Microsporogenesis in alloplasmic rye

J. R. LACADENA

Departamento de Genetica, Facultad de Ciencias, Universidad de Madrid, Spain

LEIN (1948-49) named alloplasmic rye those plants whose cells have "wheat" cytoplasm and "rye" nucleus (chromosomes). Later SASAKI (1956) obtained alloplasmic rye too.

In 1967, the author (LACADENA 1969) obtained two plants of alloplasmic rye (namely, CAL-1 and CAL-2) of the type Triticum durum-Secale cereale whose pedigree was [F₃ Amph. (T. durum x S. cereale)] x S. cereale⁵. Observations on microsporogenesis were made in both plants. Meiosis of pollen mother cells appeared to be quite normal until the formation of tetrads. Nevertheless, in the young pollen cells of the CAL-1 plant asynchronous cycles of condensation and replication of the chromatids were observed. The young microsporocytes showed a gradual chromatid condensation cycle which, like an unaccomplished mitotic process (interphase-prophase-metaphase), brought about young pollen cells with 7 single metaphase-like chromatids (see figure). Sometimes nuclei belonging to the same tetrad showed different "mitotic" stages: interphase, prophase or prometaphase. It was remarkable the high degree of uncoiling of the centromere region observed in the metaphase like young microsporocytes: the two fully condensed arms of the chromatids were connected by an apparently single chromatic thread. It seems reasonable to attribute the asynchrony of the condensation and replication cycles of chromatids to the peculiar cell constitution of this plant, namely, alloplasmy.

However, in spite of the anomaly indicated, the metaphases and anaphases of the first pollen mitosis appeared to be quite normal, the metaphasic chromosomes having a duoblechromatid constitution.

The plant CAL-1, which is being referred to, had both female and male gametes fertile. The following results were obtained when it was reciprocally crossed to the rye commercial variety Elbon:



It was not possible to observe any young pollen cells of the CAL-2 plant. Pistillody phenomena were not found either in CAL-1 or CAL-2 plant.

Literature

LACADENA, J.R. 1969. Cytogenetic studies in alloplasmic rye. Genet. Iber. (in press).

LEIN, A. 1948-49. Uber alloplasmatische Roggen (Roggen mit Weizenplasma). Zuchter 19 : 101-108.

SASAKI, M. 1956. Pistillody in a rye strain with wheat plasms. Jap. J. Genet. 31 : 310.

(Received March 10, 1969)