فصلنامه علوم زراعی ایران
سال نهم شماره 4 (پیاپی 36، زمستان 1386)

In cotton (Gossypium hirsutum L.) transformation, for regenerating plants from a single cell, an optimized tissue culture system is necessary. Successful production of transgenic cotton depends on regenerating of many plants; therefore, somatic embryogenesis was investigated for three cotton cultivars. Hypocotyls of cvs. Sahel, Varamin and Coker 312 were isolated and placed on two cotton callus induction media containing MSB medium supplemented with 0.1 mg/l 2,4-D, 0.1 mg/l kinetin, 0.75 g/l MgCl2; and MS medium supplemented with 0.1 mg/l Kinetin and 0.2 mg/l IBA. In medium containing 2,4-D and Kinetin, Sahel and Coker312 explants produced callus earlier than Varamin and the volume of calli were larger, too. The percentage of callus production for Sahel cultivar was higher than Varamin. For embryogenesis induction and maturation of embryos, produced calli were transferred onto MSB medium supplemented with 0.75 g/l MgCl2 and 1.9 g/l KNo3. Numbers of embryogenic calli for Coker312 were higher than Sahel. Germination of somatic embryos for Coker312 and Sahel on embryo germination medium containing MSB supplemented with 0.1 mg/l Zeatin and 2 g/l activated charcoal were earlier than Varamin. Percentage of somatic embryos produced from Coker 312 was higher than Sahel. For rooting, there were no significant differences among cotton cultivars and five rooting media.

In order to evaluate rice genotypes for tolerance to terminal drought stress and to identifying tolerant and sensitive genotypes to this stress, 49 rice genotypes were studied in two environments (stressed and non – stressed conditions) using randomized complete blocks design with three replications in Research Field, Faculty of Agricultural Sciences, Guilan University in 2006 cropping season. The studied traits were included: plant height, panicle number plant, grain number panicle, spikelet number panicle, paddy yield, harvest index, relative water content, etc. Analysis of variance showed that there were significant effect (p < 0.01) of genotypes on all traits in two environments, which implies genetic variation among genotypes. Mean comparison of genotypes showed that in two environments, the highest paddy yield belonged to Nemat cultivar (7.31 and 7.07 t/ha respectively), whereas the least paddy yield in non - stressed environment belonged to Dom - sefid,s cultivar (2.74 t/ha) and in drought stressed environment to Diwani,s cultivar (1.46 t/ha). Considering yield components (panicle number/ plant, spikelet number/ panicle, grain number/panicle in Nemat contributed to its higher paddy yield in stressed and non - stressed conditions. Percentage of reduction in traits means by drought stress showed that the paddy yield (40%) was the most affected trait. According to drought resistant indices, the highest mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), stress tolerance index (STI), relative water content (RWC) and the least stress susceptibility index (SSI) and tolerance index (TOL) belonged to Nemat,s cultivar. Relationship between drought resistant indices and paddy yield in stressed and non - stressed environments showed that MP, GMP, HM, STI and RWC indices had positive and significant correlation with yield in stress and non - stress environments and would be suitable indices in both environments for selection of drought tolerant cultivars. It is concluded that STI, is the most suitable index among drought indices.

Large amount of potato seed in the world is produced by in vitro virus free mini tubers. Therefore, evaluation of commercial varieties for production of virus free potato minituber is critical. In this study the effects of different hormones BA and KIN at three levels 0, 0.5 and 1 mgl-1 and GA3 at four levels 0, 2, 2.5 and 3 mgl-1 either alone or in combinations were evaluated in meristem culture of four potato cultivars; Agria, Marfona, Sante and Burren. Plantlets were sub-cultured into the semi-solid media including four hormones combinations of MS0 medium, MS medium containing 0.5 mgl-1 BA + 0.5 mgl-1 IBA, 0.5 mgl-1 IBA + 1.5 mgl-1 GA3 and MS medium containing 0.5 mgl-1 BA + 1.5 mgl-1 IBA + 2 mgl-1 GA3 to achieve the best medium for sub-culture. Then ELISA test was conducted and virus free plantlets were selected and transferred to the greenhouse. After 90 days, number of minitubers for each cultivar were counted and recorded. The best medium for primary establishment of meristem for Burren was MS medium containing 2 mgl-1 GA3, for Agria was MS medium containing 2.5 mgl-1, for Marfona and Sante the best medium was MS containing 0.5 mgl-1 KIN + 3 mgl-1 GA3. The best media for sub-culture of virus free plantlets for meristem culture for Burren, Agria and Marfona was semi-solid MS medium containing 1.5 mgl-1 IBA + 0.5 mgl-1 BA + 2 mgl-1 GA3 and for Sante was 0.5 mgl-1 IBA + 1.5 mgl-1 GA3. Marfona had the greatest and Agria the least number of minituber.

