مجله علوم گیاهان زراعی ایران
سال چهل و چهارم شماره 2 (تابستان 1392)

Low seed germination and seedling emergence is one of the main problems in saline areas. Seed priming technique has been known as a challenge to improve germination and seedling emergence under different environmental stress. The objective of this research was to evaluate the effect of seed priming with gibberellin، NaCl and water on seed germination and seed reserve utilization and germination of Mountain Rye (Secale montanum) seeds under salinity stress in the Seed Laboratory of Department of Agronomy and Plant Breeding، the University of Tehran، Karaj، Iran. Treatments were combinations of 5 levels of salinity stress (0، -4، -8، -12 and -16 bar) and 4 levels of seed priming and control with 3 replications. Results indicated that with increase in salinity stress، germination components such as germination percentage، germination index، mean time to germination، seedling dry weight of utilized (mobilized) seed، seed reserve utilization efficiency and seed reserve depletion percentage decreased، but seed priming showed lower reduction. The highest germination percentage (85. 3%) was obtained by hydro-priming and halo-priming in control conditions. The highest germination index (42. 2) and the minimum mean germination time (1. 02) were obtained from hydro-priming in control conditions. But in higher levels of osmotic pressures، the highest germination percentage، germination index and the minimum means germination time were obtained from priming with gibberellin. In all of the drought levels، primed seeds possessed more germination rate and seedling dry weight than control. Across salinity osmotic pressures، halo-priming had a greater weight of utilized (mobilized) seed reserve. The highest seed reserve depletion percentage and seedling dry weight were achieved from halo-priming and minimum osmotic pressure. Also، seed priming increased antioxidant enzyme activity during seed germination process. It is concluded that priming results in improvement in germination components of Mountain Rye in salinity stress conditions and increases the resistance of Mountain Rye to salinity stress in germination phase.

Plant growth is a result of cell division and cell enlargement. Expansins are proteins that mediate long-term extension of isolated cell walls and they play a variety of roles in plant cells. In this study the AtEXPB2 gene was over-expressed in Arabidopsis thaliana. The gene was isolated from genomics DNA of Arabidopsis and cloned into mediated vectors; pGEMT and pBI121 vectors. Transformation of Arabidopsis thaliana was performed by floral dip method using Agrobacterium-mediated. The produced seeds by infected plants were planted on MS medium containing kanamycin antibiotics، then، the tolerant seedlings were transferred to pot. Polymerase chain reaction was used to confirm the transgenic plants. RT-PCR analysis with AtEXPB2 specific primers showed that transferred gene is active and expressed. Obtained results illustrated that over-expression of expansin family genes may utilize for developing drought tolerant plants.

In order to evaluate the effects of ethephon and nitrogen fertilizer on sweet sorghum cv. Sofra، an experiment was conducted as split plot on a randomized complete block design with three replications at Agricultural Research Station of Isfahan University (Isfahan، Iran). Experiment was conducted with four nitrogen levels (0، 100، 200 and 300 Kg urea ha-1 from Urea with 0، 46، 92 and 138 Kg nitrogen ha-1، respectively)، as main plot and four ethephon concentrations (0، 800­، 1000 and 1200 ppm) as sub-plots. Preparing land، fertilizing and weed control with Tereflan herbiside at 1. 5 L/ha performed pre-sowing was conducted before planting. Every plot was 3×4 meter with 6 rows. The final populations of plants were 200،000 plants/ha and used seeds were 10 Kg/ha. Ethephon was sprayed on shoot at booting stage. Irrigation was performed every 10-12 days with flooding irrigation method. Plants were harvested at physiological maturity stage. Biological yield as well as stem yield was increased by increasing ethephon and nitrogen fertilizer. The highest biological yield (32. 53 t ha-1) was obtained at 1200 ppm of ethephon and 300 Kg ha-1 of urea application. The maximum amount of stem yield (30. 91 t ha-1) was obtained by application of the highest levels of nitrogen and ethephon (300 Kg urea ha-1 and 1200 ppm Ethephon). The highest harvest index (35. 20%) was obtained at control (no ethephon application) and the lowest (9. 70%) with the application of 1200 ppm of ethephon. The highest hundred grain weight (1. 91 g) was obtained with the application of 800 ppm of ethephon.

