فصلنامه تحقیقات غلات
سال چهارم شماره 4 (زمستان 1393)

Proper water management in the paddy fields has an important role in the efficacy of other production inputs in rice cultivation. One of the important parts of paddy water management is midseason drainage. To investigate the influence of surface mid-season drainage on growth and yield of rice cultivar Tarom-Hashemi، a field experiment was carried out in randomized complete block design with six treatments and three replications in Haraz Promotion and Technology Development Center in 2013 growing season. The experimental treatments were continuous drainage of zero (control)، 5، 7، 9، 11 and 13 days and their effect was evaluated on plant height، number of tillers، panicle length، grain filling percentage، harvest index، dry weight، leaf area index، crop growth rate، net assimilation rate and grain yield. Statistical analysis showed that the effect of midseason surface drainage on dry matter was significant and there were no significant difference for other studied characteristics in compared with control treatment. Application of midseason drainage increased the crop growth rate and net assimilation rate than control treatment. Increasing midseason drainage duration to 13 day caused in decreasing grain yield as 13% with compared to control treatment. Therefore، in drought condition and due to midseason drainage benefits، duration of midseason drainage could be increased to 13-day without not-significant decreasing in grain yield.

Rice false smut disease caused by Ustilaginoidea virens (Cooke) Takahashi was known as one of the diseases of rice in some paddy fields of Guilan province in recent years. The present study was conducted to chemical control evaluation of rice false smut by application of tricyclazole (WP 75%), carbendazim+iprodion (Rovral-T-S® WP 52.5%), copper oxychloride (WP 35%), propiconazole (Tilt® EC 25%), and azoxystrobin+cyproconazol (Amistar Xtra® SC 28%) fungicides with dose rates of 0.5, 1, 3kg, 1 and 0.6 liter per hectare, respectively on a rice susceptible cultivar, namely Khazar at the mid boot and beginning of panicle emergence stages, in a field having multi-year infection in Abkenar location near the Anzali lagoon for two years. Data analysis showed that propiconazole, copper oxychloride and azoxystrobin+cyproconazol fungicides had significant effects on reducing of infected tillers (panicles) and pathogen sporeballs number per square meter and disease severity in first year (2011). Whereas the effects of tricyclazole and carbendazim+iprodion were not significantly differ from control treatment. In second year (2012) the disease severity was seriously developed in the field, but the application of propiconazole was more effective than other fungicides to reduce number of infected tillers (panicles) and pathogen sporeballs per square meter and disease severity in comparison with control treatment by percentage rates of 80.62, 83.92 and 83.01 respectively. So application of propiconazole at booting stage can be introduce to reduce disease incidence of false smut in paddy fields of northern Iran.

To study the structure of morphologic and physico-chemical traits and determining of the heterotic pattern of rice varieties, the ninety four selected rice varieties from the existing germplasm of Rice Research Institute of Iran were evaluated during the growing season for two consecutive years of 2011 and 2012 and 24 rice morphologic and physico-chemical characteristics were measured. Factor analysis for morphologic traits showed the first four independent factors explained 75.66 percent of total variance in all genotypes. The first factor with 24.5 percent of variance was included the yield and its components and was named as yield factor. The second, third and fourth factors with 19.025, 17.134 and 14.963 percent of variance were nominated as grain shape, phonology and filled grains factors, respectively. Factor analysis for physico-chemical traits also revealed the three independent factors explaining 36.3, 21.2 and 18.6 percent of variance in all cultivars, respectively, and were nominated as eating, cooking quality and milling rice recovery factors, respectively. All of the studied genotypes were classified in 9 different and heterotic groups using complete linkage method and Euclidean distance with a 92.6 percent of original grouped cases correctly classified. Results of this study can be utilized for selecting the suitable parents from different clusters to establish new varieties in rice breeding programs.

Mutation has been accepted as a useful tool in plant breeding programs to provide inheritable variability for selection. In this research, the effect of chemical mutagen Ethyl Methane Sulfonate (EMS) at three levels, 0.17%, 0.35% and 0.51% was studied to create the variation on morphological characteristics of Tarom Mahali, Sange Tarom and Tarom Hashemi varieties. The M1 generation was examined using a factorial experiment based on randomized complete block design with three replications and the agronomic traits including plant height, number of tiller, panicle length, number of filled and unfilled grains per panicle, number of total grains per panicle, grain width and length and 100 grain weight were measured. Analysis of variance showed that the interaction effect of cultivar×EMS concentration was significant for total number of grains per panicle, number of unfilled grains per panicle and grain length at 5% probability level and for filled grains per panicle and 100 grain weight at 1% probability level. The effect of variety was significant for plant height and 100 grain weight at 1% and for panicle length at 5% probability level, while the EMS concentration was significant for the number of tiller, total number of grains and number of filled and unfilled grains per panicle at 5% probability level. Results of the comparison of means indicated that the application of EMS lead to increase in grain length, number of grains per panicle and 100 grain weight and decrease in plant height in rice varieties. Generally, results of current research showed that the EMS had considerable and significant effect on the 100 grains weight and plant height of rice varieties in M1 generation. Thus, EMS as the mutagens can be utilized for increasing of the variation and genetic improvement in breeding programs.

Fresh water deficit is one of the most limiting factors for agricultural productions in arid and semiarid regions. Thus, to use the incompetent and brackish water for agricultural productions, it is needed that quantitative response of plant in salinity stress to be analyzed in those regions. A plant vegetative growth stage is the most critical period of its growth, because the final production is dependent on this early phonologic stage. Thus, developing appropriate models for quantitative characterization of durum response to salinity at different vegetative growth stages was the main objective of this study. A greenhouse experiment was conducted in a loamy sand soil using salinity treatments comprising one non-saline water (0.4 ds.m-1) and five natural saline waters (2, 4, 6, 8 and 10 dS.m-1). Maas and Hoffman, vanGenuchten and Hoffman, Dirksen et al., and Homaee et al. models were used to predict relative seedling number and relative transpiration (Ta/Tp). The models were compared by using of the modified efficiency coefficient, modified agreement index and residual mass coefficient. Results indicate that the Homaee et al. model provides a reasonable prediction at the first growth stage, while the Maas and Hoffman model provides better predictions at the second and third growth stages.

To study the effect of different irrigation levels on yield, yield components and water percent of grain corn varieties, an experiment was conducted in a split plots experiment based on randomized complete blocks design with three replications in Agriculture research station of Ilam University. Irrigation in four levels (Irrigation after 70, 105 and 140 mm evaporation in evaporation pan class A) were considered as main plots and four grain corn hybrid (SC 704, SC 677, SC 666 and SC 524) assigned to subplots. Results from analysis of variance showed that variety×irrigation interaction effect were not significant on studied traits, but the effect of irrigation levels on grain yield, biological yield, harvest index, 100 grain weight, grain number per rows and ear length and diameter were significant and on the number of rows in ear and plant water percent were not significant. Also, differences among hybrids were significant for grain yield, number of row per ear, 100 grain weight, biological yield, ear diameter and plant water percent. Grain yield in I70 (10306.5 kg.ha 1) was more than the other irrigation levels. The number of grain per row was the crucial yield component led to 19% and 42% decreasing of grain yield in I105 and I140, respectively. Among evaluated hybrids in this experiment, SC 677 (8820.7 kg.ha-1) and SC 524 (7784.7 kg.ha-1) had the highest and lowest grain yield, respectively. Furthermore, the maximum number of rows per ear and the maximu 100 grain weight were observed in SC 704 and SC 524, respectively.