To determine potential productivity of Red clover varities, an experiment was carried out with six treatments and four replications using RCBD, under different environmental conditions in 2002–2004. Results showed that there was a significant difference (p<0.05) between Red clover varities for fresh and dry forage yield over years and locations. Karaj with 87.99 tha-1 fresh yield and 15.5 t ha-1 dry forage yield produceed the highest yield and Shahr-e-Kord with 38.14 tha-1 fresh yield and 8.76 tha-1 dry forage yield produced the lowest yield. Mean comparison of fresh and dry forage yield of Red clover varities over years and locations showed that the best adapted varieties for different locations as follows: in Karaj and Sharh-e-Kord Redquin and Kulubara; in Sanandaj and Gorgan; Redquin and Bosa, in Kermanshah and Arak Redquin, Tolidi-e-FAO and Tolidi-e-Karaj Results also showed that years and locations significantly affected on potential productivity of Red clover varities. Fresh forage yield varied between 91.8-40.2 tha-1 and dry forage yield varied between 9.02-16.42 tha-1. In all locations, forage yield of Red clover varities followed a decreasing trend from the first to the third year, forge yield potential of Red clover varities was the highest in the first year and the lowest in the third year, respectively. Kulubara was more tolerant, and Tolidi-e-FAO the most sensitive to powdery mildew, respectively. The final results showed that although in each locations there were more adapted variety, but Redquin and Kulubara are recommended as wide adapted varieties for all locations.

In order to determine grain yield and its components of seven canola cultivars in competition with wild mustard, a field experiment was conducted at the Araqai Mohaleh agriculture research station in Golestan province, in 2005-2006 growing season. The experiment was established as factorial arrangement using a randomized complete blocks design with three replications. The seven canola cultivars (Hayola‏401, Hayola‏330, RGS‏003, Option500, Sarigol, Zarfam and Talayeh) were planted in weed-free and weed-‏infested (with 30 wild mustard plants per square meter) plots. Grain yield, harvest index, number of pods/plant, number of grains/pod and 1000-grain weight were measured. Result showed significant differences in grain yield among cultivars. Results also indicated significant differences in yield components in weed-free and weed-infested conditions. Mean comparisons among cultivars showed that Hayola330 produced the highest grain yield with average of 2836 kg/ha and Talayeh produced the lowest grain yield in weed-free condition with average of 1729 kg/ha. Under weed-infested condition Hayola330 produced the highest grain yield with average of 870 kg/ha and option500 had the lowest grain yield with average of 101 kg/ha. Although, Hayola330 produced the highest grain yield in weed-infested but it had higher yield loss than Zarfam cultivar. Therefore, the degree of tolerance in canola cultivars differed, in competition with wild mustard. To develop cultivars with high grain yield in both weed-free and weed-infested conditions are to be included as a strategy in canola breeding program.

