0
Views
4
CrossRef citations to date
0
Altmetric
Articles

Induced Hybridization in Graminicolous Smut Fungi. III. Further Studies of Ustilago Hordei × U. Bullata

&
Pages 549-562 | Published online: 12 Sep 2018
 

SUMMARY

An account is given of hybridization between Ustilago hordei and U. bullata. Several contrasting spore characters were available for study in crosses between these species. Spores of U. hordei are small (5-8μ), smooth, and lighter colored on one side; those of U. bullata are larger (8-11 μ), verrucose, and, in some collections, lighter colored on two sides.

Seventy-four different monosporidial combinations, representing one collection of U. hordei and five collections of U. bullata, produced Ft spores on Elymus glaucus or E. canadensis.

The F1 spores were echinulate; most were lighter colored on two sides and intermediate in size. The hybrid spores germinated, but lysis of the promycelia and sporidia defeated attempts to obtain complete sets of monosporidial lines. Therefore, hybrid teliospores were used as inoculum to obtain subsequent generations.

Sixty-two of the 74 F1 hybrids produced a second generation. Segregation in the F2 resulted in the recovery of parental types and in the appearance of a number of types unlike either parent. Most F2 sori contained spores more or less echinulate and lighter colored on two sides like those of the F1; some contained smooth spores lighter colored on one or two sides; and others contained a mixture of spore types. The F2 spores ranged from smaller than U. hordei to larger than U. bullata.

Teliospores of representative F2 segregates were used to obtain F3 hybrids; representative F4 types were then used to obtain F4 hybrids. The F4 generations represented nine of the original 74 monosporidial combinations of U. hordei and U. bullata.

In most cases, the F3 and F4 hybrids resembled their respective F2 or F3 parents; in others, segregation produced different types as in the F2. In a few instances, segregates were recovered which possessed characteristics, not attributable phenotypically, to either parent. These included smooth spores notched on the lighter sides, echinulate spores with laminated exospore, and smooth spores broadly indented on one side.

Some of the segregates were sufficiently distinct to be considered as independent species. This production of new morphologic types by hybridization experimentally is indicative that new species may originate likewise in nature.

Populations were too small to permit ratio studies, but the predominance of intermediate types, the gradation of characters from one parental extreme to the other, and the occurrence of heterosis suggest that most of the characters are governed by multiple factors.

Reprints and Corporate Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

To request a reprint or corporate permissions for this article, please click on the relevant link below:

Academic Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

Obtain permissions instantly via Rightslink by clicking on the button below:

If you are unable to obtain permissions via Rightslink, please complete and submit this Permissions form. For more information, please visit our Permissions help page.