Chlorophyll Synthesis Retardation and Ultrastructural Alterations to Solanum tuberosum Chloroplasts in Solanum nigrum Cells

Photosynthetic pigment contents of the second sexual generation of a cybrid plant (C-18-1) resulting from Solanum nigrum genome and Solanum tuberosum plastome were compared to those of the original (S. nigrum). Chloroplast ultrastructure alterations among S. tuberosum, cybrid, and S. nigrum were also studied. Leaf segments of both the cybrid and S. nigrum plants were cultured on shoot induction medium [B5 supplemented with 0.56 g m−3 benzylaminopurine (BAP)] for one week in light, to induce adventitious bud formation. These leaf segments were then placed in darkness for 5 weeks to form a white shoot. The respective cybrid plant had the same phenotype of the fusion recipient plant (S. nigrum) and was fertile. The rate of photosynthetic pigment biosynthesis in the white cybrid shoots was lower than that of the original plant shoots after subjecting the two plants to the same conditions of different irradiation periods (0, 2, 4, 6, 8, and 10 d). At the 10-d irradiation period of two white shoot plants, the total pigment content of S. nigrum shoot increased approximately 3-fold over that of the cybrid shoot. Numbers of grana and thylakoids as well as chloroplast size were decreased in cybrid cells in comparison to those in S. tuberosum cells. Under atrazine stress, while the chloroplast ultrastructure of the cybrid cells (atrazine sensitive) was strongly influenced, the chloroplasts of S. nigrum (atrazine resistant) were not affected.