مجله علوم گیاهان زراعی ایران
سال چهل و چهارم شماره 4 (زمستان 1392)

Genotype by environment interaction is one of the most important subjects in crop improvement، so that different statistical measures have been proposed to estimate this interaction. In the present study، nine varieties and hybrids of spring rapeseed were evaluated in five warm dryland areas including Sarpol-e-Zahab، Gonbad، Gachsaran، Pol-e-Dukhtar and Masjedsoliman in two growing seasons 2002-03 and 2003-04. Varietal trials were conducted in a RCBD with three replications in rain-fed conditions. The analysis of stability of the varieties was based on nonparametric statistics. Results showed that based on four nonparametric measures Si (1)، Si (2)، Si (3) and Si (6)، three varieties including Regent، Goliath and Global were selected through their seed yield were less than the overall mean. Use of three nonparametric measures NPi (2)، NPi (3) and NPi (4) led to the selection of two varieties Goliath and Regent with yield less than the overall mean. NPi (1) recognized two varieties Kristina and Goliath as yield stable genotypes which yield of the first one was more than overall mean and the second one was less than that. All eight nonparametric measures showed negative or non-significant correlation with yield. RI and Li measurements selected four genotypes، including Hyola401 and Quinta with yield more than overall mean and Global and Goliath with yield less than the overall mean. Calculation of rank sum measure revealed that selection of stable genotypes based on this measure led to genotypes with a yield higher than the overall mean. In this study rank sum measure was the best method among different non-parametric measures. On the base of this measure Quinta، Shiralee and Option500 selected as seed yield stable genotypes.

The time of duration of plant developmental stages could have an effect on crop yield and adaptation in a specific environment. The aim of this study was to evaluate the phenological behavior in a wide range of wheat cultivars and their relation with adaptation and potential of crop production in a specific climate (semi-arid and cold). By using a simple lattice design with three replications in irrigated condition 36 genotypes of wheat were evaluated at the university of Tehran research farm during 2010-2011 growing season. Different stages of development، including emergence، stem elongation، booting، heading and anthesis were recorded. At maturity، grain yield، 1000 kernel weight، number of kernels per spike، biological yield، and harvest index were measured. Dry matter production was determined at the end of the cool season. Mean separation was accomplished with Duncan test at the 5% level of significance and correlations were determined between traits. The results showed that cultivars with similar date of anthesis showed a different duration of stem elongation due to shortening of previous growth stages. Duration of booting to anthesis (floret death stage) effected on grain number. In the present experiment، late flowering significantly reduced yield. Cultivars with higher dry matter production at the end of the cool season entered earlier to reproductive stage and had more tillers.

To determine the optimum weed management method and plant population density on chickpea yield، a split plot experiment based on RCBD with four replications was carried out at the University of Tehran Research Farm (located in Karaj) during 2010-2011. The Main factor consisted of nine treatments including: 1. Trifluralin pre-plant، 2. Pendimethalin pre-plant، 3. Complete weeding، 4. Imazethapyr post-emergence، 5. Mechanical weeding، 6. Imazethapyr pre-emergence، 7. Pyridate along with mechanical weeding، 8. Pyridate post-emergence، 9. Control (no weeding) and sub factor included of three crop densities of 35، 45 and 55 plants/m2. The predominant weeds were Chenopodium album L.، Amaranthus retroflexus L. and Amaranthus blitoides L. Results revealed that weed management had a significant effect on weed population and dry mass reduction. At the end of the growth period after hand weeding treatment، Pyridate + mechanical control، pre-emergence Imazethapyr and pendimethalin were the most effective treatments based on weed dry mass reduction، but due to weed population decline at this time، after hand weeding treatment، pendimethalin was the most effective and produced the highest chickpea grain yield. Chickpea population densities of 55 and 45 plants/m2 produced the highest grain yield and simultaneously reduced the weed population and dry mass as compared with 35 plants per m2، significantly. Therefore، application of both pendimethalin and use of 45 chickpea plants per m2 were the effective weed control method and produce a higher grain yield at a similar condition to this experiment.

