Molecular Cytological Studies On Virus-infected Host Plants

Bean broad wilt virus (BBWV), Sugarcane mosaic virus (SCMV) and Sorghum mosaic virus (SrMV), reported in many regions of China, caused serious loses in economic crops. In this paper, the ultrastructural alteration of several host plants respectively infected with BBWV, SCMV and SrMV were systemically studied by transmission electron microscope (TEM) and immunological technique.1. The typical mosaic symptoms occurred on the leaves of Vicia faba, Pisum sativum and Chenopodium quinoa inoculated with the B935 isolate of BBWV2. Under the TEM, several similar ultrastructural changes were observed in the thin sections of the infected leaves of V. faba and P. sativum, such as membranous proliferation composed of the fibril-containing vesicles, virus-form tubular structures 160nm in diameter, crystals composed of virus particles, virion-containing plasmodesmata, as well as the lineable virus particles between the proliferous mitochondria. In addition, some chloroplasts were often disrupted in the B935-infected cells of P. sativum leaves. By contraries, the similar cytopathological changes never been found in thin sections of C.quinoa leaf tissue infected with B935 isolates.2. Several physiological parameters of health and B935-infected V.faba were measured, and the statistical data revealed that B935 infection caused the significant reduce of net photosynthetic rate, the noted increase of intercellular CO2 concentration, and little influences on transpiration rate and stomata conductance.3. The leaves of V.faba and C.quinoa were infected with PV131, one of the BBWV2 isolates from Italy, and the mosaic symptoms developed in 10d after infection. Checked the thin sections of infected leaf tissue by TEM, the membranous proliferation, virus-formed crystals and tubular structures 80nm in diameter, were found in parenchyma cells. In addition, the thin sections of PV131-infected leaves of V.faba were examined, howerve, only proliferation of membranes located in the cytoplasm.4. The ultrastructural alterations of maize infected with SrMV and SCMV, respectively, were examined under transmission electron microscope. A large number of filamentous SrMV and SCMV particles were observed to be present as scattered or in more or less dense bundles in the cytoplasm of infected cells. Three types of cylindrical inclusions (CIs), pinwheels, scrolls and laminated aggregates, located in the SCMV-infected cytoplasm, andthe similar CIs occur in the SrMV-infected cytoplasm except for the absence of laminated aggregates. According to Edwardson, SrMV and SCMV were placed in subdivision I and III. In this paper, not only cytopathological alterations of maize infected with SrMV and SCMV were compared with each other, but also some ultrastructures possibly associated with the virus movement were analyzed.