hassan amiri oghan

oilseed rape is one of the most important oilseed plants for supplying required oil and its products. To extent its cultivation area, the introduction of new cultivars with higher genetic diversity is necessary via breeding programs.

To establish of new genetic diversity and evaluation of genetic parameters, the 11 oilseed rape genotypes were crossed in full diallel method; consequently, different traits of parents and their F1 offspring were evaluated in a randomized complete block design replicated thrice.

Analysis of variance revealed that traits including days to flower initiation, physiological maturing, plant height, number of pods per plant, number of grain per pod, thousand-grain weight, and grain yield were significant. The genetic parameters analysis by Griffing's method I model II showed significant GCA, SCA, and REC effects of different traits which represent the evaluated traits were controlled by additive, non-additive, and cytoplasmic gene action effects. Analysis of combining ability represented that among parents, genotype SRL-97-1 had the highest GCA for physiological maturing, number of pod per plant, thousand-grain weight, and grain yield. Also, cross SRL-97-4×SRL-96-20 and SRL-97-15×SRL-97-3had the highest SCA and REC for grain yield, respectively. Besides, the broad sense heritability was higher in traits such as plant height, number of pod per plant and grain yield (H2=0.99); meanwhile, grain yield had a higher narrow sense heritability (h2=0.39).

Consequently, results showed that there was sufficient genetic diversity among evaluated genotypes in which the achieved diversity from the crossing of these genotypes could be applied in cultivar introduction. It is recommended that, genotypes with higher GCA and SCA are suitable for the foundation of a desirable population for selection of promising pure lines with higher yield attributes.

Genetic diversity is key to breeding programs and increasing selection efficiency. In this study, 19 promising advanced lines (F7 generation) along with two cultivars, Dalgan and, RGS003 were evaluated in a randomized complete block design with three replications in three experimental field stations (Gorgan, Sari and, Zabol) during the 2020–2021 growing season. The highest phenotypic and genotypic coefficient of variations was found for number of lateral branches and number of pods per plant, respectively. The highest broad sense heritability was estimated for days to end of flowering, and days to start of flowering and the lowest broad sense heritability was estimated for the plant height. The genotypes G16, G18, G15, G1, G2, G5, and G20 with a higher SIIG values as well as a higher seed yield above average were introduced as superior genotypes with respect to yield and other agronomic traits. Therefore, these genotypes can be used for further testing, including adaptation tests. Also, the results of factor analysis and genetic correlation coefficients indicated a positive relationship between number of lateral branches, number of pods per plant and number of seeds per pod with seed yield and seed yield. Generally, it can be concluded that number of lateral branches, number of pods per plant and number of seeds per pod traits could be used as the appropriate criteria to select for increasing seed yield in rapeseed breeding programs.

Rapeseed is one of the most important oilseed plants in the world. Therefore, the selection of high-yielding genotypes is especially important in this plant. Production of high yielding hybrid cultivars is the main objectives of breeding programs in rapeseed. Also, study on relationships between yield and other agronomic traits will improve the efficiency of a breeding program with appropriate selection criteria. Therefore, the objectives of this research were to the selection of new rapeseed hybrids and to find interrelationships among traits.

In this research, 21 rapeseed hybrids (yielded crossing between 3 restorers with 7 cytoplasmic male sterile lines) along with four cultivars Okapi, Ahmadi, Nima and, Nafis were evaluated in a randomized complete block design with three replications in Seed and Plant Improvement Institute (SPII), Karaj during the 2018–2020 growing seasons. The phonological, morphological characteristics and yield and its components including days to flowering starting, days to end of flowering, flowering period, days to physiological maturity, plant height, number of lateral branches, number of pods per plant, number of seeds per pod, and head, thousand seed weight, oil content, seed yield, and oil yield were measured. In this study, the selection index of ideal genotype (SIIG) and factor analysis were used to select rapeseed genotypes and study the relationships between the traits.

