IOSR Journal of Agriculture and Veterinary Science (IOSR-JAVS) e-ISSN: 2319-2380, p-ISSN: 2319-2372. Volume 6, Issue 6 (Jan. 2014), PP 17-22 www.iosrjournals.org www.iosrjournals.org 17 | Page Increase In Protein, Oil, Amylose and Amylopectin Contents of Two Populations of Maize (Zea Mays L.) After Two Cycles of Reciprocal Recurrent Selection 1 Okporie, E.O., 1 S.C. Chukwu, 2 G.C. Onyishi, 1 L.G. Ekwu and 3 G.O. Oko 1 Department of Crop Production and Landscape Management, Ebonyi State University, Abakaliki 2 Department of Crop Science and Technology, Federal University of Technology, Owerri 3 Department of Crop Science, University of Nigeria, Nsukka Abstract: This research was conducted at the teaching and research farm of the Department of Crop Production and Landscape Management, Ebonyi State University, Abakaliki, from 2006 to 2012 cropping seasons to develop maize populations of increase protein, oil, amylose and amylopectin contents. Total of eight (8) maize varieties were used for the study and were grouped into two populations, A and B. Population A was coded A 1 , A 2 , A 3 and A 4 while population B was coded B 1 , B 2 , B 3 and B 4 . These two populations were genetically variable based on the time of maturity, percentage protein, oil, amylose and amylopectin. The mean protein content of the parents was 8.74% while their progenies after second cycle had percentage protein content of 13.27%, showing an increase of 4.53% with mid parent heterosis of 52%. The oil content of the open-pollinated maize varieties was pushed towards increasing order from 6.19% for population A and 4.19% for population B of the original populations to 5.61% and 5.62% for populations A and B respectively of the first cycle populations. These were further pushed up to 8.08% and 8.46% of the second cycle populations A and B respectively. The mean amylose content of the original population was 24.25% and the mean amylose content of the progenies after the first cycle was 22.02%. The second cycle synthetics had mean amylose content of 19.72%, showing a decrease of 4.53%. The mid parent heterosis was -9.2%. The mean amylopectin content of the original population was 75.75% and the mean amylopectin content of the selected high amylopectin was 82.13%, showing an increase of 6.38% over the mean amylopectin content of the original population. The breeding programme seems to be very effective in improving both the high, medium and low protein, oil, amylose and amylopectin contents of the original maize populations to all high protein, oil and amylopectin contents, except amylose, after the second cycle. In all, this method offers definite promise. Further progress in improving chemical constituents as well as other characters is theoretically possible in future cycles. Key words: Maize, Protein, Oil, Amylose and Amylopectin, Selection. I. Introduction Maize (Zea mays L.) is the second most important cereal crop in the world economy. It is globally the top cereal in productivity and has worldwide significance as human food, animal feed and as a source of many industrial products [1]. The major seed storage proteins of maize grain belong to the Prolamin family and are called the zeins. These proteins make up 40-60% of the total endosperm protein and are so abundant that their properties have a large impact on the properties of maize grain protein as a whole. Zeins lack the essential amino acids like lysine and tryptophan, and this deficiency is reflected in the amino acid balance of the grain. Thus, plant breeding strategies for improving the amino acid balance often involve some type of modification of the zein content [2]. Quantitative genetic approaches treat amino acid levels as a multigenic trait with continuous variation, and incremental improvements are made by recurrent selection. This is analogous to the way that total protein was manipulated in the Illinois Long-term Selection experiment [3]. One approach to improving levels of essential amino acids is to select for total protein content. The problem with this approach is illustrated in the Illinois Long Term Selection populations in which a high protein population yielded less grain per land area than did a low protein population [4]. This exemplifies a well known correlation between protein content and grain yield. While nitrogen fertilization is an effective way to increase grain yield of the high protein varieties [4], increasing total protein remains a costly approach to increasing essential amino acid levels. Among all the cereals, maize is the richest source of oil. High oil (HO) maize is an important value-added maize type developed artificially, and a great contribution of modern science to maize breeding. Compared with normal maize, HO maize not only greatly raised the oil content and total energy level, but also increased the protein content, lysine content and other li mited amino acids‟ content [5, 6]. The “added value” of HO maize reflected mainly in the gain-feed-ratio of livestock, swine, and poultry [7, 8, 9], as well as in the products of maize processing. The development of first HO maize strain (IHO) started in 1896 by Hopkins [10] was really a historical event which demonstrated the feasibility for altering oil content in maize kernel [11, 12]. Alexho HO