Karyotype analysis in grass pea (Lathyrus sativus L.)

In order to understand the chromosome morphology and structural variation, somatic chromosomes of nine accessions of grass pea (Lathyrus sativus L.) viz., ‘Pusa 24’, ‘Ratan’, ‘Pratik’, ‘IC120455’, ‘IC120500’, ‘IC120505’, ‘IC345392’, ‘IC345401’, and ‘IC345403’ were studied using young root tips. The study revealed variation not only in physical dimension and morphology of the chromosomes but also in the position of the primary and secondary constrictions. Although all accessions were diploid (2n=14), variations in karyotype formula, chromosome length, total haploid complement, arm ratio and centromeric index were observed. The secondary constriction was observed in at least one of the metacentric chromosomes of ‘Pusa 24’, ‘IC120500’, ‘IC120505’, ‘IC345392’ and ‘IC345403’. Telocentric chromosomes were absent in all the accessions while variable numbers of sub-metacentric and acrocentric chromosomes were observed in these accessions. These chromosomes differed in their lengthwise positions in the karyotype. Total length of the largest chromosomes did not differ significantly among accessions. However, chromosomes with satellites were longer. Total length of smallest chromosome was variable among the accessions. The total haploid chromosome length (TCL) varied from 5.11 µm in ‘IC345403’ to 7.30 µm in ‘IC345401’. The arm ratio and centromeric index value ranged from 1.21 in ‘IC120455’ to 1.44 in ‘IC120505’ and 40.94 in ‘IC120505’ to 45.19 in ‘IC120455’, respectively. These results clearly showed structural variation in karyotype at genotypic level in grass pea.