Tilletia indica: cytology and teliospore formation in vitro and in immature kernels

Abstract

In teliospores of Tilletia indica Mitra meiosis occurred at germination, followed by a series of mitoses in teliospores, promycelia, or both, resulting in promycelia with numerous haploid nuclei. Primary sporidia initially were single, monokaryotic cells. After abstriction cell division occurred, but each cell stayed monokaryotic. Mycelia isolated from incipiently infected wheat caryopses formed teliospores on potato sucrose agar after 2–3 weeks and continued to do so for about 2 years. Nuclear stages of the fungus in culture and host tissue were demonstrated with haematoxylin, HCl–Giemsa, and (or) the Feulgen nucleal reaction. During formation of teliospores in vitro, conjugately associated nuclei of sporogenous mycelia migrated to probasidial initials which formed at right angles to the parent hypha. The dikaryotic probasidia usually were subtended by Y-shaped septa. Karyogamy was not seen, but circumstantial evidence suggested that it occurred during very early stages of probasidial development because even immature teliospores were monokaryotic. The process of teliospore formation and the concomitant changes in nuclear condition were easily observed in cultures, but in vivo the gelatinoid nature of the mycelium in the host tissue made this much more difficult. Moreover, some stages of teliospore formation observed in vitro were not seen in soral sections and presumably did not form in son on the host.