Knowledge about genetic diversity is an essential step towards conservation of genetic resources and developing further strategies for plant improvement. The objective of this research was to evaluate the agronomical and morphological traits and determine the level of variation within wild barley ecotypes especially for acclimation traits. In this study 188 ecotypes of wild barley (Hordeumspontaneum) were evaluated for qualitative and quantitative traits in a trial. Evaluated traits in this study included 24 agronomical, phenological, morphological and physiological traits which were measured in the field or laboratory. Different characters showed different levels of diversity based on descriptive statistics and Shannon diversity index. Flag leaf area, and flag leaf weight represented the highest diversity among quantitative traits based on coefficient of variation (CV) in qualitative traits, stem nod color and spike erectness were the most diverse traits. Cluster analysis based on morphological and agronomical traits and the origin of ecotypes were more in line with geographic data. Based on these traits, populations from cold climates were clearly distinguished from desert populations.

Cold stress during the beginning of the season usually causes damage to rice plants in the north of Iran. In this study، the expression of four genes namely OsP5CS2، OsTTP1، OsCOIN and OsLti6a، was studied in 14-day-old seedlings of a cold tolerance PR genotype and a cold sensitive Hashemi variety during cold stress (5°C for 24h) by means of Differential Display method. PCR products were quantified using Total Lab (Ver 1. 10) software and significant differences in gene expression were determined using Wilcoxon Test of SPSS. ver. 18 software. Different genes displayed diverse expression patterns in tolerant and susceptible plants under cold stress condition. The expression level of OsP5CS2 and OsLti6a genes increased in PR and suppressed significantly in Hashemi genotypes. Two other genes، OsTPP1 and OsCOIN، were significantly up-regulated in PR، but did not have detectable expression in Hashemi. The results suggest that the expression of studied genes changes in response to cold stress and so probably the expression changes of these genes could be applicable in breeding projects in order to develop rice cold tolerance.

To study the effects of different N fertilizer on berseem clover forage quality in an intercropping with basil، this experiment was conducted in Research Farm of College of Agriculture، University of Tehran in 2011. Experimental treatments were arranged as split plots based on a randomized complete block design with three replications. Different N fertilizers consisted of control (no N fertilizer)، 100% chemical fertilizer، biological fertilizer، and integrated fertilizer (biological fertilizer + 50% N fertilizer) were assigned to the main plots while different additive intercropping patterns of basil sole cropping (weed free)، basil sole cropping (weed contaminated)، berseem clover sole cropping (weed free)، berseem clover sole cropping (weed contaminated)، berseem clover + 25% basil، berseem clover + 50% basil، berseem clover + 75% basil، berseem clover + 100% basil were assigned to the sub plots. The results showed that the highest forage DMD (60. 07%) and WSC (11. 2%) were obtained from berseem clover + 100% basil when received biological fertilizer، and no fertilizer، respectively. The highest CP (30. 1%) was observed in berseem clover + 50% basil when received integrated N fertilizer. The highest ash content (8. 04%) was measured in berseem clover sole cropping (weed free) treatment when received 100% chemical fertilizer. The highest CF content was measured in berseem clover + 25% basil when received biological fertilizer. The highest berseem clover forage yield (in two harvests) (4833. 33 kg/ha) was obtained from berseem clover sole cropping (weed free) treatment when received 100% chemical nitrogen fertilizer. The highest Land Equivalent Ratio (LER=1. 573) related to berseem clover + 75% basil. The results concluded that the highest forage quality was obtained from berseem clover + 50% and 100% basil at integrated N fertilizer treatment.

