A Database for Triticeae and Avena
II. 27. Further studies on the telotrisomic plant for the short arm
of chromosome 6, Triplo 6S, in barley.*
Lindy Seip and T. Tsuchiya, Department of Agronomy, Colorado State University,
Fort Collins, Colorado 80523 U.S.A.
* Supported in part by Research Grant No. 12-14-5001-265 from USDA/SEA
to the junior author.
Morphological and limited meiotic information for the telotrisomic plant,
Triplo 6S, were reported in BGN 9 (Seip and Tsuchiya, 1979).
Further data concerning meiotic behavior and transmission rates of the
telocentric chromosome 6S have been obtained and are reported here. At
the diakinesis stage of meiosis, the satellite chromosomes 6 and 7 associate
with the nucleoli. One mean of definite identification of telocentric 6S
is its association with the nucleolus. Telo 6S was seen to associate with
the nucleolus as a univalent (7II + 1I) in 52.36%
of the sporocytes and as a trivalent (1III + 6II)
in 47.64% of the sporocytes. The high value of univalent formation may
be partially due to artifacts of preparation, causing broken trivalents.
At metaphase I, Telo 6S was found as a univalent in 24.18% of the sporocytes
and as a trivalent in 75.82%. The most common types of trivalents were
ring-and-rod and tandem chain.
The telocentric chromosome remained at the equatorial plate as a laggard
in 13.24% of the anaphase I sporocytes. This value is quite comparable
with that found by Singh (1974) in the other seven telotrisomic types (16.27%).
Transmission rates of the telocentric chromosome were determined for
three conditions: self-pollinated and reciprocal crosses between the Triplo
6S plant and S.E. 16 diploid. In selfed F2 populations, the transmission
was 40.87%. Using the Triplo 6S plant as a female, the female transmission
rate was 48.0%. Using the Triplo 6S plant as male, the transmission rate
was 10.53%. These three values exceed those determined by Singh and Tsuchiya
(1977) for the average of seven telotrisomics and by Tsuchiya (1972) for
Triplo 1L. Especially high is the male transmission of 10.53%, compared
with 1.2% for the average of seven telotrisomics (Singh and Tsuchiya, 1977).
This high male transmission may be due to time of pollination, condition
of the plants, and the behavior of the Triplo 6S pollen. Although no ditelotetrasomic
plants were found in this study, it should not be difficult to obtain such
a plant with these high male transmission rates.
The next step in this work is to cross the Triplo 6S plants with several
mutant marker lines such as uc2, o and gs4 to more
accurately map these genes and eventually to locate the centromere on the
genetic linkage map of chromosome 6.
Seip, L. and T. Tsuchiya. 1979. Telotrisomic plant for the short arm
of chromosome 6 (Triplo 6S) in barley. Barley Gen. Newsl. 9:91-92.
Singh, R.J. 1974. Cytogenetics of telotrisomics in barley. Ph.D. Thesis,
Colorado State Univ., Fort Collins, Colorado.
Singh, R.J. and T. Tsuchiya. 1977. Morphology, fertility and transmission
in seven monotelotrisomics of barley. Z. Pflanzenzüchtg. 78:327-340.
Tsuchiya, T. 1972. Cytogenetics of telocentric chromosome of the long
arm of chromosome 1 in barley. Seiken Ziho. 23:47-62.
BGN 10 toc
BGN Main Index