هاشم امین پناه

Intercropping and plant growth-promoting rhizobacteria improve sustainability of agro-ecosystems. To evaluate the effect of Azotobacter (Azotobacter chroococcum) inoculation on productivity of a peanut /maize intercropping system, a two-year study was design as a randomized complete block in a factorial arrangement with three replicates at Astaneh-ye Ashrafiyeh, Guilan province. Factors were Azotobacter inoculation [control (non-inoculated) and inoculated with Azotobacter chroococcum) and intercropping pattern (Sole cropping of peanut and maize, additive intercropping pattern at three levels (100% peanut + 100% maize, 100% peanut + 50% maize, and 50% peanut + 100% maize), and replacement intercropping pattern at three levels (50% peanut + 50% maize, 67% peanut +33% maize, and 33% peanut + 67% maize). Results showed that gain yields of maize and peanut were significantly affected by Azotobacter inoculation and intercropping pattern. Inoculation with Azotobacter chroococcum significantly increased grain yields of peanut and maize by 10% and 16%, respectively. Maximum and minimum of land equivalent ratio (LER) were observed at 100% peanut + 50% maize and 50% peanut + 50% maize, respectively and inoculated intercropped plots with Azotobacter chroococcum had 12-16% grater LER that non-inoculated ones. Regards to impossibility of mechanical weed control by machines in additive intercropping patterns, to obtain the highest productivity in maize/peanut intercropping system, intercropping pattern of 100% peanut + 50% maize along with Azotobacter application will be suitable in fields with low weed density. Otherwise, based on LER and grain yield of peanut, the intercropping pattern of 67% peanut + 33% maize along with Azotobacter application will be suitable.

A two-year field experiment was conducted in flooded rice fields of Islamic Azad University, Astara Branch in 2018-2019. Experiments in the form of randomized complete blocks in two places (in saline and normal soils) and experimental treatments including inoculation with plant growth-promoting microorganisms at five levels (Pseudomonas putida; Pseudomonas fluorescent; Arbuscular mycorrhiza; P. putida + P. fluorescent + mycorrhiza; as well as a non-inoculation treatment as a control). The results of the combined analysis showed that the effect of microorganisms and soil salinity on sodium (Na+) and potassium (K+) concentrations of roots, stems, young and old leaves, and yield and yield components were significant. Soil salinity increased Na+ concentrations in roots, stems, young and old leaves, while microorganisms significantly decreased Na+ concentrations in all organs except roots and increased K+ concentrations in them, especially in young leaves. Also, microorganisms increased rice grain yield in normal soil by 34% -25% in the first year and 67% -21% in the second year and in saline soil by 45% -22% in the first year and 67% -45% in the second year compared to the treatment. Witnesses increased. Among microorganisms, except P. putida, other microorganisms showed significant superiority over control in most of the measured traits. In general, P. fluorescens + AM fungi + P.putida inoculation is recommended for rice cultivation in saline soils of northern Iran.

Changing rice cultivation system from puddled-transplanted rice production to direct seeded rice greatly reduces labor and crop production cost. A field experiment was conducted at Rice Research Institute of Iran-Rasht in 2018 as split plot based on a randomized complete block design to evaluate the effect of seeding date and planting method on growth and grain yield, cv. Hashemi, in direct seeded rice. Main plots included seeding date (1, 8, 15, 22, 29 May, 5 and 12 June) and sub plots were planting method (broadcast seeding, row seeding and hill seeding). Moreover, transplanting plots were included to the experiment as control treatment. Analysis of variance showed that seeding date had significant effect on paddy yield, but planting method and the interaction effect between them had no significant effect on paddy yield. Maximum paddy yield were recorded at the dates of 1 and 15 May (4414 and 4325 kg ha-1, respectively). Paddy yield was significantly reduced when seeding date delayed, as grain yield reduce by 41, 43, and 70% at the seeding dates of 22, 29 May, and 5 June compared to the seeding date of 1 May. There was no significant difference in paddy yield between direct-seeded (4295±215 kg ha-1) and transplanting (4414±184 kg ha-1) production systems. Moreover, seeding date and planting method had no significant effect on weed biomass. In general, results revealed that optimum paddy yield in direct seeding was recorded at the seeding date of 1–15 May.

Barnyardgrass is the most important and most abundant weed of paddy fields in Iran and chemical control (butachlor) play a major role in its management. The usage of butachlor in most rice growing countries is restricted or prohibited due to health and environmental hazards, and its production and trade in Iran will be banned in the next future. Due to the dangers posed by widespread usage of herbicides integrated weed management with more weed competitive varieties to reduce herbicide dependence is taken into consideration. This study aimed to study the efficacy of some new herbicides for introducing as a substitute for butachlor and also to investigate the effect of rice cultivar on herbicide performance.

The experiment was conducted as a factorial experiment based on randomized complete block design with three replications at Rice Research Institute of Iran-Rasht in 2018. Factors included rice genotypes (Hashemi, Khazar and Line 203 “Line”) and herbicide type (recommended dosage of butachlor, clomazone, pendimethalin and flucetosulfuron herbicides). Moreover, hand weeded and weedy plot were included to the experiment as controls.

