Fertilization, inter- and intera- specific hybridization in Pistacia sp.

In pistachio, the majority of fruits does not reach maturity and drop up to 8 weeks after pollination. The fruits that reach maturity, a proportion are abnormal, seedless (blank) or their shell is not split. In this study, pollination and fruit development were investigated in relation to abscission and abnormalities.
A medium containing 1% agar and 10% sucrose was used to assess the pollen quality. Fresh and 24 hours dried pollen showed high germination in vitro as did pollen stored at freezer (-15°C) up to usage time. The stigma surface of Pistcia vera turned to pale red with some secretion on top and among papillas at anthesis. Female Pistacia vera trees were hand pollinated with pollen from male of P. atlantica and P. vera at 0, 1, 2, 3, and 4 days after anthesis. Results were measured by mature fruit set and by fluoresence microscopy of pollen germination and tube growth in the pistil. Maximum pollen tube growth and fruit set of split nuts were achieved following pollination within two days of anthesis. Three days old pistils supported pollen tube growth, but fruit set was low. Four days old pistils supported little pollen tube growth and fruit set. Significant differences were also apparent between pollen parent, with low pollen tube growth and fruit set following inter-specific pollination with P. atlantica pollen. All pollen tubes were observed to penetrate chalazogamously, and parthenocarpic production of blank fruits occurred in both unpollinated and pollinated treatments. The results indicated that for optimum fruit production of pistachio, pollen transfer must be achieved within two days of anthesis and inter-specific pollinator genotypes should be abandoned.