The effects of arbuscular mycorrhizae on water use efficiency and some growth characteristics of maize were studied at three water regimes. An farm experiment was carried out using a split plot based randomized complete block design with 3 replications. Main plot was under water deficit condition (100%FC، 66%FC، 33%FC) and sub plot included application of two species of mycorrhizae، M1: Glomus mosseae، M2: Glomus intraradices and M0: no application of mycorrhizae. The results showed that the interaction effects of water deficit condition and application of mycorrhizae on water use efficiency، root colonization percentage، harvest index، LAI، CGR، statistically was significant. The highest of water use efficiency was detected under water deficit condition (33%FC) and Glomus mosseae and the least allocated to non application of mycorrhizae under without water deficit condition (2. 34 Kg/m3، 1. 23 Kg/m3، respectively). The results revealed a high correlation among root colonization percentage and water use efficiency under water deficit condition (33%FC) and application of mycorrhizae.

In order to study genetic variation and relationship between traits، 615 accessions of local bread wheat from wheat collection of National Plant Gene Bank of Iran were evaluated. Seeds of the accessions were planted in 2. 5 meter long rows in an observatory design and 17 agro-morphological traits were measured. Grain yield of 5 spikes، number of tillers and number of seeds per spike were of highest diversity among quantitative traits based on coefficient of variation. Among qualitative traits، glume color had the highest Shannon index. Two independent variables of number of seeds per spike and 100-seed weight were entered the model of stepwise regression determining 98% of grain yield of 5 spikes as dependent variable. The results of PCA indicated that the first five components comprised 63. 28% of the total variation in data. Based on coefficient of variables the components were designated as large seed size and high yield، yield components، biomass production، qualitative characteristics of spike and lodging resistance indices، respectively. The results of principlal component analysis distinguished accessions 200 (West Azarbayjan)، 763 (Gilan)، 835 (Lorestan) and 845، 846 (Isfahan، Both) as superior ones. The cluster analysis distinguished origins of the accessions in four groups. The result of this investigation showed a valuable variation in local wheat germplasm which could be exploited in breeding programs.

A 7×7 complete diallel cross experiment was performed to study the genetic relationships of grain yield and some agronomic traits in rice. Analysis of variance showed significant differences among genotypes for all traits. Results of correlation analysis showed that rice grain yield was positively and significantly correlated with BY (rp = 0. 81، rg =0. 55)، HI (rp =0. 35، rg =0. 79)، NP (rp = 0. 80، rg =0. 67)، PW (rp = 0. 78، rg =0. 83) and GSH (rp = 0. 32، rg =0. 81). Correlation between PH and GY (rp =-0. 09، rg =-0. 53) was negative at both type of correlation، but only rg was significant. The results of path analysis indicated that number of panicles (NP)، panicle weights (PW) and plant height (PH) strongly (92% of total variation) influenced grain yield (GY) as the predictor variables. Among these characters، PW reflected the highest direct effect (0. 73) towards grain yield; while minimum direct effect was indicated by PH (0. 15). NP and PW can be used as effective selection criteria for grain yield increase. Factor analysis indicated that five important factors accounted for about 81. 05% of the total variation among traits. The first factor assigned 23. 0% of total variation between traits and was significantly related with grain yield، its components and flag leaf area. Other factors accounted for 18. 65، 16. 20، 14. 20 and 9 percent of variation between traits. Applying genotype × trait (GT) biplot to the multiple traits illustrated that GT biplots graphically displayed the interrelationships among GY، PH، PW، HI، NP، GSH and BY. The results of this research indicated the use of NP and PW could be applied as a breeding strategy to obtain high yield rice cultivars.

