Effect of genotype on somatic embryogenesis in pistachio (Pistacia vera L.)

Genotypes representing eight botanical cultivars of pistachio (Pistacia vera L.) were assessed for somatic embryogenesis and subsequent plant conversion from immature kernels. Embryogenic masses (EMSs) were produced from kernels of immature fruit of pistachio cultured in liquid MS medium with Gamborg vitamins, supplemented with 100 mgl(-1) casein hydrolysate, 100 mgl(-1)L-Ascorbic acid, 3% sucrose, and BAP. EMS differentiated directly from the kernels after culture for 2 weeks in liquid medium with 0.5 mg P BAP. Genotype x collection date had large effects on initiation of somatic embryogenesis. Embryogenic tissues containing embryoid or individual somatic embryos were isolated from the original tissue and used to initiate repetitive liquid or agarified cultures. To determine the effects of genotypes during maturation on the subsequent germination and plantlet generation, clusters of EMSs from the different genotypes were transferred from liquid medium onto the surface of 5.7% agar solidified MS medium with Gamborg vitamins, containing 4% sucrose, 1.0 mg l(-1) BAP and 0.5 mg l(-1) IBA. After 4 weeks, individual or clusters of mature somatic embryos were transferred from maturation medium onto the germination medium (GM). The number of matured and germinated somatic embryos was influenced by the genotype in the maturation medium. Acclimatized plantlets resumed growth after transfer to a soil and peat mixture, and many developed to maturity.