FRAGMENTS WITH ACCESSORY CHROMOSOME CHARACTERISTICS IN CULTIVATED BARLEY (HORDEUM VULGARE)

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Abstract
A number of fragment chromosomes were isolated from the progeny of barley triploids and their trisomic derivatives. They were smaller than normal barley telocentrics, with a globular appearance, and some carried a small satellite. Their number per cell varied in both somatic and germinal tissue. At meiosis, pairing was observed between fragments, but pairing with the normal chromosomes was virtually absent. Unlike normal chromosomes when univalent, the fragments were always positioned on the equatorial plate at MI. Paired fragments behaved normally, but univalent ones divided precociously, rarely lagging at MI. At second division, lagging occurred frequently, with micronuclei forming at the quartet stage. Fertility was reduced substantially only in plants carrying more than one fragment. The behavior of these fragments in general conformed to that of "accessory chromosomes." They were assumed to have arisen from normal chromosomes which had lost their pairing arms, and/or from fragmentation of satellited telocentrics.

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