Investigation of physiological responses to water deficit in sesame (Sesamum indicum L.) genotypes can help to identify effective mechanisms of plant resistance to stress. Therefore, chlorophyll content, proline, soluble carbohydrates, net photosynthesis rate, stomatal conductance, maximum quantum efficiency (fv/fm), plant height and shoot dry weight in a complete block factorial pot experiment with three replications were conducted at the College of Agriculture, Isfahan University of Technology, Isfahan, Iran. Four levels of irrigation included irrigation when the soil, water potential of pots was approximately -0.2 MPa (control) =W1, -0.5 MPa (low water deficit) =W2, -1.0 MPa (intermediate water deficit) =W, and -1.4 MPa (severe water deficit) =W4 and 12 sesame genotypes. The highest reduction in chlorophyll content (46%) in the severe water deficit and the genotype was Non-branching Naz. Net photosynthesis rate, stomatal conductance, total chlorophyll content and maximum quantum efficiency (Fv/Fm) were decreased by 43.8%, 39.6%, 46.6% and 17.7%, respectively, compared to control. Proline and soluble carbohydrate content of sesame genotypes was increased by 129.8% and 35.6%, respectively, under severe water deficit compared to control. Plant height and plant dry weight decreased with severe water deficit by 21.5% and 52%, respectively, due to severe water deficit. Severe water deficit, with negative effects on photosynthetic systems by limiting stomatal conductance and reduce the net photosynthesis rate, was due to the decrease in maximum quantum efficiency. Decrease in maximum quantum efficiency on one side and the chlorophyll content reduction in other side, reduces the photosynthetic production and reduce the yield (dry matter) per genotypes.

Salinity and drought are two major abiotic stresses that affect rice (Oryza sativa L.) production in worldwide. Salt and drought tolerance and high seedling vigor of rice is one of the important traits in the establishment of seedling in direct planting system and saline and drought environments. In this research، the mapping population of F2:4 families derived from the cross between local variety Gharib (salt and drought tolerant) and improved variety Sepidroud (salt and drought sensitive) was used for identification of molecular markers linked to salt and drought tolerant genes at Faculty of Agriculture and Natural Resources، Gonbad Kavous University and Biotechnology Laboratory، Guilan University in 2010-2012. A linkage map of 2475. 7 cM with an average interval of 10. 48cM was constructed using 105 AFLP markers and 131 SSR markers. QTL analysis using composite interval mapping detected ten QTLs for germination stress index، vigour seed index، traits germination rate، germination percentage، radicle length، plumule length، coleorhiz length، plumule dry weight، coleoptile fresh weight and seedling dry weight under drought stress conditions of either mannitol (8) and salinity (8 dS). Among the identified QTLs، seven QTLs associated with drought stress، and seven QTLs associated with salt stress، explained over 15% of the total phenotypic variance of traits. It seems that these QTLs can be the major QTLs controlling traits of drought and salinity tolerance and with more confidence they could be used in marker assisted selection program.

To assess heritability، gene action and combining ability of rice varieties for characteristics related to grain appearance and cooking quality، the progenies derived from direct and reverse crosses of the 6×6 complete diallel together with their parents included Hashemi، Hassani، Shahpasand، Kadous، Vandana and IR36 were grown in a randomized complete block design with three replications in the research field of the Rice Research Institute of Iran (RRII)، Rasht، Iran، during 2011 cropping season. The studied traits were included amylase content، gelatinization temperature، grain length، width and thickness and grain length to width ratio (grain shape). Results showed that mean squares of both general and specific combining ability for all studied traits except grain width were significant that indicate both additive and non-additive gene effects have an important role in the expression of the traits، but the role of the additive gene effects was more important than the non-additive gene effects. The results of graphical analysis of Hayman showed that the share of additive variance (D) of grain length، width and thickness، grain shape and gelatinization temperature was greater than dominance variance (H1). Genetic analysis of these traits represents the role of partial dominance gene action in controlling the traits that indicate the potential of selection for these traits. The role of partial to complete dominance gene actions were observed in the controlling amylase content، so using selection and hybrid seed production can be considered by reformers to improve this trait. Thus، to improve the grain appearance and cooking quality in the studied population، selection method can be firstly used to increase favorable genes and finally hybridization method is performed to use the dominance gene effects. Comparing different methods of Griffing in evaluation of combining ability of varieties showed that using parents in diallel analysis probably cause a bias in the results of combining abilities. So using third and in the absence of maternal effects fourth method of Griffing’s، in addition to fewer treatments and expenses، are applied and better methods in assessment of combining ability.

