جستجوی مقالات مرتبط با کلیدواژه « Non-additive effects » در نشریات گروه « کشاورزی »

Leaf litter decomposition plays a key role in the nutrient cycle of forest ecosystems. However, there is not a comprehensive understanding of the non-additive decomposition effects in leaf litter mixing experiments. In this study, the dynamics of nutrients and the rate of decomposition of Iranian oak (Quercus brantii), tree of heaven (Celtis caucasica), and wild pistachio (Pistacia atlantica) were investigated in both pure and mixed stands. For this purpose, 81 single- and double-litter bags were placed in the study area and incubated for 180 days. According to the results, at the end of the incubation period, the decomposition of oak litters in combination with tree of heaven, tree of heaven in combination with wild pistachio, and wild pistachio in combination with oak showed positive results. Based on the results, the nitrogen concentration in oak mixed with tree of heaven was higher than in its pure state. But the concentration of phosphorus in its pure and combined states did not show any significant differences. In general, the findings showed the positive non-additive effects of litter on its decomposition rate. Regarding the dynamics of nutrients, these effects were considered positive only for nitrogen.

Maize (Zea mays L.) is the fourth most important cereal after wheat, barley and rice in Iran (Ahmadi et al., 2018). Given the future demand of corn as a food for humans and as a feed for livestock, there is a continuous need to evolve new hybrids with high yield. To achieve this, combining ability study is one of the best options (Reddy Yerva et al., 2016). Griffing diallel method (Griffing, 1956a;b) is one of the methods that examines how genetic control of traits in parents. It also evaluates the general and specific combining ability of parents and hybrids. The purpose of this study was to estimate the general and specific combining ability of parents and hybrids.

In order to estimate the gene action and heritability of important agronomic traits, five S7 maize lines were crossed in a 5×5 half-diallel and F1 hybrids derived from them were cultivated in a randomized complete block design with three replications at the Research Farm of Graduate University of Advanced Technology, Kerman, Iran in 2017. Number of ear, grain number per row, grain row number, grain number per ear, ear length, 100-grain weight and grain yield per square meter were evaluated. Analysis of data for general and specific combining ability was carried out following Griffing (1956) method IV model I using DIALLEL-SAS05 program (Zhang et al., 2005).

Analysis of variance showed that there was a significant difference between genotypes for all studied traits that showed the role of additive and non- additive effects in controlling these traits. The low ratio of GCA variance to SCA for the grain row number and number of ear traits, and in other words, the lack of significant GCA variance of these traits showed that genetic control of these traits has a non-additive effect. General (GCA) and specific (SCA) combining ability variances for grain number per row, grain number per ear, ear length, 100-grain weight and grain yield per square meter were significant at 1% probability level, indicating the control of these traits by additive and non-additive effects of genes with a greater proportion of additive gene effects.

The results of this study showed that although genes with both additive and non-additive effects played a role in controlling of yield and its component traits. In controlling traits of ear number and rows, the role of non-additive effects was greater. Whereas, other traits were more controlled by the additive gene effects. The Line14 had positive and significant GCA for the yield trait and most of its related traits, which indicated that the line could be used in breeding programs to improve yield and increase it. The results also showed that the P1 × P2 and P3 × P5 crosses had positive and significant SCA for yield and its related traits, so these hybrids might be the best for improving and increasing maize grain yield.

