Maize is among the most staple food consumed in almost every region of the world. Gain the maximum oil, protein, and carbohydrate yields of maize grain (Zea mays L.) can be attained either by increasing grain contents percentages or by increasing grain yield per land unit area. Wang et al. (2001) informed that both of these factors are important breeding objectives for improving grain quality traits and improving maize grain yield per land unit area via improving high-density tolerance.
Dhliwayo et al. (2014) informed that Egyptian maize varieties are currently grown under low plant population density that is around half of the density used in the USA. These Egyptian maize varieties cannot give higher production under elevated plant densities. This might be one of the major reasons that the yield from land unit area cultivated by maize in Egypt is lesser than that in the USA. One of the prospective technologies to maximize corn crop is via increasing plant density is the using of maize dense tolerant hybrids. Tollenaar et al. (1999) reported that the mean grain yield of corn per unit land area in the USA increased distinctly during the last 50 years due to the development that occurred in agricultural practices and breeding for tolerance to high plant density. So, breeding dense tolerant maize cultivars in Egypt could be considered as an imperative objective to maximize grain, oil, protein, and starch yields from the land unit area.
Al-Naggar et al. (2016) informed that competition between dense plants leads to the reduction in plant grain protein, grain yield, and oil contents. In contrast, several investigators including
Tetio-Kagho et al. (1988) reported that the use of elevated plant density along with dense tolerant genotypes can compensate for the negative effects and result in maximizing oil, protein, and grain yields per hectare. Several reports in the available literature were published on the existence of genotypic variation in maize grain quality traits, which is a prerequisite for starting a successful breeding program.
However, Al-Naggar et al. (2016) further reported that breeding progress has been limited by a negative correlation between maize grain yield and each of oil and protein content. Recently, research carried out by Younis et al. (2021) published in Asian Journal Of Plant Sciences to assess the effects of increased plant density and maize genotype on grain oil, protein, and carbohydrate contents and yields along with the identification of several genotypes characterized. The researchers informed that elevated plant density resulted in significant reductions in grain yield plant and the grain quality traits content. They further stated that the use of high-density could overcome such reduction and maximize the grain oil, protein, and starch yields per hectare.