Cytoplasmic-nuclear interaction and medium effect for protoplast culture in sunflower

Protoplasts of 6 alloplasmic and 2 euplasmic sunflower inbred lines were is olated from dark grown seedling hypocotyls with a density of 2x10(4) protop lasts/ml. The protoplast suspension was mixed with a solution of 0.5% agaro se (sigma - type 1), then pipetted in droplets of about 1000 protoplasts. D roplets were surrounded by two different liquid media. After 30 days drople ts from both media were transferred to solid differentiation medium. Protop last division, microcolony frequency and the number of calluses produced we re strongly dependent on medium composition and genotype. The number of cal luses per 1000 protoplasts plated range from 0.3 to 5.0 according to the ge notype and the method used. The alloplasmic line RHA274-PEF1, was the best responding genotype for calluses produced in both media used. In all cases, the percentage of calluses for alloplasmic lines were significantly higher when compared with the nucleus donor genotype. H. petiolaris fallax cytopl asm increased both the number of calluses produced and the percentage of mi crocolonies. The complex interaction among genotypes tested indicates that protoplast culture responses are affected independently by nuclear-cytoplas m interactions. Some nucleus-cytoplasm combinations can improve the protopl ast culture responses in sunflower.