Based on the SIIG index, the genotypes G15, G3, G10, G5, G22, G8, G4, and G25 with the highest SIIG values (0.706, 0.680, 0.667, 0.665, 0.647, 0.641, 0.610, and 0.607 respectively) were the superior genotypes. On the other hand, G23, G18, G1, G24, G21, G7, and G13 genotypes with the least amount of SIIG value (0.219, 0.315, 0.334, 0.383, 0.397, 0.398, and 0.402 respectively) were the weakest genotypes for most studied traits. The genotypes G15, G5, G22, G3, and G10 with high SIIG values as well as higher oil yield that total averages were recognized as superior genotypes from the point of yield and other agronomic traits. Also, the results of factor analysis indicated a positive relationship between thousand seed weight with seed yield and oil yield.

Generally, the results indicated that the genotypes of G15, G5, G22, G3, and G10 were recognized as superior genotypes from the point of oil yield and other agronomic traits. Also, the trait of thousand seed weight could be used as a suitable criterion in selecting for increased yield in rapeseed breeding programs.

In order to increase the motivation of farmers to cultivate open pollinated oilseed rape cultivars, new cultivars with appropriate yields should be introduced. Also, due to the effects of climate change, increase in temperature, early arrival of heat and intensification of drought stress at the end of the season in the warm and dry regions, it is also necessary to pay attention to traits such as early maturity in identifying oilseed rape genotypes. Accordingly, the purpose of this study is to identify the most desirable lines compatible with warm and dry climates.

In order to investigate agronomic characteristics of the promising oilseed rape spring lines, an experiment was conducted with 21 spring genotypes in the Sistan region in a randomized complete block design with three replications during cropping season 2020-2021.

Analysis of variance showed that there are significant differences for traits including day to end of flowering, plant height, number of branches per plant, number of pods in sub-branches, number of pods per main stem, total number of pods per plant, main stem length, yield and biological yield among the studied genotypes. The study of broad sence heritability showed that phenological traits were more influenced by environmental factors; while quantitative traits of yield and its components were more influenced by genetic factors. Also, the number of branches per plant, the number of pods per main stem and grain yield had the highest values of genetic coefficients of variance, respectively. In addition, the number of pods per main stem, plant height, length of main stem, number of pods per plant, number of branches per plant, seed yield, day to end of flowering and biological yield, had the highest broad sense heritability among the studied traits, respectively. In terms of grain yield, G9 line (SRL-99-1) had the highest yield with a value of 2992 kg/ha. This genotype showed a significant difference with the control cultivar RGS003. Also, G11 (SRL-99-9), G2 (SRL-99-2), G1 (SRL-99-1), Dalgan,G18 ( SRL-99-16),  G20 (SRL-99-18), G21 (SRL-99-19)  and  G13 (SRL-99-11) lines were in the next ranks in terms of yield, respectively. Additionally, using various statistical methods such as mean comparison, principal component analysis and cluster analysis, lines were grouped based on the studied traits in this study.

  In this study, 8 lines with desirable characteristics were identified. The superior lines which were identified in terms of yield and its components in this study, could be introduced as new lines compatible with the warm regions if the trend of superiority continues in adaptability tests.

Genotype by environment interaction is one of the complicated issues in plant breeding programs for development of high-yielding with yield stability genotypes. To evaluate seed yield and yield stability of oilseed rape in four southern and northern warm regions of Iran (Zabol, Gorgan, Haji Abad and Sari), nine open pollinated spring oilseed rape lines together with seven cultivars were evaluated using randomized complete block design with three replications in two cropping cycles (2017-19). The results showed that G9 (SRL-95-16) and G12 (OG-AL) genotypes had the highest and the lowest seed yield with mean seed yiled of 3412 and 2507 kg.ha-1, respectively. In this study, seed yield wassignificantly different in different environments. The genotype × environment interaction was investigated using GGE-bioplot stability analysis. According to the which-won-where model of the GGE-biplot model, most of the studied environments were located in or close to the mega-environment 2 which included genotypes G2 (SRL-95-7) and G9 (SRL-95-16) as the best genotypes in this mega-environment. Also, the study of the average tester coordinates showed that G2 and G9 genotypes as superior to all check genotypes like G11 (Dalgan which ranked third) and as the best genotypes considering both seed yiled and yield stability. Also, these two genotypes had the shortest distance from the hypothetical ideal genotype in comparison with other lines and check cultivars. Therefore, considering seed yield and its stability, two genotypes G9 and G2 were identified as suitable genotypes for the southern and northern warm regions of Iran.

