Abstract
Two Digitaria hybrids were compared with pangolagrass, Digitaria decumbens Stent., using both the light and electron microscope. The purpose of the study was to develop a diagnostic method of screening breeding lines for resistance or tolerance to pangola stunt virus (PSV). Pangolagrass from Surinam and Guyana, naturally infected with PSV, was found to have occassional bundle sheath cells with very thick cell walls. One of the two hybrids, which appeared to be highly susceptible to PSV, also showed similar thick cell walls. It had spherical particles 70 nm in diameter, resembling PSV, maize rough dwarf virus (MRDV) and rice dwarf virus (RDV). Sieve element cells of the phloem were the primary site of particles and the probable site of virus replication. The second hybrid, an apparently resistant line, was found to be completely free of thick-walled bundle sheath cells, and no viruslike particles were found in the bundle sheath or phloem cells. The presence of thick-walled bundle sheath cells appears to offer an excellent diagnostic test for PSV.
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