فصلنامه علوم زراعی ایران
سال سیزدهم شماره 2 (پیاپی 50، تابستان 1390)

To study the effect of nitrogen levels on grain yield and grain growth of wheat genotypes under optimum and post-anthesis heat stress conditions, two separate field experiments were conducted in delayed and optimum sowing dates in Ahvaz, Iran in 2006 - 2008 cropping seasons. The experimental site had a mild winter and dry, hot summer. Wheat genotypes in delayed sowing date experienced heat stress in post anthesis. Each experiment was arranged as split plot in randomized complete block design with three replications. The N application rates were (50, 100, and 150 kg.ha-1) assigned to the main-plots. Sub-plots consisted of six bread and durum wheat genotypes. Results indicated that in both optimum and delayed sowing date, grain yield decreased significantly as nitrogen level decreased. The effect of N treatments on 1000-grain weight (TGW), effective grain filling rate (EGFR) and effective grain filling period (EGFP) was not significant. The longest and the shortest EGFP under optimum (26 days) and in delayed sowing date (13 days) belonged to cv. Star, respectively. High temperature during grain filling period, enhanced EGFR (15%) and reduced TGW (31%) and EGFP 40%). Therefore, although the rate of assimilate accumulation increased under stress conditions, but this enhancement could not compensate EGFP reduction and led to 31% reduction in TGW. Results also showed thatgenotypes that headed late (Star and D-84-5) generally had higher reduction in TGW and EGFP than those genotypes headed earlier under post-anthesis heat stress conditions.

Twenty Iranian and introduction maize hybrids in five different maturity groups were studied in Zarghan, Shiraz for two cropping seasons (2007-2008). Three planting dates (27 May, 5 June, 15 June) and twenty maize hybrids were in split plot arrangements using randomized complete block design with three replications.. The planting dates were assigned to main plots and hybrids were randomized in sub-plots. Results indicated that late maturing hybrids will reach to proper harvestable moisture about early Oct., 18-22 Oct. and early-mid Nov. from 26 May, 5 June and 15 June sowing dates, respectively. In delayed planting, late maturing hybrids are to be replaced by medium and medium- early maturing hybrids to be harvestable in proper time with reasonable grain yield. While late commercial hybrid, KSC 704 in 5 June sowing date ripe in early Oct. with grain yield of 8667 kg.ha-1, medium hybrid KSC 400, 10-15 days earlier with grain yield of 8809 kg.ha-1. This differences in maturity increased with further delay in planting as for 15 June to 15-20 days with grain yield of 9341 kg.ha-1 without significan difference with KSC 704 with 11670 kg.ha-1 of grain yield. There was significant difference between KSC 704 and KSC 400 for desirable grain quality as well as the time interval for land preparation for next crop.

Twenty Iranian and introduction maize hybrids in five different maturity groups were evaluated in Zarghan, Shiraz, for two cropping seasons (2007-2008). Variation in temperature were created by three planting dates (27 May, 5 June and 15 June). Duration to flowering was estimated by heat units using both thermal indices, GDD and CHU, were reliable for different maturing groups and led to similar grouping for maize hybrids. Both indices, based on heat units to flowering, grouped hybrids KSC 320, KSC 250, NS 540, and OSSK 552 as late floweiring and hybrids KSC 500, KSC 400, BC 504, and OSSK 444 as early flowering as compared to former FAO maturing groups. Based on duration to maturity, grouping based on GDD was more reliable and conformed with grouping based on estimation of duration from planting to flowering.

