Effect of pistil receptivity, pollen mixtures, and pollen application distances on fruit set of pistachios (Pistacia vera)

This study was carried out at the pistachio (Pistacia vera) orchards of Ceylanpinar State Farm, Turkey. The cultivar 'Siirt' and Male 13 were used in the experiments. The aim of the study was to investigate the effect of pistil receptivity, pollen mixtures, and pollen application distances on fruit set using artificial pollination in pistachios. To determine the receptivity of female flowers, anthesis was accepted as day 0, and then one application was carried out on 0, 2, and 4 days after anthesis; and repeated applications were done on 0+2, 0+4, 2+4, and 0+2+4 days, separately. Pollen and wheat flour was mixed to obtain 1%, 5%, 10%, 50%, and 100% pollen mixture, and these pollen mixtures were sprayed from 25, 50, and 100 cm distances from the inflorescence clusters with a small hand sprayer. Thus, fruit set was determined for the applications. Different pollen mixtures were applied to a microscope slide, covered with Vaseline, from three different application distances to determine the number of pollen grains per unit area by artificial pollination. The number of pollen grains per unit area was counted under a light microscope and calculated per 1 mm2. Finally, adequate pollen numbers to pollinate a flower were determined. The results indicate that for optimum fruit production of pistachio, 5% and 50% pollen mixtures should be sprayed at a distance of 100 cm at 0 and 4 days after anthesis. The adequate number of pollen grains to pollinate a flower was calculated as 14 or 15 pollen grains per flower in pistachio. Increased number of pollen per stigma area would cause excessive flower abscission after a certain point, and this could be the cause of low fruit set in pistachios. © The Royal Society of New Zealand 2008