فصلنامه تحقیقات غلات
سال پنجم شماره 4 (زمستان 1394)

To study the effect of planting density (11.11, 16 and 25 plants.m-2) on dry matter remobilization and grain yield of rice cultivars, Hasani and Hashemi, a field experiment in factorial layout based on randomized complete block design with four replications carried out at Rice Research Institute of Iran (RRII) in 2011. Results showed that the plant height, number of tillers.plant-1, biological yield, grain yield of main stem and other tillers, number of panicles.m-2, number of grain.panicle-1, number of filled grains.panicle-1, number of grains.m-2, grain weight, grain length and its width and dry matter remobilization efficiency were significantly differ between Hassani and Hashemi cultivars and the effect of density on grain yield, harvest index, secondary tillers and main stem harvest indices, the number of filled grain.panicle-1, grain density.panicle-1, dry matter remobilization, current photosynthesis rate were significantly different. Apart number of tillers.plant-1, other traits were increased with plant density. An increasing in plant density, increased the number of grains.m-2 and leads to increase in grain yield of rice cultivars. The average total grain yield (4853 kg.ha-1) obtained from 25 plant.m-2 and the main stem produced 791 kg.ha-1 (16.3%) of grain yield. Also, there was a significantly increasing in the current photosynthesis in grain filling duration with 3380 kg ha-1 in 25 plant.m-2 treatment and greatly enhance the total grain yield. The rice cultivars, Hasani and Hashemi, with an average of 59.8% and 39.3% in the current photosynthesis efficiency were significantly different. Grain yield of both rice cultivars increased alongside increase in current photosynthesis rate and the dry matter remobilization was less than the current photosynthesis. It seems that in order to increase the grain yield of rice, plant density should be increased for dry matter remobilization and current photosynthesis enhancement.

Seed germination is an important step in the growth period that often is influenced by environmental stresses. The objective of this study was to identify the germination components with greatest role in discriminant between Iranian and aerobic rice genotypes based on tolerance to drought stress. The standard test for seed germination was conducted in three levels of osmotic stress (distilled water, -8 and -16 bar using manitol) for 53 rice genotypes (including 31 foreign and aerobic genotypes and 22 Iranian varieties). The various germination characteristics were measured. The grouping of genotypes based on germination components, the genotypes were assigned in the three groups at normal and stress conditions -8 bar and two groups at -16 bar respectively. The results showed that some of genotypes were in the group with average values higher than the general average under all the three conditions. These genotypes includes AE6, AE8, AE10, AE12, AE13, AE15, AE15, AE16, AE18, AE29 and AE30, that all were aerobic and foreign genotypes. Then, genotypes were classified as ‘Aerobic and foreign’ and ‘Iranian’ rice and discriminant functionanalysis was performed. Wilk’s Lambda statistic was estimated 0.286, 0.213 and 0.397 at normal condition, -8 and -16 bar, respectively. Showing the significant difference between the two groups based on germination characteristics. According to the results, the variables of seed vigor, germination percentage, the maximum percentage of germination, planting time required to reaching 90% and 95% of maximum germination and germination energy with greatest role and Allometric coefficient with lowest role were effective to distinguish between the two groups.

This research was carried out to identify drought tolerant genotypes on the basis of physiological, phonological and morphological traits and drought tolerance indices in bread wheat. Twenty wheat genotypes were assessed in two field experiments based on randomized complete block design with three replications under non-stress and drought stress conditions in Dryland Agricultural Research Sub-Institute, Sararood, Kermanshah. The studied traits were number of grains per spike, peduncle length, spike length, plant height, 1000-grain weight, days to heading, days to physiological maturity, grain yield, flag leaf area, relative water content, a, b and total chlorophyll, proline content, water retained in cut leaves, cell membrane stability and leaf water potential. Futhermore, drought tolerance indices based on grain yield under stress and non-stress conditions were also evaluated. The results showed that there is significant genetic variation among the studied genotypes for improving drought tolerance. Results of the yield index (YI), yield tolerance index (YTI), mean productivity (MP), geometric mean productivity (GMP), tolerance index (TOL), stability tolerance index (STI) and stress susceptibility index (SSI) identified relatively similar genotypes as the drought tolerant genotypes, but according to the high and significant correlation coefficients among MP, GMP, HMP and STI indices with grain yield under both stress and non-stress conditions, these indices were suitable to identify the high yielding genotypes under both conditions. According to these indices, the genotypes 72YRRGP, T179, T189, 914GB, MARAGHEH(1379-80) and Sardari were detected as the drought tolerant genotypes. Correlation coefficient analysis also revealed that among the evaluated traits, proline content of flag leaf, cell membrane stability and spike length had the stronger relationship with stress tolerance index (STI) and are introduced as the most important traits for selecting drought tolerant genotypes in this research.