The barnyardgrass biomass and rice yield were affected by rice genotype, herbicide type and their interaction. The barnyardgrass biomass in weedy control in Khazar, Hashemi and Line cultivars was 227.7, 246 and 334 g m-2, respectively, which in Khazar and Hashemi cultivars was 57% and 16% higher, compared with line respectively, indicating different ability of cultivars to inhibit the barnyardgrass growth. The reduction in grain yield of rice in weedy control in Khazar, Hashemi and Line cultivars was 63, 74 and 87%, respectively, compared to hand weeded control. More reduction in line grain yield despite more inhibitory effect on barnyardgrass is due to late maturing of this line and longer period of interference with barnyardgrass. The dry weight of barnyardgrass in plots treated with pendimethalin was similar to or less than the treatments treated with butachlor, flucetosulfuron and clomazone. Also rice yield in all genotypes in plots treated with pendimethalin herbicide was not statistically different from that in the plots treated with butachlor and hand weeded control treatment. The good efficacy of pendimethalin in controlling barnyardgrass and producing grain yield similar to butachlor and hand weeded control indicates the potential of this herbicide to be introduced as a replacement for butachlor. Also, the yield of line in plots treated with clomazone and flucetosulfuron was statistically similar to the yield of hand weeded control plot, while the yield of Hashemi and Khazar cultivars in plots treated with the two new above mentioned herbicides were significantly lower than hand weeded control. These results indicate the competitive advantage of line over Hashemi and Khazar cultivars in barnyardgrass control.

In the last decade, more than 95 percent of paddy fields in the north of the country have been treated with butachlor herbicides for chemical control of barnyardgrass. In recent years, concerns have been raised about the adverse effects of butachlor on the health of the community and the environment, and the herbicide will be removed from the countries authorized pesticides list in the near future. Due to the good performance of pendimethalin in barnyardgrass control and the high grain yield in treated plots with this herbicide, it could be introduced as a butachlor substitute for barnyardgrass control in Iranian rice fields, although the cultivation of new competitor cultivars will also contribute to be successful.

Drought is one of the most important factors limiting crop yield and foliar application of phytoprotectants is an important management strategy for increasing crop resistance to drought stress. This research was conducted at Rice Research Station of Tonekabon, Iran, in 2018 by using a split-plot based on a Randomized Complete Block Design (RCBD) with three replicates. Main plots were irrigation regimes [common irrigation (control), and irrigation withold from tillering stage (45 days after transplanting)] and subplots were foliar application of phytoprotectants (control, selenium, silicon, ascorbic acid, salicylic acid). The results showed that irrigation withold from tillering stage caused a 29.3% reduction in grain yield in the absence of foliar application. Drought stress decreased plant height, tiller number and 1000-grain weight by 15.5, 14.95 and 3.34%, respectively. Drought stress increased proline content by 115%. Also, in the irrigation withold from tillering stage, foliar application with selenium, silicon, ascorbic acid, and salicylic acid led to increase in floret fertility percentage and 1000-grain weight, thereby increasing the grain yield up to 32.6, 31.9, 35.3 and 33.3%, respectively, compared to no foliar application (control). In general, the results of this study showed that foliar application of phytoprotectants can reduce the adverse effects of drought stress and improve the grain yield of rice under drought stress conditions.

Rice is one of the major global food crops, which is the second crop in Iran after wheat. Rice grain yield is strongly influenced by environments and breeders often determine the stability of high yield genotypes across environments before recommending a stable cultivar for release. Genotypial adaptability to environmental fluctuations is important for the stabilization of crop production over regions and years. The purpose of this study is the distinguishing the superior genotypes in terms of grain yield and yield stability in nine selected rice lines from preliminary yield test.

The nine selected lines obtained from crosses beteen IRRI lines and Iranian improved and landrace vareties and resulted from preliminary yield test of 2008-2009 cropping season, along with control cultivar Shiroudi, were evaluated in a randomized complete block design with four replications in three regions including Tonekabon, Amol and Gorgan during three cropping seasons of 2009-2012. Stability analysis were performed with environmental variance (S2i), coefficient of variation (CVi), Shukla's variance (2i) and deviation variance (S2), Wrick equivalence (Wi), regression coefficient (bi), coefficient of determination (R2), Eberhart-Russell analysis of variance, yield sability index (YSi) and nonparametric methods, , , TOP and mean and standard deviation of rank.

Simple analysis of variance showed genetic differences among genotypes. Combined analysis of variance was performed after Bartlett test and not significant of it and assurance of uniformity of experimental errors. The combined analysis of variance indicated the significant effects of genotype, year, location and interactions of genotype × year, genotype × location and genotype × year × location. Comparison of means of showed that genotypes 2, 5 and 4 were in the same group with 6565.1, 6495.1 and 6450.1 kg.ha-1, respectively and produced the highest grain yield. Analysis of variance indicated significant effect of genotype on plant height, tiller number, unfilled grain number, filled grain number, panicle length and 1000 grain weight. According to parametric stability G5, G3, G10 and G2 were stable genotypes. YSi indicated G2, G3, G4, G5 and G10 had the highest grain yield stability. Also, according to the TOP nonparametric index, genotypes 4, 10, 1, 2 and 5, and based on two criteria and , genotypes 1 and 5 were the most stable genotypes. Correlation between indices showed the use of a number of them is not very necessary and some of them that have a high correlation with each other can be removed from the analysis.