In the absence of herbicides، cover crops play an important role for weed management in organic than in conventional farming. Therefore، in order to evaluate the effects of cover crop management and plant density of buckwheat (Fagopyrum esculentum) as cover crop on weed suppression، a field experiment was conducted at the Research Farm of University of Zanjan، during the growing season of 2011. The experimental design was a randomized complete block design on the factorial basis with three replications per treatment. The experiment included cover crop management (dead mulch and living mulch) and cover crop plant density (0، 36، 78، 100 plants m-2). A plot also assigned as weed free check (sunflower monocropping). It was observed that weed biomass significantly affected by buckwheat density (P≤0. 01). However، weed biomass did not affected by cover crop management. In other words، dead or living mulch had similar effects on weed biomass production. Buckwheat as living and dead mulch reduced weed biomass up to 91% and 88%، respectively، compared with no cover crop plots (the density of zero). There was also a negative correlation between cover crop density and weed biomass. Moreover، sunflower grain yield was also reduced with increasing buckwheat density from 36 to 100 plants m-2. Buckwheat at the density of 36 plant m-2 significantly decreased the weed biomass and saved grain yield، indicating that using this plant as cover crop can be more cost-effective and more environment-friendlier than chemical weed control in sunflower.

Potato virus Y (PVY) and potato leafroll virus (PLRV) are two major viruses which reduce 10-90 percent of yield and quality of potato tubers. In the present study، the efficiency of different methods، including meristem culture، thermotherapy followed by meristem culture and electerotherapy followed by meristem culture in two cultivars (Agria and Marfona) infected by PLRV or PVY were evaluated. Each virus elimination method performed as a factorial experiment basis on a randomized complete block design and for virus elimination methods the combined analysis was used. The percentage of virus elimination was determined by ELISA and RT-PCR، respectively. The percentage of plant regeneration and some agronomic traits، including stem length، stem diameter، shoot fresh weight، number of nodes، internode lenght، number of minitubers، tuber weight and total tuber weight were investigated in virus-free seedlings. The interaction effects were significant for the percentages of plant regeneration and virus elimination method. The highest rate of plant regeneration was obtained in meristem culture method (70%). The highest rate of virus elimination was observed in thermotherapy followed by meristem culture (88%). In this study، three-way interaction of cultivar، virus and method for virus elimination efficiency was significant and the highest virus elimination efficiency (64%) was obtained by the interaction of thermotherapy followed by meristem culture، PVY، for cultivar Marfona. The three-way interaction was also statistically significant for the most agronomic traits. The results of the correlation coefficients، regression and path analysis of yield (number of minitubers per plant) and its related traits showed that the number of nodes per shoot had the highest impact on the number of minitubers in virus-free seedlings.

Abiotic stress such as cold and drought has adverse effects on plants growth and development. Abiotic stress resistance is one of the most important goals in plant breeding. This goal can be achieved through transcription factor gene transfer to plants. Recent studies show many successes in improving abiotic stress resistance by use of transcription factor gene transfer. The objective of the research was to clone wheat alpha isoform of WDREB2، effective abiotic stress responsive element، in suitable expression vector، and its transfer to tomato in order to improve cold stress resistance. The gene was cloned in expression vector pBI121، and transferred to tomato through Agrobacterium tumefaciens C58 strain. In order to admit transformation، DNA extraction and PCR with specific primer was done on transgenic and nontransgenic tomato plants. Verification of WDREB2 expression was done by RT- PCR after RNA extraction and cDNA synthesis. Bioassay test of transgenic plants under cold stress treatment was performed. Phonotypical comparison between transgenic and normal plants under cold stress confirmed cold stress resistance of transgenic lines.

