الفهرس 
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Abstract
Objectives : This investigation aimed to study the effects of genotype, levels of 2,4-D (2,4-dichlorophynoxyacetic acid) concentrations and their interaction on mature embryo induction in maize and in vitro salt tolerance using NaCl. In addition, to partition the phenotypic variances presented in this process to its components and subsequently, estimating the heritability percentages for all traits.
Methods & Results :
Four maize hybrids (122, 168, 173 and pioneer) were evaluated to callogenesis using 2,4-D (2,4 dichlorophynoxy acetic acid) and in vitro salt tolerance using NaCl.A callus was initiated from mature embryos cultured on MS media supplemented with 0, 2, 4 mg/l of 2,4-D. The produced calli from media which contain 2 mg/l 2,4-D for each genotype were then exposed to different salinity levels (0, 1500, 3000 and 6000 ppm) NaCl to evaluate calli physiological responses to salt stress produced from the studied genotypes.
Conclusion:
1. The results of ANOVA revealed that the mean squares of genotypes at all levels of 2,4-D were significantly indicated the presence of differences between them for all in vitro traits. Furthermore, the mean squares of levels and genotypes × levels interactions were highly significant for all traits. This indicated that these genotypes gave different responses at different 2,4-D levels. The genetic variation was high and positive with respect to the in vitro traits at each 2,4-D level. This indicated that these traits are mainly controlled by genetic factors. This finding was emphasized by the heritability values, which were more than 80% for all studied traits at each 2,4-D level.
2. In relation to callus response to salt stress, the results indicated that the presence of significant differences between these genotypes for ion content in callus cells (K+%, Na+%, Na+/K+ and Cl-%) with respect to the four salinity levels except for K+% at S1,S3 levels, Na+% at levels S1, S2, S3, Na+/k+ at levels S0, S1, S3 and Cl-% at levels S2, S3. Regarding to, the organic solutes accumulation (sugar and proline mg/g f.wt), the magnitudes of the mean squares for genotypes were significant at the four salinity levels except for proline mg/g f.wt at S3 level. For membrane permeability, relative growth rate and water content, the magnitudes of the mean squares for genotypes were significant at the four salinity levels except for water content at levels S0, S3.The results revealed that the genetic variation was high and positive for ion content in callus cells (K+%, Na+%, Na+/K+ and Cl-%), organic solutes accumulation (sugars and proline), membrane permeability and relative growth rate as well as water content with respect to the four levels of salinity. This finding is emphasized by the heritability values, which were more than 80% for most of the studied traits.
3. A positive and significant correlation was found between responding embryos and callus weight (0.98). Owing to these results, responding embryos could be used as indicator trait for selection the genotypes which suitable for mature embryos culture purpose in maize. A negative and significant correlation was found between water content and K+ content. This indicated that K+ content increase with decreasing water content. A negative and significant correlation was found between Na+/k+ and Cl- content. This indicated that increasing Na+/k+ ratio will decrease Cl- content. Proline showed a high significant and negative correlation with electrolyte leakage. This indicated that with increasing proline membrane damage will decrease. Also, Na+ showed a high significant and negative correlation with electrolyte leakage. Suggesting that compartmentation of Na+ in vacuoles is an essential mechanism to cope with salinity.