Grain hardness is one of the most important quality characteristics of cultivated bread wheat (Triticum aestivum L.) that has main effect on milling yield، particle size، and water absorption of wheat flour. Kernel hardness is mainly controlled by Ha locus on the short arm of chromosome 5D in bread wheat. In this study، we have employed a multifaceted approach to investigate aspects of grain hardness in bread wheat cultivars with different origins. We conducted mechanical experiments by compression testing (CT) and near infrared reflectance (NIR). We used STS and SNPs primers by switch temperature PCR for identification of allelic variation in puroindoline genes for Pina-D1b، Pina-D1a، Pinb-D1b، Pinb-D1c، Pinb-D1d and Pinb-D1a in the germplasms. The results indicated that more than half of the cultivars were categorized as hard grains. Other cultivars showed grain softness. In general، the most frequent alleles were Pina-D1b and Pinb-D1b and after that Pinb-D1d allele have the most frequency in cultivars. Suprisingly Pinb-D1c allele was found in none of cultivars. Most of germplasms that showed hardness belong to warm and humid or warm and dry conditions. Coefficient correlation between CT and NIR، molecular results (genetically soft or hard) with NIR and CT (α<0. 0001)، were r =0. 74، 0. 87 and 0. 79، respectively. This study validated a series of recent STS-PCR and SNPs markers were employed for grain hardness. Our knowledge about the genetic and mechanical basis of kernel hardness could provide useful information for breeders in breeding programs of bread wheat.

To identify QTLs controlling grain yield and yield components، an F2 population consisting of 188 plants derived from the cross between two rice pure lines، Binam and Kadous، were grown in research field of Faculty of Agricultural Sciences، University of Guilan، Rasht، Iran، in 2008، and were recorded for 9 important traits related to grain yield. To construct linkage map، 85 marker of SSRs and 20 primer combinations of AFLP markers were studied، which 37 SSR markers and 10 AFLP primer combinations including 35 loci showed polymorphic bands between parents and were used for construction of linkage map. The total length of linkage map and the average distance between markers were 1445. 7 and 21. 57 cM، respectively. Using the composite interval mapping (CIM) method، 16 QTLs were mapped for studied traits including two QTLs for plant height both on chromosome 7، three QTLs for panicle length on chromosomes 3، 6 and 7، one QTL for 1000 grain weight on chromosome 3، two QTLs for number of panicle per plant on chromosomes 6 and 10، two QTLs for number of grain per panicle on chromosomes 3 and 9، one QTL for empty spikelet number per plant on chromosome 4، two QTLs for grain yield on chromosomes 3 and 6، two QTLs for days to 50% flowering on chromosomes 1 and 6، and one QTL for days to maturity on chromosome 6. Among these mapped QTLs، gy3 for grain yield، tgw3 for 1000 grain weight، ph7a for plant height، esnp4 for empty spikelet number per panicle and pl6 for panicle length controlled 20. 1%، 18%، 16%، 16%، and 15% of phenotypic variance، respectively، and were identified as major QTLs. The tight linked markers to these major QTLs can be used for marker assisted selection programs، but for the other markers، it is necessary to firstly construct the high density linkage map and then the markers near to major QTLs can be used to improve the studied population by marker assisted selection method.

Legumes are the second important source of food and consumption of legumes in Iran، similar to other countries، mainly due to consumer demand as human food. Common bean has first ranked among legumes in the world with an annual production of 20 million tons. In this research morphological and agronomic characteristics of 89 genotypes of Bean) Phaseolus vulgaris. L) were evaluated in an augment design under irrigated and drought stress conditions in research field of University of Tehran in Karaj in 2011. Relationships among different characteristics using multivariate statistical analysis methods were analyzed. The result of coefficient correlation analysis revealed significant positive correlation between yield and pod number، seed weight and seed number per pod under normal condition. Also there was a significant positive correlation between yield and pod number، seed weight and seed number per pod under stress condition. Regression analysis by stepwise method showed that number of pods، number of seeds per pod، seed weight، number of flower in normal condition and number of pods، numbers of seeds per pod and seed weight in stress condition have the most effects on yield. Factor analysis of 4 factors described almost 78. 5 and 77. 3 percent of total variance under normal and stress conditions، respectively.

