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 F
1 hybrids were sterile but showed hybrid vigour and were morphologically intermediate between the two parents except in siliqua shape where the F
1 hybrid resembled the maternal parent more closely.
Very few seeds classified as small and large were obtained from F
1 hybrid plants. The small seeds gave an F
2 segregation of plants that resembled the parental and F
1 hybrid types. Those F
2 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 F
1 hybrids. The C
2 plants from small seeds showed a similar segregation as F
2 plants from small seeds. Those from intermediate sized seeds were morphologically intermediate but varied considerably towards the
I. amara parent. The C
2 plants from large seeds were allotetraploids and were morphologically intermediates like F
1 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, F
1 and C
1 populations revealed that the sterility of the F
1 hybrids was largely of a chromosomal type and that the C
1 plants were mixoploids. Although C
1 plants produced triploid and tetraploid gametes, hexaploid and octoploid plants were not found in C
2 populations.
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