Isozyme characterisation of Indian maize inbreds

The need for precise characterisation of crop materials has assumed importance in any established sui generis system for effective protection of plant varieties. Considering this requirement, 37 Indian maize inbreds were analysed for allozyme variations. Seven enzyme systems comprising 16 isozyme loci were analysed using starch gel electrophoresis. The allelic variants were designated using the well-characterised maize inbred Mo 17 as a standard. A total of 29 alleles were scored at the 16-isozyme loci studied. Malate dehydrogenase (Mdh), acid phosphatase (Acp), phosphoglucoisomerase (Pgi), 6-phosphogluconate dehydrogenase (Pad) and isocitrate dehydrogenase (Idh) were the most informative isozyme systems for characterisation of the maize inbreds. These enzyme systems were also useful in detecting and quantifying the extent of 'off-types' in each seed lot analysed. The percent off-types (inclusive of the admixtures and segregates) were as high as 47 to 50 percent in seed lots of a few of the inbreds. The results of the study were also useful in studying genetic diversity among the inbreds. An UPGMA based cluster analysis of the allozyme data revealed presence of only moderate genetic diversity among the Indian maize inbreds. This is of significance in crop yield stability as these inbreds have been used extensively in the production of F-1 hybrids occupying large area under maize cultivation in India.