مجله علوم گیاهان زراعی ایران
سال چهل و یکم شماره 1 (بهار 1389)

To investigate the efficiency of Eradicane application, using herbigation as compared with conventional method (spraying), concerning weed biomass and density reduction and change in corn grain yield, a factorial experiment was conducted based on randomized complete block design in 2006 at Research Fields of University of Tehran (Karaj). Eradicane was applied at 4.5 (labeled rate), 3.15 or 5.85 kg ai/ha while applying four application methods, namely: conventional spraying, herbigation via the first irrigation, herbigation via the second irrigation and applying Eradicane through both the first and second irrigations each at half a dose of a single application rate. Weed infested, weed free and Atrazine plus Alachlor (at labeled rate, 0.8+2.4 kg ai/ha) were also included as controls. The results showed the least weed density at early growth season observed with conventional spraying method. However, at physiological maturity stage, there was no significant difference between conventional spraying and herbigation (via the second irrigation). Both conventional spraying and herbigation (via the second irrigation) had the same efficacy in reducing weed biomass at season-long. Herbigation via the first irrigation did not provide an acceptable weed control, since the highest weed biomass and density accompanied this treatment. Maximum corn grain yield was obtained with conventional spraying, however, it did not differ from herbigation via the second irrigation. Eradicane applied at either rates of 4.5 or 5.85 kg ai/ha resulted in the highest corn grain yields along with the least weed biomass or density. No Eradicane treatment yielded as much grain as Atrazine plus Alacholr, because of not being as effective in controlling weeds. However, if farmers are about to apply Eradicane through furrow irrigation, a herbigation via the second irrigation at a maximum rate of 5.85 kg ai/ha could be recommended.

To investigate the effect of nitrogen rate and split form of application on dry matter remobilization among different rice cultivars, a field experiment was carried out in the Rice Research Institute of Iran (Amol) – during 2005. A split–split experiment on the basis of a randomized complete block design with 3 replications involving 3 factors was employed in which fertilizer rates (100, 150 and 200 kgha-1 from urea source), split form of fertilizer application (in varied ratios at the stages of transplanting, tillering and heading namely: S1 (50%, 25% and 25%), S2 (25%, 50% and 25%) and S3 (25%, 25% and 50%)) and finally crop cultivar (Tarom, Shafagh and GRH1 Hybrid) constituted the treatments. Results indicated that nitrogen fertilizer rates and split application exerted a significant effect on dry matter remobilization in total shoot, stem and leaves (except flag leaf), in which among the experimented cultivars, Shafagh stood top in terms of stem and total shoot dry matter remobilization. Also, among the fertilizer rates application the highest rate of dry matter remobilization was related to the 100 kg nitrogen fertilizer level. Among split form of applications, the first form (50%, 25% and 25%) treatment resulted in the highest rate of dry matter remobilization. The highest rate of dry matter remobilization in other leaves and in flag leaf belonged to GRH1 hybrid. Based on the obtained results, dry matter remobilization of total shoot (r=0.60**), stem(r=0.62**) and other leaves (r=0.34**) had significant and positive correlation with paddy yield.

Plant density affects yield components and seed yield by influencing the changing vegetative growth and environmental resources. These effecting factors were studied in the spring of 2006 at Ramin Agricultural Research and Natural Resources University, Mollasani in Northeast of Ahwaz, using a randomized complete block design of a factorial layout with 4 replications. Main factors were planting density of 4 levels (10, 15, 20 and 25 cm) and 3 cultivar levels (Gohar, VC1973A and NM92). The highest seed yield was obtained in plant density of 13.3 plants/m2, 15 cm planting distance (3471 kg/ha), for NM92 cultivar, and the lowest yield obtained at a density of 20 plants/m2, 10 cm planting distance (2110 kg/ha), for Gohar cultivar. Among yield components, pod number per unit area made the most contribution to seed yield. Any change of increase or decrease in plant density as compared to optimum, limited seed yield of the crop mungbean. Increase in plant density enhanced intercompetition while decrease in plant density reduced yield potential. Therefore, NM92 cultivar with a plant density of 13.3 plants/m2 might be suggested as appropriate for growing mungbean under conditions similar to those in this experiment.

Barley (Hordeum vulgare L.) is a model plant, as genetic and physiological studies are concerned. Abiotic stresses such as drought adversely affect the growth of plants. The objective of this experiment was to identify the responsive genes to osmotic stress, using macroarray (covering 13050 genes). RNA was extracted from 5 barley genotypes in stress as well as in normal conditions at 3 times of 1, 3 and 7 days after PEG application. ANOVA reveald significant condition effect on 744 genes. PCA was done on interaction effect matrix of gene × condition with most of the selected genes being related to lipid metabolism, stress response pathway and amino acid metabolism. The same analysis on interaction effect matrix of gene × conditions × genotype, and gene × condition × time led to genes which most of them were related to stress, hormone and amino acid metabolism. Dehydrins and lipid transfer protein gene groups had the highest numbers, in responsive gene cluster, to osmotic stress.

