The viability, pollen source, pollen tube growth and fertilization were considered in pistachio fruit production. Dropped ovaries were produced via unpollinated flowers, pollination with incompatible pollen or degeneration after zygote formation. Abscission or blankness also may affected by time of pollination or flower age. In order to study the state of germination and tube growth of 4 overlap male genotypes pistachio that were crossed with two female pistachio cultivars at different time, Finally fruit set were studied. The results of this experiment were conducted by RCBD design.
Highest percent of pollen germination in lab condition was belong to pollens of R28 and N16 (85 and 81%), R27 (72%) and N2 (69%).
Maximum number of germinated pollen grains were seen in Kalleghoochis flower pistils in the first and second days of anthesis when pollinated with R27 (42 and 40 no). From interaction effects of all factors on number of pollen tubes number in nucellus cleared that "Kalleghoochis" flowers which pollinated in third day of anthesis with R28 pollens after 48 hours, had the highest number of pollen tube in nucellus (1/4 no). Maximum number of pollen tube in flower's nucellus of "Ahmadaghaii" were obtained in the second time of anthesis with R27 pollens and study after 48 hours (1/3 no).The highest rate of fruit set determined with pollination in third days of anthesis in both of varieties.