Pre-soaking seeds before treatment enhances sensitivity to many chemical mutagens; but little
work has been done with maleic hydrazide (MH), a chromosome breaking agent and preferential
inducer of micromutation and streptomycin (SM), a cytoplasmic mutagen. In the present investigation
on pre-soaking (PS) effects in finger millet (Eleusine coracana, Gaertn).these two mutagens were
included besides one commonly used mutagen, EMS to determine a common effective PS range
using M1 seedling traits. Since different M1 parameters, mutagens and their doses showed different
peaks of response, a taxometric approach was adopted using all characters together. Combinations
of chemicals, doses and six attributes of M1 seedlings gave 48 characters for the numerical classification
of PS periods (0, 8, 10, 12, 14, 16 and 18 h) as Operational Taxonomic Units(OTUs). Dendrogram
from the similarity matrix using UPGMA clustering showed two clusters : (1) Cluster.1 of three OTUs
(0, 8 and 10 h PS) and (2) Cluster.2 of four OTUs(12-18h PS).The effective PS range was 12-18hr
and 0-10h was considered as ineffective for all kinds of mutagens. The effective range would
contain the major peak of sensitivity; the ineffective range might show a small peak. These inferences
were confirmed with SM induced albinism as an indicator of plastid mutations. Higher doses shifted
the peak within the effective range towards lower PS and low dose towards longer PS. Hence
taxometrics could be usefully adopted in mutagenesis studies for meaningful analysis.