Optimum Plant Density for Maximizing Yield of Six Inbreds and their F1 Crosses of Maize (Zea mays L.)

One of the reasons Egypt do not achieve very high maize crop yield is that cultivars used commercially are bred and grown under low plant density (ca 20,000 plants/ fed; one fed= 4200 m2). Therefore, the objective of the present study was to identify maize genotypes of tolerance to high plant density in order to enhance grain productivity from unit area. Six inbred lines of maize differing in adaptive traits to high plant density were crossed in a diallel fashion. Higher plant densities (30,000 and 40,000 plants/fed) caused a significant increase in grain yield/fed (GYPF) compared with the low-density (20,000 plants/fed) by 5.7 and 6.3% for inbreds and 14.0 and 27.6% for F1 crosses, respectively. The inbreds L17, L18 and L53 proved to be tolerant (T), while the L29, L54 and L55 inbreds were sensitive (S) to high density. The T×T group of crosses exhibited better performance in most studied traits than T×S and S×S groups of crosses under the three plant densities. The cross L17 × L54 came in the 1st rank under all plant densities for both grain yield/plant and grain yield/fed; this cross gave 42.7 ard/fed (ca. 14 ton/ha) [one ard (ardab) = 140 kg] under the high plant density (40,000 plants/fed) and showed a significant superiority of 28.6% over the best check cultivar in this study (SC 2066) under this density. The crosses L17 × L18, L29 × L55, L53 × L54 and L53 × L55 came in the 2nd, 3rd, 4th and 5th ranks, for grain yield/fed under all plant densities. Grain yield/fed of all studied genotypes showed a quadratic response of increase to the increase in densities from low to high levels, except L29, L54 and L55 inbreds, which showed a quadratic response of decrease. Optimum plant density in this study differed from genotype to genotype and was the lowest (20,000 plants/fed) for the three inbreds L29, L54 and L55, but was the medium one (30,000 plants/fed) for the inbred L53 and the two crosses L17 × L29 and L54 × L55 and was the highest density (40,000 plants/fed) for the inbreds L17 and L18 and the rest of F1 crosses.