CYTOLOGICAL CHANGES OBSERVED IN THE SUCCESSIVE PHASES OF THE WHEAT-RUST CAUSED BY PUCCINIA-RECONDITA F-SP TRITICI AFTER THE TREATMENT WITH TILT 250EC

The disease process of wheat (Triticum aestivum) cv. Parada caused by rust (Puccinia recondita Rob. ex Desm. f. sp. tritici) and the effect of applying the fungicide Tilt 250EC are described. The application of spraying at the time of inoculation, during incubation and at the beg inning of the actual disease is most effective, thus attests to the hi ghest pathogen susceptibility to that chemical agent at these phases o f the disease. Tilt 250EC (propikonazole) inhibits the ergosterol bios ynthesis in the fungus cells. Application of the preparation caused th e inhibition of the development and necrosis of the intra- and extrace llular mycelium. Observed were: irregular growth of intercellular hyph ae, perforation of septas, homogenization of protoplasts and collapsin g of cells. In the haustoria observed were: the thickening of the cell wall, modification of the perihaustorial space, protoplast degenerati on and finally the haustorium obliteration.