The yield of maize in Iran is very low as compared to other maize producing countries. One of the most important EFFECTIVE factors is non application of optimal plant population per hectare AND maize hybrids differ in their response to plant density. In order to study the effect of different plant densities on yield, RATE AND EFFECTIVE GRAIN FILLING PERIOD in maize hybrids, a factorial experiment based on rANDomized complete block design with three replications was conducted in 2007 at the Research Farm of the Faculty of Agriculture Mohaghegh Ardabili University. Experimental treatments were: maize hybrids in three levels (SC-404, DC-370, SC-504) with different plant densities (8, 10 AND 12 plants.m-2). The results showed that yield AND yield attributes characters (except of the number of GRAINs rows) varied significantly due to the variation in population densities. The number of kernel per ear AND number of GRAINs per ear row increased with increasing plant density. The highest GRAIN yield was obtained from 10 plant.m-2 density. Response of maize hybrids wasn’t the same for plant densities. The highest GRAIN yield belonged to SC-504 hybrid AND the least was in DC-370 hybrid. A two part linear model were used to quantifying the GRAIN FILLING parameters. Cultivars AND plant densities affected all GRAIN FILLING parameters significantly.Maximum kernel weight, RATE AND EFFECTIVE GRAIN FILLING PERIOD was obtained in low plant densities.Means of comparisons showed that maximum of kernel weight (0.35 mg) AND EFFECTIVE GRAIN FILLING PERIOD were obtained in SC-504 hybrid×8 plants.m2 AND SC-404 hybrid×8 plants/m2. Minimum of it was obtained in DC-370 hybrid×12 plants/m2.

In order to study two GRAINs FILLING characteristics (specific EFFECTIVE GRAIN FILLING PERIOD AND EFFECTIVE GRAIN FILLING RATE) to improvement of GRAIN yield this study was conducted during 1999 AND 2000 growing season in Koohdasht dry lAND Research Station in Lorestan Province. An experiment using complete rANDomized block design which ten rain-fed wheat (Triticum aestivum L.) genotyps treatments with four replications was used. Also, to determine correlation coefficients between triats, parameters were measured consist of GRAIN yield, 1000 Kernel weight, harvest index, biological yield, straw yield, EFFECTIVE GRAIN FILLING RATE, test weight. Results showed that a significant positive correlation between GRAIN yield with 1000 Kernel weight, Harvest index, biological yield, straw yield, EFFECTIVE GRAIN FILLING RATE test weight AND with number of days, to steming was a negative significant correlation. Results of the growth GRAIN process indicated that overall, at the end the linear of (Tr 8010200, Zagross) No. 4 AND No.10 genotypes were the most final GRAIN weight (40mg) AND genotypes (Pik/opatacm, Maya 74 "s") No. 2 AND No. 7 were the least final weight GRAIN with 32 mg. EFFECTIVE GRAIN FILLING PERIOD were among genotypes 18.39 to 25.03 days. The most EFFECTIVE GRAIN-FILLING PERIOD was 25 days related to No.10 (Zagross) genotype AND the least No. 7 (Maya 74 "s") genotype with 19 days. EFFECTIVE GRAIN FILLING RATE among genotypes were 1.43 to 1.74 mg.days-1. The most AND the least EFFECTIVE GRAIN-FILLING RATE was for No. 2 (pik/opata) AND NoA (Tr8010200) respectively. Between EFFECTIVE GRAIN FILLING RATE AND PERIOD were significant negative correlation (r=-46 %**).

