A Cytogenetic Study of Interspecific and Allopolyploid Hybrids of <i>Iberis amara</i> L. and <i>I. pectinata</i> Boiss (Cruciferae)

Abstract

Hybridization between Iberis amara varieties and I. pectinata was successful only when I. pectinata was the female parent. The seeds recovered from such crosses were much smaller than the control seeds from parents. The F1 hybrids were sterile but showed hybrid vigour and were morphologically intermediate between the two parents except in siliqua shape where the F1 hybrid resembled the maternal parent more closely.Very few seeds classified as small and large were obtained from F1 hybrid plants. The small seeds gave an F2 segregation of plants that resembled the parental and F1 hybrid types. Those F2 plants from large seeds were vigorous and fertile, and proved to be allotetraploids.Abundant seeds of three grades, small, intermediate, and large, were set by colchicine treated F1 hybrids. The C2 plants from small seeds showed a similar segregation as F2 plants from small seeds. Those from intermediate sized seeds were morphologically intermediate but varied considerably towards the I. amara parent. The C2 plants from large seeds were allotetraploids and were morphologically intermediates like F1 hybrids. They were vigorous and fertile. The allotetraploids were genetically isolated from the I. amara parent but not from I. pectinata.Cytological investigations in the parents, F1 and C1 populations revealed that the sterility of the F1 hybrids was largely of a chromosomal type and that the C1 plants were mixoploids. Although C1 plants produced triploid and tetraploid gametes, hexaploid and octoploid plants were not found in C2 populations.