جستجوی مقالات مرتبط با کلیدواژه « افزایشی » در نشریات گروه « زراعت »

In order to find an alternative to summer monoculture forage maize (Zea mays), intercropping systems of pearl millet (Pennisetum glaucum): soybean (Glycine max) (P:G) and maize: soybean (Z:G) and intercropping patterns, substitutive (XXG, XXGG and XGG) and additive (X%100G%25, X%100G%50 and X%83G%67) were evaluated as factorial in RCBD at research field of Agriculture and Natural Resources College of Tehran University in Karaj during 2013 and 2014 (G and X respectively: soybean and cereal including maize, Z, or pearl millet, P). Results showed that yields of cereal forage and mixed forage in Z:G were significantly higher than P:G. Cereals were dominant component in intercrop and the dominance of maize was higher than millet. Intercropping system or pattern did not affect total land equivalent ratio (LER).The highest LER was recorded 1.15 by P%100G%25 in 2013 and 1.07 by Z%83G%67 in 2014 without 2nd cut of pearl millet, and 1.10 by PGG in 2014 with sum of 2 cuts of pearl millet. In X%83G%67 despite the 83% cereal density of monoculture, partial LER was 0.95 for maize but 0.70 for pearl millet. It is concluded that additive patterns with a small ratios of soybean or with some decrease in ratios of cereal component, tend to have potential to achieve higher LERs. Thus intercropping, specially additive pattern can provide suitable alternatives to monoculture in production of forage with customized quality and higher diversity in ecosystem, in consistent with sustainability.

Wheat is the oldest and most important cultivated crop in the world and has fundamental role in human food security. Drought is one of the most common environmental stresses that affect growth and development of plants. Most parts of Iran’s cultivation land are located in arid and semiarid regions and because of water deficiency, plant stress appear and wheat performance reduces severely in these regions. In such circumstances, the production of drought tolerant varieties has special importance. Understand the genetic basis of yield and yield related traits is necessary in breeding programs. One of the best approaches to determine genetic parameters is generation means analysis method, due to it allows breeders to predict epistasis. In order to estimate genetic parameters and evaluation of gene action controlling agronomic traits in bread wheat under moisture stress, F4 families derived from cross between Roushan and Kavir along with F2, F3 and parents, were evaluated under moisture stress.
Field experiment was carried out in research field of Shahid Bahonar University of Kerman, during growing season of year 2013-2014 using Augmented design with 5 known check cultivars (Roushan, Falat, Mahdavi, Karchia and Shahpasand). Stress treatment was cut off irrigation at heading stage. Grain yield and some agronomic traits were measured. Generation means analysis method was used to determine genetic parameters including additive effect (d), dominance effect (h), additive × additive [i], and dominance × dominance effect [l] were evaluated for different traits. Generation means analysis was carried out using equation 1.
Y= mα[d]β[h]α2[i]αβ[j]β2[l] (1)
Broad and narrow sense heritability of evaluated traits were estimated according to equation 2 and 3.
The study revealed a complex genetic control for studied traits. Genetic variation in F2, F3 and F4 was more than parents. Five-parameter model including m, [d], [h], [i] and [l] explained genetic variation for plant height, awn length, grain number per plant, 1000-grains weight, biology and grain yield. While, a four parameter model including m, [h], [i] and [l] were explained genetic diversity of grain filling period and a four-parameter model including m, [d], [h], and [l] was valid for explaining genetic variation of number of spike per plant and harvest index. A three parameter model including m, [d], [i] made the significant contributions to the inheritance of spike length. The additive genetic variance was detected as the most important genetic effect in controlling grain yield, biologic yield, harvest index, 1000-grian weight, awn length, spike length and grain filling period. Therefore, selection in early generations is effective for these traits. High narrow sense heritability of these traits proposes that the most part of genetic variance could be fixed in segregating generations. Broad and narrow sense heritability of studied traits in the present population were 0.46 to 0.96 and 0.16 to 0.93, respectively. 1000-grian weight, grain yield, biologic yield, grain filling period and harvest index had the highest narrow sense heritability, respectively. Therefore in the present population, selection based on these traits could result in good genetic gain. While, dominant effect was more important for plant height, number of spike per plant and grain number per plant. Significant differences between broad and narrow sense heritability of these traits has confirmed the fact that the dominance effect is very important. Therefore, selection should be made in later generations until desirable genes are fixed. Low narrow sense heritability was observed for number of spike per plant (0.16). Therefore, selection based on this trait can not have good genetic gain in present population. In this study, environmental variation was less than additive and dominance variance that show accuracy of the estimations and low impact of the environment on evaluated traits. Plant height, number of spike per plant and grain number per plant showed one degree greater than of dominance. These result showed over dominance of genes controlling mentioned traits.
Based on the results obtained in this experiment, it can be concluded that there is a considerable genetic diversity in the population F2, F3, F4 derived of Roushan and Kavir cross which can be used as a high potential population for genetic improvement of evaluated traits. The Results showed that additive variance was more important than dominance in genetic control of evaluated traits. So, selection during early generations is recommended in wheat breeding program of this population.

Diallel crosses of eight genotypes of safflower were conducted and F1 and F2 generations were evaluated to estimate genetic parameters for seed-quality related traits including protein contents (%), fiber, ash and oil yeild. Griffing’s methods 1 and 2 for F1 and F2 generations was used, respectively. Sixty four genotypes including 8 parents and 56 F1 progenies, and half diallel crosses of F2 generation were grown using a complete randomized block design. Results of analysis of variance based on Griffing’s method revealed significant general combining ability (GCA) and specific combining ability (SCA) of all studied traits in F1 and F2 generations, implementing the importance of additive and non-additive genetic effects. Significant reciprocal mean squares were estimated by Griffing’s method indicated the importance of cytoplasmic genetic factors for controlling oil yield. Low narrow sense heritability estimates and high estimates of dominance effects for ash content indicated the importance of non-additive genetic efficiency for it. Hence the efficiency of hybrid production method would be high to improve it. High narrow-sense heritability estimates and high degrees of additive effects for oil yeild and fiber indicated the prime importance of additive genetic effects for these traits, therefore, the efficiency of selection would be high to improve these traits. The estimates of genetic variance components proposed the importance of both additive and dominance genec effects which contribute to variation in protein content.

In order to study the genetic control of resistance to common smut in maize, two resistant inbred lines, K1264/1 and K47/2-2-21 and two susceptible inbred lines, K3304/1-2 and K47/2-2-1-3-3-1, were crossed as K1264/1 × K3304/1-2, K47//2-2-21 × K3304/1-2 and K1264/1 × K47/2-2-1-3-3-1. The F1, F2, BC1 and BC2 progenies were produced and evaluated along with parents using randomized compelet block design with three replications. All generations were artificially inoculated with spordia of Ustilago maydis suspension. Inoculation was carried out 7-10 days after silking through injection of 3 ml of 106 spores/ml fungal suspension, using tip injection method. At maturity, disease severity was determined based on ears infection and analysed according to generation means analysis method for three crosses. Joint scaling test showed that the presence of additive, dominance and epistasis effects, especially additive × additive and dominance × dominance type, and in lesser extent, additive × dominance, in genetic control of resistance to maize common smut. Average broad and narrow-sense heritability based on three crosses data were estimated 80.3 and 57.3, respectively.