Half F2 diallel crosses of six spring cultivars of rapeseed (Brassicanapus L.) were used to estimate heterosis effects of yield components, seed yield, oil percentage, and oil yield under limited nitrogen condition. Significant mean squares of general and specific combining abilities (GCA and SCA) were detected for pods per main axis, pods per plant, length of pod, seeds per pods, 1000-seed weight, seed yield, and oil content and oil yield indicated respectively the importance of additive and non-additive genetic effects for these traits. High narrowsense heritability estimates for 1000-seed weight, oil percentage, and oil yield indicating the prime importance of additive genetic effects for these traits. Most of the cross combinations with significant positive heterobeltiosis for seed yield had also significant heterobeltiosis effects for pods per plant and pods on main axis; therefore these traits can be used as indirect selection criteria for improving seed yield. Significant positive correlation of mean performances with heterosis and heterobeltiosis effects for most of the traits except 1000-seed weight indicated that selection of the superior crosses based on heterosis and heterobeltiosis effects will be effective for their mean performances improving these traits except 1000- seed weight. Significant positive correlation was determined between pods per plant and seed yield, indicating that this trait can be used as good selection criterion for seed yield improvement. The crosses including RAS-3/99 × RW-008911 and RAS- 3/99 × RGS-003 with high significant positive heterobeltiosis effects of seed yield were superior combinations for seed yield increasing.
Half F2 diallel crosses of eight spring cultivars of rapeseed were used in partial circulant diallel analyses to estimate biometric genetic parameters for phenological traits, yield components and seed yield. The greatest variation in the GCA-to-SCA mean square ratio was related to days to flowering, and its lowest variation to days to maturity. A high coefficient of variation of the narrow-sense heritability estimate was obtained for days to maturity, followed by plant height and seed yield. For diallel analysis with a low number of parents, the differences of the heritability estimates of the traits were small; therefore, for precise estimation of heritability, a high number of diallel crosses will be preferred.
Information on estimates of combining ability of the promising lines of breeding material is important for evolving higher yielding varieties of oilseed rape (Brassica napus L.). An experiment was conducted to quantitatively examine the genetic parameters of phenological traits, plant height, pods on main raceme, pods per plant and seed yield for eight oilseed rape genotypes using a half-diallel crosses. The result of the diallel analysis revealed significant mean squares of general and specific combining abilities (GCA and SCA) for all studied traits, indicating the importance of additive and non-additive genetic effects for these traits. On the other hand estimation of high narrow-sense heritability estimates for days to flowering, duration of flowering and pods on main raceme, indicated the prime importance of additive genetic effects for these traits. L420 and L401 with significant negative GCA effects for days to flowering and days to maturity were suitable for yielding early maturity combinations. L41, Zafar and L22 with significant positive GCA effects for seed yield were superior parents for increasing seed yield. The crosses with significant positive SCA effects for seed yield had at least one parent with significant positive GCA effects for this trait. The crosses including L41×L22, L41×LF2, Zafar×L22 and Zafar×L420 with seed yield of 3421.7, 3400, 3348.1 and 3311.3 kg ha-1 could be promising for determination of superior recombinants for high seed yield coupled with other growth characters in advanced generations of segregation.
Crops growing in salt-affected soils may suffer from physiological drought stress, ion toxicity, and mineral deficiency which then lead to reduced growth and productivity. Eight rapeseed genotypes were evaluated at control and two salinity levels of irrigation, i.e. ECe=0 dS m-1 (control), 6 and 12 dS m-1. A factorial experiment based on completely randomized design with 4 replications was considered for evaluation of 24 treatments. Significant mean square of the salinity levels and genotypes were exhibited for 1000-seed weight, pod length, seed yield, Mg, K and Cl, indicating significant differences of genotypes for the traits at three salinity levels. Pods per plant and Mg had lowest variations among the genotypes at the high salinity levels. Hyola401, LRT1 and KRN1 with seed yield of 3.09, 2.78 and 2.30 g/plot, respectively were considered as salt tolerant genotypes. Stress (12dsm-1 ) to control ratio (S/C) which is indicating of salinity tolerance was high for seed yield of DSM12 and Hyola401.Significant positive correlation of seed yield with K and Cl, indicated that these shoot ions can be considered as good indicators for seed yield improving at saline environment.
Among the various abiotic stresses limiting the crop production, salinity stress is the most important problem, which needs to be addressed and answered straight away. A pot experiment was carried out with rapeseed breeding lines in order to study the effects of salinity stress on phenological traits, plant height and seed yield of rapeseed. A factorial experiment was applied for evaluating the eight rapeseed genotypes under three salinity levels including 0, 6 and 12 dS m-1 taking NaCl:CaCl2 in the ratio of 1:1, which were equal to 42.8 mM and 85.7 mM, respectively. The results of analysis of the variance revealed significant variations among different salinity levels, genotypes and interaction effects of salinity levels × genotypes for days to flowering, days to end of flowering, days to maturity, plant height and seed yield. Due to increasing salinity levels, days to flowering, days to end of flowering and days to maturity were shortened. Although with increasing salinity levels plant height and seed yield of the genotypes were decreased but the ranks of genotypes were different in 0, 6 and 12 dS m-1 salinity levels. The genotypes had significant genetic differences for the traits and the increments of differences also were decreased due to increasing salinity levels. The genotypes had high amount of genetic coefficient variation for days to flowering and seed yield, therefore the efficiency of selection of these two traits will be high. The genotypes including KRN1, LRT1 and Hyola401 with high amounts of seed yield in all salinity levels were considered as tolerant genotypes.
Rice (Oryza sativa L.) is an important crop in Iran and other parts of the word and it is also a staple food of nearly one-half of world‘s population contributing high calorie intake. Silicon is considered as a beneficial and nitrogen as an essential element for rice production. In order to study the effects of silicon and nitrogen on some yield components and shoot nutrition ion compositions in rice, a hydroponic culture experiment was conducted under the greenhouse condition. Two factors, including silicon and nitrogen, each one with three levels (0, 50, and 100 ppm) were studied in a completely randomized design in factorial arrangement with 3 replications. The traits including panicle length, unfilled grains, 1000- grain weight and shoot ions including silicon, potassium, and nitrogen were significantly affected by applied silicon levels. All the traits were affected by nitrogen levels except unfilled grains and shoot potassium concentration. The highest grain yield was detected at 100 ppm of silicon application. Shoot silicon ranged from 5.01 to 6.92 ppm in 0 and 100 ppm silicon application. Shoot potassium was increased in high levels of silicon treatment. Significant negative correlation of unfilled grain with shoot silicon and potassium indicated that increasing these shoot ions had reduction effects on unfilled grains. Significant positive correlation was determined between shoot potassium and 1000-grain weight, implied that this trait was affected by indirect effect of silicon via shoot potassium increasing.