JOURNAL OF AGRICULTURAL SCIENCE AND SUSTAINABLE PRODUCTION
Year:2004 | Volume:14 | Issue:1|Papers Count:10

In years 2000 and 2001 field sampling from roots of conifers seedling in nurseries of Kerman province led to isolation and identification of four pathogenic Fusarium sPrcies as F. moniliforme, F. solani, F. oxysporum, and F. lateritium. Population densities of these species were not uniform throughout the Province nurseries, but were more in Joupar district. F. moniliforme had highest, 47%, and F. lateritium had the lowest, 11%, and F. solani, F. oxysporum had moderate abundance.  Pathogenicity of the fungi was postulated on 20-days old seedlings of Pinus eldarica. This is also the first report on isolation and proof of pathogenicity of F. lateritium on Iranian conifers seedlings.      

In order to study and identify crown and root fungal pathogens of wheat and their importance at Zanjan province, 187 wheat fields were visited during 1999 to 2000. Suspected samples with symptoms such as chlorosis, withering, whiting of spikes, growth reduction, crown and root necrosis were collected. After isolating and purification, finally 98 fungal isolates belonging to five genus and seven species were identified. Rhizoctonia solani, Fusarium culmorum and Dreschlera sp. were most frequent. Pathogenicity test of these fungi and Rhizoctonia cerealis were done on wheat Flat cultivar. The results showed that, about 40 percent of wheat fields were infected by at least one of these fungi in different parts of Zanjan province. The infection percentage was 1-15 percent in studied areas. The rate of damage depended on the rate of infection and population dynamic of causal agents, which was 1 to 9 percent of yield. Results of this research also demonstrated that wheat was highly affected by soil-borne fungi in poor soil and low organic matter in comparison to fertile soils.      

Improvement of water use efficiency through the optimum use of water and fertilizer, especially nitrogen, is considered as one of the main objectives of scientists. A split plot experiment was conducted in three replications in Tikmehdash station on 1998-1999.The irrigation regime arranged in main plots in three levels including rainfed, supplemental irrigation and traditional or normal irrigation and nitrogen at five levels (0,60, 120, 180 and 240 kg /ha) in subplots. The results showed that the effect of irrigation on yield and yield components such as pod number per plant, seed number per pod and 1000 kernel weight and the effect of nitrogen on yield and pod number per plant was significant. Therefore, yield could be increased in rapeseed via increasing in pod number per plant. It seems that the rainfed cultivation of rapeseed in Tikmehdash is impossible, because of high temperature and low precipitation in September. Supplemental irrigation and normal irrigation. (3733 and 6045 m3/ha respectively together) with 180 kg N/ha produced the highest oil yield (1049 and 1754 kg/ha, respectively). Application of 60 kg N/ha increased seed oil percent (44.28%) but applying more nitrogen decreased the seed oil percentage (40.77%). Nitrogen use efficiency in normal irrigation condition was higher than the supplemental irrigation regime. In normal irrigation condition, the increases in nitrogen led to yield increase. However, in supplemental irrigation regime, nitrogen application of more than 180 kg decreased the yield.    

Entomopathogenic nematodes of the families Steinemematidae and Heterorhabditidae are obligate parasites on a wide range of insects which have been used in biological control of insects. In recent years satisfactory results have been obtained from the nematodes of the genera Steinemema and Heterorhabditis. The use of nematodes for monitoring soil- inhabiting insect pest populations seems promising because these natural habitats provide the nematodes a protection against environmental extremities of temperature, humidity and ultraviolet radiation. The black cutworm, Agrotis ipsilon, is regarded as a pest of economic importance of field crops in West Azarbaijan, Iran. To evaluate the efficacy of entomopathogenic nematodes as potential control agents against this insect pest, field and laboratory experiments conducted in randomized complete blocks with four replications in 1996 and 1997.H bacteriophora was applied at concentrations of 0, 1×105, 2×105, 4×105 and 8×105 Individuals per m2, The results indicated that, H. bacteriophora at the rates of 4×105 and 8×105 individuals per m2 was able to parasitize 76.57% and 75.22% of the pest larvae, respectively. The difference was significant at p=1% in comparison to the 1×105 individuals/m2 treatment.    

In order to evaluate the effect of crop rotation on weed community, a 3 - year field study was conducted with four crops including wheat, canola, fodder corn and sorghum in Mashhad. The statistical design was randomized complete block, with rotation factor in four levels, and three replications. Weed study was undertaken on two periods, first before crop canopy closure and second before crop harvesting. The effect of rotation was investigated on the last crop. The results indicated that both rotation and previous crop have significant effect on weed dry matter and density. Weed dominant species and weed flora also affected by rotation. All variables were higher in the first period than the second. In most cases board leaf weed dry matter and density were higher than narrow leaf weed. In both periods, only forth rotation had highest weed dry matter and density. Previous crop especially canola was a volunteer plant on the next crop and only in the first period.      

