ABSTRACT - A set of 45 maize inbreds maintained at the Millet Breeding Station, Centre for Plant Breeding and Ge- netics, Tamil Nadu Agricultural University, Coimbatore was subjected to genetic diversity analyses based on eight qualitative traits, 10 quantitative traits and 42 SSR primer pairs. Among the eight qualitative traits, leaf pubescence did not show any variation across the genotypes. Traits viz., silk colour at emergence, ear shape, kernel colour, grain texture and grain shape were the predominant phe- notypic variants. Ten quantitative traits observed across the 43 maize inbreds showed wide variation. Hundred seed weight was maximum (36.8 g) in UMI 603 and mini- mum (11.1 g) in UMI 27. SSR analysis involving a set of 22 primer pairs derived from maize genome and 20 primer pairs derived from rice genome generated 132 and 181 markers with an average polymorphism information content (PIC) value of 0.83 and 0.38, respectively. Cluster analysis using 8 different qualitative traits across 43 maize genotypes resulted in grouping of genotypes into two major clusters of 19 and 24 genotypes where as cluster analysis based on 10 quantitative traits resulted in 2 major clusters, one with 39 genotypes and the other with 4 genotypes. Clustering pattern of maize genotypes based on SSR marker profiles were different from that of mor- phometric traits. KEY WORDS: Genetic diversity; Maize; Morphometric traits; SSR markers; Cluster analysis. INTRODUCTION Maize (Zea mays L.) otherwise known as corn, is the only cereal crop of American origin that is cultivated in tropical and subtropical regions throughout the world. The increasing use of maize as a staple food reflects higher yields per hectare, compared with wheat, rye and barley. Since maize is cheap, it has become the dominant food and main source of dietary energy and protein for poor people, particularly those in rural and underprivi- leged segments of the society. There is an urgent need to promote maize breeding on priority basis by adopting various approaches to meet the in- creasing demand for maize grain and its products. In this context, maize hybrid breeding remains the choice of the methods considering its success over years. For exploiting the potential of hybrid breed- ing in maize, many maize inbreds have been devel- oped from a limited number of elite lines and elite line synthetics, a practice that heightens the risk of decreased genetic diversity in commercial maize production fields (HALLAUER et al., 1988). Better un- derstanding on the genetic diversity ensures the breeder in planning crosses for hybrid and line de- velopment, in assigning lines to heterotic groups, and in plant variety protection (PEJIC et al., 1998). Meanwhile, there have been frequent warnings about the genetic vulnerability of maize (GOODMAN, 1990). This made the maize breeders to realize the need for both maintaining genetic diversity and im- proving the management of genetic resources (GOODMAN, 1994). The developments during the past three decades in the DNA marker technology are enormous and an array of DNA markers is made available as a tool to assess the genetic diver- sity in plants and animals. In the present study, an attempt was made to study the extent of genetic di- versity available across the maize inbreds exclusive- Maydica 54 (2009): 113-123 GENETIC DIVERSITY ANALYSIS OF MAIZE (ZEA MAYS L.) INBREDS DETERMINED WITH MORPHOMETRIC TRAITS AND SIMPLE SEQUENCE REPEAT MARKERS M.A.B. Ranatunga 1,3 , P. Meenakshisundaram 1,4 , S. Arumugachamy 2 , M. Maheswaran 2,* 1 Department of Plant Molecular Biology and Biotechnology, Centre for Plant Molecular Biology, and 2 Centre for Plant Breeding and Genetics, Tamil Nadu Agricultural University, Coimbatore - 641 003, Tamil Nadu, India 3 Tea Research Institute of Sri Lanka, Talawakelle, Sri Lanka 4 Plant Biotechnology Division, SBST, VIT University, Vellore - 632 016, India Received June 29, 2009 * For correspondence (e.mail: mahes@tnau.ac.in).