Twenty-eight Years of Pistachio Improvement

A discussion of pistachio breeding and genetics activities at UC Davis over the 28 years of our project is presented. The project was initiated in 1988-9 by DE Parfitt and J Maranto, with the objective of developing improved cultivars for California growers. CE Kallsen joined the project after J Maranto’s retirement. Approximately 6900 seedlings from 438 crosses were tested at 3 California central valley locations. 12 accessions were selected for advanced trials and an additional 117 items were retained for later evaluation. Genetic analysis of phenological traits was conducted by CT Chao in the 1990s. N Arjmand helped develop disease screening protocols for Botryospharia dothedia. Two of the female advanced selections were released as ‘Golden Hills’ and ‘Lost Hills’, along with a male cultivar ‘ Randy’. These cultivars have been well received by the industry due to their earlier harvest, good yields, high split percentage, few blank nuts, and less Navel Orangeworm damage. We estimate that more than 30,000 acres of ‘Golden Hills’ and ‘Lost Hills’ have been planted since release in 2006-7. We have continued to make new cross combinations with an emphasis on expanding the harvest season, reducing tree chilling requirements, increasing scion vigor, and improving nut quality. An earlier harvest female is being released in 2016, along with 2 males for better pollenization of both new and existing cultivars.