[Inheritance of protein content and its relationship with grain-yield and its components in some maize hybrids (Zea mays.L)]

The present investigation was undertaken during 2008, 2009 and 2010 growing seasons in Agricultural research Center at Homs, to study the estimates of general (GCA) and specific (SCA) combining ability, heterosis, phenotypic and genotypic coefficient of variability, heritability, genetic advance, potence ratio, inbreeding depression, gene action and correlation coefficient as well as the path coefficient results. Eight parental yellow maize (Zea mays, L.) inbred lines were crossed in a half diallel fashion during 2008 growing season and the resulted 28 F1 hybrids in addition to the two check variety Bassel-1 and Sbero S-4-985 were evaluated during 2009 growing season. Based on evaluation results, the F1 plants of the three superior crosses were self-pollinated and back-crossed to respective parents. The six populations (P1, P2, F1, BC1, BC2 and F2) of each of the three crosses were grown in separate experiments during 2009 growing season. Results could be summarized as follows: 1- The mean values of genotypes were higher for all studied characters. 2- Crosses, GCA and SCA mean squares were significant for all traits . 3- Showed lines IL.767-06, IL.840-06 and IL.291-06 good GCA in grain yield per plant. While showed lines IL.767-06, IL.840-06 and IL.233-06 good GCA in protein. 4- Showed SCA that the better crosses for grain yield per plant were IL.256-06 × IL.797-06 and IL.136-06 × IL.797-06. While for protein were(IL.136-06× IL.233-06), (IL.840-06× IL.291-06) and (IL.233-06× IL.767-06). 5- Achieved 27 hybrid heterosis percentage for grain yield per plant relative to better parent. 25 hybrid relative to the local check variety (Bassel-1) and 2 hybrid relative to the check variety (Sbero S-4-985). While achieved 4 hybrid heterosis percentage for protein relative to the local check variety (Bassel-1) and 27 hybrid relative to the check variety (Sbero S-4-985). 6- Potence ratio indicated over dominance for all studied traits except some traits in cross two and oil in cross 1,3 which showed partial dominance in some cases. 7- Inbreeding depression values were non-significant in most traits except plant height, ear length and grain yield per plant and it was positive for most studied characters in the three crosses except days to silking trait. 8- Heritability percentages in broad and narrow senses were calculated for each environment. The highest narrow sense heritability values were 76% to cross1,3 for days to silking, 58% to cross1,3 for leave area index, 37% to cross3 for specific leave weight, 60% to cross3 for specific leave area, 73% to cross1for stay green, 74% to cross1 for plant height, 64% to cross3 for ear height, 42% to cross1 for ear length, 47% to cross2,3 for ear diameter, 58% to cross1 for number of rows per ear, 53% to cross2 for number of kernels per row, 63% to cross3 for 100-kernel weight, and 81% to cross1 for grain yield per plant, 50% to cross3 for protein, 76% to cross1 for starch and 54% to cross1 for oil. 9- The highest expected genetic advance (∆g %) was obtained for grain yield per plant (29.18%) in cross1, (24.78%) to cross1 for stay green, (24.09%) to cross3 for leave area index, (24%) to cross3 for ear height, number of kernels per row (21.09%) in cross2, (17.61%) to cross3 for days to silking, (15.39%) to cross3 for 100-kernel weight, (15.30%) to cross3 for specific leave area, (15.10%) to cross1 for plant height, (13.48%) to cross1 for number of rows per ear, (9.19%) to cross3 for specific leave weight, (8.25%) to cross1 for ear length, 50% to cross3 for protein, (6.30%) to cross2 for ear diameter, (5.76%) to cross1 for oil and (3.05%) to cross1 for starch. 10- In most cases, dominance (h) occupied the first rank, while dominance × dominance (l) the second, but additive (d) and additive × dominance (j) occupied third contributor to the genetic effects in order of importance according to cross. So the select is better from middle and later for development this traits. 11- The highest positively values of correlation between grain yield per plant and other traits were noted for each of ear diameter, number of rows per ear, number of kernels per row and 100-kernel weight in the three crosses. 12- Path coefficient analysis estimates indicated that ear diameter, number of rows per ear, and number of kernels per row can be considered as the most important sources of plant grain yield variation for cross1. While were ear length, ear diameter and number of kernels per row for cross2 and were ear diameter, ear length and number of rows per ear. 13- Path coefficient analysis estimates indicated that leave area index, plant height and ear length can be considered as the most important sources of protein variation.