VIEW ARTICLE

Cytology and Histology

Somatic Nuclear Division in Tilletia Species Pathogenic on Wheat. B. J. Goates, Agricultural research technician, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Utah State University, Logan, 84322; J. A. Hoffmann, research plant pathologist, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Utah State University, Logan, 84322. Phytopathology 69:592-598. Accepted for publication 15 December 1978. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1979. DOI: 10.1094/Phyto-69-592.

Somatic nuclear division was studied in secondary sporidia and hyphae of Tilletia caries, T. foetida, and T. controversa by means of HCl-Giemsa and H₃PO⁴-acetic orcein staining techniques. The morphology of division figures was determined by observing individual nuclei from different perspectives in cells suspended in glycerine. The chromatin in resting nuclei was granular to filamentous; one or more dark-staining bodies were observed near the periphery of the nucleus. During sporidia formation, most of the parent cell protoplast migrated into the developing sporidium concomitant with basipetal septation of the parent cell. In the bud cell, the nucleus contracted into an intensely staining spherical mass. The contracted nucleus was transversed by a linear, unstained area (the spindle) that usually was positioned eccentrically and oriented parallel to the long axis of the bud cell. Chromatin separating from the contracted nucleus was in the shape of a cylinder surrounding the unstained spindle. In side view, the chromatin appeared as two elongating parallel lines stretching out from the contracted configuration. During chromatin migration, most of the chromatin aggregated on opposing sides of the spindle forming two parallel lines which separated transversely as the chromatin aggregated at the poles. The spindle transversed the daughter nuclei giving them a bisected appearance in side view. In polar view, chromatin at the ends of division figures and the daughter nuclei were doughnut-shaped, with the unstained spindle occupying the hole in the doughnut. After division, one daughter nucleus returned to the parent cell and usually remained contracted; the other migrated to the distal end of the bud cell and entered an interphase-like condition. Septation occurred between the parent and daughter sporidium and then the parent sporidium usually senesced. The same division process was observed in monokaryotic and dikaryotic sporidia and hyphae of the three species studied. Chromosomes could not be counted, but our observations cast serious doubt on previous reports that n = 2 in these Tilletia spp.