Submitted to: Walnut Research Conference
Publication Type: Research Technical Update
Publication Acceptance Date: 3/1/2010
Publication Date: 1/1/2011
Publication URL: http://walnutresearch.ucdavis.edu/2010/2010_41.pdf
Citation: Caprile, J., Mcgranahan, G., Leslie, C., Sudarshana, M.R. 2011. Evaluation of blackline resistant (hypersensitive) cultivars. Walnut Research Conference. pp. 41-46. Interpretive Summary:
Technical Abstract: The purpose of this trial is to evaluate blackline resistant cultivars developed by the UC Walnut Improvement Program for growth and performance, nut quality, flower response to blackline infected pollen, and to further the breeding program stock. Three blackline resistant cultivars 92-16-1, 95-29-4, 97-27-55 and Howard were planted in mid April 2005 in a single row, randomized complete block design with four double tree replicates per variety. In spring of 2007, 95-29-4 was grafted over to 94-22-44. Trees were a uniform size at planting. By 2010, 97-27-55 was the largest followed by 92-10-01 and Howard with the late grafted 94-22-24 being the smallest. With regard to phenology, 94-22-224 is the earliest leafing, blooming, and harvesting while Howard is the latest. The other two varieties are intermediate with 92-10-01 blooming before 97-27-55 but harvesting slightly afterwards. Leafing order of these two varieties is variable by year. In the second year of production (2010) Howard and 97-27-55 have the highest yield ratings and the late grafted 94-22-44 the lowest. Quality data was not available from Diamond as of this writing. Studies testing the varietal response to infected pollen show that none are prone to PFA. However, there is an indication that infected pollen my reduce set and further tests need to be conducted to verify these results.