BGN 2: Hypertriploid plants in the progenies of primary trisomic for chromosome 4, Robust BARLEY GENETICS NEWSLETTER, VOL. 2, II. RESEARCH NOTES
Tsuchiya and Singh, pp. 100-103

II 39. Hypertriploid plants in the progenies of primary trisomic for chromosome 4, Robust.

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

*Reports II.33. (p.80) through II.42. (p.108) by T. Tsuchiya and co-workers are based on the results of researches supported by NSF Research Grants GB4482X and GB30493 and Colorado State University Experiment Station Project (Hatch 8).

Occurrence:

A hypertriploid (2n=22) plant in barley was first reported by Tsuchiya (1967). The frequency of its occurrence was 1.7% in the progeny of the selfed autotriploid. Recently four hypertriploid plants (2n=22) were obtained: 2 plants were found in the progeny of the primary trisomic for chromosome 4 (Robust) in the F2 population of the cross between Robust and KM 200 (Tsuchiya and Singh, 1972). The F1 hybrid of Robust x zbc and Robust x lg contained one plant each. Their frequencies are represented in Table 1.

Table 1. Frequencies of hypertriploid (2n=22) in the progenies of Robust crosses.

The record shows that the trisomics used in these studies are derived from the same original primary trisomic, Robust #1, the progeny of a triploid plant. One of the four original Robust trisomics (Robust #3) showed hypertetraploid cells (2n=30, 2III + 12II) at meiosis (Tsuchiya, 1967), giving rise to gametes having n=15 chromosomes.

Morphology:

Hypertriploid plants appear more vigorous than diploids (table 2). It seems that one additional chromosome to the triploid complement does not have a harmful effect on plant vigor.

Table 2. Measurement of various organs of hypertriploid and their diploid siblings.

From the above table, it is clear that the hypertriploids are relatively short in comparison to their diploid siblings. On the other hand, there are marked increases in leaf size and stomata length of hypertriploids compared to diploid sibs. Furthermore, hypertriploids and diploids, obtained in an F1 generation seem to be more vigorous than those obtained in an F2 generation. It is speculated that stomata length may have an effect on leaf length, as hypertriploids of the F1 have long stomata with long leaves compared to the hypertriploids of the F2, while there seems to be no significant differences between diploids.

Cytology:

At meiosis, chromosomes of the hypertriploid formed either a quadrivalent, trivalent, bivalent, or univalent. The V, Y and L shape chromosome configuration was very common for the trivalent. However, a triple arc shape configuration (O) was observed in only one out of 33 cells studied. The frequencies of different types of chromosome configurations are shown in Table 3.

Table 3. Chromosome configurations at first meiotic metaphase in hypertriploid barley.

The average frequency of trivalents per cell was 4.75 followed by bivalents (1.88), univalents (1.24) and quadrivalent (0.64). The maximum number of univalents per cell was 4. Most of the univalents were observed outside the metaphase plate.

Pollen and seed fertility:

The pollen fertility of only the F2 hypertriploid was studied. Compared to the pollen fertility of the diploid (96%), the medium awn hypertriploid showed poor pollen fertility (57%). On the other hand, the pollen fertility of hypertriploids having short awns was 50%.

Crosses of the F2 hypertriploid x diploid and diploid x hypertriploid were conducted. Their seed fertility is shown in Table 4. There was very poor seed set in the cross of the diploid x hypertriploid. However, there was no seed set after selfing of the hypertriploid.

Table 4. Seed fertility in the hypertriploid barley.

The progenies of the above crosses have not yet been studied. However, it is expected that more aneuploids will be obtained in the progenies.
Two other hypertriploid plants with 2n=23 were obtained in the progeny of primary trisomics for chromosome 6 (Purple) and for chromosome 4 (Robust). Both plants are growing well but slowly.

References:

Tsuchiya, T. and R. J. Singh. 1972. Trisomic analysis of short awned mutant in barley. BGN 2:99.

Tsuchiya, T. 1967. The establishment of a trisomic series in a two-rowed cultivated variety of barley. Can. J. Genet. Cytol. 9 :667-682.

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