Electron microscopic observations of mycoplasma-like organism in chlorotic zoysia grass

Abstract

Electron microscope observations were carried out for the leaves and shoots from zoysia grass (Zoysia tenui folia Willd, ex Thiele) showing symptoms of leaf chlolosis in association with stunting and witches-broom growth of shoots. In all samples examined, a large number of polymorphous bodies were detected consistently in the siebe tubes and occasionally in the phloem-parenchyma cells. The most abundant bodies were nearly round, 100 to 250 mμ in diameter, and contained ribosome-like granules and fibrous materials corresponding to nuclear net-strands. Budding-like protrusion and constriction of large bodies were also observed. The presence of these structures suggests that leaf chlolosis and abnormarity in growth of zoysia plants mentioned above may be caused by mycoplasma-like organism, and a new name “yellow dwarf” is proposed for this disease. In chlorotic leaves, cessation of lamella structures at the beginning of chloroplast development and destruction of immature chloroplasts were suggested to be the cause of chlorosis.