A study was conducted during 2000-2001 in sugarbeet fields of Miandoab plain (West Azarbaijan) which resulted in collecting and identifying of the following 14 species, 14 genera and 12 families belonging to the oribatid mites. Brachychochthonius near immaculatus Forssland**, (Brachychthonidae) **; Ceratozetes sp.,* (Ceratozetidae); Protoribates capucinus Berlese:* (Haplozetidae); Microppia**minus Paoli**,Multioppia wilsoni Aoki**(Oppiidae); Hemileius sp.,* (Scheloribatidae) ; Aphelacarus acarinus (Berlese)*, (Aphelacaridae)*; (Ceratozetidae)*; Phyllozetes emmae (Berlese)*, (Cosmochthonidae)*; Epilohmannia cylindrica cylindrica*; (Epilohmaniidae)*; Rhysotritia ardua penicillata Perez -Inigo*, (Euphthiracaridae)*;Galumna sp*., (Galumnidae)*; Protoribates* sp., (Haplozetidae)*; Lohmannia turcmenica Bulanova- Zachvatkin*, (Lohmanniidae)*; Multioppia radiata Hammer*, (Oppiidae)*; Zygoribatula,. connexa(Berlese*), Z. hortobagyensis Mahunka*, Z. undulata (Berlese)*, (Oribatulidae) * ; Scheloribatesfimbriatus Thor*, (Scheloribatidae).* Families, genera and species indicated with **and * are new records for the Iran's and Miandoab plain's (West Azarbaijan) mite fauna, respectively. Family Oribatulidae with two speceis of Zygoribatula connexa and Z.hortobagyensis had the highest population density.    

An experiment based on a randomized complete block design with three replications was conducted in 2001, to determine a suitable sunflower cultivar as a second crop, in Varamin region. The cultivars under study were belonged to three early (Zariya, Hybrid 25 and Chemianka), middle (Armavirski, Hybrid 33 and Golshid) and late (Progress, Record and Gabor) maturity groups and in two types, hybrid (Hybrid 25, Hybrid 33 and Golshid) and commercial (other cultivars). The stem dry matter in all cultivars increased until the stage of 50 percent flowering, but decreased afterwards. Total dry weight of shoots increased in all cultivars, but a slight decrease in some cultivars, due to falling of leaves and other plant parts, which was observed in later stages. CGR, due to the presence of proper environmental conditions, increased from beginning of growth period, and reached to its maximum value in the flowering stage and then decreased. RGR of different maturity groups was decreased from the beginning of growth period. The rate of decrease was faster at the beginning but slower in the later stages when interplant competition, due to canopy expansion, decreased. LAI increased until the stage of 50 percent flowering and decreased afterwards. The rate of increase was slow at first and then, due to relative leaf area expansion and higher rate of photosynthesis, increased rapidly and reached to its maximum value in the stage of 50 present flowering. It was finally decreased because of shading and senescence of lower leaves, decreased. The Hybrid 25 was the highest yielding cultivar but was not significantly different from Progress, Record, Gabor, Hybrid 33 and Chemianka. Among maturity groups, late maturing cultivars, because their longer period from planting to 50 percent of flowering and seed filling duration, yielded more than the others.    

In this research, the governing equation of the spatially varied flow for a circular pipe was derived and its applicability in determining the flow conditions and the drain pipe diameter computation was evaluated. Also, the discrete forms of the governing equations were solved numerically using the Newton-Raphson method. The assumptions accepted in deriving the traditional equations eliminated the pipe length from the formulation, while this parameter affects the spatially varied flow solution. Therefore, it was necessary to establish a criterion, which makes the comparison between the result of the traditional equations and that of the spatially varied flow method possible. It was assumed that a discharge, which forces the water surface profile to reach the pipe crown at upstream end, is comparable to that of the traditional equation. Numerical results of discharge diameter relationship for different pipe lengths and longitudinal slopes indicated that for the practical slope range, i.e. 0.001 to 0.005, the results of the SVF approximately correspond to the non-uniform flow equation results for the lower limit slopes within the range. But they precede towards the uniform flow equation results as the slope increases. However, this correspondence or even the concordance does not reflect identical results, since the flow condition in the SVF along the conduit is free surface one, while the traditional equations assume a pipe running full and having hydraulic grade line which concords with the pipe crown or sits a slightly higher than the top of the pipe. In other words, if any cross section rather than the upstream end one was considered full in the determination of the discharge-diameter relationship based on the spatially varied flow method, different results would be expected. That is, smaller diameters would be determined to convey the same discharge values. Therefore, the results of the non-uniform formula, although still conservative are more realistic compared to the results of the uniform flow formula. This is because of the inherent safety factor in the diameter computation. A diameter determined based on the non-uniform formula would even bear some pipe obstruction (such as sedimentation) without drastically reducing the conveyance capacity of the pipe.      

The inheritance of cold hardiness in six inbred lines of Brassica napus L., Orakel, PF704591, Maluka, Global, Lisandra and Shiralee was investigated based on the field and laboratory evaluations, using a diallel mating system. A randomized complete block design with three replications was used to evaluate the winter survival of genotypes in the field. In order to evaluate genotypes in the laboratory, a split plot design with two replications was conducted and the amount of tissue water loss, percent of tissue water content and soluble carbohydrates after acclimation of plants along with percent of ion leakage, amount of tissue water loss and survival rate at freezing temperatures of -4, -7, -10 and -13 °C were measured. There were no significant differences among genotypes regarding to survival rate. However, under laboratory condition significant differences were observed among genotypes for all characters, except percent of tissue water content in the cold stress condition. Comparison of means indicated superiority of Orakel over other parents for most of characters under both the cold stress and non-stress conditions and Maluka × Global was the best hybrid with respect to cold resistance traits. This hybrid showed high parent heterosis for all the characters studied and was better than Orakel for soluble carbohydrates and survival rate. Diallel analysis showed that Maluka and Global were better general combiners with respect to all characters studied before and after cold stress. These parents had suitable combination of genes with additive effect which could be used in breeding programs for cold hardiness. Among hybrids the largest specific combining ability was observed for Maluka × Global with respect to most of the characters. Therefore, more genes with dominant effect involved in controlling cold resistance of this hybrid. Narrow- sense heritability estimates for all characters under study were low, but except for survival rate after freezing, the broad - sense heritability estimates ranged from %43.86 to %70.47 which indicated the importance of dominance gene action in controlling the traits under consideration.