Comparison between Two Genera, Species and Cultivars in Lactuceae

I. Karyotype analysis

Abstract

Karyotypes of three cultivars of Lactuca sativa (Webb's Wonderful, Lobjoit's Green Cos and Tom Thumb), Lactuca serriola collected from the field in the county of Essex, U.K. and a cultivar of Cichorium intybus (Witloof Chicory), were analysed in detail so that essential comparative information was available for use in later studies (Haque and Godward, Papers II, III and IV). Statistical data on chromosome lengths and centromere positions, together with the recognition of the nucleolar-organising chromosomes, enabled the nine chromosomes of the haploid sets to be recognised individually, and these were designated A, B, C, D, E, F, G, H and I, C and E being the nucleolar organising chromosomes, these being recognised in C. intybus for the first time. There were slight differences in chromosome lengths, the Lactuca sativa cultivars and L. serriola being distinguishable by their mean lengths, but only those of C. intybus were significantly smaller. Comparisons with the previously published data on Lactuca and Cichorium are made.