Frequency Distribution Analysis of a Maize Population as a Tool in Maize Breeding

Abstract

The objective of this study was to investigate the distribution of progressive selection generations in order to define the maximum efficiency of increasing yield in relation to the stage of selection procedure. Experimental procedure lasted five years on open-pollinated lines selected in two contrasting environments under low plant population. Mean grain yield of individual maize plants increased by 79% from C0 to C4 generation in environment A and 32% in environment B. Yield of individual plants was increased by 58% from C0 to C2 when selection was fully practiced in environment B. The progressive reduction of CV values through the selection generations revealed gene fixation and lack of segregation in selected lines which tended to be more uniform and homozygous. Low to medium negative kurtosis and low to medium positive skewness, accompanied by a more “squared” shape of distribution curve may indicate more homozygous genetic material that was categorized in clusters of similar C4 lines as was observed in environment A, depicting the end of selection procedure. In C4, a breeder may choose from the upper part of distribution curve (higher yielding plants) in order to avoid possible selection of deleterious genes at the kurtosis-biased lower part of the distribution curve. Our findings suggested the selection of cultivars of narrow adaptation, because at the initial stages of the selection program the effect of environment lead to different genetic materials, favouring certain genotypes. In our study environment B favoured selection procedure for developing high yielding open-pollinated lines for breeding and farming purposes.