HIGH TEMPERATURES DURING BLOOM CAN INHIBIT POLLEN GERMINATION AND TUBE GROWTH, AND ADVERSELY AFFECT FRUIT SET IN THE PRUNUS DOMESTICA CULTVARS ‘IMPROVED FRENCH’ AND ‘MUIR BEAUTY’

Prune production areas in California experienced unusually high temperatures during three of the past four bloom seasons (2004, 2005, 2007). This has been accompanied by marked reductions in fruit set for many growers.
We have been investigating the effects of temperature on pollen germination and pollen tube growth.
Pollen from ‘Improved French’ and ‘Muir Beauty’ was incubated on agar-solidified medium on a temperature-gradient bar.
Pollen germination and pollen tube growth were determined from these samples.
Interpolations of parabolic regressions indicate optimum temperatures for pollen germination are 22.6°C for ‘Improved French’ and 22.2°C for ‘Muir Beauty’, and temperature optima for pollen tube growth are 24.0°C for ‘Improved French’ and 24.3°C for ‘Muir Beauty’. In vivo analyses of pollen tube growth for ‘Improved French’ were conducted under ambient and elevated temperature conditions for two years, one characterized by relatively cool temperatures during bloom and one with warmer conditions.
Flower samples were collected at intervals after hand pollination and pollen tube growth analyzed from aniline blue stained samples examined under a fluorescence microscope.
Results indicated that supraoptimal temperatures inhibit pollen tube growth at the upper style.
In addition, results of our experiments indicate mid-day microsprinkler irrigation may moderate temperatures during bloom sufficiently to enhance fruit set under high temperature conditions.

IX International Symposium on Plum and Prune Genetics, Breeding and Pomology

M.T. DeCeault, V.S. Polito

Prunus domestica, pollination, pollen germination, pollen tube growth, fruit set, temperature

https://doi.org/10.17660/ActaHortic.2010.874.22