Low temperature storage of pistachio pollen

Summary

Pollen from four male pistachio (Pistacia vera L.) clones was stored at −196°C and −20°C for up to 12 months and tested for ability to germinate in vitro following a period of hydration at high humidity. Germination of fresh pollen was high (>80%) for each clone. At −196°C, pollen of cv. Peters survived freezing, storage and thawing with no loss of germinability; pollen of the other three clones had sharp declines in germination possibly attributable to cellular lesions incurred during freezing or thawing. When the relative humidity of the −20°C storage environment was maintained at or near 33%, ‘Peters’ pollen had high rate of germination through 12 months storage. Without control of relative humidity, ‘Peters’ pollen germination was high at 4 months, but declined at 12 months. Germination requirements became more exacting for pollen stored at −20°C for 12 months at suboptimal humidity conditions. Pollen of the other three clones did not tolerate storage at −20°C as well as ‘Peters’ pollen regardless of the storage humidity environment.