Estimation of Combining Ability for Some Yellow Maize Inbred Lines Using Line × Tester

INTRODUCTION

Maize (Zea mays L.) is an important cereal crop in Egypt, which plays an important role in human and animal nutrition. Developing a high yielding maize hybrid is based mainly a development of better inbred lines. Top crosses testing were used to evaluate new inbred lines for combining ability in maize breeding program. Davis (1927) was the first who suggested this method. Singh and Chaudhary (1985) found that line × tester analysis provides information about general and specific combining ability of parents and at the sometime is helpful in estimating various types of gene action. Khalil et al. (2016) found that the tester with the narrowest genetic based exhibited the highest genetic variation in test crosses for most of the studied traits. Venkatesh et al. (2001) andAkhi et al. (2018) suggested the use of an inbred line as a tester. While the use of a single cross as tester has been reported by Soliman et al. (2001) and Fan et al., (2009). Many investigators suggested that general combining ability (G.C.A) effects were relatively more important than specific combining ability (SCA) effects in inbred lines Abd El-Mottalb (2017) and El-Hosary (2020). While Mousa et al., (2021) found that the SCA effects were more important than GCA effects in the inheritance of grain yield.

The main objectives of this study were:

(1)  To estimate general and specific combining ability of inbred lines for grain yield and some other traits.

(2)  To identify the most superior lines and top crosses for their use in hybrid maize breeding programs.

MATERIALS AND METHODS

The experiment were carried out in the summer seasons 2023 and 2024 at Sakha, Gemmeiza and Sids Agricultural Research Stations. In 2023 season the three inbred lines Gz.658, Mall.5035 and Gm.6052 were used as testers and crossed with thirteen female parents according to line × tester design to produce 39 crosses. The resulting 39 crosses and two checks; SC.168 and SC.3444 were evaluated at three locations; Sakha, Gemmeiza and Sids Agricultural Research Stations in 2024. The experimental design was a randomized complete block design (RCBD) with three replications. Each hybrid was grown in one row, 6 meter long, 80 cm apart and 25 cm between hills, and one plant were left per hill.Data were recorded on; days to 50% silking, plant height (cm), ear height (cm), ear length (cm), ear diameter (cm) and grain yield (ardab/fed) adjusted to 15.5% grains moisture content.Bartlett's test has been done for the means squares of the three locations errors. Homogeneity was found and therefore, the Statistical analysis of the combined data across three locations was performed according to Snedecor and Cochran (1980).Combining ability analysis was computed according to Kempthorne (1957).

RESULTS AND DISCUSSION

Combined analysis of variance across three locations of 39 crosses for the studied traits is presented in Table (1). The results showed that highly significant differences between the three locations (Loc.) for all studied traits indicating that the three locations differed from each other in their environmental conditions. These findings were congruent with the results obtained by Abd El-Azeem (2011), Abd El-Mottalb (2014), Tesfaye et al. (2019), Ibrahim et al. (2021), Ismail et al. (2022), Abd El-Latif et al. (2023), El-Gonemy et al. (2023), Hamada et al. (2024) and Ismail et al. (2024).

Table (1).  Analysis of variances for days to 50% silking, plant height, ear height, ear length, ear diameter and grain yield traits under cross three locations.

*,** significant at 0.05 and 0.01 level of probability , respectively

Mean squares of genotypes (G) and their interaction with locations (G x loc) were significant or highly significant for all studied traits except for days to 50% silking, ear length, ear diameter of G. × loc. meaning that the genotypes were differ among them and influenced by change locations. Mean squares due to lines (L), tester (T), line × tester (LxT) and their interaction with locations are shown in Table (2).Mean squares due to lines (L) and tester (T) and their interaction (L x T) were significant or highly significant for all studied traits except ear diameter for lines, ear length and grain yield for testers,except ear length, for (L x T), indicating that lines differed in their order of performance in crosses with each of the testers. These results are in agreement with that those obtained by  Ibrahim et al. (2012), Abd El-Mottalb (2014), Murtadha et al. (2018), Abd El-Mottalb (2017), Gamea (2020), Abu shosha et al. (2020), Ibrahim et al. (2021), Alsebaey (2021), and Ismail et al. (2024). Mean squares due to lines × locations (L x loc.)were highly significant for all studied traits except ear length and ear diameter,meanwhile testers × locations (T x loc.) was highly for ear height and grain yield and significant for plant height while lines × testers × locations (L x T x loc.) was highly significant for plant height, ear height and grain yield. These results are in agreement with these reported by Abu Shosha et al. (2020), Alsebaey (2021) and Ismail (2024).