To compare dry forage yield and quality of hairy vetch and triticale in pure stand and mixed cropping, a field experiment was carried out in Zanjan Agricultural and Natural Resources Research Center, in 2007-2008 and 2008-2009 growing seasons. The experiment was layed out as randomized complete block with five treatments and four replications. Treatments were mixing ratio including, hairy vetch and triticale pure stand,mixtures of 75% hairy vetch+25%triticale, 50% hairy vetch+50% triticale, 25% hairy vetch+75% triticale. The seeding rate of hairy vetch and triticale were 90, 125 kg.ha-1, respectively. Analysis of variance showed that there were significant difference between two growing seasons and cropping components. Dry forag yield, nitrogen, phosphorous, potassium and protein yield were significantly higher in second year. Mixed cropping of 50% hairy vetch+50% triticale showed higher performance than other treatments for dry yield, uptake of nitrogen, phosphorous, potassium and crude protein yield. This mixed cropping had 8850 kg.ha-1 dry forage and 1412.26 kg.ha-1. For all mixed cropping, land equivalent ratio (LER) was greater than 1, and 50% hairy vetch + 50% triticale treatment had the highest LER and LER for crude protein yield. LER for dry forage yield of the mixed cropping of 50% hairy vetch+50% triticale was 1.32, 1.35 and LER for crude protein yield was 1.54, 1.57, respectively.

To study the effect of planting pattern on phonological and physiological characteristics of safflower in rainfed conditions a field experiment was conducted in Shirvan-Chardvol in Ilam in 2008-2009 cropping seasons. The experiment was performed using factorial arrangement in randomized complete block design with three replications. Treatments included of three row spacing (30, 40 and 50 cm) and three plant spacing (10, 15and 20 cm). Results showed that differences between treatments were significant for all phonological characteristics except days to emergence. The lower row spacing and plant spacing had shorter days to heading, flowering and maturity as compared to higher row and plant spacing. Results also showed that in the lower row and plant spacing, plant canopy closed quickly. The highest LAI (2.1 and 2.1), CGR (2.1 and 2.3 g.m-2.day-1), TDM (437.4 and 421.1 g.m-2) and NAR (0.209 and 0.216 g.g-1.day-1) were obtained in 30 cm row spacing and 10 cm plant spacing in the early and mid growth stages, however, CGR and NAR indices were negative, because of plant shading and loss of older leaves. The 30 cm row spacing and 10 cm plant spacing had maximum LAI, CGR and TDM, hence, grain yield (1971 and 1730 kg.ha-1, respectively). It is concluded that increasing grain yield in safflower in rainfed conditions can be obtained through increasing total dry matter and improving physiological indices.

To study the variation in some agronomic characteristics and soluble stem carbohydrates at anthesis in spring wheat, 196 wheat genotypes received from the International Maize and Wheat Improvement Center (CIMMYT) were evaluated in a field experiment at Hasan Abad Field Research Station, Darab, Iran, in 2008-2009 growing season. Analysis of variance of data revealed that spring wheat genotypes were significantly different (P <0.01) for days to heading, plant height, days to physiological maturity, 1000 grain weight and grain yield. The genotypes were also significantly different (P<0.05) for grain growth duration. Range of variation for some characteristics as days to heading was narrow (106-119 days). However, the range of variation for soluble stem carbohydrates at anthesis was very wide (8.5-95.5 mg.g-1 dry matter). Variation in the grain growth rate was 0.52-1.18 mg.day-1 and grain yield varied from 987–6095 kg.ha-1. Genetic correlation between soluble stem carbohydrates at anthesis and grain yield was negative but significant (-0.394**). It was indicated that the accumulation of high amount of stem soluble carbohydrates at anthesis without remobilization process can not effectively increase grain yield under terminal drought conditions. Path analysis revealed that the direct effects of four characteristics: days to heading, plant height, grain growth rate and soluble stem carbohydrates at anthesis on grain yield were significant. Early maturity and grain growth rate were under genetic control and correlated with grain yield under terminal conditions of this study that can be used in wheat breeding programs for improvement of grain yield under terminal drought conditions.

To Study the effect of different plant densities of wild oat (Avena ludoviciana L.) on grain yield and yield components in three wheat (Triticum aestivum L.) cultivars, a field experiment was conducted as split plot in randomized complete block design with three replications in 2007-2008 cropping seasons in Mehran, Iran. The main plots were three cultivars (Chamran,Vee/Nac and Dez), and sub-plots were wild oat plant densities (0, 25, 50 and 75 plant.m-2). Results showed that wild oat plant density had significant effect on wheat grain yield and yield components. Increasing wild oat plant density from zero to 75 plant.m-2, grain yield of wheat reduced from 4786 to 4349 kg.ha1. Vee/Nac had higher grain yield in high plant density of wild oat as compared with Chamran and Dez. Results of this experiment showed that Vee/Nac cultivar may perform better grain yield under wild oat infection.

