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Showing 3 results for Direct Selection
Abdul Karim Tahmasebi, Reza Darvishzadeh, Amir Fayaz Moghaddam, Esmaeil Gholinezhad, Hossein Abdi,
Volume 8, Issue 2 (3-2022)
Abstract
The selection of genotypes based on multiple traits is a fundamental issue and an important part of the process of plant breeding. In the present study, the efficiency of selection indices based on phenological, morphological and physiological traits was studied to improve sesame grain yield. The evaluation of 25 sesame populations was realized in a completely randomized design with 10 replications under Urmia conditions in 2017.The results showed that phenotypic and genotypic correlations between grain yield and No. of capsules per plant, No. of grains per capsule, No. of branches, leaf temperature, leaf index and biological weight were positive and significant. By regression and path analysis, the No. of capsules and No. of branches were identified as the variables of the first-order cause and biological weight, harvest index, leaf index, plant height and chlorophyll as the second-order cause variables, among which only plant height had a direct negative effect. In order to obtain selection indices, two optimal and basic methods and ten different vectors of economic values of traits were used. The vectors were based on the analysis of correlation, regression, path and broad sense heritability. The third and fourth indices, in which the first-order cause entered the model, showed high relative efficiency and in terms of these two indices, and the sesame populations with code number of 12, 17, 18 and 19 populations were identified as the most desirable populations. Finally, it is suggested that the efficiency of these selection indices be evaluated in the field
Maryam Ebrahimi, Reza Darvishzadeh, Amir Fayaz Moghaddam,
Volume 10, Issue 1 (9-2023)
Abstract
Protection of food security is one of the basic priorities of any country, which is achieved through the development and introduction of new, high-yielding and stress-resistant crop varieties. Considering the wide range of usage; human nutrition, livestock and poultry nutrition as well as use in industrial products production, maize is of special importance in agricultural development programs. To improve a trait with complex behavior and low heritability, indirect selection by other traits or a suitable index developed based on several traits can be used. In this research, 86 maize genotypes were cultivated in the form of randomized complete block design with three replications in the field in the Faculty of Agriculture, Urmia University under two normal and salt stress conditions. The measurement of the traits was done from the tassel appearance to kernel physiological maturity. In order to speed up genotype selection and increase the acuracy of selecting high yielding genotypes, four selection indices including Smith- Hazel, Pasek- Baker, Brim and Robinson were used and calculated. The results of present study revealed that selection based on the Smith- Hazel index with the highest selection efficiency (∆H) will increase the grain yield in normal and grain yield and plant height in salt stress conditions. This index, with its high correlation with the breeding value is introduced as a superior index. Based on this index, R59 and 6*/88 genotypes were introduced as the superior genotypes under normal and salt stress conditions, respectively. Nonetheless, these genotypes were recognized as the best genotypes considering the results of all other investigated indices. Identifying and introducing genotypes tolerant to salinity stress is of particular importance due to the expansion of saline lands and the limitation of access to water suitable for irrigation. Based on the above results, 6*/88 genotype is recommended for the development of promising hybrids for cultivation in areas with water or saline soil.
Nasrin Akbari, Reza Darvishzadeh,
Volume 11, Issue 1 (9-2024)
Abstract
Sunflower, one of the important oilseed plants, is affected by drought stress, consequently leading to yield decreases. Direct selection for improving seed yield, as the end result of multiple traits, is often ineffective due to the significant impact of environmental conditions. For many years, indirect selection through other traits or selection indices has been proposed to improve seed yield. In the present experiment, 100 oilseed sunflower genotypes were evaluated in terms of some agro-morphological traits using a simple 10 × 10 lattice design under normal and drought stress conditions during two consecutive croping seasons. In drought stress conditions, irrigation was done after 180 mm of evaporation from class A evaporation pan, compared to 90 mm in normal irrigation conditions. Brim, Smith-Hazel, Robinson and Pesek-Baker selection indices were calculated to select genotypes under two environmental conditions. In order to evaluate and compare the efficiency of selection indices and select the best index, the genetic gain of traits (∆G), expected gain (∆H) and relative efficiency of selection index (RE) were calculated. The results of this study showed that the direct response to selection for the traits including seed oil content, days to maturity and leaf length under both environmental conditions was more favorable compared to the correlated response. However, for head and stem diameter traits, the lowest efficiency of direct selection was observed under both environmental conditions compared to other investigated traits. Considering the two criteria; the genetic gain of traits (∆G) and expected gain (∆H) under normal and drought stress conditions, the two indexes of Brim and Smith-Hazel were introduced as the best index and the genotype ENSAT-254 was introduced as the superior genotype. The selected ENSAT-254 genotype can be considered in developing hybrid cultivars for cultivation under drought stress conditions, provided it is validated at the molecular level by analyzing the expression of genes related to water deficit stress tolerance.
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