II. 10. Further studies on acrotrisomic for 5S5L (formerly meta 1A) in barley. (1)
A. Shahla and T. Tsuchiya, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523 U.S.A.
(1) Supported in part by USDA/SEA Competitive Research Grant No. 5901-0410-9-0334-0 and No. 82-CRCR-1-1020 to T. Tsuchiya.
In the previous paper (Shahla and Tsuchiya, 1979) these authors reported on a new trisomic type derived from Triplo 1S in barley. The new trisomic type was designated as "metatrisomic lA" (Tsuchiya, 1982).
Many plants were grown from this metatrisomic plant. All of these trisomic plants had the typical characteristics of an extra chromosome 5 showing extremely revoluted leaves, vigorous growth and yellowish-green color of the plants. One plant with 2n=16=14+2 acrocentric chromosomes (partial tetrasomic) showed a more exaggerated expression of the extra chromosome 5. The plant was smaller than a simple trisomic plant.
Giemsa banding technique applied to the new trisomic plants showed that the extra "metacentric" chromosome was actually an acrocentric for 5S5L which had a complete short arm and a deficient long arm of chromosome 5. It was redesignated, therefore, as acrocentric chromosome 5S5L.
The morphology of this trisomic (acrotrisomic 5S5L) was similar to the primary trisomic (Triplo 5). Since the deficient segment seems to be the distal 70% of the long arm, the proximal 30% of the long arm probably carries the genetic element(s) controlling morphogenesis of all three types of trisomics (Triplo 5, Triplo 5L and Triplo acro 5S5L).
Meiotic chromosome behavior was as follows: At diakinesis 71.03% showed 1III + 6II configuration and 28.97% of the cells showed 7I + 1I. The most frequent trivalent configuration was V-or U-shape (26.23%), followed by chain (21.31%), rod-shape (13.66%) and ring-and-rod (9.83%). At MI more sporocytes showed 7II + 1I association (36.63%). The frequency of sporocytes with 1III + 6II was 63.38%. The different trivalent configurations at this stage was V-shape with 27.8% followed by rod-shape with 22.4% and ring-and-rod with 13.18%. At AI an average of 53.73% of sporocytes showed 7-8 chromosome separation followed by 7-1-7 and 7+1-1+7 separation in 29.85% and 16.42 cells, respectively.
The average pollen fertility of acrotrisomic 5S5L was 87.31%. Seed set was very high in the selfed spikes and in various cross combinations. The average percent seed set for the selfed spikes was 97.27%. When acrotrisomic 5S5L was used as the male, seed set was 100% and when it was used as female in crosses with diploid the average seed set was 90.9%.
The transmission of the extra acrocentric chromosome in the selfed pure line was 33.85% through the female and 1.54% through the male. The female transmission rate in the crosses with diploid was 36%. When the acrotrisomic plant was used as the male parent in a cross with diploid, no acrocentric chromosome was transmitted through the pollen. Genetic analysis is underway with this acrotrisomic type and various marker genes on chromosome 5 for physical localization of those genes.
References:
Shahla, A. and T. Tsuchiya. 1979. A new trisomic type in the progeny of Triplo 1S. BGN 9:94-95.
Tsuchiya, T. 1982. Aneuploidy and chromosome mapping in barley. Cytogenetics of Crop Plants (eds. M. S. Swaminathan and P. K. Gupta). McMillan, India (In press).