Genetic Variability Analysis of QPM (Zea mays L.) Inbreds using Morphological Characters

Abstract

Genetic divergence among parents is of paramount importance in selecting them for hybridization programme. D 2 statistics used to measure the genetic divergence among the genotypes has been successfully utilized by the breeders to analyze the morphological diversity. Hybridization is one the tools to create variability. One may create more variability through hybridization when parents are diversed. Hence, genetic diversity in the parents is a prerequisite for crop improvement programmes. The genetic divergence among 25 genotypes of QPM inbreds were estimated by using Mahalanobis D 2 statistic for eleven characters. The twenty five maize genotypes were grouped into seven different clusters based on the Inter-genetic distance. This indicates the presence of considerable diversity in the genotypes studied. Clustering pattern indicated that 15 out of 25 genotypes belongs to the same cluster that is cluster I followed by cluster IV with 4 genotypes, cluster III with 2 genotypes and cluster II, V, VI and VII having 1 genotype (mono-genotypic). The average intra cluster distance range from 3.19 to 12.11. The maximum intra cluster distance was observed in cluster IV (12.11), followed by cluster I (9.18), cluster III (3.19). Cluster II exhibited close proximity with cluster VI (9.22) and maximum divergence with cluster VII (50.23). Cluster III was nearest to cluster VII (15.32), while it was farthest from cluster II (33.02). Cluster IV showed close proximity with cluster V (19.13) and maximum divergence with cluster VI (29.47). Cluster V exhibited intimate relation with cluster VII (22.29) and wide diversity with cluster VI (57.85). Farthest clusters for Cluster VI is Cluster VII (39.07). Percent contribution of eleven quantitative characters to total divergence were found maximum for ear length (27.67 %) and minimum for No. of kernel rows per ear (0.33 %).The analysis of divergence indicated significant differences among parental lines for all the agro-morphological characters. On the basis of results obtained in the present investigation, it was concluded that the allelic diversity can be used for future breeding program. The traits under study are also major yield contributing traits and are largely associated with each other. Therefore, these traits should be taken into consideration either simultaneously or alone for selecting a high yielding maize genotype. Introduction Maize (Zea mays L.) is best known as golden crop because every part of this crop is useful to man, animals and the industries. Maize is currently produced on nearly 180.64 million hectares in 125 developing countries with a production of 1033.6 million tonnes and productivity of 5.77 tonnes/ha. (Annual report maize, 2018). It is characterized by translucent, horny appearance of kernel when matures and wrinkled appearance when it dries. Maize is a low cost and rich repository of carbohydrates, fats, proteins, vitamins and minerals and therefore it is also called 'poor man's nutricereal' (Prasanna et al., 2001) [20]. The nutritional qualities of maize are on par with other cereals in most of the aspects. The maize kernel contains approximately 60-70 % carbohydrates 9-11 %, crude protein 2-3.5 %, crude fiber 3-5 % lipids and 20 mg of Ca/100g of kernels. It also contains carotene which is the precursor of vitamin A. About 70-80 % of maize production is used as a feed ingredient in the world. Although normal maize contains about 8-9 % protein, the quantity of two essential amino acids, lysine and tryptophan, is below nutritional requirements for monogastric animals. Therefore, utilization of quality protein maize (QPM) can corrects this deficiency and may be advantageous in the diets of livestock, monogastric animals in particular. Inbred lines are the prerequisite for hybrid variety development in crop plants. For developing high yielding hybrids in maize, inbred lines need to be developed and evaluated for their diverged gene pool. The genetic diversity between the genotypes is important as the genetically diverged parents are able to produce high heterotic effects (Ghaderi et al. 1979). The quantification of genetic diversity through biometrical procedure made it possible to choose genetically diverse parents. D 2 analysis is a useful tool for quantifying the degree