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Sexuality and Cultural Characteristics of Aspergillus heterothallicus

Kyung-Joo Kwon and Kenneth B. Raper
American Journal of Botany
Vol. 54, No. 1 (Jan., 1967), pp. 36-48
Stable URL: http://www.jstor.org/stable/2440885
Page Count: 13
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Sexuality and Cultural Characteristics of Aspergillus heterothallicus
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Abstract

Aspergillus heterothallicus K., F. and R., isolated from Costa Rican soils, represents the first species in this genus that is truly heterothallic. Each of the eleven strains investigated is functionally hermaphroditic but self-sterile and falls into one of two cross-mating classes, A or a. The mating-type factors A and a appear to be an allelic pair segregating independently of the locus for pigmentation of mycelium which varies from yellow to pinkish orange in different isolates. The striking variation in the development of hulle cell masses that occurred among the progeny from the cross WB 5096(A) x WB 5097(a) was found to be genetically controlled. The gene responsible for a delay in the formation and maturation of cleistothecia appeared to be loosely linked to the a mating-type locus and could be recombined into the A mating type. The mechanism of fertilization has not been completely elucidated. Coiled ascogonia were found within young hulle cell masses developed in cultures where two isolates of opposite mating types were crossed; such coils have not been observed, thus far, within hulle cell masses in unmated cultures. Although no recognizable male structure has been found, the fertilizing element appears to be mycelial in form rather than conidial. Interspecific mating did not occur when strains of Aspergillus heterothallicus were paired with other members of the A. nidulans group.

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