Annexure-7: Descriptors and descriptor state of cytological characters

Sl.no

Descriptors

Classification unit

Methods

1

Chromosome number

1.1 Haploid (n=14)
1.2 Diploid (2n=28)
1.3 Triploid (3n=42)
1.4 Tetraploid (4n=56)
1.5 Pentaploid (5n=70)
1.6 Octaploid (8n=112)
1.7 Decosoploid (22n=308)
1.8 Aneuploid (Any addition or deletion in the diploid chromosome number 28)

To determine the ploidy level of each accession minimum 20 well spread mitotic plates to be counted for the total number of chromosomes per each cell.

2

Karyotype

M=centeromere in median point (r=1)
m=centeromere in median region (r=1.1 to 1.7)
sm=centeromere in sub median region (r=1.8 to 3.0)
st=centeromere in sub terminal region (r=3.1 to7.0)
t=centeromere in terminal region(r=7.1 to infinity)
T=centeromere in terminal point (r=infinity)
Centeromere index ® =l/s
where l= length of long arm
s=length of short arm

The well spread mitotic plates are to be considered for studying the karyotype of the mulberry accessions.