Iranian Journal of Crop Sciences
Year:2007 | Volume:9 | Issue:1 (33)|Papers Count:8

Significance genotype × environment (G × E) interactions effects in a major constraint in evaluation and release of new cultivars. To achieve this goal and in order to evaluate and advance towards new high-yielding and stable/adaptable cultivars suitable for the temperate agro-ecological zone in Iran, a set of yield trials was conducted with 20 elite barley lines using a Randomized Complete Block Design (RCBD) with three replicates at nine different experimental field stations during two successive years (1380-1382). Grain yield was studied and the results obtained from the combined analysis of variance revealed significance of all effects i.e. genotype, environment and genotype × environment interactions. Genotypes mean showed that the entries No. 9 (LB. Iran/Una8271//Gloria"S"/Come"s"-11M/3/Kavir) and No. 16 (L.131/Cerbel//Alger-eres/3/Gloria"s"-Copal"s") had the highest grain yield. To have a better interpretation of G × E interaction multivariate AMMI method was used, which resulted in five main principle components that explained 74.68% of the interaction mean square. Additionally, the genotypes No. 16 (L.131/Cerbel//Alger-Ceres/3/Gloria"s"-Copal"s") and No. 17 (L.131/Cerbel//Alger-Ceres/3/Kavir) had the lowest IPC1 and IPC2 and the highest levels of stability. Using the results of biplot and AMMI analysis, parameters integrated with those of grain yield, the entries 9 and 16 were selected as candidates lines with both best performance and grain yield stability.

Rice is a tropical and sub-hopical crop, which is sensitive to low temperature. Chlorophyll fluorescence is a common method for crop screening and monitoring of photosynthesis fluctuations under abiotic stresses. In this experiment, 77 rice genotypes including 49 line of International Rice Cold Tolerance Nursery (IRCTN 2005) and 28 Iranian rice were tested in split plot arrangement using complicity Randomized Design (CRD) in phytotrone for screening and monitoring of their performance. Variances International Rice Research Institute (IRRI) scoring system used for ranking of genotypes at normal and stress conditions. Chlorophyll fluorescence attributes, Chlorophyll content (SPAD values) as well as root and shoot dry weight was measured. Results showed that in low temperature 13/15°C (night/ day, respectively) qP, ETR, fPSII, Fv:Fm, SPAD value and vigor of seedlings as well as root and shoot dry weight significant 7 reduced as compared with normal temperature 22/29°C (night/day, respectively). Among genetypes of IRCTN No. 33, 34, 36 and 44 (the Philippines) had the highest values and stability of Fv:Fm and ΦPSII parameters in low and normal temperatures while Hoveizeh (from Iran) had the lowest tolerance to low temperature. In addition, there was a highly significant correlation between root dry matter and vigor, showing sensitivity of root to low temperature. Therefore, this parameter could be used as a criterion for selection of tolerant cultivars and genotypes to low temperature stress.

Changing crop canopy as to facilitating the interception of more radiation and maximizing photosythosis rate is one of the approaches to increasing crop production. In order to study this hypothesis as well as to determine the effect of the size of source and sink and the role of stem reserved assimilates in grain filling in caps, a field experiment was carried out in split plot arrangement- using complete randomized block design with four replications, in Seed and Plant Improvement Institute Field Experiment Station, Karaj, Iran. In 2006 cropping season Sowing dates (June 20, Jully 11 and Jully 31) was assigned to main plot and four plant density levels (6, 8, 10 and 10 plants m-2) and three leaf defoliation levels (without defoliation, defoliation of alternate leaves of upper half of plant and defoliation of leaves of lower half of plant) ware randomized in sub-plob and sub-sub plots, respectively. Results showed that sowing date, plant density and defoliation had significant effect on seed yield, No. of seed m-2, No. of unfilled seed and No. of total seed m-2. The interaction of three factors, however was significant on No. of filled seed and unfilled seed m-2 at 5% probability level. Increasing plant density, increased No. of seed m-2, hence the wighest grain yield m-2 was achieved for 12 plant m-2 (2538 kg/ha). Results also revealed that grain yield is more dependent on current photosynthesis and leaves in upper part of plants are more important in determination of grain yield m-2 and its components.