Eleven wheat cultivars were evaluated at 10-day intervals, beginning from anthesis, under irrigated AND drought stress conditions during 2006-2007. The effects of irrigation, genotype AND date of harvest were significant for most of the studied characters. Water deficit decreased pre-AND post-anthesis assimilation RATE, GRAIN weight per spike, GRAIN number per spike AND 1000 GRAIN weight about 5.7, 24.5, 21.2, 15.7 AND 6.4 %, respectively. Mobilization, mobilization efficiency AND contribution of pre-anthesis assimilates to kernels were considerably increased under drought stress condition. GRAIN weight, GRAIN growth RATE AND contribution of current assimilates to GRAIN FILLING decreased under drought stress about 7.18, 22.1 AND 29.6 %, respectively. However, the EFFECTIVE GRAIN FILLING PERIOD was considerably increased in the stressed plants. GRAIN FILLING RATE was correlated with the accumulation of dry matter at maturity, GRAIN weight per spike AND GRAIN number per spike in the irrigated AND drought stressed environments (r=0.87** AND 0.53, r=0.87** AND r=0.62*, r=0.75* AND r=0.63*, respectively). A negative correlation was found between EFFECTIVE GRAIN FILLING PERIOD AND GRAIN yield/spike under irrigation (r =-0.65*) AND drought stress (r =-0.76**) conditions. Furthermore, positive correlations between GRAIN FILLING RATE AND GRAIN yield were obtained in the irrigated AND drought stressed environments (r = 0.87** AND r = 0.62*, respectively). It seems that accumulation of pre-anthesis assimilates (mainly under drought stress), short EFFECTIVE GRAIN FILLING PERIOD AND high GRAIN FILLING RATE are major factors for producing higher GRAIN yield in wheat under both irrigated AND drought  stress conditions.

Relationship between GRAIN FILLING RATE, GRAIN FILLING duration, yield components AND other physiological traits of rice was investigated in 93 genotypes of rice at Rice Research Institute of Iran (Rasht, Iran) during the growing season of 2001-2002. The experiment was performed without any statistical design. Panicles of main stem were tagged AND taken at 3- day intervals during the GRAIN FILLING PERIOD. A cubic polynomial model was used to fit the GRAIN dry weight data (mean of R2= 0.98 for all genotypes) AND the GRAIN FILLING RATE AND duration estimated for the genotypes. Traits related to sink capacity such as GRAIN weight, GRAIN size AND GRAIN number per panicle correlated with GRAIN FILLING RATE but source capacity- related traits except chlorophyll content of flag leaf AND secondary leaf did not correlate with GRAIN FILLING RATE. Stepwise regression showed that final GRAIN weight, GRAIN FILLING duration AND flag leaf angle contributed to GRAIN FILLING RATE, however, path analysis showed that only final GRAIN weight AND GRAIN FILLING duration had the greatest effect on GRAIN FILLING RATE. The results of stepwise regression irrespective of final GRAIN weight showed that chlorophyll content of flag leaf, GRAIN width, GRAIN FILLING duration AND GRAIN length contributed to GRAIN FILLING RATE. Path analysis results showed that the final GRAIN weight had the greatest direct positive effect on GRAIN FILLING RATE, while GRAIN FILLING duration had negative effect on GRAIN FILLING RATE.

