to: Walnut Research Conference
Publication Type: Proceedings
Publication Acceptance Date: 12/30/2009
Publication Date: 1/1/2010
Citation: Hackett, W., Leslie, C., Mcgranahan, G., Kluepfel, D.A., Lampinen, B., Anderson, K., Beede, B., Buchner, R., Debuse, C., Grant, J., Hasey, J., Caprile, J., Manterola, N. 2010. Clonal Propagation of Walnut Rootstock Genotypes for Genetic Improvement 2009. Walnut Research Conference. pp 71-86. Interpretive Summary:
Technical Abstract: We produced over 3000 liner-sized plantlets of 26 genotypes for use in greenhouse screens and for growing in nurseries to a size large enough for grafting and use in orchard trials. In addition, over 1400 liner plantlets of 15 lines transformed for resistance to crown gall were produced for greenhouse re-testing of susceptibility to gall formation. A field plot established in 2008 at UC Davis for horticultural evaluation of these lines was partly budded to Chandler and maintained for observation of horticultural and disease performance. Tissue culture methods were developed using etiolated microshoots to improve rooting of difficult genotypes. Procedures using smaller plantlets for more rapid screening for crown gall resistance were tested and applied in screening both standard and transgenic genotypes. Hardwood cuttings were used to generate clonal copies of J. cathayensis #21 and UZ229 for nematode resistance trials and to generate clonal copies of seedlings from mother trees representing ten species of interest for their crown gall resistance. Field trials of clonal rootstocks continue to be developed by farm advisors in both replant situations and new orchard plantings at diverse locations to test the horticultural performance of rootstocks selected for disease and pest resistance and virus tolerance. Clonal rootstocks are now in commercial production by several laboratories and nurseries.