To select the suitable irrigation metod and oil rapeseed cultivar with high seed yield and oil content, a field experiment was carried out using a split plot arrangement in randomized block design with three replications in Hamedan in 2005-2006 grwoing seasons. Irrigation methods, tape and furrow irrigation, were assigned to mainplots cultivars, Opera, Licord, SLM046 and Okapi, were randomized in sub-plots. Results showed no significant differences in the grain yield of cultivars. Irrigation×cultivar intraction was significant (P 0.05). The highest seed yield (3961 Kg.ha-1) was obtained from cv. Opera with tape irrigation method and cv. SLM046 produced the least seed yield of 3710 Kg.ha-1 in furrow irrigation method. The average water use efficiency in tape and furrow irrigation was 1.34 kg.m3 and 0.74 kg.m3, respectively. The average of water use in furrow and tape irrigation methods was 2617 m3.ha-1 and 4870 m3.ha-1, respectively. Tape and furrow irrigation methods had similar seed yield, but water use in tape irrigation method was reduced by about 46%. However, despite of reduction water use in tape irrigation method, the cost of irrigation increased and net revenue decreased by about 1,329,480 Iranian Rails. Benefit:cost ratio indicated that tape irrigation method was not economical for oil rapeseed production.

Effect of wheat residues, nitrogen fertilizer levels, compost and weed control on agronomic characteristics and grain yield and its components in maize (cv. DC370) was studied in 2008 and 2009 cropping seasons at Bajgah Agriculture Research Station, Shiraz University, Shiraz, Iran. The experiment was conducted as a splitsplit plot arrangement in randomized complete block design with three replications. Two levels of weed control (weedy and weed free) were assigned to main plots and three levels of N fertilizer rates 0, 125, 250 kg.ha-1), and five organic matter application methods (0, 25 and 50% of wheat residue incorporation, 50 and 100 ton.ha-1 of compost application) were randomized in sub-plots and sub-sub-plots, respectively. Application of 125 kg.ha-1 of nitrogen fertilizer produced the highest weed biomass and N loss (2450 and 25.17 kg.ha, respectively). Grain yield was significantly affected by compost and N fertilizer application and the highest grain yield (9404 kg.ha-1) was obtained with 100 ton.ha-1 of compost and 250 kg.ha-1 of nitrogen fertilizer. Crop residue incorporation and N fertilizer also increased grain yield, but not at the level of compost and N fertilizer.Compost application was often better than residue incorporation in terms of organic matter enhancement in two depths of soil (0-15 and 15-30 cm). Therefore, application of compost with high inorganic N fertilizer could have contaminant potential for ground water. Although positive aspects of application of compost were often more pronounced than residue incorporation, but the latter is more safe and inexpensive.