Introduction: The yield of wheat in Iran is very low as compared to the other wheat producing countries. One of the most important EFFECTIVE factors is water shortage. Water shortage can damage pigments AND plastids, reduce chlorophyll a, chlorophyll b, RATE AND GRAIN FILLING PERIOD. One approach to improve the salt stress problem is the use of plant growth promoting rhizobacteria (PGPR) AND Mycorrhiza. The PGPR are a group of rhizosphere colonizing bacteria that produce substances to increase the growth of plants, synthesize different phytohormones including auxins, cytokinins, AND gibberellins, synthesize enzymes that can modulate plant growth AND development. Arbuscular mycorrhizal fungi (AMF) symbiosis is considered a valuable component in most agricultural systems due to its role in plant nutrition AND soil health. Therefore application of biofertilizers AND supplemental irrigation can improve crop yield AND water productivity especially during critical crop growth stages. Materials AND Method: A factorial experiment was conducted based on rANDomized complete block design with three replications in Agricultural Research Station of Ardabil in 2016. Experimental factors included irrigation levels (no irrigation as rainfed, supplemental irrigation at booting AND heading stages or according with 45 AND 61 BBCH code, respectively) AND four levels of biofertilizers application (inoculation with Azospirilum, Mycorrhizal, Mycorrhizal+Azospirilum, AND without application of biofertilizers as control). A two part linear model was used to quantify the GRAIN FILLING parameters. In this study, total chlorophyll, chlorophyll a, b, carotenoid, GRAIN FILLING components AND yield of wheat were investigated. GRAIN dry weight AND GRAIN number were used to calculate the average GRAIN weight for each sample. Total duration of GRAIN FILLING was determined for each treatment combination by fitting a bilinear model: { EFFECTIVE GRAIN FILLING duration (EGFD) was calculated from the below equation: EGFD = highest GRAIN weight (g)/RATE of GRAIN FILLING (g day-1 ). Results AND Discussion: The results showed that application of both biofertilizers (Mycorrhiza AND Azosprilium) AND supplementary irrigation at booting stage increased chlorophyll a, b, total chlorophyll AND carotenoids (76. 6, 42. 26, 49. 57 AND 100% respectively) compared with no application of biofertilizers under rainfed condition. Also, both application of Mycorrhizae AND Azospirilium AND supplemental irrigation at booting stage increased GRAIN FILLING RATE, GRAIN weight, GRAIN FILLING PERIOD, EFFECTIVE GRAIN FILLING RATE AND GRAIN yield (15. 26, 51. 35, 14. 04, 35. 92 AND 35. 27% respectively) compared with no application of biofertilizers under rainfed conditions. Conclusions: Based on this study, the application of Azospirillum AND Mycorrhiza AND supplemental irrigation at booting stage can improve the content of chlorophyll a, b, total chlorophyll, carotenoids, GRAIN FILLING RATE, GRAIN weight, GRAIN FILLING PERIOD, EFFECTIVE GRAIN FILLING PERIOD AND GRAIN yield compared with no application of biofertilizers under rainfed conditions. Based on the results, it seems that application of biofertilizers AND supplementary irrigation can be suggested as modulators of drought stress in wheat under rainfed conditionss.

In order to investigate the effects of free living nitrogen fixing bacteria application AND time of nitrogen spraying on contribution of stem reserves in GRAIN yield, RATE AND EFFECTIVE GRAIN FILLING PERIOD of Triticale, a factorial experiment was conducted based on a rANDomized complete block design with three replications in Research farm of the Faculty of Agriculture, University of Mohaghegh Ardabili in 2012. Treatments consisted of different nitrogen spraying times in four levels (no spraying as control, spraying in boot stage, ear emergence, GRAIN FILLING PERIOD) AND seed inoculation with plant growth promoting rhizobacteria in four levels containing (without inoculation as control, seed inoculation with Azotobacter chroococcum strain 5, Azospirillum lipoferum strain OF, Psedomunas putida strain 9). Results indicated that spraying time of nitrogen fertilizer AND seed inoculation with free living nitrogen fixing bacteria had significant effects on yield, yield components, RATE AND EFFECTIVE GRAIN FILLING PERIOD of Triticale. Maximum of GRAIN weight (0/054 gr) AND EFFECTIVE GRAIN FILLING PERIOD (34. 17 days) were obtained in seed inoculation with Azotobacter× nitrogen spraying in boot stage. Maximum of contribution of stem reserves in GRAIN yield (30. 63 %) was obtained in no nitrogen spraying × no seed inoculation with PGPR AND minimum of it (8. 12 AND 8. 13 %) were obtained in nitrogen spraying in boot stage × seed inoculation with Azotobacter AND spraying in ear emergence × seed inoculation with Azotobacter. It seems that in order to increase the GRAIN yield, RATE AND EFFECTIVE GRAIN FILLING PERIOD of Triticale, it can be suggested that nitrogen spraying is applied in boot stage AND seed inoculation with Azotobacter

