Analysis of the effects of maturation treatments on the probabilities of somatic embryo germination and plantlet regeneration in pistachio using a linear logistic method

Embryogenic masses (EMSes) of pistachio (Pistacia vera L.) were proliferate d in liquid Murashige and Skoog (MS) medium without growth regulators. To d etermine the effects of benzylaminopurine (BAP), racemic (+/-) abscisic aci d (ABA) and sucrose treatments during maturation on the subsequent germinat ion and plantlet regeneration, clusters of mature somatic embryos were tran sferred from maturation medium onto the surface of 0.7% agar-solidified Mur ashige and Skoog medium. Neither germination nor plantlet development mediu m contained BAP or ABA. Germination studies were carried out using 80 somat ic embryos at every combination of four sucrose concentrations, three matur ation periods and either five concentrations of BAP or four of ABA, and the numbers germinating were recorded after four durations of culture. A simil ar experimental plan was used to study plantlet regeneration. The number of germinated somatic embryos increased markedly with duration of the culture on germination medium, and was influenced by the concentrations of BAP or ABA in the maturation medium; the concentration of sucrose in this medium h ad little influence. Plantlet regeneration also increased with culture dura tion and was reduced at the highest levels of BAP or ABA; with ABA, the pro bability of plantlet regeneration was lower for longer maturation periods. ABA and BAP have similar effects on somatic embryo germination (except at t he highest levels used), but BAP is superior to ABA for promoting subsequen t plantlet regeneration. Linear logistic models were used to investigate th e significance of the treatments, and to estimate the optimum conditions fo r germination and plantlet regeneration.