Plant material and growing conditions
P. integerrima and UCB1 seeds were provided by Foundation Plant
Services, University of California (Davis, CA, USA), the Kresha
Agricultural Nursery (Bakersfield, CA, USA) and from the Wolfskill
Experimental Orchard (Winters, CA, USA).
Pistachio seeds were separated from shells and sterilized in a mixture
of 5% (V/V) bleach and 1% (V/V) Tween-20 in deionized water. Seeds
were germinated in vitro in ½ Murashige-Skoog (MS) medium at
adjusted pH of 5.7 containing 1% (W/V) sucrose, 0.1% (W/V) activated
charcoal, and 0.75% (w/v) agarose. The media were supplemented with 4.5
µM 6-Benzylaminopurine, 0.5 µM indole-3-butyric acid, 0.29 µM
gibberellic acid. Germinated seedlings were grown for 8 weeks for UCB1
and 10 weeks for P. integerrima in the same medium, at 22 ± 2°C
using fluorescent light (100 to 150 mmol quanta PAR
m–2 s–1) under long day conditions
(16 h : 8 h light : dark). Plants were transferred to charcoal-free
supplemented ½ MS medium for a minimum of one week prior to the start of
the experiment.