For studying genetic variation for GRAIN FILLING RATE AND GRAIN FILLING PERIOD  AND relationship with GRAIN yield, 10 barley genotype: Bomi, Torkaman, Eize, Siah, Sahra,1-yeknavakht, 14G, 11G, 5G AND 15G, cultivars ,introduced by Golestsn agriculture research centre, Were studied in rANDomized complete block design at 4 replication at 84-85.were studied. This genotype varied for both RATE AND duration GRAIN FILLING parameter AND had significant difference. Torkaman had maximum GRAIN FILLING RATE AND minimum was for 1-yeknavakht.the average of GRAIN FILLING RATE was 1.59 mg/day AND average of GRAIN FILLING duration was 29.8 days. Positive correlation between GRAIN FILLING RATE AND duration with GRAIN yield showed that, they increased from low yield genotype to high yield.14G had maximum AND Torkaman had minimum GRAIN FILLING duration. Negative no significant correlation between GRAIN FILLING RATE AND GRAIN FILLING duration.14G showed that have higher GRAIN yield than other genotype AND with receive lower GDD, achieved to the physiological maturity

In order to study the effects of seed inoculation with Plant Growth Promoting Rhizobacteria (PGPR) AND nitrogen application time of on yield, RATE AND EFFECTIVE GRAIN FILLING PERIOD of wheat (Triticum aestivum L.), a factorial experiment was conducted based on completely rANDomized block design with three replications in Research greenhouse of the Faculty of Agriculture, University of Mohaghegh Ardabili in 2011. The Factors were: nitrogen application timing in three levels (1/3 planting, 1/3 tillering stages, 1/3 before anthesis ), (1/4 at planting, 1/2 tillering AND stem elongation stages, 1/4 at anthesis), (1/4 planting, 1/4 during emergance, 1/4 stem elongation, 1/4 at anthesis) as N1, N2 AND N3 respectively AND seed inoculation with plant growth promoting rhizobacteria in four levels containing (without seed inoculation as control, seed inoculation with Azotobacter chroococcum strain 5, Psedomunas strain 41, Psedomunas strain 186). Results showed that nitrogen application timing AND seed inoculation with PGPR significantly affected all GRAIN FILLING parameters. Maximum of GRAIN weight AND EFFECTIVE GRAIN FILLING PERIOD were obtained in nitrogen application as N1´ seed inoculation with Azotobacter. Means comparison showed that GRAIN per plant, number of GRAINs per spike, weight of 100 seeds, plant height, spike length, root weight AND protein percentage increased with nitrogen application as N1 AND seed inoculation with PGPR. It seems that in order to increase of yield AND yield components, RATE AND EFFECTIVE GRAIN FILLING PERIOD can be suggested that seed inoculation with Azotobacter be applied in time of utilization of nitrogen as N1.

An experiment was conducted at Rasht Rice Research Institute, in 2001 to study trait relationships AND to determine the direct AND indirect effects of different characteristics on GRAIN yield of rice (Orgza saliva L.). A 9x2 factorial experiment in complete rANDomized block design with 3 replications was used. The two factors were 9 cultivars, namely: Hashemi, AliKazemi, Binam, Sepeedroud, Nemat, Khazar, Taichung, Chanto, AND Usen, AND 2 planting patterns (15x15 cm AND 30x30 cm). Significant differences were detected among cultivars, between planting patterns, AND their interaction effects. The direct effect of the number of panicles/m2 on GRAIN yield was positive AND significant in both planting patterns AND their combined analysis. Heading date had a positive AND significant direct effect on the number of panicles/m2 in both planting patterns AND their combined analysis. Only in 30x30 cm planting pattern, a positive correlation was found between biomass at heading date AND the number of panicles/m2. GRAIN weight per plant had a direct AND positive effect on panicle weight in the 3 cases studied. Also, in all the cases studied, flag leaf area had positive direct effects on GRAIN-weight per plant. GRAIN FILLING i"ate AND EFFECTIVE GRAIN FILLING PERIOD increased in 30x30 cm planting pattern. Native cultivars demonstRATEd longer latent PERIOD. GRAIN FILLING RATE AND EFFECTIVE GRAIN FILLING PERIOD showed positive direct effects on GRAIN yield in both plantings. According to the results obtained, an increase in the number of panicles/m2,RATE of GRAIN FILLING, AND EFFECTIVE GRAIN FILLING PERIOD would enhance GRAIN yield. Selection for heading date, GRAIN yield per plant, AND flag leaf area would also indirectly increase GRAIN yield.