Genome size determination and chromosome characterization of two marigold species (Asteraceae)

Abstract

Genome size determination by a flow cytometry (FCM) and chromosome characterization by fluorescent banding, including fluorescence in situ hybridization (FISH), were employed for cytogenetic analysis of two important marigold species, Tagetes erecta (African marigold) and T. patula (French marigold). The FCM data showed that T. erecta had a 2C value of 1.43pg, while T. patula had a 2C value of 2.54pg, showing 2-times difference in genome size. Somatic chromosome number was 2n=24 in T. erecta, while the number was 2n=48 in T. patula, indicating arise out of a chromosome doubling event. Chromomycin A3 (CMA) and 4′,6-diamidino-2-phenylindole (DAPI) bands were recognized at different positions on all chromosomes in Tagetes genome, making possible chromosome identification by fluorescent band pattern, especially in T. erecta. FISH results showed that clear telomere signals appeared at both ends of all chromosomes and eight weak 45 rDNA signals on the terminal and middle sites on certain chromosomes in diploid species T. erecta.