Ditelotetrasomic 3S was obtained from selfed progenies of telotrisomic 3S. The plant morphological studies and meiotic studies revealed that telosome elimination and abnormal division occurred in the ditelotetrasomic 3S. Spikes from different tillers were harvested separately and somatic chromosome numbers were studied carefully in order to determine the cytogenetic nature. The transmission of two extra chromosomes showed a very low rate of 7.1% in comparison with the rate 28.9 - 31.1% of other ditelotetrasomics (Tsuchiya and Wang, 1991). Different spikes of the same plant also showed varied transmission rates. Some spikes obviously showed telotrisomic transmission rate. In addition, somatic chromosomes of some cells in the same root tip showed varied extra telosome numbers which resulted from abnormal division such as non-disiunction.

So far, six ditelotetrasomic types for short arm of barley chromosome (1S, 2S, 3S, 5S, 6S, 7S) have been studied in detail (Tsuchiya, 1969; Fedak and Helgason, 1970; Tsuchiya and Wang, 1991). In general, most ditelotetrasomics and their progenies were genetically rather stable. Ditelotetrasomic 5S showed elimination of some extra telocentric chromosomes probably caused by severe environmental changes (Wang and Tsuchiya, 1988). However, after selection of stable lines and growth under normal environment for some generations, a genetically stable ditelotetrasomic 5S seems to have been established.

The cause of instability of the extra telosomes in ditelotetrasomic 3S is unknown. It could be due to a certain genetic effect under certain environmental stresses. There also could be some genetic element on the short arm of chromosome 3 which might promote abnormal division and telosome elimination under certain unfavorable environmental condition. Further study is needed to understand the cytological stability of ditelotetrasomic 3S.

References:

Fedak, G., and S. B. Helgason. 1970. The cytogenetics of ditelotetrasomic line in barley. Can. J. Genet. Cytol. 12:553-559.

Tsuchiya, T. 1969. Status of studies of primary trisomics and other aneuploids in barley. Genetica 40:216-232.

Tsuchiya, T., and S. Wang. 1990. Cytogenetics of ditelotetrasomics for short arm of four chromosomes in barley (Hordeum vulgare L.). Theor. Appl. Genet. 80:145:152.

Wang, S. and T. Tsuchiya. 1989. Elimination of telocentric chromosomes in ditelotetrasomics for 5S of barley. BGN 19:58-59.