Heat stress during crop developmental stages, particularly in reproductive phase, is considered a major factor reducing wheat yield in tropical and subtropical regions of the world. The effect of heat shock on yield components of five selected spring wheat genotypes was studied. The heat shock of 35°C and 40°C were imposed during double ridge, anthesis and grain filling stages under controlled environments (greenhouse and growth chamber). Genotypes responded differently to heat stress during all three stages. All genotypes except genotype KC-4511 were tolerant to heat stress of 35°C at double ridge stage of the shoot apex, while all genotypes examined were killed by the heat shock of 40°C at this stage. Heat shock of 40°C at anthesis dramatically reduced the number of grains per spike in genotypes Atrak, KC-4511 and KC-4512, while no kernel was produced in genotypes KC-7168 and KC-7732. Heat shock of 40°C at grain filling stage caused serious loss of grain weight and spike weight; however, it didn't have any significant effect on the number of grains per spike. Grain weight was reduced by 38% in genotype KC-7732 and 61% in genotype KC-7168. Spike weight reduction ranged from 39% in genotype KC-4511 to 64% in genotype KC-7168. According to the results of this research short periods of heat shock which may occur in wheat growing areas of Iran, could substantially reduce the wheat yield. Results reported here implies that in a wheat breeding program for heat tolerance, necessary attention should also be paid to genotypic variation for heat tolerance at anthesis stage, in addition to the grain filling stage, because heat stress, usually, takes place from anthesis stage in Iran.

Apetalous flowers is an important morphological characteristic in rapeseed (Brassica napus L.), which cause response to higher planting population, more light transmition in canopy and radiation use efficiency, higher grain yield. In order to evaluate the effects of plant density and planting pattern on grain yield, yield components of apetalous and petalled rapeseed, a field experiment was conducted in Rice Research Institute of Iran, in 2005- 2006 cropping season. The experimental design was arranged in a split plot factorial in a randomized complete block design with three replications. Planting pattern (Rectangular and Square) as the main plots and two rapeseed cultivars (petalled = Hyola 401 and apetalous = Hylite 201) and plant density (33, 67 and 133 plants per square metrer) as subplots, respectively. The number of secondary branch per plant, plant height, number of siliques per plant, number of seeds per silique, silique length, oil percentage, thousand grain weight, harvest index, biological yield and grain yield were measured. Results showed that there were significant differences between treatments in measured traits. The average grain yield in apetalous cultivar was 14.6% higher than the petalled cultivar (3441.95 and 2938.06 Kg/ha, respectively). Plant density of 67 plants per unit area was determined to be the optimum plant density for two cultivars (4870 and 4290 Kg/ha respectively). Grain yield and number of siliques per plant in apetalous rapeseed was significantly higher than the petalled rapeseed (10 and 12%, respectively). This superiority was more evident at higher density (133 plants per unit area) i. e. 17.5 and 15.5%, respectively), indicating that apetalous cultivar has higher capability for higher plant population. In spite of non significant differences between harvest indices, right harvest indices of 4.5 and 11% in apetalous rapeseed in 67 and 133 plant densities, showed its higher capability for assimilate transport to grain. It seems that the main reason of superiority of apetalous rapeseed cultivar may be due to higher radiation use efficiency (RUE) compared to petalled cultivar (2.38 vs. 2.16 g.MJ-1, respectively).

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.

In order to study the effects of tillage methods on wheat grain and its components an experiment was conducted using randomized complete block design (RCBD) with four treatments including 1-Chisel plow in depth of 5-20 Cm, 2- Moldboard plow in depth of 15 -20 Cm, 3- Moldboard plow in depth of 25-30 Cm and 4-control (No tillage) with three replications, in Khosroshahr Research Field Station in two cropping seasons (2004-2006). Tillage treatments were conducted in the same field for two years. First year safflower was grown and in the second year wheat. Data of cone index, grain yield and its components were collected for evaluation and analysis. Results showed that the effect of different tillage methods were not significant for the grain weight, spike length, grain numbers per spike. However, there were significant (P<0.05) differences among different tillage methods for grain yield and plant height. Moldboard plow in depth of 25- 30 Cm had the highest effect on grain yield (5034 Kg/ha) and No-tillage had the lowest (2903 Kg/ha). Mold board plow in depth of 25- 30 Cm had the least cone index, soil properties, but the highest soil permeability. Among the tillage methods, moldboard plow in depth of 25- 30 Cm compared to the other treatments had greater effect on soil cone index and grain yield.