| چکیده انگلیسی مقاله |
Extended Abstract
Introduction and Objective: Khuzestan, as one of the most important corn-producing provinces of the Iran, lacks improved cultivars compatible with extremely hot and dry conditions and relies on foreign cultivars, including the old single cross 704 variety. In order to prepare suitable cultivars for Khuzestan, lines should be produced and evaluated in the region that can be used in the production of hybrid and open-pollinated cultivars.
Material and Methods: In order to identify and improve the important and effective traits on maize grain yield, 289 corn lines that breed in Khuzestan, were crossed with hybrid single cross 704 and evaluated in two cropping seasons (summer 2016 and spring 2017). The experiment was carried out in the form of a simple lattice square design 17x17 with two repetitions during the years 2016 and 2017 at the Safi-Abad of Dezful Agricultural Research Center. The traits measured from the growing stage to harvest include plant height, tassel length, tassel branches number/plant, stem diameter, number of leaves/plant, ear diameter, grain depth, ear length, number of rows/ear, grain number/row, 100 grain weight, grain yield, biological yield and harvest index were based on the guidelines of the corn and fodder plants department of the country's seed breeding and preparation research institute were measured. The yield based on 14% seed moisture along with other traits were measured and calculated from the two middle lines of each experimental plot. The study of genetic parameters in this research was calculated using from the mathematical expectation of the mean square in the form of the basic design of random complete blocks in the form of genetic relationships. To analyze the correlation between the traits and to identify the common factors affecting the studied traits, decomposition into factors using the principal components method and varimax rotation were used. Eventually Analysis of variance of data and calculation of correlation coefficients between variables were done using SAS Ver 9.20 software and analysis into factors with StatGraphics Ver 19.0 software.
Results: The results of analysis of variance showed that there was an acceptable genetic diversity among promising maize lines in terms of all studied traits except ear length, number of rows / grain and number of grain/row. The results of composite analysis in two cropping seasons showed that the effect of genotype in terms of all studied traits was significant at the level of 1%, that there is significant genetic diversity among the studied genotypes in terms of all traits. The significance of the genotype × season interaction effect for all studied traits at the 1% level indicates the different response of genotypes in summer and spring seasons. The highest and the lowest amount of genetic and phenotypic variance in summer and spring are assigned to biological yield and seed depth traits, respectively.The range of genetic diversity in the studied traits in the summer season ranged from 1.96 to 32.72. Also, the range of genetic diversity in the spring season in the examined traits varied from 7.63 to 29.88. Among the studied traits, the highest amount of genetic and phenotypic diversity was assigned to the trait of the number tassel branches/plant (respectively 32.72 and 33.35). The highest heritability rate in spring season for biological yield (97.69%), grain yield (97.43%), grain depth (97.06%), ear length (96.30%) and plant height (95.74) %) was observed while the highest amount of heritability along with the highest amount of genetic improvement was observed for the traits of biological yield and grain yield. Therefore biological yield and grain yield in this study can be considered the most important criteria for selecting parental lines in breeding programs. The results of the analysis of correlation coefficients on the studied traits in the summer season showed that among the studied traits, the grain number/row with 0.81, biological yield with 0.72, ear diameter with 0.62, and grain depth with 0.52 They had medium to high grain yield. Also, in the spring season, biological yield traits with 0.86, 100 grain weight with 0.65, grain number/row with 0.64, ear length with 0.64, and ear diameter with 0.63 had a medium to high effect on seed yield.
The results of analysis in factor analysis in the summer and spring seasons showed that five hidden and independent factors justified 71.40 and 72.27 percent of the total data changes, respectively. So that five hidden factors for the summer season named share of grain yield from the total dry matter (33.10 percent), plant height factor (15.80), ear diameter component factor (8.80), tassel height factor (7.50), and grain weight factor (7.20) were named.
Conclusion: The two factors of share of grain yield from total dry matter and the plant height factor account for more than 61% of the total justifiable variation of 14 traits in 289 lines, these two factors provide the ability to define and recognize differences and similarities for the lines that grow in spring conditions of Khuzestan have been modified. |