BGN 3: Occurrence of small telocentric fragment chromosome in the progenies of a plant with 15 + 1 Acro 4A chromosome BARLEY GENETICS NEWSLETTER, VOL. 3, II. RESEARCH NOTES
Singh and Tsuchiya, pp. 55-56

II.35. Occurrence of small telocentric fragment chromosome in the progenies of a plant with 15 + 1 Acro 4A chromosome.

R. J. Singh and T. Tsuchiya. Department of Agronomy, Colorado State University, Fort Collins, Colorado, 80521, U.S.A.

One plant with 15 + 1 Acro 4A chromosome was found in the progeny of a plant with 2n = 14 + 1 Acro 4A. The plant was slow in growth and no tiller was obtained. The meiosis was not studied. In the progenies of the 15 + 1 Acro 4A chromosome plant the following plants with varying chromosome constitutions were obtained:

Meiosis of the plant with 14 + 1 small telocentric fragment chromosome was studied. The fragment was observed at meiosis in all but one plant in which the fragment was eliminated. The fragment formed either a trivalent together with two normal homologous chromosomes or a univalent (Table 1).

Table 1. Behavior of small fragment from Acro 4A at diakinesis and metaphase I of meiosis.

At diakinesis, most fragments were associated with its homologous chromosomes, but they dissociated at metaphase I. At anaphase I, in most of the cells, a chromosome separation of 8-7 was observed while in some cells the fragment lagged behind in moving to the poles. In one out of 30 cells analyzed, the fragment divided at telophase I (Table 2).

Table 2. Behavior of small telocentric fragment derived from Acro 4A at anaphase I.

Morphologically, the plant with 14 + 1 small telocentric fragment chromosome was similar to its diploid siblings. Seed fertility was very good (90%). First spike was used to study the transmission of small telocentric chromosome, and 3 out of 27 plants showed 14 + 1 small telocentric chromosome. This transmission frequency (11.1%) is less than that in primary trisomic and parental type with 14 + 1 Acro 4A chromosome. However, more information is required to reach any definite conclusion. This fragment chromosome is a useful tool to study the genetic architecture of barley chromosome. (Supported partly by NSF Research Grant GB30493 to T. Tsuchiya.)

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