The effect of concentration and timing of application of supplementary nitrogen fertilizer on dry matter remobilization and grain yield of rapeseed (Hyola401) as a second crop following rice in paddy field, was evaluated in a field experiment conducted using complete randomized block design with three replications at Rice Research Institute of Iran, Rashat, Iran, in 2008 cropping season. Fertilizer (N from Urea source) doses at two levels (5 and 10 ppm) and timing of application at 7 levels; 1: seedling stage at 6-8 leaves (1.06-1.08 based on Sylvester-Bradley and Makepeace coding system = SBMCS), 2: commencement of stem elongation (2.01- 2.03 SBMCS), 3: prior to flowering (3.9 SBMCS), 4: 1.06-1.08 + 2.01-2.03, 5: 1.06- 1.08 + 3.9, 6: 2.01-2.03 + 3.9, 7: 1.06-1.08 + 2.01- 2.03 + 3.9, plus two control treatments a: no nitrogen b: commonly applied fertilization (180 kg.ha-1) at seed sowing, stem elongation and prior to flowering in equal rates. Plant characteristics (number of siliques, number of grain.silique-1, 1000-grain weight, dry matter remobilization, dry matter remobilization efficiency, dry matter content in 50% flowering and grain maturity stages, biological yield, grain yield, oil content and harvest index) were measured. Results showed a significant difference between concentration and timing of nitrogen spray application effect on grain yield, oil content, number of siliques, dry matter remobilization, dry matter content in 50% flowering, grain maturity stages, biological yield. Spray application of nitrogen (10 ppm) in 2.01- 2.03 + 3.9 stages (Treatment. #6) had the higest grain yield 4221.7 kg.ha-1) and number of siliques.plant-1 (219.7 siliques), dry matter remobilization (694.1 g.m-2) and dry matter content at 50% flowering stage (891.5 g.m-2). There were no significant differences between number of siliques.plant-1, dry matter remobilization, dry matter content in 50% flowering stage and grain maturity stages in concentrations (10 ppm) and times of nitrogen spray application in 2.01- 2.03 + 3.9 and 1.06- 1.08 + 2.01-2.03 treatments. Results also showed that application of supplementary nitrogen (10 ppm) at 2.01- 2.03 + 3.9 stages can increase grain yield and dry matter remobilization in rapeseed cv. Hayola401.

Ascochyta blight (AB) is the major constraint and the most destructive disease for chickpea production in Central and West Asia and North Africa (CWANA) region. To study response of chickpea genotypes against this disease, a research was conducted in the International Center for Agricultural Research in the Dry Areas (ICARDA) in 2007. Effects of four pathotypes of A. rabiei in three spore concentrations were investigated on disease score (DS) and leaf infection percentage (LI) of two genotypes of chickpea (Iranian local "Bivanij" and ICC12004), using systematic and mini-dome methods. The layout of this study was factorial experiment based on completely randomized design with three replications. Results revealed significant differences between genotypes, isolates and concentrations for DS and LI. New variant of pathotype IV developed highest pathogenicity on both genotypes. Lower coefficient of variation in the second method confirmed higher precision of mini-dome trial. There was significant correlation between LI and DS. Disease score for Bivanij (susceptible to AB) were 3.5 and 4.0 under 2×103 spores.ml-1 concentration which suggested presence of some minor Ascochyta blight resistance genes in this genotype. Effect of spore concentration was divided into linear and quadratic components. Disease severity increased significantly with the increase in spore concentration and this trend was linear. Both genotypes were susceptible to pathotype IV, whereas only IC 12004 was resistant to other pathotypes. The highest spore concentration (2×105 spores.ml-1) developed the most discrimination between two chickpea genotypes.

To select wheat cultivars/lines with high grain yield and stability as well as to determine suitable sowing date for cold agro-climatic zone in Iran, 15 wheat cultivars/ lines were studied in split plot arrangement using randomized complete block design, with three replications in three sowing dates (Oct. 1, Nov. 01 and Nov. 21), at 10 field stations, for three growing seasons (2004-2007). Data on grain yield from different field stations in three growing seasons were analyzed to determine the best sowing date for each location. Results of combined analysis of variance showed that the first sowing date (Oct. 12) was suitable for all of the test locations. Therefore, the data of first sowing date were analyzed for 8 location and three grwong seasons. Since interaction of genotype × year × location was significant, stability analysis was performed using different methods. Results of these methods were almost similar. According to the results, Gascogne and C-81-14 with grain yield averages of 7841 and 8250 kg.ha-1, respectively, were the most stable genotypes. However, C-82 12 and Sissons, were superior genotypes with average yield of 8819 and 8295 kg.ha-1, respectively, but with lower grain yield stability. M-81-13, M-79-7 and Pishtaz had the least grain yield stability in cold agroclimatic zone.

