Enhanced Sensitivity to Mutagens by Pre-Soaking - A Taxometric Study Using M₁ Seedling Traits in Finger Millet

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.