Overall, genotype 5 was stable in almost all stability methods and 2, 3, 4 and 1 in some of the methods. Therefore, Ggenotype 5 [Number 16 from IR64669-153-2-3 (A8948); (4Surinam × Deilamini)] due to its higher grain yield than all genotypes except genotype 2, low plant height, higher number of tillers, filled grain and 1000-grain weight, as well as more uniform plants and better grain types, can be selected as the superior genotypes and evaluated in field trials.

Field experiment was conducted at Rice Research Institute of Iran, Rasht in 2017 to study the efficacy of some new herbicides in controlling the weeds of rice fields in comparison to current herbicides. Treatments were included: triafamone+ethoxysulfuron (Council), flucetosulfuron (Zechor), pyrazosulfuron-ethyl 10% WG (Saathi), Pyrazosulfuron-ethyl 75% WG (Piroz) (all in recommended and two times the recommended dosage) and recommended dose of current herbicides, butachlor (Machete)+bensulfuron-methyl (Londax) and pretilachlor (Rifit)+bensulfuron) plus weedy and hand-weeded control. Results showed that new herbicides, up to two times the recommended dosage, did not have any phytotoxicity symptoms on rice while recommended dosages of common herbicides led to 5-15% phytotoxicity. The efficacy of new herbicides (flucetosulfuron and triafamone+ethoxysulfuron) in weed controlling was similar to common herbicides, while the efficacy of both pyrazosulfuron formulations was not acceptable. Overall, the results of this study showed that two new herbicides (flucetosulfuron and triafamone+ethoxysulfuron), due to high efficiency in controlling a wide range of weeds has the capacity to be replaced the current herbicides (butachlor and pretilachlor) that are going to be eliminated due to environmental concerns in future.

A field experiment was conducted in Amlash, Guilan province to evaluate the effect of phosphorus rate (P), Rhizobium phaseoli inoculation and nitragin biofertilizer on growth and yield of common bean (Guilan landrace). The experiment was designed in a factorial arrangement based on a Randomized Complete Block Design with three replicates. The factors were P rate, Rhizobium phaseoli application, and application of nitragin biofertilizer. Result showed that grain and fresh pod yields were significantly increased by 28% and 21%, respectively, as P application rate increased from 0 to 50 kg ha-1. No significant increase in grain and fresh pod yields were observed as P application rate increased from 50 to 75 kg ha-1, but further increase in P rate (75 kg ha-1) reduced grain and fresh pod yields significantly. Regression analysis showed that the highest grain (1403.9 kg ha-1) and pod (8510.7 kg ha-1) yields were obtained when phosphorus was applied at the rate of 65.4 and 59.3 kg ha-1, respectively. Grain and fresh pod yields were significantly increased by 7 and 10% with nitragin biofertilizer application, respectively. Moreover, grain and fresh pod yields increased by 17% and 20% after Rhizobium inoculation.

A field experiment was conducted at Rice Research Station of Tonekabon, Iran, to determine the effect of seed inoculation with plant growth-promotingrhizobacteria on rice grain yield and yield components under different nitrogen (N) rates. The experimental design was a Randomized Complete Block with factorial arrangement and three replicates. Factors included seed inoculation with plant growth-promoting rhizobacteria [control (un-inoculated), seed inoculation with Azospirillum lipoferum, seed inoculation with Azotobacter chroococcum, and seed inoculation with a combination of A. lipoferumand A. chroococcum] and N rates (100%, 75%, and 50% of recommended nitrogen rates, i.e. 100, 75 and 50 kg N ha-1, respectively). Results showed that the highest grain yield (7875 kg ha-1) was recorded for plants inoculated with a combination of A. lipoferumand A. chroococcum, while the lowest one was recorded for un-inoculated control plants. Moreover, rice grain yield, panicle number per m2, grain number per panicle, and 1000-grain weight increased by 9%, 9%, 18%, and 6%, respectively, as N fertilizer rate increased from 50 to 100 kg ha-1. The highest grain yield (7875 kg ha-1) was obtained when N was applied at the rate of 75 kg ha-1to seeds inoculated with a combination of A. lipoferumand A. chroococcum.

In order to evaluate the effect of drought stress and determine of effective traits on grain yield and estimate of genetic parameters, 18 mutant rice lines were studied in normal and drought stress conditions. The experiments were carried out separately using randomized complete block design with three replications during cropping season 2014-2015 at Iranian Rice Research Centers in North of Iran, Rasht. High values of heritability, genetic advances and genetic variances were observed for plant height, tiller number, filled grain number and unfilled grain number in both conditions, but grain productivity and grain yield were appeared only under drought stress conditions. This indicated the additive effects of genes in controlling of these traits and, therefore, these traits can be improved by selection in breeding programes. There were positive correlations between grain yield and tiller number, panicle exsertion, grain productivity and width and length of flagh leaf in normal irrigation condition. Grain yield had also positive correlation with flagh leaf width, panicle exsertion, filled grain number, grain productivity and width and length of grain under drought stress conditions. Regression and path analyses indicated positive effects of grain width, grain productivity, flagh leaf width, filled grain number, tiller number and internode length in normal irrigation conditions and grain productivity, grain width and tiller number under drought stress conditions. Therefore, it is possible to improve grain yield using these variables. The genotypes including G1, G2, G3 and G4 had the highest values of grain yield (2788, 2163, 2178 and 2194 kg ha-1) under drought stress conditions, and influencing traits on grain yield. Due to the stress index (SI), these genotypes were also as drought tolerant and, thus, can be used for introducing the drought tolerance cultivar.

