Assessment of molecular diversity in selected maize inbreds

Abstract

Analysis of the extent and distribution of genetic diversity in crop plants is essential for optimizing sampling and breeding strategies. Randomly amplified polymorphic DNA marker was used to assess genetic diversity in a selected group of maize inbred lines. A high level of polymorphism of 73.02 per cent was detected among the genotypes. The maximum genetic distance of 29.7 per cent was detected between CM-202 and KDMI-16. While, the minimum genetic distance of 12.8 per cent was observed between KDMI-04 and CI-05. The results indicated that variation can be attributed to use of random primers as well as variation that naturally occur in the genotypes. Therefore, the study indicated that RAPD marker are successful in identifying genetic diversity in maize inbred lines. Intro duction Assessment of the extent and distribution of genetic variation in a crop species and its relatives is essential in understanding pattern of diversity and evolutionary relationship between accessions that helps to sample genetic resources in a more systematic fashion for conservation and plant improvement. Ideally, the study of polymorphism is best done at the level of arrangement of nucleotide bases in DNA, the primary source of all biological information. At this level, even seemingly identical accessions could display enormous differences, if only we could employ appropriate DNA profiling techniques. Besides, availability of virtually unlimited number of markers in any study group and the fact that they can be determined unequally at any stage in the life cycle of an organism under any growth environment is of great practical value. Randomly amplified polymorphic DNA (RAPD) is one of the polymerase chain reaction (PCR) based DNA markers, which is an assay based on the amplification of genomic DNA with single primer of arbitrary nucleotide sequence. RAPD can be used in studying genetic diversity, phylogeny, quantitative tract loci, varietal identification etc. (Weising et al., 1995). In the present study eight inbreds and Arabhavi local were assessed for diversity using RAPD analysis to use them in evolving heterotic hybrids. Material and methods A set of eight maize inbred lines and Arabhavi local were used in the study. DNA was extracted by CTAB method. Seed samples were germinated in plastic tea cups until seedlings were 2-3 leaf stage. At least 5-6 such seedlings were harvested from each genotype with a razor blade and were placed in an autoclaved pestle and mortar containing liquid nitrogen. The lypholized tissue sample was ground into fine powder. The ground tissue was transferred to tubes containing about 10 ml of 2 per cent CTAB solution. The tubes containing ground tissue samples were placed in water bath (with gentle shaking) for 10-15 minutes at 65°C with periodical shaking at an interval of 5 minutes. Later, the tubes with tissue extract were incubated at room temperature for 15 min. About 10 ml of chloroform and isoamyl alcohol mixture (24:1) was added to the tissue extract and the contents were mixed by shaking gently. The contents were then transferred to fresh centrifuge tubes and spinned for 10 minutes at 5000 rpm at room temperature.