Safflower is one of the important oil seed crops and is grown in Iran for many years. Selection of stablecultivars with high seed yield is an important objective in safflower breeding programs for rainfed conditions. To study stability of seed yield and genotype × environment interaction, sixteen cultivars/ lines of safflower and a check variety (Local Isfahan) were evaluated using randomized complet block design with three replications in Gachsaran Agricultural Research stations in2004 to 2006 cropping seasons. Results of combined analysis of variance showed that year × genotype interaction was significant. Various stability methods were used to identify cultivars/lines with high yield stability. Based on yield mean comparisons of selected stable genotypesusing different yield stability parameters, two parameters: mean of rank (R) and yield-stability statistics (Ysi) were identified as suitable parameters in selection of genotypes with high yield and yield stability. Using these two stability parameters(R and Ysi), five cultivars and lines namely Sina, Cyprus Bergon, Syrian, CW-4440 and Leasaf were identified as cultivars with high yield and yield stability for rainfed conditions of Gachsaran and similar warm rainfed areas.

To determine the gene action, heritability and number of genes controlling important traits in rice, two Iranian rice cultivars, Deylamani and Sepidroud were crossed in 2006. After selfing of F1 plants and back crossing with two parents in 2007, F2, BC1 and BC2 were developed. Seeds of two parents (P1 and P2) together with seed of F1, F2, BC1 and BC2 generations were grown in randomized complete block design with threereplications at Research Field of the University of Guilan, Rasht, Iran, in 2008 cropping season. Eleven important agronomic traits including plant height, panicle length, panicle number per plant, spikelet number per panicle, grain number per panicle, empty spikelet number per panicle, panicle fertility percent, 1000 grain weight, days to 50 % flowering and days to maturity and grain yield were measured. Analysis of variance showed significant differences between generations for all traits, except 1000-grain weight and grain number per panicle. Therefore, generation mean analysis was performed to determine gene action and heritability of the traits of interest. Results showed that additive gene action for days to 50% flowering and days to maturity was more important than the dominance gene action, but for other traits, the dominance gene action was more important, expect for grain yield that was controlled by both additive and dominance gene actions. Furthermore, additive, dominance and epistatic effects had important roles in the inheritance of plant height, number of empty spikelets per panicle and grain yield. Estimation of degree of dominance also showed that days to 50% flowering, days to maturity and grain yield were controlled by partial dominance, panicle length by complete dominance and other traits by over-dominance effects. Average broad-sense heritability ranged from 0.36 to 0.82 for panicle length and days to 50% flowering, respectively, on the other hand, the average narrow-sense heritability varied from 0.07 to 0.69 for plant height and days to 50% flowering, respectively. Average number of genes controlling the traits ranged from at least one gene for panicle number per plant, spikelet number per panicle, panicle fertility percent and number of empty spikelets per panicle to 24 genes for grain yield. In conclusion, hybrid development will be an appropriate approach to improve plant height, panicle number per plant, spikelet number per panicle and number of empty spikelets per panicle.. However, for other traits, recurrent selection in segregating populations can be used to increase the frequency of favorable alleles, and then by hybridization between the selected lines with high performance the dominance gene effects are utilized.

Phylogenetic analysis of 23 species of Medicago (Fabaceae) was performed based on 90 morphological characteristics by maximum parsimony approach as implemented in PAUP software-using heuristic search and branch swapping option of tree bisection-reconnection. Analysis of the characters with successive weighting using rescaled consistency index generated more reasonable phylogentic trees than the analysis with equally weighting characters. M. radiata was as outgroup. The analyses showed that there are five clades in Medicago that to some extent are in accordance with sections in Medicago genus. Perennial species, M. sativa and M. lupulina, with 91% confident intervals grouped together in the clade and among annual medics. This implies that annual medics are paraphyletic and in evolutionary process cross-pollinated species (M. sativa) have been evolved from self-pollinated species (annual medics). The most phylogenetical relationships was observed between M. rugosa and M. scutellata, M. sativa and M. lupulina, M. coronata and M. minima, M. rigidula and M. rigiduloides, M. polymorpha and M. arabica, M. tornata and M. turbinata. This information can be used in determining the dgree of success of inter-specific hybridization between different species in Medicago genus.