BGN 12: A barley plant with 2n=24 chromosomes BARLEY GENETICS NEWSLETTER, VOL. 12, II. RESEARCH NOTES
Hang et al., pp. 47-48

II. 19. A barley plant with 2n=24 chromosomes.*

An Hang, J. D. Franckowiak and A. B. Schooler, Agronomy Department, North Dakota State University, Fargo, North Dakota 58105 U.S.A.

* Supported in part by Competitive Research Grant No. 59-2381-0-1-460-0 from USDA/ARS.

A barley plant with 2n=24 chromosomes (Fig. 1) was found in the F2 progeny of the cross Hordeum vulgare L. var 'Ono' (4X)/Elymus mollis Trin (4X)//'Glenn' 2X. Sister F4 plants to 'Ono'/E. mollis plant have a range of 2n=27-30 chromosomes associated with typical plant phenotypes. The F1 plant was obtained via embryo culture and presumably a triploid plant. It was vigorous; spike and spikelet characteristics were intermediate between six-rowed and two-rowed barley and selfed seed set was about 5 percent. Compared with the diploid sibs, the plant with 24 chromosomes was more than 14 days later. Initially, the plant developed only one large tiller; later additional tillers were produced.

Figures 1-3. Chromosomes of the 2n=24 chromosome plant. 1) Somatic metaphase chromosomes, 2n=14. 2) Meiotic metaphase I configuration, 1IV + 3III + 5II + 1I.  3) Meiotic anaphase I separation

Cytological study of chromosome associations at MI showed an array of configurations, similar to those observed in tetraploid barley (Morrison and Rajhathy, 1960; Nilan, 1964; and Tsuchiya, 1953). The frequency of different chromosome associations is summarized in Table 1. No pentavalent or higher valency configurations were noted.

Table 1. Chromosome associations at MI of the plant with 2n=24.

In a hypertriploid plant (2n=22) studied by Singh and Tsuchiya (1975), the total of multivalents and bivalents were usually equal to seven. In the plant with 2n=42 chromosomes, the total of multivalents and bivalents usually found nine or ten (Table 1). The most frequent MI configuration observed was lIV + 3III + 5II + 1I (Fig. 2).

Chromosome separations noted at anaphase I were 9-15; 11-13; 10-14; 9-1-14; 11-1-12; 11-2-11. Also one with a bridge without fragment was observed. The 11-13 AI separation of chromosomes was the most frequent class (Fig. 3).

The 2n=24 plant was self-sterile. Pollen fertility estimated with acetocarmine stain was very low, about 20 percent. Seed set was about 15 percent when pollinated with a diploid male. Female fertility is higher than anticipated if only female gametes with 7 or 14 chromosomes were viable. The progeny of the 2n=24 plant from crosses to diploid Glenn are being investigated.

References:
Morrison, J. W. and T. Rajhathy. 1960. Chromosome behavior in autotetraploid cereals and grasses. Chromosoma 11:297-309.

Nilan, R. A. 1964. The cytology and genetics of barley. Monographic supplement No. 3. Washington State Univ. Press.

Tsuchiya, T. 1953. Fertility of autotetraploids and their hybrids in barley. I. Meiosis and fertility in some autotetraploids. Seiken Ziho 6:46-52.

Singh, R. J. and T. Tsuchiya. 1975. Hypertriploid plants in barley (Hordeum vulgare L.). Caryologia 28:89-98.

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