New reports of somatic chromosome number and symmetric or asymmetric karyotype estimation of Sechium edule (Jacq.) Sw. (Cucurbitaceae)

Sechium edule (Jacq.) Sw. distributed well in Eastern Himalayan region, four-teen genotypes collected randomly from Kigwema village, Kohima (Nagaland) at an average altitude of 1538 masl (meter above sea level) with 25.61 degrees N latitude and 94.35 degrees E longitudes. Somatic chromosome numbers are diploid in nature. Chromosome numbers are in agreement and comparable with earlier reports except 2n=2x=22. The chromosome number 2n=2x=22 could not be traced out in the present material collected for study. Two (2) new chromosome numbers 2n=2x=32 and 2n=4x=52 were recorded and expected to be diploid and tetraploid in nature respectively. It was expected that tetraploid (2n=4x=52) number of chromosome might be originated from the earlier reports of diploid chromosome number 2n=2x=26. Both chromosome numbers 2n=2x=32 and 2n=4x=52 are reported for the first time by the authors in the present study. Range of chromosome length was recorded in between 0.501 - 1.343. The range of chromosome length are in agreement with earlier reports of 0.700 - 0.900 approximately. Range of chromosome length suggested minute (<1 mu m) and small (1-3 mu m) size of chromosomes with small differences and variations in chromosome length (CVCL). Inter-chromosomal indices (A(2) and Rec), intra-chromosomal index (particularly, Stebbin's classification) and both inter and intra chromosomal indices (DI and GI) estimated symmetric nature of the karyotype.