To evaluate rice genotypes to drought stress and determine the effective traits on grain yield, 18 rice genotypes (14 M5 mutant lines and four drought sensitive cultivars) were studied in two separately experiments under normal irrigation and drought stress conditions in reproductive stage based on randomized complete block design with three replications at Rice Research Institute of Iran (RRII), Rasht, Iran, during 2014-2015 growing season. Genotype by trait (GT) biplot analysis indicated positive correlations between grain yield and tiller number, grain productivity and width of grains in normal irrigation condition and width and length of grains, number of tillers, grain productivity and number of filled grains in drought stress condition. Stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP) and harmonic mean (HM) indices were as suitable indices to select the high-yielding genotypes under drought stress condition. Based on drought stress tolerance indices and overall performance of traits under drought condition, Khazar, Hashemi, Tarom and Gilaneh were as the most sensitive genotypes and mutant lines G1, G2, G3, G4 (derived from Tarom) and G7 (derived from Hashemi) with 2788.33, 2163.00, 2178.33, 2194.00 and 2375.00 kg.ha-1 grain yield in drought stress condition, were the tolerant genotypes. Stress tolerance score (STS) were also introduced the above genotypes as tolerant genotypes. Therefore, it is seems that use of mutations has been able to increase drought tolerance on the progenies. The above mutant lines in addition to use as parents in crosses, could also be used in the introduction of drought tolerant cultivars.

Water resources shortage threatens the sustainability of continuous flooding rice culture. To investigate the effect of initial flooding duration on herbicide efficacy and rice yield loss,a field experiment was conducted at Rice Research Institute of Iran, Rasht, Iran, in 2015. The experiment was arranged in a factorial arrangement based on randomized complete block design with three replications.The experimental factors were two rice cultivars (Hashemi and Gilaneh) and five initial flooding durations (flooding for 2, 4, 6, 8 and 12 weeks after transplanting and then applying intermittent irrigation). Consistent with the paddy fields irrigation method in northern Iran, 12-week flooding duration was considered as continuous flooding irrigation. Results showed that there was no significant difference in herbicide efficacy between Hashemi (87.9%) and Gilaneh (85.6%) cultivars. No significant reduction in herbicide efficacy was observed when initial flooding duration reduced from 12 to 6 weeks, but with further reduction in initial flooding duration to four and two weeks, herbicide efficacy was significantly reduced. The highest paddy yield (3989.2 kg.ha-1) was observed in permanent flooding(flooding for 12 weeks) + herbicide application treatment and the paddy yield was decreasedabout 10% by reducing theinitial flooding duration to six weeks but it was not statistically significant. With further decrease in initial flooding duration to four and two weeks, rice paddy yield reduced significantly by 16% and 31%, respectively. In conclusion, results of this experiment revealed that under water shortage conditions, it is necessary to apply initial flooding duration at least for 6 weeks after transplanting for obtaining favorable herbicide efficacy (more than 90%) without paddy yieldloss compared to permanent flooding treatment.

