II.33. Double trisomics in barley.
R. J. Singh. Department of Agronomy, Colorado State University, Fort Collins, Colorado, 80521, U.S.A.
Four sixteen-chromosome plants were obtained in the progenies of hypertriploid (2n = 22) plants (Singh and Tsuchiya, unpublished data). One plant out of four could not survive beyond the second leaf stage. Morphologically, it appeared that chromosome 1 (Bush) (SE72-3-10), 4 (Robust) (SE72-3-14), and 7 (Semi-erect) (SE72-3-11) were involved. Three plants grew to maturity and produced seeds, except Semi-erect, when artificial self pollination was conducted. However, meiosis of these plants was not studied due to lack of tillers. The progenies of these plants were studied and they produced diploid and simple trisomic plants. The meiosis of these trisomic plants was studied and no ring trivalent was observed indicating that they were all primary trisomics. An interesting sixteen chromosome plant (SE71-15-44) was obtained in the selfed progeny of a primary trisomic for chromosome 7 (Semi-erect). Morphologically, it was similar to the primary trisomic for chromosome 7 (Semi-erect). Meiosis of this sixteen chromosome plant was studied. At diakinesis and Metaphase-I, chromosomes either formed 1III+6II+1I or 2III+ 5II. A few metaphase I cells (4.88%) formed 7II+2I (Table 1).
The formation of two trivalent chromosome configurations indicate that the two extra chromosomes are not homologous. Absence of quadrivalent chromosome configurations indicate that this plant is not a tetrasomic.
At diakinesis and metaphase-I, chromosomes formed different types of trivalents (Table 2). The occurrence of a ring trivalent indicates that one chromosome is an isochromosome.
At anaphase I a bridge without fragment was observed indicating that no inversion was involved. Normal chromosome separation was observed in 42.59% cells (Table 3). Furthermore, 24.07% of the cells showed one lagging chromosome.
Table 3. Chromosome separation at anaphase I in a 16 chromosome plant of barley.
Artificial self pollination was conducted to obtain seed, but no seed was obtained. (Supported partly by NSF Research Grant GB30493 to Dr. T. Tsuchiya).