Soil and water salinity are the main agricultural problems in arid and semi arid areas in the world and Iran. In order to investigate salinity tolerance of Kochia، two experiments were conducted in a completely randomized design with four replications، seven levels of salinity (0، 10، 20، 30، 40، 50 and 60 dS m-1) and two growth stages (planting and early seedling) with gradually salinity application. Results showed that the reduction of root dry weight، root volume، membrane stability index with increased salinity at planting were more than increased salinity at early seedling stages. Relative water content increased with increasing salinity levels in both experiments. Proline، osmotic potential، catalase، glutathione reductase، DPPH - radical scavenging activities and total phenol increased with increasing salinity levels. Sodium concentration and sodium to potassium ratio in shoot and root increased with increasing salinity levels. Generally، kochia survive and tolerate 60 dS m-1 of salinity and salinity tolerance in early seedling was higher than the planting stages.

To investigate the effects of sowing date on yield and quality of six forage maize cultivars in Rasht region، a field study was conducted in 2010. The experimental design was a randomized complete block using a factorial arrangement with three replications. Treatments consisted of four levels of sowing date (22 May، 3، 15 and 25 June)، and six maize cultivars (SC 260، DC 370، SC 500، SC 647، SC 700 and SC 704). Results showed that the sowing date had significant effects on forage yield and quality traits. Cultivars had also significant effects on forage yield، protein yield، water soluble carbohydrate percentage، and ash percentage. Results indicate that sowing date of June 15th and cultivar SC 700 for traits including forage yield (dry 28220. 6 kg ha-1 and fresh weight 87017 kg ha-1)، dry matter digestibility (72. 69%)، ADF (11. 98%)، water soluble carbohydrate percentage (32. 97%)، and total ash (6. 81%)، were better than other cultivars and sowing dates.

Drought stress is considered as one of the main important factors reducing field crop yield، thus leading researchers to study the related physiological characteristics may reduce drought effects. This experiment was conducted in research farm of seed and plant improvement institute (SPII) in Karadj، Arak and Jolgeh Rokh for three cropping seasons (2008-2011) to evaluate drought tolerance of bread wheat genotypes through irrigation cut-off from anthesis and 20 days after anthesis comparing to full irrigation in 19 winters and facultative wheat genotypes using RCBD in split plot arrangement with 3 replicates. The main and subplots were irrigation regimes and wheat genotypes، respectively. The statistical analyses of coefficients of correlation، stepwise regression، path analysis، factor analysis via principal component analysis were done to discard insignificant or less effective and to consider the most important characteristics directly or indirectly influencing grain yield. Path analysis was only done on independent variables suggested by the stepwise regression model. The final study of the relationships among the variables was according to the results of principal component analysis and varimax rotation. The results showed significant correlations of spike and biomass weight (0. 86**)، biomass weight with seed number per spike (0. 89**) and also seeds number per spike with seed weight per spike in normal condition. The number of seeds per spike had significantly positive correlation with spike and biomass weight characteristics (0. 92**). In S2 condition the highest correlation attributed to grain yield with seed number per spike (0. 79**). In this condition، there was a significant and positive correlation between seed number per spike and seed weight per spike (0. 88**). In S1 condition significant and positive correlations of grain yield with TKW (0. 76**) and harvest index (0. 78**) and also with seed number per spike (0. 69**) were observed. The highest direct effect of seed number per spike was seen in all three conditions and stepwise regression also showed the same result. Further path analysis results showed that yield components of seed number per spike، seeds weight per spike and TKW incorporated in the path analysis model as the potentially effective characteristics in wheat grain yield improvement program in normal and terminal drought conditions. Due to direct and indirect effects of seed number per spike on grain yield، it can be considered as an effective characteristic in the wheat breeding program. Principal component analysis results confirm that boosting 1st factor related characteristics of yield and yield components have the largest effect on grain yield and should be considered as the best selection criteria for improvement.