To evaluate and compare the chlorophyll content, carotenoid, protein, peroxidase and polyphenol oxidase in different barley species in Iran, 49 genotypes belonging to 5 barley species were employed in a completely randomized design with three replications in greenhouse conditions. A high level of within and between species variation was detected. In all the species, significant positive correlations were obtained for chlorophyll a and b and total chlorophyll contents. Moreover, in both H. marinum and H. bulbosume species, a negatively significant correlation was obtained between peroxidase and protein, while the correlation between peroxidase and polyphenol oxidase being positive in H. bulbosume. With the principal component analysis the first two principal components with eigenvalues more than 1 contributed 78% of the variability amongst genotypes. PC1 exhibited 57% of variation and was positively related to carotenoid, chlorophyll a and b and total chlorophyll contents. While, the second PC contributed 21% of the total variability and the characters with the greatest weight on PC2 being protein, peroxidase and polyphenol oxidase contents. The results of this research indicated that the genotypes of each barley species were different for evaluated physiological characters and some of these characters being more prounounced in wild barley species.

A study of physiological responses of different wheat cultivars to saline conditions can lead to an identification of the main mechanisms in salt tolerance. Seven bread wheat cultivars differing in salt tolerance with varying ability of sodium accumulation in their different tissues were employed to assess ion distribution and sodium accumulation under saline conditions. Ion distribution and Na+, K+, as well as K+/Na+ ratio in different tissues including root, leaf-3 blade, flag leaf sheath and flag leaf blade at three salinity levels (0, 100 and 200 mM NaCl, with supplemental Ca2+), and also the effects of salinity on yield and dry biomass were assessed using a factorial experiment based on a randomized complete block design with three replications. Salt tolerance in wheat species was related to lower Na+ accumulation in leaves. Different ranges of sodium accumulation vs exclusion were detected in roots and shoots. Sodium contents reduced from root to shoot and were found more in old leaves’ blades than in young flag leaves. Flag leaf sheath was identified as the main tissue for Na+ sequestration. Salt tolerant cultivars sequestered higher Na+ concentrations specifically in root, old leaves and in leaf sheath. Moreover these cultivars maintained lower Na+ concentrations along with higher K+/Na+ ratios in flag leaf blade than in other tissues. Differences in ion partitioning and lower Na+ accumulation and also a maintenance of higher K+/Na+ ratios, specially in flag leaf, young growing and expanded organs, would appear to be the most important mechanisms contributing to the improved salt tolerance in different cultivars.

Tall fescue is a cool season grass widely distributed and adapted to different environmental conditions of Iran. Superior seed-yielding potential of the plant is an important criterion during the seed reproduction phases of breeding new cultivars and as well under commercial seed production conditions. In order to evaluate germplasm and investigate the pattern of genetic variation of seed traits in the crop, 46 accessions (local and foreign cultivars) were made to germinate in greenhouse and were then transplanted into the field in the form of a replicated design. Significant differences were observed for all the studied traits indicating broad variation in germplasm. The range of genotypic coefficients of variability varied from 14.78 (for panicle length) to 42.04 (for seed yield) showing high rate of variation. The estimates of broad sense heritability for all traits were more than 60 percent except for flag leaf width and flag leaf length. Applying cluster analysis on the studied attributes, five groups of clusters were obtained. Entries and accessions with same country were clustered in the same groups. The results could be useful in choosing genetically distinct populations for improving high seed cultivars, synthetics, and development of useful populations for future breeding projects.

Low- temperature (LT) tolerance is an economic trait in winter wheat that determines the plants’ ability to successfully cope with below freezing temperatures. To identify the genomic regions associated with LT tolerance in hexaploid wheat, an F2:3 population was produced from crossing between winter type and tolerant parent, Mirnovoskaja 808 (LT50 = -20oC), and spring type and susceptible parent, Pishtaz (LT50 = -7oC). The LT50, temperature at which 50% of the plants are killed by LT stress, was an LT tolerance index of F3 families. An F2:3 genotypes demonstrated a continuous distribution of trait values (LT50 = -3 to -23oC), in agreement with the distribution expected for a polygenic and quantitatively inherited trait. The results of molecular analyses for parent were assessed using 170 SSR primer pairs and 22 AFLP primer combinations. Seventy five polymorphic marker loci consisting of 20 SSR markers and 55 AFLP markers were selected for screening of F2 individuals. Linkage map was constructed using polymorphic markers. The markers were assigned to six linkage groups. Single marker analysis and interval mapping of phenotyped F2:3 individuals revealed a quantitative trait locus (QTL) on chromosome 5B. This locus explained 11.3% of the LT50 phenotypic variations.

