Two ditelotetrasomic plants with normal 14 chromosomes plus two extra telocentric chromosomes for short arm of chromosome 5 (ditelotetra 5S) were found in the progenies of monotelotrisomics for 5S (Wang and Tsuchiya, 1988). Five ditelotetra 5S plants developed from the progenies of one of the ditelotetra 5S were grown in the greenhouse in late April 1988. In mid-May, these plants were moved to growth chamber (14-17 °C) for increasing tillers since the temperature in greenhouse was too high (23-30 °C). One month later these plants were moved back to the greenhouse. When some young spikes were studied for meiosis, the chromosome configurations at Diakinesis and Metaphase I showed different chromosome numbers among spikes of the same plant. Chromosome configurations varied from cell to cell with 7II, 71I+lI, 7II+2I, and so on. This indicated that chromosome elimination occurred on some tillers. Further investigation was conducted and many root tips for each plant were studied. The results are shown below in Table 1.

The data in Table 1 showed that all these five plants were chimera for their chromosome numbers, with 2n=14, 2n=14+1 telo and 2n=14+2 telos. These suggested that the extra telocentric chromosome(s) were eliminated in some roots and maybe in tillers.

What caused the elimination of telocentric chromosome is unknown. A possible explanation is that the warm-cool-warm temperature fluctuation during early growing stages might have induced chromosome elimination. Further study is necessary to find causes for elimination of the telosome 5S in the ditelotetrasomics for 5S.

Reference:

Wang, S., and T. Tsuchiya. 1988. Ditelotetrasomics for the short arm of chromosome 5 (ditelo 5S) in barley. BGN 18:21-23.