Hybrid Vigor, Heterosis, and Genetic Parameters in Maize by Diallel Cross Analysis

Abstract

A field experiment was conducted at the experimental farm of Field Crop Sciences Department, College of Agriculture / University of Baghdad. Five maize (Zea mays L.) inbred lines were tested for general and specific combining ability by using full diallel cross. Seed of inbred were planted in spring and fall season of 2013. In first season, seeds were planted, and at anthesis crossing between inbreds were done. In the fall season varietal trial for crosses and parents were conducted by using RCBD design with four replications to evaluate crosses and parents and to estimate some genetic parameters. Statistical analysis revealed high significant increases for all traits, ear height, leaves area, no of ears/plant, no. of grain/plant, grain weight, dry weight/plant and yield t/ ha. The genetic analysis showed that inbred 2 was superior and gave high grain yield (5.74 t/ha.), due to its high dry weight (207.82g/plant), and no. of grain /plant (704.49). In addition, it had positive GCA. The reciprocity cross 4×1 was superior and gave highest yield 6.98 t/ha. due to superiority in 100 grain weight (18.53g). It also had positive and higher hybrid vigor (45%) for grain yield, and positive effect of sca (1.56). All reciprocity crosses were higher than crosses; the highest one is 4 × 3, which gave 8.69 t/ha. All parent and crosses had had positive variance for yield, but all reciprocity crosses were negative. Mean square for SCA and RCA were more than GCA, and therefore the σ2 GCA was less which made σ2 A less than σ2D and σ2 Dr, so σ2 GCA / σ2 SCA and σ2 GCA / σ2 RCA became less than one and the degree of dominance was more than one, making h2 n.s very little. Thus, the trait was governed by non-additive gene action. We can conclude that there is a possibility of using superior inbreds to produce hybrids or use selection for it and produce synthetic varieties.