Weeds are the major constraint on rice production. It has been reported that weeds cause rice yield losses by 30-40% in Bangladesh, 36 to 56% in the Philippines, 40 to 100% in South Korea and up to 90% in Iran. Extensive application of graminicides, flooding, and continuous hand weeding have increased the population of more problematic weed species like bulrush (Bolboschoenus maritimus (L.) Palla in rice fields of northern Iran. Bulrush is a perennial weed belongs to cyperaceae family and resistant to most paddy herbicides, flooding and also hand weeding. Yield reduction of rice was estimated up to 100% due to bulrush competition. Despite environmental concerns, theeffect of herbicides on non-target organisms, and the increase of herbicide-resistance weeds, chemical control is still the most commonly used and reliable method for weeds control in paddy rice production in Iran.
Field experiments were conducted at Rice Research Institute of Iran during 2013 and 2014, Rasht, (36° 54' N, 40° 50' E, -21 masl) to assess the efficacy of paddy herbicides for bulrush control. In the first experiment (2013), commonly used paddy herbicides in Iran including bensulfuron-methyl, butachlor, oxadiargyl, pretilachlor, and thiobencarb were evaluated for bulrush control. Two control treatments (hand weeded and weedy check) were also included for comparison. Based on the result of the first experiment, second experiment (2014) was designed to evaluate the efficacy of some new herbicides including flucetosulfuron, penoxulam, metsulforun-methyl, pyrazolate and also bensulfuron-methyl for bulrush control. Both experiments were conducted as randomized complete block design with three replications. Individual plots were 3m wide by 3m long and rice seedlings (cv. Hashemi) manually were transplanted on 23 May 2013 and 2014, with planting distance of 20cm × 25cm. Visual injury evaluation for rice (chlorosis, and growth stunting) and visual weed control (chlorosis, necrosis, and plant stand reduction) was conducted at 2, 4 and 6-WAT (a week after transplanting) in each plot. Visual ratings of rice toxicity and weed control were based on a scale of 0 to 100%, where 0 means no injury or no weed control and 100 means complete death or complete weed control. Also, bulrush biomass was determined at 2, 4 and 6- WAT in the first experiment and 4 and at 12-WAT in the second experiment from a randomly selected 1m2 quadrate in each plot. Weed samples were oven dried at 70 °C for 72 h and weighted. At the maturity stage, rice grain yield (based on 14% humidity), and rice biomass was determined from 5 and 1 m2 per plot, respectively. Rice biomass from each plot was dried at 75°C for 96 h and weighted. Harvest index was calculated by dividing the dry weight of the grain by the dry weight of aboveground (biological yield). Data were subjected to analysis of variance (ANOVA), and means were compared using Fisher's protected LSD test at the 0.05 probability level. All statistical analyses were conducted using SAS (ver. 9.1) software program.
Results of the first experiment showed excellent control of bulrush by bensulfuron-methyl (≥98) followed by pretilachlor (≥85%) at 6-WAT, at the end of critical weed control period in transplanting rice. The efficacy of other herbicides was ≤60%. The lowest biomass of bulrush was recorded for plots treated with bensulfuron-methyl (1.5 g m-2) and pretilachlor (10.6 g m-2). Results also showed that the highest grain yields were observed in plots treated with bensulfuron-methyl (4000 kg ha-1) or pretilachlor (4231 kg ha-1). This was mainly due to optimum weed control in these plots. Grain yield in weedy plots reduced by 76% compared to hand weeded plots, indicating the severe infestation of the plots to bulrush and the ability of this weed to cause rice yield loss. The reduction in grain yield in weedy plots could be mainly due to severe competition for nutrient, especially nitrogen, and light. Because of adequate moisture in paddy fields, reduction in rice growth due to weed-crop competition for water is negligible. The highest harvest indices were observed in plots treated with pretilachlor (52.4%) and butachlor (50%) and weed-free plots (48.8%), while the lowest one was recorded for weedy plots. This result indicates that assimilate partitioning to grain or photosynthesis is reduced under weedy condition. The result of the second experiment also confirmed the result of the first one and indicated that bensulfuron-methyl had good efficacy (≥85%) on bulrush control. The result also indicated that bulrush was controlled very well by flucetosulfuron (88%) and pyrazolate (85%). In contrast, penoxulam and metsulforun-methyl had fair efficacy (≤ 49%) on bulrush control. Moreover, flucetosulfuron, and pyrazolate showed good compatibility with rice, and grain yield in these treatments did not statistically differ with gain yield in plots treated with thiobencarb bensulfuron-methyl. Grain yield was significantly lower in weed-free plot compared to plots treated with bensulfuron-methyl, flucetosulfuron, and pyrazolate. This may be due to that manual weeding can be performed only when weeds have reached a sufficient size to be pulled out easily by hand. By that time, yield losses may have already occurred. At the same time, it seems that weed control by 2- or 3-times hand weeding induced severe stress on rice plant, resulted in a decrease in grain yield. Grain yield in a weedy plot was reduced by 51 and 62% compared with weed-free plots and with plots treated with thiobencarb bensulfuron-methyl, respectively. These results indicate the importance of bulrush control in paddy fields.
Of the current paddy registered herbicides in Iran, bensulfuron-methyl was the most effective herbicide for bulrush control followed by pretilachlor with partial efficacy on bulrush. Newly investigated herbicides, flucetosulfuron, and pyrazolate, could be registered as good options for bulrush control in paddy rice. In respect to the different mechanism of action of new herbicides and their compatibility with rice, the alternative application of new and current herbicide is recommended for controlling bulrush and delaying weed resistance to the herbicide.