In order to evaluate the effect of different levels of irrigation and plant density on grain yield and its components in chickpea cv. Kaka, a field study was conducted at Research Field Station of Agricultural Faculty, Mohaghegh Ardabili University during 2006 cropping season. Treatments were arranged as split plot in randomized complete block design with three replications. Different irrigation levels (full irrigation, irrigation to flowering stage, irrigation after flowering stage and no-irrigation) were assigned to main plots and sub-plots comprised of different plant densities (16, 32 and 64 plants/m2). Results showed that irrigation and density levels significantly affected pod number per plant, 1000-grain weight, grain yield per unit area and harvest index. Number of pod per plant, 1000-grain weight, grain yield and harvest index were greater in full irrigation and irrigation to flowering stage in comparison to other irrigation levels. Grain yield per plant, pod number per plan, 1000-grain weight and harvest index were greater at 16 and 32 plants/m2 in comparison to 64 plants/m2. In contrast, grain yield per unit area at 64 plants/m2 were significantly greater than other plant densities. Interaction of irrigation × plant density indicated that the highest and the lowest grain yield was achieved in 64 plants/m2 in full irrigation and no-irrigation. However, there was not significant difference between 64 and 32 plants/m2 in no-irrigation treatments. It is concluded that irrigation to flowering stage and 64 plants/m2 produced reasonable grain yield under the conditions of this study.

In order to evaluate the effects of plant density and planting pattern on yield, yield components of apetalous flowers and petalled rapeseed, a field experiment was conducted in Rice Research Institute of Iran located in Rasht in 2005- 2006. The experimental design was arranged as a split plot-factorial in a randomized complete block with three replications in which, planting pattern (rectangular and square) assigned to main plot and two rapeseed cultivars (petalled = Hyola 401 and apetalous = Hylite 201) and plant densities (33, 67 and 133 plants per unit area) as factorial in sub-plots. Results showed that there were significant differences between cultivars, plant density and planting patterns in growth indices and radiation use efficiency (RUE). At the flowering, the leaf area index in apetalous cultivar was 3% greater than the petalled rapeseed (3.22 and 3.12, respectively). Dry Matter of apetalous rapeseed was 11% higher than the petalled rapeseed (1441 and 1280 g/m2, respectively). Similar results were obtained for crop growth rate (CGR) and net assimilation rate (NAR) (1.5 and 23%, respectively). Maximum LAI and TDM were obtained earlier with the high plant density. Leaf area index, Dry Weight, CGR and NAR in square planting pattern were higher than the rectangular planting pattern. Radiation use efficiency in apetalous rapeseed was 9.2% higher than the petalled cultivar (2.38 and 2.16 g/Mj) which caused 14.6% increase in grain yield.

Accuracy of sugar beet trials, particularly variety comparisons, depends on several factors including; statistical design, treatments oriented, experimental techniques, and replication numbers in order to estimate various components of a statistical model precisely. Testing agronomic treatments or evaluating new varieties for plant protection (PVP) or value for cultivation and use (VCU) under both field and glass-house conditions needs a reliable statistical design. There are many factors and circumstances like response of genotype, location, year, agronomic techniques etc. that affect performance of a sugar beet trial. Some of these factors are usually unknown before conducting the experiment that may influence the precision and accuracy of a field experiment. In addition to these, uncontrolled variations are usually summed in the experimental error. Type and quantity of the “variance of error” may be originated from different sources in which mainly are the precision of measurements and techniques as well as choice of the experimental design. The experimental design is also function of a number of other factors. When using RCBD, plots should be oriented in such a way to minimize soil variation, nutrient and pesticide residuauls within a block. In practice, treatments should be applied in parallel to the directions of blocks of a trial to minimize variance of error. A well-prepared field trial is effective in reducing the experimental error; however, a good and homogenous field emergence depends on the quality of seedbed preparation. Size of plot and plant number within a plot is essentially important. Homogeneity of a plot depends on its size; too big plots increase the error and too small plots would leads to lack of precision. An optimum plot size and average number of plants at harvest time needs to be sufficient to stabilize the error at a low level. If a trial carried out at different locations for several years, effects of these factors must be considerd precisely. Random or fixed effects of entries are very important for the estimation of variances. In sugar beet variety trials, it is common to apply either RCBD or lattice designs, each of them has advantages and limitations. In order to reduce variance of error and consequently increasing experimental accuracy of variety comparison, complete block or incomplete blocks (lattice design) should be arranged on a homogenized soil. Since there are close competitions among commercial sugar beet varieties, an appropriate statistical model based on the type of variation sources is essential to select superior varieties within a trial and increases the efficiency of selection for superior lines and varieties in plant breeding programs.