General and specific combining ability of some rice lines and cultivars with IRRI sources were determined using the line × tester procedure (5 pure lines were crossed with 4 local cultivars as tester). Parents and their progenies were planted in a randomized complete block design with three replications in the research field of Iran Rice Research Institute. Traits such as yield and its components were recorded. Analysis of variance showed significant differences among genotypes for all traits but panicle/plant. Line x tester analysis showed that lines effect was significant for all traits at 1% level and the tester’s effect was significant for all traits but seeds/panicle at the 1% level. The significance of the line × tester effect in all of the traits except plant height، flag leaf width and seed length indicated that lines’ response was different depending on the tester they were crossed to various testers. The line PR 27137-CR 153 (with an average yield of 5. 045 t/h) had highest GCA and the cross Hassani × IR 73688-57-2 (with an average yield of 5. 613 t/h) had the highest and significant SCA. The amount of additive and non-additive variances varied in different traits resulting in a different heritability estimate. Narrow-sense heritability for most of the traits was low. The highest narrow-sense heritability was observed for the seed length (0. 27).

To study the effect of soil moisture variation on growth and steviol glycosides contents in Stevia (Stevia rebaudiana B)، a potexperiment based on a randomized complete design with four treatments and three replications were conducted in a greenhouse of Agricultural Biotechnology Research Institute of Iran (central region، Isfahan)، in 2012. Experimental treatments applied as a combination of visual symptom appearance in plant (normal to severe wilting) and soil moisture. So، treatments irrigated in 19. 1، 15. 1، 11. 9 and 9. 1% of soil moisture content (w/w) that are created in greenhouse situation with irrigation of 3، 6، 9 and 12 days interval، respectively. Results showed that soil moisture reduction up to 9 days irrigation interval had no effect on plant height and leaf dry weight، but plant growth significantly reduced in 12 days irrigation period. Maximum of harvest index obtained in 6 days irrigation period (51. 36%). Soil moisture reduction caused significant increment in stevioside and dulcoside A، but not affected the rebaudioside types (A، F and C). Total steviol glycosides increased with the soil moisture reduction and plant grown with 3 days irrigation interval had minimum steviol glycosides. Stevioside was highest in steviol glycosides in all treatments. Plants grown under 6 days irrigation interval had the maximum of steviol sugar yield. Totally، the results of this experiment showed that leaf dry weight decreased with decline of soil moisture content (below 11. 9 w/w)، but steviol glycosides content had significant increment. The highest of harvest index and steviol sugar yield were obtained in the 6 days irrigation interval. Although، steviol glycosides content increased with the soil moisture reduction، it means that intensify of drought stress more than 6 days irrigation interval (reduction of soil moisture content below the 15. 1 w/w) caused downfall of Stevia yield due to significant reduction of leaf yield and steviol sugar yield in severity of drought stress.

Detopping in some plants reduces vegetative growth and increases transporting of photosynthate materials to specific sinks such as seeds. To study the effects of detopping removal and plant density on yield and yield components of faba bean (Vicia faba L.)، an experiment was carried out as a factorial arrangement based on a randomized complete block design with three replications at farm research of Gonbad University in 2009-2010. The detopping factor performed at before flowering، beginning of flowering، pod setting and none removal. Plant density included four levels of 4، 6، 8 and 10 plants m-2. Results showed that the effects of top removal and plant density on number of pods/plant، number of seeds/pod، number of seeds/plant، 100-seed weight، plant yield، seed yield/ha، pods coat weight and seeds weight/pods coat weight were significant at the 1% level. Maximum number of pods/plant and pods coat weight belonged to top removal at pod setting stage; whereas the maximum number of seeds/pod، 100-seed weight and seeds weight/pods coat weight belonged to top removal at before flowering; number of seeds/plant، plant yield and seed yield/ha obtained from top removal at flowering. The density of 4 plants m-2 had the highest number of pods/plant، number of seeds/pod، number of seeds/plant، 100-seed weight، plant yield، pods coat weight and seeds weight/pod coat weight، whereas the highest seed yield/ha belonged to the treatment of 10 plant m-2. This study showed that the best time for detopping of faba bean was at the beginning of flowering and optimum plant density was 10 plants m-2 that produced the maximum yield.