Investigation of inheritance، mode of gene action and determination of effective breeding strategy for improvement of physiological and morpho-physiological traits specifically in drought stress conditions is very important. To determine the inheritance pattern and genetic parameters of quantitative characters in bread wheat (Triticum aestivum)، P1، P2، BC1، BC2، F1، F2 generations derived from crosses between Bezostaya×Bolani and Bezostaya×518 Line were evaluated under normal and limited water conditions using a complete Randomized Block design with four replications. Five traits including harvest index، grain yield، 100 grains weight، and peduncle and spike length were measured. Broad sense heritability means in normal water condition ranged from 0. 22 to 0. 83 ranged from 0. 19 to 0. 95 in limited water condition، while mean narrow sense heritability ranged from 0. 17 to 0. 71 and from 0. 07 to 0. 71 for normal and limited conditions، respectively. The results obtained from analysis of variance indicated that mean squares in generations were statistically significant for most of the traits so generation means analysis was performed for these traits. In Bezostaya×Bolani cross dominant gene action were mostly observed while in the Bezostaya×518 additive effects were seen، suggesting the application of early generation selection in first cross and the application of later generation selection in the second one. The genetic control of environmental conditions was similar and water stress did not alter genetic control.

Cold tolerance is an adaptative mechanism that plants in temperate climates require to survive and grow in suboptimal temperatures. Exposed plant to low temperature produces a myriad of measurable changes in biochemical characters that are often highly correlated with plant cold tolerance. A key element of cereal adaptation to cold is represented by the capacity for physiological adjustments that allows plants to retain growth and photosynthetic capacity at low temperature. Four bread wheat cultivars were planted to examine the frost tolerance and its relationship with accumulation of cryoprotectant and some of the biochemical changes in controlled environment and field conditions. Prolonged cold treatment accelerated the transition to reproductive development in winter and facultative cultivars but not in the spring one. Exposure to low-temperatures also enhanced frost tolerance of the winter and facultative wheats. Maximum frost tolerance was detected around the vernalization fulfilment. The highest frost tolerance potential was observed in the winter cultivar، where the longest cold treatments were necessary for fulfilment of vernalization response. Frost tolerance responses were highly correlated with chlorophyll concentration and proline accumulation in cultivars. Frost tolerance capacity was associated with reduced malondialdehyde content and hydrogen peroxide accumulation in cultivars. According to the chlorophyll fluorescence parameters، cold acclimation treatments in controlled environment condition had no effect on induction of cold stress symptoms. These data support the hypothesis that vernalization fulfilment is the critical point in the down-regulation of cold tolerance expression، and vernalization with cold acclimation pathways are interconnected in cereals to delay the spring floral-development allowing acclimation to low-temperatures and accumulation of cryoprotectants during the vegetative stage.

Abiotic stresses and lack of nutrients are one of the most important factors in reducing the crop yield. Vigorous and developed roots can facilitate uptake of water and nutrients more efficiently making it essential for enhancing the yield. Association mapping is currently one of the approaches for detecting quantitative trait loci (QTLs) influencing complex traits. This approach was used to detect QTLs for some root traits in a diverse collection of 100 winter barley (Hordeum vulgare). Association panel was sown in the greenhouse in a randomized complete block design with three replications and root dry weight، root volume، average diameter and average secondary roots were measured. Population was genotyped using 3964 SNPs having minor allele frequencies (MAFs) greater than 10 percent. The population was classified in two subpopulations based on spike row number. In the whole genome، average LD was observed to decay at 4cM. Using a mixed linear model with kinship for controlling spurious LD effects، we found a total of 15 significant marker-trait associations. SNP_2981 was associated with the number of secondary roots at maximum -Log P. Comparative study with previously mapped agronomic traits showed that several QTLs of root traits were related to the characters such as yield، kernels per spike، heading date، lodging and plant height.