Some ultrastructural aspects of the pollen transmission of barley stripe mosaic virus in barley

Abstract

To study the pollen transmission of barley stripe mosaic virus (BSMV) in barley with the transmission electron microscope, ultrathin sections of ovaries of pollinated pistils were examined. Healthy pistils were cross-pollinated with virus-infected pollen and collected at various intervals of time after pollination. When thin sections of the ovaries were viewed, virus particles were detected in specific sporophytic and gametophytic cells during critical developmental stages of pollination, fertilization, and embryogenesis. Before fertilization, BSMV particles were seen in the pollen tube between the integument and ovary wall, and in pollen tube discharge within the degenerating synergid. During and after fertilization, virus particles were found not only in the pollen tube and its discharge but also in the zygote, endosperm, persistent synergid, and nucellus. During embryogenesis, BSMV particles were very evident in the embryo, integument, and ovary wall. Some particles were scattered throughout the cell cytoplasm, while others were in mono- or multi-layer aggregates within the cytoplasm. Many particles were associated with spindle or cytoplasmic microtubules or with abnormal plastids. The prevalence of virus particles in the cells associated with sexual reproduction suggests that the nucleoprotein particle form of the virus plays some role in the pollen transmission of BSMV in barley.