Genetic Diversity among Elite Maize (Zea mays L.) Inbred Lines using Simple Sequence Repeat Markers

Abstract

In Ethiopia maize productivity still remain far below the world average due to several factors such as; lack of improved and wide adapted varieties, acidity, drought, and foliar disease of maize. Thus genetic improvement of the crop is vital to address some of the constraint. Therefore, the present study was conducted to assess the extent of genetic diversity among elite maize inbred lines using simple sequence repeat markers. Thirty seven elite maize inbred lines were obtained from Bako National Maize Breeding Center and CIMMIYT and twenty nine Simple Sequence Repeat markers with wider genomic coverage were obtained from the maize genomic data base. The research was conducted at molecular biotechnology laboratory of the National Agricultural Biotechnology Research Center (NABRC) at Holeta. Genomic DNA was extracted following DArT (Diversity arrays technology) protocol. Out of 29 SSR markers one showed monomorphic pattern and excluded from analysis. The rest 28 markers were polymorphic and revealed a total of 104 alleles. The number of alleles generated by each marker varied from 2 to 6 with average number of 3.71. The number of effective alleles ranged from 1.11 to 3.53 with a mean of 2.04. Fixation index varied from 0.70 to 1 with a mean of 0.96. The highest observed and expected heterozygosity was 0.17 and 0.626 respectively. The polymorphic information content of the markers ranged from 0.1 to 0. 74 with a mean of 0.5. Analysis of molecular variance showed highly significant (P<0.001) molecular variances. The highest (77%) of the variation was attributed to genetic variability among individuals (AI) within populations, while 23 % of the variation was observed in among population. The highest and lowest Fst value was observed between inbred lines sourced from lowland Mexico and South America, Bako and lowland Mexico respectively. The highest and lowest value of gene flow was observed between inbred line of Bako and lowland Mexico, South America and lowland Mexico population respectively. The highest genetic distance (0.42) was observed between inbred lines obtained from South America and lowland Mexico, whereas the lowest genetic distance (0.27) was showed from inbred lines obtained from Bako and (CIMMIYT) lowland Mexico.The highest number of private alleles was identified in Bako population. The principal coordinate analysis accounted for 69.27% of the total genetic variation. Cluster analysis revealed grouped the inbred lines in to three major groups by merging inbred lines from different populations in cluster I and III. Generally, the present study showed the existence of wide genetic variation among the studied materials. Thus, it provided precise information to use promising combination for exploitation of heterosis and establishment of heterotic group as source materials in maize breeding program.