Although the opening of the silique is a valuable mechanism for the distribution of seeds in nature, it is also a significant problem in oilseed rape cultivation. Seed shedding from siliques at and after maturity is commonly referred to as pod shatter, and it reduces the grain yield of oilseed rape (Brassica napus). This factor, also called dehiscence, can cause losses of up to 50% of potential grain yield if harvesting is delayed and in adverse weather conditions. As a general consideration, canola is susceptible to shattering, and there is little genetic diversity associated with silique shattering tolerance in its commercial lines hence, increasing shatter tolerance is an important breeding objective.

In the present study, eleven parents were used to generate 55 hybrids. The experiment was carried out as a complete randomized block design with three replications at the seed and plant improvement institute. Silique Shattering Tolerance Index (SSTI) using Random Impact Test (RIT) and other related traits were measured during 2018. Griffing's model I of method II was used for the analysis of variance and the estimation of genetic parameters. Correlation coefficients for the studied traits and other calculations were performed using the SPSS software and Excel program.

Analysis of variance of genotypes showed high genetic diversity for the studied traits. Similarly, the general and specific combining ability variances were significant for most traits such as grain yield and the silique shattering tolerance index. This indicates the contribution of additive and non-additive effects in the genetic control of these traits. The general heritability of the studied traits was observed in the range of 78.81% to 93.87%. Correlation coefficients of traits showed a positive and significant correlation between silique shattering tolerance index with grain yield and oil content. Moreover, Zarfam and ES Artist with a good performance and silique shattering tolerance index are considered the best general combiners. Okapi×Zarfam, Nafis×ES Artist, Ahmadi×Nafis, Ahmadi×ES Neptune, Zarfam×ES Neptune, Nafis×ES Natalie, and Nima×ES Natalie are recommended as the best specific combinations for mechanized oilseed rape harvest and improvement of the shattering tolerance trait.

Low specific heritability of grain yield can be due to the more outstanding contribution of non-additive effects than additive effects. Various research studied variable estimation for general and specific combining ability and other parameters due to the difference in genetic materials and different weather conditions.

Given the importance of estimating combinability, heritability, genetic variance components and gene performance in designing breeding programs, an experiment based on the line×tester method with fifteen hybrids of oilseed rape derived from crosses of five average yielding cultivars includes SPN3, SPN9, SPN36, SPN30, DH4, with three spring and high yielding testers (SPN34, RGS003, SPN1) was performed using a randomized complete blocks design with two replications. The differences between hybrids for all traits, except flowering time, were significant. In the genetic control of traits, the importance of addictive effect of genes for all studied traits were estimated except for stem diameter and grain yield. The general heritability of the traits was very high and was estimate from 86.03% for stem diameter to 98.53% for the days to end of flowering. Minimum and maximum of the private heritability were also moderately high for the studied traits were56.83% and 91.63% for stem diameter and number of branches, respectively. Among the studied genotypes, SPN1 as a tester and DH4 and SPN30 as lines had the most combinability. Due to the superiority of DH4×RGS003، RGS003×SPN36 and SPN30×RGS003 hybrids, they can be recommended for hybrid cultivars production in the future breeding programs.