This investigation was conducted to compare the genetic variation of alfalfa Syn0 vs Syn1 and Ghara Yonja (parental cultivar) using seed storage proteins. Results of electrophoresis SDS-PAGE in seed storage protein, indicated that there are no significant differences between the means of distance intra-population obtained for Syn0 and Ghara Yonja (0.274 ± 0.0045, 0.270 ± 0.0081, respectively) as based upon simple matching coefficient. The mean of Syn1 genetic distance was significantly lower (0.251 ± 0.0081) than those of Syn0 and Ghara Yonja, indicating more similarity of intra-population in Syn1. Therefore, the results demonstrated the most within population genetic distance of Syn0 and Ghara Yonja in the inspected proteins (S1, S2, S3, total proteins). Information concerning genetic distance by protein marker along with other techniques such as morphological and DNA marker technique can be useful for an identification of suitable parents in hybridization breeding programs and as well in development of hybrids.

To determine the phenotypic diversity, eighty one ecotypes of Medicago sativa, collected from different areas of Iran, were evaluated. High variation was observed among ecotypes for all the evaluated characteristic. Results of correlation coefficient among traits indicated that the role of stem in forage yield is more pronounced than that of the leaf. Also the correlation between the "ratio of leaf to stem" and "wet forage yield" was observed as negative and significant. Therefore, the components most affecting forage quantity are plant height and stem weight. By Principal Components Analysis (PCA), the first three principal components with eigen values of more than 1 contributed 89.71% of the variability among the ecotypes. PC1 was positively correlated with leaf fresh weight, stem fresh weight, leaf dry weight and stem dry weight. The traits with the biggest values on PC2 were leaf/stem ratio of fresh weight and leaf/stem ratio (dry weight), whereas PC3 was positively correlated with plant height, and negatively with the 10% flowering date. The ecotypes were grouped into three clusters using cluster analysis. Clusters were clearly separated from each other by specific characteristics. Ecotypes obtained in this study, provide useful information for collection management and make these genetic resources more accessible to breeders

To evaluate symbiotic effectiveness and salt tolerance of Sinorhizobium meliloti strains, 50 rhizobial strains were isolated from root nodules of Medicago sativa cultivated in Tehran and Zanjan fields. Under N-free conditions, the symbiotic effectiveness of different Sinorhizobium meliloti strains of Bami cultivar were evaluated under greenhouse conditions using 50 Sinorhizobium meliloti strains, one uninoculated treatment with no nitrogen and two uninoculated treatments receiving 70 and 30 ppm Nitrogen. Shoot dry weight, nodule dry weight and nodule number recorded from two harvests were taken as the parameters of plant productivity. Salt tolerance of 50 rhizobial strains were evaluated in Yeast Manitol Agar medium involving different salt concentrations (0, 200, 400, 600 and 700 mM NaCl) according to colonies’ diameters. Significant differences were observed among rhizobial strains for shoot dry weight, nodule dry weight, nodule number and salt tolerance. Strain No. 30 was recorded as the most effective strain as indicated by the maximum values recorded for plant dry weight (1.31 gr/10 plants), while strain No. 6 was the least effective one because the plant inoculated with this strain was as poor in growth as control. The plants inoculated with other strains demonstrated higher shoot dry weight as compared with the uninoculated control. A Positive correlation between symbiotic effectiveness and shoot dry weight, nodule dry weight and nodule number was obtained. On the basis of analysis of correlation coefficient it was found that shoot dry weight, nodule dry weight and nodule number emerged as best criteria for selection of effective strains. Moreover, salinity slowed the growth of all strains. Strain No. 49 with 0.8 cm colonies’ diameter was able to grow well in the medium supplemented with 700 mM NaCl as compared with other strains. Strains with high effectiveness and high salt tolerance are promising for inoculant formulation in order to promote cultivation of alfalfa in saline soils. However, futher field experiments are needed to further evaluate improvement of M. sativa yield by inoculation under saline conditions.