To investigate the effect of terminal drought stress on wheat, 35 lines and varieties were evaluated as split plot arrangement based on randomized complete block design with three replications under normal irrigation (based on crop water requirement) and terminal drought stress (no irrigation from flowering stage) in Darab Agricultural Research Station in 2009. Drought stress (normal irrigation and terminal drought stress) and wheat genotypes were considered as the main and sub-plots, respectively. The studied traits were included grain yield, yield components and canopy temperature depression (CTD). To select drought tolerant varieties, five drought tolerance indices including stress susceptibility index (SSI), stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP) and tolerance (TOL) were also calculated. The results indicated that drought stress reduced grain yield and its components, so that average grain yield under normal and terminal drought stress conditions was 4691 and 3659 kg.ha-1, respectively. The correlation coefficients between grain yield and CTD at three measured stages from heading to physiological maturity as well as average CTD at all three stages under both normal and terminal drought conditions were moderate to relatively high. In total, the results of this research indicated that the CTD could be used as a rapid and effective criterion for screening high yielding genotypes in early generations of breeding programs. Evaluating drought tolerance indices also showed that the MP, GMP and STI are the more effective to select high yielding and drought tolerant varieties. All three indices identified the genotypes 14 and 16 as drought tolerant genotypes. These genotypes had the high yield in both normal and drought stress conditions.

To evaluate the genetic diversity and the effect of terminal drought stress on grain yield and some morphological traits of wheat, an experiment was conducted using 56 wheat genotypes in a latis (7×8) with three replications under normal and terminal drought stress conditions in research farm of the Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran, in 2010-2011 cropping season. The result of combined analysis of variance indicated high significant differences among genotypes for all studied traits including grain yield, number of grain per spike, 1000-grain weight, spike yield, biomass, harvest index and plant height. Terminal drought stress reduced 34.5% of spike yield, 30% of biomass, 27.2% of grain yield, 21.6% of number of grains per spike, 15.9% of 1000-grain weight, 6.13% of harvest index, 5.64% of plant height and 0.15% of peduncle weight, but it increased 1.47% and 0.20% of peduncle and penultimate internode length, respectively. There were high negative significant correlation between grain yield and penultimate internode length and also between biomass and harvest index under both non-stress and drougth stress conditions, whereas correlation between number of grain per spike and harvest index and between plant height and spike length was highly positive significant. The correlation analysis among grain yield under non-stress and terminal drought stress conditions with different drought tolerance indices showed that stress tolerance index (STI), mean productivity (MP) and geometric mean productivity (GMP) indices were appropriate indicators to identify the high grain yield genotypes. On the basis of these indicators, Moghan-1, Navid, Golestan, Darab-2 and Marvdasht genotypes had the highest grain yield under both experimental conditions.

To determine grain yield and its components of four wheat cultivars in competition with Japanese brome (Bromus japonicus L.), a field experiment was carried out in factorial arrangement using randomized complete blocks design with four replications at the Chah-Nimeh Station, University of Zabol, Iran, in 2014-2015 growing season. The experimental factors were four wheat varieties (Hamoon, Hirmand, Boolani and Kalak Afghani) and weed densities in seven levels of Japanese brome (0, 100, 150, 200, 250, 300 and 400 plants per m2). In this research, grain yield and its related traits including harvest index, biological yield, number of tiller per plant, 1000-grain weight, number of grain per spike, number of fertile tiller per plant and number of spike per m2 were measured. Results of analysis of variance showed that there were the significant differences among wheat varieties and among weed densities for all studied traits and variety × weed density interaction for all studied traits except for harvest index. The results also indicated that reaction of varieties were significantly different in terms of competition with Japanese brome, so that the highest number of tiller, plant height, biological yield and grain yield were obtained from the Kalak Afghani variety and biologic and grain yield of the Japanese brome in competition with this variety was far less than the other varieties. Totally, results of this research revealed that the grain yield more than the biologic yield of wheat varietieswas affected by competition with Japanese brome and interference tolerance index (ITI) of wheat varieties in biologic yield was more than the grain yield.

Identification of tolerant genotypes to rainfed condition is one of the important breeding objectives in cereals such as oats. Therefore, this research was performed to evaluate 21 oat genotypes under rainfed and irrigated conditions each in a randomized complete block design with three replications in Sarpol-e-Zahab, Kermanshah, during 2011-2012 cropping season. The results of analysis of variance showed significant variation among genotypes for yield, yield components and other studied morphological traits under both conditions. All studied traits except number of grain per spike were reduced under rainfed condition compared to irrigated condition. Factor analysis identified two factors that explained the correlation among the drought tolerance indices. The first factor was named of yield potential and drought resistance and the second factor was called drought tolerance. The compatible and incompatible genotypes to rainfed conditions were separated by cluster analysis. Totally, based on the drought tolerance indices and the other analyses, the genotypes Potoroo, Brusher, Euro and Ufrgs940886-4 were known as the genotypes with higher grain yield in both conditions and Nasta, Arnold, Kaloptt and 13Zop95 were known as the genotypes with lower grain yield and incompatible to rainfed condition.