IntroductionDrought is a major problem that limits the adoption of high-yielding rice varieties in drought-prone rainfed rice environments. To improve crop productivity, it is necessary to understand the mechanism of plant responses to drought conditions with the ultimate goal of improving crop performance in the vast areas of the world where rainfall is limiting or unreliable. Safaei Chaeikar et al. (2008) reported that MP, GMP, HM and STI indices, which showed the highest correlation with grain yield under both optimal and stress conditions, can be used as the best indices to introduce drought-tolerant genotypes in rice breeding programs. They also were introduced Nemat, Sepidrood, IR64, IR50 and Bejar genotypes as tolerant varieties. The present study was conducted to determine how drought affects grain yield in rice mutant lines and also to test this hypothesis in order to identify the most suitable indices/genotypes.
Materials and MethodsA field trial was conducted at Iranian Rice Research Centers in North of Iran, Rasht (latitude 37◦28', longitude 49◦28'E and altitude 7m below the sea level), during the 2014-2015 growing season. The seeds were sown in a nursery on the 10 May and 25 day old seedlings were transplanted to the field. Two separately experiment was carried out under reproductive stage drought stress and controlled conditions based on randomized complete block design with three replications, in four-row plots of three m length. Transplanting was done using 1 seedling per hill; at hill spacing of 25 cm × 25 cm. 18 rice genotypes were consisted 14 M5 mutant lines and their four parental cultivars.
Results and DiscussionAnalysis of variance indicated significant effects of drought stress, genotype and interaction effects of two factors on grain yield, plant height, flag leaf area, tiller number and grain fertility percentage. Drought stress at reproductive stage caused reduction in grain yield (59.47%), grain fertility percentage (19.08%), plant height (9.35%), flag leaf area (8.59%) and panicle length (1.61%). Different drought indices probably measure similar aspect of drought tolerance/resistance. Significant yield reduction was observed under drought stress in majority of the rice genotypes studied. Drought tolerance indices were varied significantly indicating genotypic variability. Selection based on these stress tolerance indices will results in identification of drought tolerant genotypes for rainfed ecosystems. The stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP) and harmonic mean (HM) were superior in genotype indicating that they can be used as alternative for each other to select drought tolerant genotypes with high yield performance in both stress and non-stress conditions. To determine the most desirable drought tolerance criteria, the correlation coefficients between Yp, Ys and other quantitative indices of drought tolerance were calculated. The results indicated that there were positive and significant correlations among Yp and MP, GMP, STI and HM. There were also significant and positive correlation between Ys and YI,HM,GMP,YSI,STIandMP. In this experiment, the principal component analysis was performed on eight indices and grain yield under stress and non-stress in 18 rice genotypes. Results showed that the first two components explained 82.8% and 17% of total variation, respectively. The relationship between principal components and studied indices showed that the higher values of first and the lower values of second components were related to drought tolerance and sensitivity to stress, respectively. Selection based on a combination of indices may provide a more useful criterion for improving rice drought-tolerant lines; therefore, studies of correlation coefficients are useful in finding out the degree of overall linear association between any two attributes. According to these drought stress indices, G1, G2, G3, G4 and G5 (M5 mutant lines of local lanrace, Tarom) and (M5 mutant line of Hashemi) were as drought tolerant and G14 (mutant lines of Khazar), G15 (Hashemi), G16 (Khazar) and G17 (Tarom) were sensitive to drought stress.
ConclusionsResults of present study showed that MP, GMP, YI and STI are best indices for selecting and specifying of rice tolerant genotypes in arid areas. The use of mutation caused drought resistant on the progenies and the above lines can be used in a project of introduction of drought tolerant rice varieties.

Growing berseem clover (Trifolium alexandrinum) prior to rice can be a good strategy for reduction of chemical fertilizer consumption and increasing the sustainability of the rice cropping systems. For this purpose, a field experiment was conducted by using a split-plot based on randomized complete block design (RCBD) with three replications, at the Rice Research Station of Tonekabon, Iran in 2014-2015. Growing berseem clover and use of fallow (control), were assigned to main plots, and amount of phosphorus fertilizer (without P and 25, 50, 75 and 100 kg.ha-1 P) to the sub-plots. At crop maturity, seed yield, yield components and phosphorus content of seeds were evaluated. The results showed that seed yield of rice (7566.3 kg.ha-1) after clover was significantly higher than after fallow (6465.1 kg.ha-1) (p

To evaluate the effect of previous crop, N rate and N split application on rice (Oryza sativa L. cv. Hashemi) growth and paddy yield, a field experiment was conducted at SowmaehSara, Guilan province, in 2014 as a split-factorial arrangement based on Randomized Complete Block Design with three replicates. Main plots were previous crop [Berseem clover, faba bean, and control (fallow)] and subplots were the factorial arrangement of N rate (50, 75, and 100 percent of N recommended rate which was 50, 75 and 100 kg Urea ha-1, respectively) and N split application (100 percent at transplanting stage, 100 percent at tillering stage, and 50 percent at transplanting stage and 50 percent at panicle initiation). Results showed that rice paddy yield was significantly affected by previous crop and N rate, but N split application had no significant effect on paddy yield. The highest paddy yield (4142.8 kg ha-1) was obtained when rice was cultivated after berseem clover and the lowest paddy yield (3494.0 kg ha-1) was obtained when rice was cultivated after faba bean. Rice paddy yield was increased significantly by 8% as N application rate increased from 50 to 78 kg urea ha-1, but further increase in N rate (100 kg urea ha-1) had no significant effect on paddy yield. Based on the result of this experiment, the highest rice paddy (4142.8 kg ha-1) was obtained when rice was cultivated after berseem clover and N was applied at the rate of 75 kg urea ha-1.

A three-phase Delphi study was conducted to identify factors affecting efficiency of tea factories in Gilan Province of, Iran. In this context, 20 experts from the Iranian Tea Organization (ITO) and agricultural offices of Roudsar, Amlash, Langaroud, Lahijan, and Siahkal of Gilan Province were selected as the members of the research panel. According to the consensus of Gilan’s tea processing experts provision of suitable tea leaves, benefitting from skilled tea and acquisition of well-established and organized factorywill result in 97.17%, 92.44% and 90.37% efficacy in management of tea processing factories respectively.. Further paying attention to cultural practices, particularly pruning and providing adequate fertilization as well as implementation of mechanized irrigation should be regarded and practiced by tea growers as well as Iranian Tea Organization (ITO). Moreover, training and educating the tea processors in tea factories through conduction of educational courses by using experienced educators as well as coordination of supply of tea leaves by producers according to the processing capacity of factories in each region are considered as important factors and are recommended.

