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Cytology and Histology

Alterations in Chloroplast Ultrastructure and Chlorophyll Content in Rust-Infected Pinto Beans at Different Stages of Disease Development. I. Sziráki, Research Institute for Plant Protection, Department of Pathophysiology, Budapest, Hungary; L. A. Mustárdy(2), Á. Faludi-Dániel(3), and Z. Király(4). (2)(3)Institute of Plant Physiology, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary; (4)Research Institute for Plant Protection, Department of Pathophysiology, Budapest, Hungary. Phytopathology 74:77-84. Accepted for publication 8 July 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-77.

An increase in chlorophyll level compared to healthy controls was detected from the time of the appearance of chlorotic flecks caused on bean leaves by Uromyces phaseoli until the end of symptom development. A similar pattern was found in the changes of carotenoid level. This may provide an explanation for the appearance of green islands. Seven days after inoculation, aggregation of cell organelles was observed around the haustoria at the center of infection sites. Starch accumulation was found in plastids of cells containing fungal haustoria as well as in the plastids of neighboring cells. The starch accumulation spread as the colonized area enlarged. By the 14th day, the starch grains had disintegrated in the center of green islands and chloroplast degradation had begun in the cells around their margins. Twenty-three days after inoculation, chloroplasts of these cells were completely disrupted. Degradation of chloroplasts also was observed in the central zone, but even at that stage some thylakoids were seen near the center of the colony. Chloroplasts in the green islands of leaves kept under low light intensity appeared normal but contained abundant peripheral reticula. Comparison of Hill activity of chloroplasts isolated from infected and uninfected tissues revealed that the electron transport chain of chloroplasts is more stable in the infected tissue than in that of the controls.