جستجوی مقالات مرتبط با کلیدواژه "genetic variance" در نشریات گروه "باغبانی"

Cucumber (Cucumis sativus L.) is an annual plant in the Cucurbitaceae family, which has 90 genera and 750 species. Iran, with an under-cultivation area of 89,632 hectares and a production rate of 1,804,184 tons of cucumbers, yield of 201,289 tons per hectare, and it is the third largest cucumber producing country in the world in terms of production. Use of fruits of these vegetable is different depending on the country and the consumer's taste and demand, and it is cultivated for fresh consumption as well as processing (pickled vegetables or cucumbers). The utilization of local genotypes or unmodified native reserves for production has led to very low yield of cucumbers in some countries of the world. The general objectives of cucumber breeding are resistance to diseases and pests, fruit quality and yield increase. Considering the history of cultivation of this product in Iran and due to the large under-cultivation areas of cucumber in the country, little breeding research has been done on this product and the country's required seeds are supplied annually through imports. Therefore, practical and applied research on the breeding of cucumber plant seems necessary. The present study was conducted to evaluate 27 cucumber plant lines using factor analysis and cluster analysis as a tool to identify superior genotypes and more effective traits.

This study was carried out in the research greenhouse of Department of Horticultural Sciences, Faculty of Agricultural Sciences, University of Guilan, with a longitude of 49 degrees and 36 minutes east and latitude 37 degrees and 16 minutes north with a height of 7 meters from the level of the open sea in February 2021. Overall, 35 cucumber inbred lines, available in the Germplasm Bank, University of Guilan, were selected and on completely randomized design, in three separate rows, and with three replications. A code was assigned to each of the lines in order to facilitate the naming of lines and easier evaluation. In the winter of 2019, the desired genotypes were first planted in the seedling tray and kept there until the second true leaves were observed. Then they were transferred to the greenhouse in the form of a completely randomized design with 27 lines of inbred cucumbers, in three separate rows with 3 replications and 3 observations. The length of the plant breeding period continued until the economic fruiting of the plant. During the growing season, various traits were checked and recorded according to the national guidelines for tests of differentiation, uniformity and stability in cucumber prepared by the Research Institute of Registration and Certification of Seeds and Seedlings. These traits are the Fruit diameter (mm), Fruit length (mm), Fruit number, Weight of single fruit (g), Total fruit weight (g), Number of female flowers in 15 nodes, Number of female flowers per node, Width of the end of the terminal leaf(cm), Length of the end of the terminal leaf(cm), Number of lateral branches in 15 nodes, Length of 15 internodes (cm).

Genetic diversity in plant genotypes is essential for a successful breeding program. Understanding the degree of variability in plant species is of importance because it provides the basis for selection. The results of variance analysis show that there is a highly significant variation between the studied lines at the level of 1%. The significant difference observed between genotypes for all traits indicates the existence of inherent genetic variation among genotypes.The evaluation results show that the average fruit weight trait varied from 1371.7 grams (L57) to 157.71 grams (L35) among the examined lines. Furthermore, genotype L57 (117.56 grams) had the highest statistical position in terms of single fruit weight. The results of the mean comparison table showed that L34 line had the highest fruit length values (161.84 mm) and L49 line had the highest fruit diameter values (39.83 mm). Moreover, L55 and L34 lines had the lowest values of fruit length (92.46 mm) and diameter (24.61 mm), respectively. The leaf area variable varied from 426.52 cm2 (L57) to 204.24 cm2 (L31) among the studied lines. The results of chlorophyll index traits investigation and total soluble solids showed that L51 line had the highest values in both traits.The results of statistical analyses pertaining to genotypic and phenotypic variance, as well as general heritability, revealed that the trait with the highest heritability, at 99.44%, was fruit weight. With the exception of five traits-length of 15 primary internodes, leaf surface, length and width of the terminal leaf, and single fruit weight-whose heritability values were 87.35%, 73.83%, 63.59%, 61.27%, and 26.23%, respectively, the heritability exceeded 90% for the remaining traits. These findings indicate that most of the traits examined exhibited high heritability, suggesting they were less influenced by environmental factors. Factor analysis, an essential multivariate technique, was employed to explore trait relationships and assess the genetic diversity among genotypes. The results of factor analysis for 27 evaluated cucumber genotypes show that eight factors were identified. They were 23.52, 12.63, 11.81, 9.95, 8.6, 7.34, 6.27, 4.21 percent. in total explained 88% of the total diversity of traits in the studied population. In total, they justified 88% diversity of total traits in the studied population. The results of the cluster analysis placed the studied genotypes in four different groups based on the mean of traits. To ensure the cut-point in the dendrogram and to determine the actual number of groups, the discrimination function analysis method was used. The results of discrimination function analysis showed that the success of cluster analysis in grouping genotypes was 100%. Since the genotypes in each of the clusters have a greater genetic affinity with the genotypes in the same cluster and, conversely, a greater genetic distance with the genotypes in different clusters, hybridization can be done among the genotypes in different clusters according to the value of traits average for each cluster for more productivity of phenomena such as heterosis and transgressive segregation. On this basis, it seems that it is possible to produce hybrids that are superior to their parents in terms of various traits by hybridization between the genotypes in the first and second clusters with the genotypes in the third and fourth clusters.

