Some Nuclear Phenomena in Venturia inaequalis

Venturia Inaequalis (Cke.) Wint. I. A Groundwork for Genetic Studies

“…inaequalis offers an advantage lacked by most, if not all, of the rust and the smut fungi in that it is strictly haploid throughout the parasitic stage; therefore, it affords opportunity for study of the effects on parasitism of one set of genes without the complications that arise in diploid or dicaryotic phases of organisms (ct. Dodge, 1939). Furthermore, as is shown in the present paper, it is readily cultured and bred in vitro; and, since the vegetative cells are uninucleate (Backus and Keitt, 1940), it seems free from the possibility of heritable variation because of heterocaryosis. With some disadvantages, its suscepts offer the advantage of many diverse species or varieties that can be propagated vegetatively.…”

“…provided a means for maintaining lines of 17. inaequalis with a high degree of constancy for the characters thus far studied. Each monoascosporic isolate of this fungus is a haploid pure line; and, as has been stated, the fact that the vegetative cells are uninucleate (Backus and Keitt, 1940) seems to eliminate heterocaryosis as a cause of heritable variation in this organism. It is recognized that some changes in pure lines carried by the method employed in these studies might escape visual recognition, and that a among the thirty-two isolates of the four sets studied, sixteen colony types were apparent.…”

Karyology During Conidiogenesis in Gliomastix Murorum: Light Microscopy

“…Except in Spilocaea pomi, where actual figures of nuclear division were not illustrated by Backus and Keitt (1940), these non-phialidic species apparently exhibited divisional events (stages I-IV) like those described above for the phialidic species. Thus, there is no reason to believe that nuclear divisions during conidiogenesis are any different from somatic nuclear divisions.…”

“…However, there are some variations in other aspects of nuclear behavior in these non-phialidic species. Spilocaea pomi (Backus and Keitt, 1940) apparently exhibited the same pattern of nuclear behavior as the phialidic species discussed above, i.e., uninucleate annellides and conidia, with a single nuclear division correlated with development of each conidium (Kendrick and Chang, 1971). In the annellidic Scopulariopsis spp., however, nuclear behavior was different in several ways from S. pomi and the phialidic species.…”

“…Research being reported here was initiated in an attempt to provide karyological data relevant to the above areas and to add to the existing published data of Backus and Keitt (1940), Cole (1975), Hammill (1977), Hashmi, Kendrick, and Morgan-Jones (1972a) , Hashmi, Morgan-Jones, and Kendrick (1972b) , Huang and Patrick (1972), Kendrick and Chang (1971), Tinline (1971), Zachariah and Fitz-James (1967), and Zachariah andMetitiri (1970, 1971). The fungus selected for this study was Gliomastix murorum (Corda) Hughes, a species characterized by the production of colorless, long, narrow phialides (ca.…”