Tagging of restorer genes for wild abortive (WA) of cytoplasmic male sterility was carried out by studying 10000 individuals from an F2 population of a cross between IR58025A × IR42686R. This study was primarily carried out to reduce the distance of the already known markers for RF gene. This F2 population was identified to be unique as four RF genes could be tagged to SSR markers on chromosomes 1, 7, 10, & 12. The RF3 gene on chromosome 1 was flanked on either side with RM443 and RM315 at a genetic distance of 3.3 and 20.2 CM, respectively. RF6 located on chromosome 10, was flanked with tightly linked SSR markers on either side at a genetic distance of 2.2 and 4.3 CM. Here a new molecular marker RM519 is reported to be linked to RF7 on chromosome 12 at a genetic distance of 7.8 CM. Moreover, RM6344 was confirmed to be linked to RF4 on chromosome 7 at a genetic distance of 12.2 CM. Tagging of closely linked flanking SSR markers to four RF genes will be extremely useful for breeders to have this source screened. In addition, pyramiding of each RF genes with other known sources will be an excellent provision for developing super restorers

To shorten the dormancy period of potato minitubers and to increase a tuber's capacity to be planted sooner after being harvested, an experiment was conducted at Pishtaz Tissue Culture Company in Karaj, using factorial experiment on the basis of a completely randomized design with three replications. The first factor was comprised of cultivars (Agria, Marfona and Burren), the second minituber weight (0.3, 0.7 and 1.5gr), and the third one being the methods of dormancy breaking using Carbon disulphide (Cs2, 25ml/m3), Gibberellic acid (GA3, 50mg/L) and control. Results of the study indicated that by applying GA3 in Agria and Marfona cultivars, 72 and 35 percent reduction, respetively, in the length of dormancy duration was observed, while the rate of dormancy period decreased through use of Cs2 in these two cultivars. Dormancy breaking treatments prompted the removal of apical dominance while increased the number of sprouts in minituber. Agria cultivar with an average of 2.62 sprouts per minituber bore the highest number of sprouts. By increasing the minituber weight, the length of dormancy duration decreased but the number of sprouts per minituber increased. Minitubers of 0.3 gr weight sustained the highest rate of decay.

To study drought resistance indices of eight potato cultivars and to determine the most tolerant variety, two experiments were conducted in the form of complete randomized block design with three replications (stress and non-stress conditions) in 2002. Seven indices, SSI, TOL, STI, MSTI, GMP, TOL, and MP were used to determine tolerant varieties. It was found that MP, STI, GMP, and MSTI were appropriate indices since they were correlated with yield in both stress and non-stress conditions. Using three dimensinal diagram, four defined groups of Fernandez were determined. The cultivars, Remarca, Ramus, Maradona and Agria were high yielding in both conditions and were classified in group A. The results of biplot diagram and MP, STI, MSTI and GMP indices, showed that Ramus and Remarca are the most tolerant varieties for drought stress conditions.

Crop production in arid and semi arid environments has been affected by drought stress. Forage production have important role on animal production in this area. In order to determine the effect of irrigation intervals on the yield and morphological characteristics of forage millet, sorghum and corn, an experiment was conducted in a split plot with a randomized complete block design with four replications. The main plots include irrigation intervals (one week (I1), two weeks (I2), three weeks (I3) and four weeks (I4)) and the subplots include three different forage species: Millet (M), Sorghum (S) and Corn (C). Dry matter, plant height, stem diameter, number of nodes, number of tillers per plant, leaf yield, stem yield, sheath yield, inflorescence yield and leaf/stem ratio were recorded. The results showed that there were significant differences between irrigation intervals for number of tillers per plant and leaf/stem ratio at the first harvest. In addition significant differences were observed between different forage species on all studied traits at the first harvest. Irrigation intervals and different forage species had significant effect on all traits at the second harvest. The highest and the lowest total dry matter yields (17.24 vs.3.41 ton/ha) in corn were obtained at one and four weeks irrigation intervals, respectively.

Although water deficiency has been seriously taken up as a subject in reducing crop production in arid and semi–arid areas, nevertheless little information has been published regarding its effects on seed quality. To evaluate the effects of irrigation regimes (full irrigation (control), irrigation until flowering stage, irrigation until doughing stage and irrigation until eight-leaf stage) on grain yield, yield components and some germination attributes in grain sorghum (Sorghum bicolor L. CV. Kimia), experiments were conducted at research farm and laboratory of Agricultural College, University of Tehran, Karaj, Iran in 2005. The experiments were arranged with a Randomized Complete Block Design (RCBD) and Completely Randomized Design (CRD) with four replications in farm and laboratory, respectively. The results idicated that irrigation levels had significant effects on grain yield and yield components (p<0.01). Control plants had more grain yield and yield components than the other irrigation levels due to the longer growth season and better use of environmental conditions. Withholding irrigation at eight-leaf stage decreased grain yield and its components. Nevertheless, qualitative attributes i.e. germination percentage, germination rate and seed vigor index were not significantly affected by irrigation levels. Thus, it doesnt seem that water deficiency would have a direct effect on metabolic activity of seed and consequently on seed quality. However, the foregoing treatments exhibited negative effects on seed yield.