Effects of dormancy-breaking treatments on seed germination and seedling growth of <i>Pistacia khinjuk</i> Stocks using as rootstock for pistachio trees

Abstract

This study was carried out to determine the effects of different dormancy-breaking treatments including stratification, sulphuric acid scarification, dehulling (removing the mesocarp and exocarp from the nut) and gibberellic acid (GA₃) on seed germination and seedling development of two different Pistacia khinjuk genotypes (A and B) using as rootstock for pistachio cultivars. Seed dormancy-breaking treatments were shelled (control), shelled + GA₃, dehulled, dehulled + GA₃, sulphuric acid scarification and sulphuric acid scarification + GA₃ applications in the present experiment. The seeds of both genotypes were stratified at 4 ºC for 50 days after the dormancy-breaking treatments. Stratified seeds were sown in the vials filled with peat in the greenhouse to determine the germination percentage. Plantlets were transplanted to plastic containers to determine the vegetative growth. The highest germination rate was obtained from sulphuric acid scarification in both P. khinjuk genotypes. In P. khinjuk-A seedlings, the highest stem growth was obtained from scarification and dehulled applications, whereas the poorest development was observed from dehulled + GA₃ application. The best growth in the P. khinjuk-B seedlings was obtained from scarification + GA₃ application. The effect of the dehulled application on the root development of P. khinjuk-A seedlings was better than the other applications; however the effect of dormancy-breaking applications on root development of P. khinjuk-B seedlings was found to unsteady. Scarification increased the number of leaves in both genotypes. As a result, dormancy-breaking applications have been found to be effective on seed germination and seedling growth of P. khinjuk. It was determined that GA₃ applications negatively affected both seed germination and root, stem and leaf growth of P. khinjuk-A.