Chromosome numbers and karyotype criteria of nine
species of the genus Cuscuta L. (Convolvulaceae) in Saudi
Arabia were investigated. Chromosomes counts were
recorded in four species for the first time in this study.
Chromosome number, based on x=7 has been found in the
majority of the studied Cuscuta species. A diploid number
(2n=14) was recorded in five species, while tetraploid
number (2n=28) was recorded in two species whereas 2n=56
was recorded in C. campestris. However, 2n=30 based on
x=6 was recorded in C. monogyna. The chromosomes in the
studied species of Cuscuta are generally small with a mean
size ranging between 0.74 and 1.10 μm. Short chromosomes
were particularly found in C. planiflora (MCL=0.74 μm) and
C. chinesis (MCL=0.79), whereas longer chromosomes were
scored in C. campestris (MCL=1.10). The karyotype in the
studied species is mostly comprised of metacentric to
submetacentric chromosomes as indicated by their mean arm
ratio that ranges between 1.31 in C. monogyna and 1.83 in C.
planiflora. The degree of karyotype asymmetry is indicated
by high values of TF% ranges between 28.33 in C. planiflora
and 40.54 in C. campestris. The A1 value ranged between
0.22 in C. planiflora and 0.43 in C. palaestina. Among the
examined 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.