Releasing new adapted oilseed rape cultivars among the available resources of rapeseed would be a valuable method to increase the cultivar diversity in the tropical regions. Low adaptable and high yield cultivars resources of oilseed rapes are now available in the tropical regions of Iran. The current research aimed to identify new high yield and adaptable genotypes adaptable across various tropical regions. To this end, 20 new genotypes and a check variety (Dalgan) were cultivated in the five tropical regions of Iran based on a randomized complete block design (RCBD) with three replications during the 2019 to 2020 cropping season. The experimental sites are composed of five locations in Iran, including Gorgan, Sari, Rasht, Borazjan and Zabol. During the growth season, several phenological and quantitative traits were recorded. Combined ANOVA revealed significant genotype by environment interaction for all studied quantitative traits. Days to start flowering and days to end flowering showed the highest heritability. Correlation analysis showed a significant positive relationship between yield and flowering period, the number of sub-branches and also the number of pods per plant, but a negative and significant correlation with the days to maturity. Path analysis showed that the days to maturity had the most negative direct effect on yield and the days to start flowering, while the number of sub-branches had the most positive direct effect on yield. Canonical correlation showed that yield is correlated positively with phenological traits. The principal component analysis showed that the two first components covered 68.07% of all data variations which 12 genotypes were correlated with these two components. Cluster analysis categorized evaluated genotypes into three main groups. Finally, eight genotypes were selected in the current study, which had high yield and adaptability in the tropical regions of Iran.

To study of inheritance of oilseed rape quality traits in normal and late sowing date conditions, 31 genotypes including 7 winter lines as females, and 3 winter testers and their 21 F1 generation were grown under normal sowing date (early October) and late sowing date (early November) conditions in two separate RCB designs with two replications at the field of Seed and Plant Improvement Institute, Karaj (2011-12). Combined analysis of variance showed significant differences between treats of oil seed content and most fatty acids traits in both sowing dates. Therefore, significant genetic variation existed for all traits among the genotypes studied. Estimates of broad and narrow heritability of most traits under late sowing date were less than the normal sowing date and this was mainly due to less esti mation of variance components under late sowing date conditions. In addition, broad heritability was estimated to be generally medium to high (between 72.01 to 100) in both normal and late sowing date conditions. The narrow heritability of traits in both sowing conditions ranged from 20.81% to 80.20%. Therefore, selection for traits with moderate to low narrow heritability in early generations would not be much useful, and it is preferable to use heterosis to improve these traits. In both sowing dates non-additive effect was more evident in control of quality traits. Therefore, selection for these traits would not be effective without using the effect of gene dominance.

Compatibility and stability assessment of plant cultivars under various environments are of particular interests in crop breeding programs. In this study, stability of 17 spring oilseed rape promising lines was evaluated using GGE biplot analysis. The experiments were carried out in warm southern regions (four locations) of Iran in a randomized complete block design with three replications and in two growing seasons.  The results of GGE biplot analysis indicated G12 is the most stable genotype in two locations where the G14 is stable in other two locations. However, according to average tester coordinate criteria G12 is the most stable genotype across average test environment representing the highest yielding genotype among all investigated genotypes and environments. Based on the mean yield and Shukla Stability Index, as well as Superiority Index, G12, G14 and G18 genotypes are recommended for all warm regions of the country.

Nima variety, is resulted from the selection and purification of single plants in segregating generations derived from the cross Okapi´Modena. Single plants in F2 and their segregating generations were cultivated for five consecutive years until pure-lines were obtained in F6 generation. Selected pure lines were evaluated in a preliminary yield trial conducted in Hamedan in 2008-09. The result showed that seed yield of line SW102 (Nima) was 7% higher than Okapi (check cultivar). The study of selected lines in Karaj, Hamedan, Arak, Khosroshah near Tabriz and Islamabad-e-Gharb during 2009 and 2010 showed that seed yield of line SW102 (Nima) was 18% higher than Okapi. Based on stability parameters of environmental coefficient of variation and mean and variance of ranks for grain yield, SW102 had a good yield stability across different environments in all experinments. Evaluation of resistance to common oilseed rape diseases in Iran indicated relative resistance of SW102 to blackleg and sclerotinia diseases. Results of on- farm trials in Hamedan in 2012 showed that SW102 with grain yield of 4983 kgha-1 produced the highest seed yield. Results of on- farm trials in Isfahan showed that grain yield of SW102 and Okapi under drought stress decreased 13.4 and 23.6%, respectively, compared to normal irrigation. Based on desirable characteristics of line SW102 such as high grain and oil yield, good adaptability, relative tolerance to terminal drought stress and resistance to blackleg and sclerotinia stem rot compared to Okapi (check), this line was released as Nima and is recommended for cultivation in cold and moderately cold regions of Iran.