Variance components:

Table (2). Mean squares due to lines, testers, and lines × testers for six traits and their interaction with location for six studied traits.

*,** significant at 0.05 and 0.01 level of probability , respectively.

Table (2). Shows the estimates of combining ability variances k²GCA, k²SCA and their interactions for all traits with locations, the results revealed that values of SCA were larger than those of K²GCA for all traits indicating that the non-additive gene effects were more important that additive in the inheritance of all traits. Furthermore, the magnitude of the interaction variances of K²SCA × location interaction was greater than those of K²GCA × location for all studied traits except for ear height and ear diameter indicating that the non-additive gene action interacted more with the environmental conditions than the additive component of gene actions for these traits. These results are in agreement with the findings of several investigations who reported that specific combining ability variances were more sensitive to environmental changes than general combining ability variances Sadek et al. (2000), El-Zeir (2000), Gamea(2015), Gamea (2020), Abu Shosha et al. (2020), Ibrahim et al. (2021) and Ismail et al. (2024).

Mean performance:

Table (3). Mean performance of thirty nine crosses and two checks for days to 50%silking, plant height, ear height, ear length, ear diameter and grain yield traits across three locations.

Mean performance of the 39 crosses and two checks hybrids for all studied traits are presented in Table (3), for days to 50% silking, fourteen hybrids were significantly earlier than the earliest check Sc.168 (64.0 days). The earliest cross among them was (L7 × Mall.5035). Plant height ranged from 229.89 cm for the crosses (L4 × Gz.658), (L7 × Mall.5035) to 272.22 cm for the cross (L1 × Gm.6052) out of the 39 crosses, eleven crosses were significantly shorter than the check hybrid Sc.168. Ear height ranged from 122 cm for the cross (L7 × Mall.5035) to 161 cm for the cross (L13 × Gz.658). Five crosses were significantly lower ear placement than the check hybrid Sc. 3444 for ear length, all crosses werelower for ear length than the better check hybrid Sc.3444 for ear diameter, two crosses were not significant surpassed than the best check Sc.168 for grain yield, four crosses; (L9 × Mall.5035), (L13 × Gz.658), (L13 × Mall.5035) and (L13 × Gm.6052) were significant out-yielded the best check hybrid Sc.3444. Meanwhile, eight crossesnamely (L1 × Gm.6052), (L4 × Gm.6052), (L5 × Gz.658), (L8 × Gm.6052), (L10 × Mall.5035), (L11 × Gz.658), (L11 × Mall.5035) and (L11 × Gm.6052) were not significant out yielded than the best check SC.3444. These crosses are recommended for the further evaluation to accurately identify the promising crosses as future commercial hybrids for high yielding.

General combining ability effects.

Table (4).General combining ability (GCA) effects of the 13 inbred lines and 3 testers for grain yield and the other studied traits across three locations.

General combining ability effects for parental inbred lines and three testers are presented in Table (4). Positive GCA effects are desirable for improvement of grain yield and yield components traits, while negative GCA effects are desirable when selecting for earliness, short plants and lower ear placement. For days to 50% silking three inbred lines L3, L7 and L8 and tester Gm.6052 exhibited negative and highly significant for GCA effects, indicating these inbred lines are considered the best combiner for earliness. For plant height and ear height six inbred lines L3, L4, L5, L6, L7 and L12 and tester Mall.5035 had significant and negative GCA effects toward shortness and lower ear placement. For ear length, two inbred lines L11 and L13 had significant and positive GCA effects. for ear diameter, the tester Gm.6052 exhibited significant and positive GCA effects. for grain yield, two inbred lines (L11 and L13) had significant and positive GCA effects. from above results the inbred lines which exhibited desirable GCA effects are recommended for plant breeding programs. These results are in agreement with other investigations Motawei et al. (2019), Abd El-Latif et al. (2020), Gamea (2020), Ibrahim et al. (2021), Emam and Mohamed (2021) and Ismail et al. (2024).

Specific combining ability effects.

Table (5). Specific combining ability effects of 39 top crosses for days to 50%silking, plant height, ear height, ear length, ear diameter and grain yield across three locations.