Litter quality plays a key role in the decomposition process and nutrients dynamics. In most studies, it is assumed that litter has a higher rate of decomposition in its ecological site. Evidence for this theory has not yet been fully confirmed. Therefore, in order to test this theory and also to investigate the effect of litter quality on its decomposition rate in two stands of european black pine (Pinus nigra Arnold) and tree of heaven (Ailanthus altissima Mill.) leaf-litters of P. nigra Arnold and A. altissima Mill were incubated for 180 days using the litterbag method in Shahed's forest park of Malayer. The chemical quality of litter, the rate constant for decomposition, the main ecological site advantage and the effects of mixtures litter were investigated through the relevant relations. Results showed that the rate constant for decomposition of A. altissima litter (with high levels of nitrogen and calcium and low C/N ratio) was higher than P. nigra (0.09 and 0.05, respectively). Competitive status was observed in all compounds except P. nigra samples in their sites. Also, the decomposition rates of the litters had a significant positive relationship with the concentrations of nitrogen (r = 0.76, p <0.05) and phosphorus (r = 0.62, p <0.05) and had a significant negative relationship with the concentration of potassium (r = -0.74, p <0.05) and C/N ratio (r = -0.76, p <0.05). The theory of home-field advantage was confirmed about european black pine and tree of heaven in their own ecological sites. In general, the results showed that the decomposition process is affected by both litter quality and home-field advantage of leaf-litter decomposition. According to the research results, mixed afforestation of these two species was suggested in the temperate cold climates of the west of the country.

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.

Biochemical and physiological traits are affected by environmental stresses and therefore the breeding of these traits will play an effective role in stress tolerance. In this study, hybrids of five S7 lines of maize in a 5 × 5 half-diallel design were investigated in order to study the combining ability of biochemical and physiological traits of maize at the Research Farm of Graduate University of Advanced Technology, Kerman, Iran during the 2017-18 crop year based on randomized complete block design with three replications. The results of analysis of variance by fourth Griffing's method showed that the general (GCA) and specific (SCA) combining ability variances were significant for protein, proline, sugar content, carotenoid, chlorophyll a, chlorophyll b and total chlorophyll traits. Therefore, the role of additive and non-additive effects was identified in controlling these traits. Protein, proline, chlorophyll a and total chlorophyll traits were more controlled by additive effects, whereas the carotenoid trait was more controlled by non-additive effects and the role of additive and non-additive effects in controlling other traits was almost equal. The KSC704-S7-11 line showed positive and significant general combining ability for most of the studied traits, suggesting this line can be used in breeding programs to improve and increase stress tolerance. In addition, P1 × P3 and P4 × P5 crosses showed the most positive and significant specific combining ability for proline, chlorophyll a, total chlorophyll and carotenoid traits; thus they can be considered as the best hybrids to improve and increase stress tolerance in corn.

To evaluate the general and specific combining ability of maize lines, five S7 maize lines and their offsprings were evaluated in randomized complete block design with two replications under normal and water deficit conditions at the research field of Graduate University of Advanced Technology, Kerman, Iran, in 2017 and grain yield and its components were measured. The results of analysis of variance indicated that there was a significant difference between lines as well as general and specific combining ability of parents and hybrids. Based on the results of the diallel analysis by second Griffing’s method, number of grain per row, number of grain rows, number of grain per ear, ear length and 100 grain weight were more influenced by the additive effects than the non-additive gene effects, while the number of ear was more controlled by the non-additive gene effects and grain yield per plant was approximately controlled by equal portion of the additive and non-additive gene effects. The line KSC704-S7-1 showed significant and positive general combining ability for grain yield and more related traits under both water deficit stress and non-stress conditions, so this line can be used to improve grain yield in breeding programs. In addition, P1×P3 and P2×P5 hybrids showed significant and positive specific combining ability for grain yield and most related traits under water deficit stress and normal conditions, respectively, which are introduced as the best hybrids for improving maize grain yield under water deficit stress and normal conditions, respectively.

 Ten diallel combinations of five maize tester lines were evaluated for grain yield and some related traits using randomized complete block design with two replications in Karaj and Gorgan during year 2004. Combined analysis of variance over two locations revealed significant differences among crosses for all the traits. Diallel analysis indicated presence of additive and non-additive gene action for grain yield, plant height, ear row number, kernel width and number of kernels per ear, as well as, additive effects for tassel length and tassel main axis length above the branches, ear length, kernel number per ear row and kernel thickness. MO17 and B73 were identified as efficient testers in screening maize germplasm, and K1264/1 and KL17/2-5 as non-efficient ones.