The present study was conducted in two separate experiments under drought stress and normal irrigated conditions using randomized complete block design with three replications at Rice Research Institute of Iran in Rasht, Guilan, Iran, during 2014-2015 growing season. Plant materials included 14 mutant lines (7 lines from Hashemi, 6 lines from Tarom and one line from Khazar) and four commercial rice cultivars (Hashemi, Tarom, Khazar and Gilaneh). Factor analysis resulted in five and four main factors for normal irrigated and drought stress conditions, which explained 81.5% and 79.3% of the total variation, respectively. The results indicated that under drought stress and normal irrigated conditions, selection of plants with high grain fertility (%) and panicle length and shorter plant height and internode length leads to increased grain yield. Cluster analysis classified the genotypes into five groups under both conditions. Discriminant function analysis indicated very high accuracy (100%) of grouping based on cluster analysis. The results of different analyses identified rice lines; TM6-230-VE-8-4-1, TM6-250-10-7-1, TM6-B-2-1-E and HM5-250-E-1-1 as superior genotypes with higher grain yield (2227.6 kg.ha-1) and the other desirable traits including high grain fertility (80.9%) and low panicle exsertion (6.3 cm) under drought stress condition. The average grain yield of these genotypes was 4739.9 kg.ha-1 in normal irrigated condition. Reduction of grain yield due to drought stress was 53% for these genotypes, and 60% for all of genotypes. Therefore, these selected genotypes can be considered in rice breeding programs to improve drought tolerance germplasm.

A field experiment was conducted at Rasht, in 2014, to investigate controlling weeds in native Hashemi cultivar paddy fields by different methods of herbicide applications and inoculated with Azotobacter chroococcum. The factorial experiment based on a randomized complete block design with three replicates was performed. Factors were Azotobacter application with two levels (inoculation with or without Azotobacter chroococcum) and weed management regimes with six levels (pretilachlor plus a supplementary hand weeding, bensulfuron methyl plus a supplementary hand weeding, and pretilachlor bensulfuron methyl plus a supplementary hand weeding, hand weeding during rice growing period no herbicide, un-weeded during rice growing period no herbicide). Results indicated that paddy rice yield was significantly increased by 16% after Azotobacter chroococcum inoculation. Rice paddy yield was significantly reduced in un-weeded plots compared to hand weeded and herbicide treated plots. ANOVA also revealed that there was no interaction effect between Azotobacter chroococcum applications and weed management regimes on paddy and biological yields, indicating that the herbicides had no adverse effect on Azotobacter efficiency in promoting growth and paddy yield of rice. Weed dry weight was reduced by 88, 91, 92, and 94 percentages in weeded plot and plots treated with pretilachlor, bensulfuron methyl, and pretilachlor bensulfuron methyl, respectively, compared to un-weeded plots. Azotobacter chroococcum inoculation had no significant effect on weed biomass. Overall, the result of this experiment confirmed the feasibility of chemical weed control in paddy fields inoculated with Azotobacter chroococcum.

Adequate knowledge of the interrelationships among traits is essential in planning and evaluating breeding programs for rice improvement. The objectives of this research were to study the stability of seven rice genotypes over the studied environments, determining the interrelationships among traits and identifying suitable traits for indirect selection to improve rice grain yield. Six promising rice lines selected from preliminary yield trial in 2011-2012, including Shirodi as control cultivar were evaluated using randomized complete block design with three replications in two locations of Mazandaran province (Tonekabon and Sari) during three growing seasons from 2012-2014. Combined analysis of variance showed significant effects of genotype and genotype × environment interaction for grain yield. The GGE biplot analysis showed that genotype 6 (G6) with the highest grain yield (6218.06 kg.ha-1) was ranked in second place in term of stability. The GT biplot analysis revealed that grain yield was positively correlated with number of filled grain, number of total grain and plant height and negatively correlated with number of tillers per plant and panicle length. Therefore, number of filled grain, number of total grain and plant height were suitable traits for indirect selection to improve rice grain yield. In conclusion, G6 [No. 39 from IR 67015-22-6-2-(A37632) × (Amol3 × Ramzanalitarom)] and G5 [No. 126 from IR 67015-22-6-2-(A37632) × (Amol3 × Ramzanalitarom)] were the best genotypes that can be considered to release the new varieties.

In order to investigate yield stability, genotype×environment interactions and estimation of a number of genetic parameters related to yield and yield components, seven promising rice lines together with Shirodi and line 843 (as control cultivars) were evaluated. The experiment was carried out base on randomized complete block design with three replications in three locations of Mazandaran province, Iran (Tonekabon, Amol and Sari) during three growing seasons from 2012 to 2014. Analysis of variance revealed that there were significant differences among genotypes for yield at almost all three locations. Combined analysis of variance indicated that there were no significant differences among locations and years, whereas year×location×genotype interaction was found significant for grain yield, plant height and thousand grain weight. Results of stability analysis by univariate methods showed that genotype number 6 was the most stable genotype over all three locations, having less variance within locations and smaller coefficients of variance and a high grain yield (6020.8 kg ha-1). The high coefficient of phenotypic and genotypic variation was indicative to genetic variability for all of the studied traits. The broad-sense heritability ranged from 49.06% (plant height) to 92.48%% (number of filled grain per panicle) and was 59.46% for grain yield. The highest phenotypic and genotypic coefficients of variation and genetic gain over total average obtained for the number of grains per panicle. Thus, it is possible to improve this trait by selection method and could be used as a selection index to improve grain yield. Overall, genotype number 6 could be considered as a superior genotype to achieve a dwarf cultivar with stable yield.

