The cytopathology and isolate relationships of sorghum yellow banding virus

Abstract

Electron microscopy of SYBV showed icosohedral particles with maximum and minimum diameters of approximately 28 nm and 27 nm. The two isolates are statistically the same population at a probability greater than 95%. Virus-like particles were found in epidermal, spongy mesophyll, sieve tubes, phloem parenchyma, and palisade cells. The cells in green areas of infected leaves contained chloroplasts with reduced starch. The cells in chlorotic areas of infected leaves showed the most deviation in cellular make-up of the tissues sampled compared to controls. Starch content appeared reduced by a minimum of 70%. Virus-like particles increased to levels much higher than in cells of green infected tissue. Large tonoplast invaginations into the central vacuole contained large numbers of virus-like particles. Invaginations were observed to rupture with virus-like particles present in the central vacuole. The greatest aggregations of virus-like particles were concentrated in crystal lattices in regions between the plasmalemma and near-by chloroplasts or nuclei. A dramatic change was seen in the nuclei. Portions of the nuclear membrane expanded outward and areas within the membranes were sometimes void of any staining or appeared to contain clusters of virus-like particles. The nuclear matrix was highly uniform. Antiserum to SYBV-TX was produced in rabbits to a titer of 1:16,384, and in mice to 1: 32,768. DAS-ELISA gave positive readings at 1:200,000 dilutions of infected plant sap and at 1 ng of purified SYBV-TX. Virus titer in the plant sap was estimated at approximately 0.25-2 mg/ml. Indirect ELISA using mouse antiserum gave positive readings at 0.5 ng of purified SYBV-TX. Twenty stable monoclonal antibody secreting hybridomas were produced to SYBV-TX. All the generated monoclonal antibodies gave positive readings to both SYBV-TX and SYBV-CA. The readings were approximately the same for a given CSN and either the Texas or California isolates. Ascitic fluid was produced for 4 clones. The clones DL6, DL17, DL19, and Y2A1 were determined to be IgG1 with kappa light chains. The remaining clones were found to be IgG2a with kappa light chains.