Karyotypic studies of the genus Cuscuta L. (Convolvulaceae) in Saudi Arabia and their taxonomic significance

Abstract

Chromosome numbers and karyotype criteria of ninespecies of the genus Cuscuta L. (Convolvulaceae) in SaudiArabia were investigated. Chromosomes counts wererecorded in four species for the first time in this study.Chromosome number, based on x=7 has been found in themajority of the studied Cuscuta species. A diploid number(2n=14) was recorded in five species, while tetraploidnumber (2n=28) was recorded in two species whereas 2n=56was recorded in C. campestris. However, 2n=30 based onx=6 was recorded in C. monogyna. The chromosomes in thestudied species of Cuscuta are generally small with a meansize ranging between 0.74 and 1.10 μm. Short chromosomeswere particularly found in C. planiflora (MCL=0.74 μm) andC. chinesis (MCL=0.79), whereas longer chromosomes werescored in C. campestris (MCL=1.10). The karyotype in thestudied species is mostly comprised of metacentric tosubmetacentric chromosomes as indicated by their mean armratio that ranges between 1.31 in C. monogyna and 1.83 in C.planiflora. The degree of karyotype asymmetry is indicatedby high values of TF% ranges between 28.33 in C. planifloraand 40.54 in C. campestris. The A1 value ranged between0.22 in C. planiflora and 0.43 in C. palaestina. Among theexamined species, karyotype features were used to assess the classification of the Cuscuta species in Saudi Arabia in the light of the current systems of classification.