Experiments on the physiology and genetics of the smut fungi.—Seedling infection

Abstract

In a previous paper (1) the behaviour, on conjugation, of certain cultures of smuts was described. The origin of these cultures was as follows:—By means of the Dickinson Isolator (2) the first formed sporidium, arising from each of the four segments of the promycelium of a germinating smut chlamydospore (obtained from the infected ears of a known race of oats or barley) was isolated. Of the four cultures grown from the isolated sporidia of a single chlamydospore, two were found in every case to be of one gender (sex), and two of another gender. This gender distinction was determined by observing the behaviour of the hyphæ at the meeting of two colonies; when the colonies were of different gender, the opposing hyphæ fused, whereas when the colonies were of the same gender the opposing hyphæ did not fuse. Up to the time of such conjugation the cells of the mycelium, hyphal or conidial according to the conditions, were found to be uninucleate. On the conjugation of two hyphæ a migration occurred of the nucleus and contents from one hypha into the other. Then followed the growth of a hypha called the “fusion-hypha,” containing the two associated nuclei. Under certain conditions it was shown that the fusion-hypha gave off uninucleate hyphæ and conidia at either end, which resembled the original (pre-conjugation) hyphæ in gender. The further history of the fusion-hypha will be described in a later paper. In the present paper experiments are described, in which various combinations of the above-mentioned genders are used in the inoculation of seedling plants.