According to the results obtained from this study, L57 and L54 genotypes had higher values than the rest of the genotypes in terms of fruit number and total fruit weight. Also, according to the results of cluster analysis, L57 line had higher total mean values in traits of total fruit weight, single fruit weight, diameter of the tail of the fruit, fruit, kernel diameter, fresh and dry weight of leaves and leaf area. In this study, the genotypes of the second and third groups in the fruit number trait, and the genotypes of the first and third groups in the fruit weight trait, due to having the maximum difference, were found suitable for use in crosses in order to create more diversity. In general, the results of this research showed that there was a suitable diversity among the studied lines in terms of all measured traits. In addition to the fact that the results obtained from this research can be used in future breeding programs, the results of multivariate statistical methods also show solutions for the scientific crossing of genotypes in future research. So that the genotypes placed in different groups in cluster analysis (Group 1: L57, Group 2: L54, L52, L47, L32, L49, and L27, Group 3: L43 and L35, Group 4: L59, L53, L51, L34, L26, L55, L25, L39, L31, L30, L33, L28, L29, L36, L24, L44, L22, and L20) and had superior characteristics in terms of different components, can be crossed together to create recombinant genotypes.

Breeding for drought stress is one the important purposes in wheat cultivars breeding programs. Grain yield under drought stress is depended on phonological, morphological and physiological features. In order to investigate the general and specific combining ability and genes function under drought stress in three and two bread wheat lines and cultivars respectively, diallel one way cross was performed in Agricultural and Natural Resource Research Station, Tehran. Parents and hybrids (F1) seeds in the fall 2013, were planted in a randomized completely block design with three replicates. Number of grain in spike, number of infertile florets in spike, days to flowering, kernel weight and grain yield traits were evaluated. Results from analysis of variance showed that there are significant differences between genotypes. Results from diallel analysis based on Griffing’s experimental Method II, Model B showed that general combining ability (GCA) effect in all traits and specific combining ability (SCA) effect in all traits except number of infertile florets in spike were significant (P≤0.01). In addition, the ratio of GCA to SCA mean of squares was significant in all traits except days to flowering. Higher portion of additive genetic variance in mentioned traits indicate the higher heritability of these traits and this prepares the selection possibility in early generation for these traits.

Wheat (Triticum aestivum L.) is a major staple food crop for more than one third of the world population and is the main staple food of Asia. Over 800 million hectares of land throughout the world are salt affected. Salinity is a major obstacle to food production because it substantially reduces the average yield of major crops. This study was conducted to evaluate the response of 24 cultivars and genotypes of wheat (Triticum aestivum L.) to NaCl salinity at early seedling growth and correlation between affected morphophysiological traits and molecular markers. Genotypes grew in hydroponic nutrient solution, under control (tap water) and salt stress (45 and 90 mM NaCl) conditions. Results of ANOVA analysis showed that there are significant difference (in one percent P-value) between genotypes and all of measured traits in different levels of salinity. A total of 20 RAPD and 34 ISSR primers were tested to investigate genetic diversity in 24 wheat genotypes. Of these, only 15 ISSR and 6 RAPD primers produced polymorphic bands and were further used for genetic diversity and regression analysis. Cluster analysis was performed based on jaccard coefficient and all genotypes were divided into 4 groups. Average genetic distance between genotypes was 0.486, showed that there is considerable variation among these genotypes. Regression analysis, also, revealed that there are significant relations between measured traits and using markers were investigated.