A considerable portion of chemical N fertilizer in rice field is lost through denitrification, volatilization, leaching, causing environmental pollution problems. It seems that incorporation of winter legume crops in rotation with rice and using plant growth-promoting rhizobacteria can be alternative approaches in reducing N chemical fertilizer and increasing sustainable crop production in rice fields. This experiment was conducted at Rice Research Station of Tonekabon, Mazandaran province, during growing season of 2013-2014 to evaluate the effect of crop rotation, Azotobacter chroococcum inoculation and N rates on rice (Oryza sativa L. cv. Shiroudi) paddy yield.
The experiment was conducted as split-factorial arrangement based on a Randomized Complete Blocks with three replications. Main plots were crop rotation [berseem clover - rice, faba bean- rice, and fallow – rice (control)] and subplots were the factorial arrangement of Azotobacter chroococcum (inoculated and un-inoculated) and N rate (50, 75, and 100 percent of N recommended rates which were 50, 75 and 100 kg N ha-1, respectively) levels.
Analysis of variance showed that rice paddy yield was significantly affected by crop rotation, Azotobacter chroococcum and N rate. Rice paddy yield in faba bean – rice crop rotation (6174.8 kg ha-1) was significantly lower than fallow – rice (7352.3 kg ha-1) and berseem clover – rice (7554.8 kg ha-1) crop rotations. Moreover, there was no significant difference in paddy yield between fallow – rice and berseem clover – rice crop rotations. Rice paddy yield was significantly increased by 8% after Azotobacter chroococcum inoculation. Rice paddy yield was significantly increased from 6628.8 to 7340 kg ha-1 as N rate increased from 50 to 75 kg ha-1, but further N application (100 kg ha-1) had no significant effect on paddy yield. Of the yield components, panicle number per m2 was significantly affected by crop rotation, Azotobacter chroococcum inoculation and N rate, while grain number per panicle was significantly affected only by crop rotation. Moreover, 1000-grain weight was not significantly affected by any factors. The highest panicle number per m2 was observed in berseem clover – rice crop rotation (352.1 panicles), N fertilizer at the rate of 100 kg ha-1 (362.0 panicles) and Azotobacter chroococcum inoculation (353.2 panicles). The highest grain number per panicle (105.8 grains) was observed in berseem clover – rice crop rotation, while the lowest one (96.3 grains) was observed in faba bean – rice crop rotation.
Based on the result of this experiment, in all crop rotations with rice, the highest paddy yield was obtained in nitrogen application at the rate of 75 kg ha-1 and plants inoculated with Azotobacter chroococcum.

One of the crucial issues before the second cropping is having enough knowledge about the residue effect of first crop herbicides on second crops. This experiment was conducted to investigate the possible inhibitory effect of some selective paddy herbicides residues to second cropping. Experimental factors were included common paddy herbicides (thiobencarb, butachlor, oxadiargyl, bensulfuronmethyl, and non- herbicide control) and test plants (lettuce (Lactuca sativa L.) and cress (Lepidium sativum L.)). At first, herbicides were applied in paddy field and bioassay was carried out by using the soils of plots treated with those herbicides and test plants. Results showed that, in general, residual effect of paddy herbicides on the growth of second crops was different depending on plant type and herbicide. Compared with aerial parts, roots of the plants tested were more sensitive to residual herbicides. Butachlor showed the least (≤9%) and oxadiargyl the most (≥60%) inhibition on test plants, and bensulfuronmethyl and thiobencarb also had statistically similar inhibitory effect on the roots of the test plants. Based on results of this study, the growth of lettuce and cress as second crops in paddy fields could be significantly reduced by the residue of some paddy herbicides including thiobencarb, oxadiargy and Bensulfuronmethyl.

Incorporation of winter legume crops in rotation with rice and using plant growth-promoting rhizobacteria can be a proper alternative approach in increasing sustainable crop production in rice fields. A split factorial field experiment using randomized complete block design with three replications was conducted at the Rice Research Station of Tonekabon, Mazandaran province, Iran, in 2014 to evaluate the effects of previous crop, Azospirillum lipoferum inoculation, and N rate on growth and seed yield of rice (Oryza sativa L. cv. Shiroudi). Main plots were consisted of previous crop [berseem clover, faba bean, and control (fallow)] and subplots of Azospirillum lipoferum (Inoculated and Un-inoculated) and recommended rate of N applications (50, 75, and 100 kg.ha-1). Analysis of variance showed that rice paddy yield was significantly affected by previous crop, Azospirillum lipoferum and N rate. Result also showed that rice paddy yield was increased only by 3% when rice was planted after berseem clover as it compared with rice plant after fallow. However, rice paddy yield was significantly reduced by 16% when it was planted after faba bean as compared to that it was planted after fallow. Rice paddy yield was significantly increased by 14% after Azospirillum lipoferum inoculation. Rice paddy yield was significantly increased by 11% when N application increased from 50 to 75 kg N ha-1, and further N application (100 kg N ha-1) did not affect paddy yield significantly. Based on the result of this experiment, planting rice after berseem clover, Azospirillum lipoferum inoculation and application of kg N ha-1 of recommended rates can be used to obtain highest paddy yield in the experimental site.