To evaluate the grain yield stability of rapeseed promising lines in different environmental conditions, thirteen spring oilseed rape genotypes were assessed in a randomized complete block design with three replications in four locations (Karaj, Sari, Gorgan and Zabol) during two years (2015-2017). Simple analysis of variance showed that there was a significant difference between rapeseed lines in terms of grain yield at a probability level of 1%, which indicates that there is enough genetic diversity between them. In combined analysis of variance, the effects of year, location, year × location and genotype × location were also significant at 1% probability level. The comparison of mean grain yield showed that the rapeseed lines Simba, L104 and RGS003 produced the highest grain yield of 3105, 3058, 3032 kg ha-1, respectively. For stability analysis, different methods of stability including one-variable and regression methods (12 methods in total) were performed. Based on the integration of the results of these methods, three rapeseed lines Simba, L104 and RGS003 were stable and high yielding. For complementary studies, it will be recommended that these stable and high-yielding rapeseed lines be used in farm trials in target areas under farmer's conditions.

Development of high yielded varieties is important to balance between production rates and grewing food needs of human population. For genetic analysis of yield and some important traits in oilseed rape (Brassica napus L.), We conducted line×tester analysis with ten lines and ten testers (three winter parents and seven spring parents). First generation hybrids as well as 20 parents (120 genotypes) were cultivated as a alpha lattice design with two replications under two different conditions (normal and delayed planting date) and days to flowering, flowering duration, plant height, number of primary branchs in plant, thousand seed weight and yield were studied. The results showed that the difference between genotypes is significant and the environment had a different effect on genotypes. High levels of broad sense heritability (from 73.65% for number of primary branches in plant to 87.65% for grain yield) showed that the genetic variance was more than environmental effect. Estimation of less than unit for the mean squares of the general combining ability to the mean squares of thespecific combining ability ratio and low to moderate value of narrow sense heritability (from 29% for plant height to 70% for grain yield) showed that non-additive variance is the major factor in controling of studied traits. The spscific combining ability of hybrids and hetero estimation showed that introduced hybrids in this study could be successfully used in breeding programs and improve the oilseed rape traits. The T9 × L2, T3 × L2, T3 × L9 and T3 × L5 hybrids in normal condition and T3 × L5, T7 × L6, T5 × L10 and T7 × L7 in delayed planting conditions with maximum heterosis for yield were potential hybrids for using in breeding programs for increased yield.

In order to study of variation and correlation between yields and yield components in oilseed rape, an experiment was designed using line×tester method. Fifteen hybrid derived from crosses of three spring type and high yielding testers (SPN34, RGS003, SPN1) with five spring lines with moderate yield (SPN3, SPN9, SPN36, SPN30, DH4) were tested using a randomized complete blocks design with two replications in Seed and Plant Improvement Institute during 2014-15. Totally 21 traits were studied. Mean squares for all 21 traits except flowering time were significant at 5% to 1% levels. Grain yield positively correlated with, oil yield (0.999), biological yield (0.868), first pod height from ground level (0.627), the number of seeds per pod (0.546) and the pod length (0.523). According to the results of path analysis, oil yield (1.016) and oil percent (0.379) had the most direct and indirect effects on grain yield, respectively. Cluster analysis based on the square Euclidean distance and Ward's method, classified crosses in three clusters and the accuracy of the results of clustering was confirmed by discriminant analysis. Six independently principal components were identified in the analysis of principal components, and this component could explain 89.20% of the total variation. In general, the most important affecting traits was grain yield, which can be used to for direct selection of grain yield in segregating generations.