BGN 18: Developing 9-paired (9II) barley from two 8II barley lines

Developing 9-paired (9II) barley from two 8II barley lines*

A. Hang and T. Tsuchiya
Dept. of Agronomy
Colorado State University
Fort Collins, Colorado 80523, U.S.A.

* Supported by USDA-CSU Cooperative Research
Project No. 58-9AHZ-2-265 and CSU Hatch Project.

A barley strain with 2n=12+4 telos [2(lL + 1S)] was found (Tsuchiya, 1973) in the progeny of a selfed plant with 2n = 13 + 2 telos (lL + 1S) which was obtained from a cross between a diploid and a telotrisomic for 1S (Tsuchiya, 1971). Another barley strain with 2n = 12 + 2 acro 3L1 + 2 telo 3S was also reported by Singh and Tsuchiya (1981). The pedigree of this latter plant can be traced back as follows: In the population of a cross between 14 + 1 acro 3L3S × yst2, a plant with 2n = 13 + 1 acro 3L3S + 1 telo 3S was obtained. In the selfed progenies of this plant, 39 plants with 2n = 12 + 2 acro 3L3S + 2 telo 3S were obtained as well as plants with parental type and 2n=14.

In this study, the plant with 2n = 12 + 2 (11, + 1S) was used as female, and crossed with the plant with 2n = 12 + 2 (acro 3L3S + telo 3S) as male, and vice versa. The F1 plant showed 2n = 12 + 1L + 1S + 3L3S + 3S as expected.

This plant showed almost normal morphology and was very vigorous, and could not be distinguished from the normal diploid plant. The pollen and seed fertility of this F1 plant was 61% and 78%, respectively.

Meiosis was studied in some F1 plants; 103 sporocytes analyzed at metaphase I showed 89.3% sporocytes with 2III + 5II chromosome configuration, while the remaining (10.7%) cell had 1III + 1I configuration. At anaphase 1, 135 sporocytes were analyzed; 59.3% with 8:8 separation and 40.7% with 7:9 separation.

Due to the presence of 2 trivalents, many different types of gametes are expected to be produced in F1 plants. F1 gametes expected from AI separations were the following four types:

a. 5 + IL.lS + 3L.3S = 7
b. 5 + 1L + IS + 3L.3S = 8
c. 5 + 1L.1S + 3L3S + 3S = 8
d. 5 + 1L + IS + 3L3S + 3S = 9
As a result, the selfed progenies of the F1 plant with 2n = 12 + 1L + 1S + 3L3S + 3S will give plants with many different cytotypes or karyotypes. The combination of two gametes with n = 9 chromosomes (d + d) will result in a plant with 2n = 18 = 10 + 2 (1L + 1S) + 2 (3L3S+ 3S) = 9 bivalents. If this simple type of segregation (four types shown above; a, b, C, d) occur frequently, at least one in the 16 of the progenies of selfed F1 hybrids will be the plants with 2n = 18 chromosomes. In a preliminary study of a population of 74 F2 plants in the progenies of the selfed F1 plants, four plants (5.4%) were 2n = 18 = 10 + 2 (1L + 1S + 3L3S + 3S). This value does not deviate much from the expected value of 6.25% (1/16).

References:

Singh, R. J., and T. Tsuchiya. 1981. A novel compensating partial tetrasomic diploid plant of barley. Barley Genetics Newsl. 11:66-67.

Tsuchiya, T. 1971. Occurrence of a plant with 2n = 13 + 2 telocentric chromosomes in barley. Barley Genetics Newsl. 1:63.

Tsuchiya, T. 1973. A barley strain with 2n = 12 + 4 telocentric chromosomes (2 pairs). Cereal Res. Comm. 1(3):23-24.

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