Abstract
Presence of a quadrivalent at meiosis in allohexaploid wheat (Triticum aestivum L.) can indicate a heterozygous reciprocal chromosome translocation. Such a translocation has significant genetic consequences. This study was initiated to determine the source and trace the inheritance of a heterozygous reciprocal translocation in 'Atlas 66' wheat. Meiotic analyses of hybrids between 'Frondoso', the Brazilian parent of 'Atlas 66', and 'Chinese Spring' ditelosomic lines suggest 'Frondoso' carries the same 2A/2D translocation as 'Atlas 66'. Because of this and because 'Frondoso' is a parent of 'Atlas 66', 'Frondoso' is the probable source of the 'Atlas 66' translocation. Detection of a 2A/2D translocation in 'Fronteira', the only Brazilian parent of 'Frondoso', traces this chromosome interchange to an earlier Brazilian origin. Six of nine varietal derivatives of 'Frondoso' ( 'Atlas 50', 'Coastal', Wakeland', 'Key', 'Laura', and 'Karl') formed a ring or a chain quadrivalent at meiosis. Frequencies of quadrivalents and the proportion of rings versus chains depended on the variety, irrespective of the genetic closeness of a variety to 'Frondoso'. Meiotic analyses suggest these varieties also carry a 2A/2D translocation. Trivalent-formation in aneuploids was considered evidence that non-cooriented segregations from quadrivalents occurred. Production of aneuploids could impact genetic studies and breeding when these varieties are used.
