Summary
Secale cereale A series of three experiments was carried out to see if varying sowing density had any differential effect upon the survival of plants with and without B chromosomes. In all experiments it was shown that as sowing density increased, and therefore the selection pressure increased, so the mean B frequency decreased. This was accounted for by an increasing survival at high densities of plants without B chromosomes.
Lolium perenne In contrast to the results in rye, increasing sowing density in Lolium perenne caused an increase in the mean B frequency. This was accounted for by a decrease in the number of plants without B chromosomes and a corresponding increase in the frequency of plants with 2B chromosomes.
From the results of these experiments in Secale and Lolium it is concluded that the change in B frequency within and between populations is an adaptive response to lhe different kinds, and degree of selection to which the populations are exposed. The results argue against the view that B chromosomes are “nuclear parasites” with, invariably, detrimental consequences.
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Hutchinson, J. Selection of B chromosomes in Secale cereale and Lolium perenne. Heredity 34, 39–52 (1975). https://doi.org/10.1038/hdy.1975.4
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DOI: https://doi.org/10.1038/hdy.1975.4
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