فصلنامه علوم زراعی ایران
سال دهم شماره 3 (پیاپی 39، پاییز 1387)

Effect of microtuber size and planting density on traits related to minituber production, in two potato cultivars; Agria and Marfona with three size: <5, 5-10 and >10 millimeter were studied. Microtubers were cultivated with three density (50, 75 and 100 microtuber /m2). The experiment was carried out using a RCB design, with three replications. In this research, number and weight of minitubers per m2 and also means of diameter and weight of minituber were measured. Analysis of variance indicated significant effect of genotypes, size and planting density of microtubers on all traits. In this research, cv. Marfona with 292 minitubers per m2 had greater yield than Agria. Although the diameter and weight of minitubers, Agria showed superiority, but With increasing diameter and weight of microtuber, minituber weight per m2 increased, while minituber diameter decreased.

German chamomile a frequently used phytopharmaceutical, is used as a component of tea-mixes as well as a valuable ingredient of many galentic preparations. In order to investigate the effect of different planting date and nitrogen fertilizer rates on flower yield and its components in German chamomile (Matricaria recutita), an experiment was conducted in split plot arrangement –using a randomized complete block design with three replications and two factors, planting dates were March 5, March 20 and April 4, Nitrogen fertilizer rates were 75, 150 and 225 kg/ha of urea. Number of flower/plant, fresh and dry weight of flower per plant, days to budding, days to 50 and 100% of flowering, number of lateral branches, plant height, stem diameter, and number of tiller per plant were measured. Mean comparison showed that the highest and lowest number of flowers, fresh and dry weight of flower per plant, days to budding, days to 50 and 100% flowering and of essential oil content were related to planting date of March 5 and April 4, respectively. Results also indicated that by increasing nitrogen fertilizer, number of flower, fresh and dry weight of flower per plant, plant height, number of tiller, and essential oil content were increased. The highest number of flowers, fresh and dry weight of flower per plant belonged to planting date of March 5 and 225 kg/ha urea. Regression analysis showed that number of flowers per plant, days to budding and plant height were the main traits contributed to flower yield per plant.

Drought stress often is a limited factor in world that threatns crop yield. Application of breeding and selection of tolerant genotypes to abiotic stresses are logical approach for determination of tolerant genotypes that have a high performance under drought. In order to study quantitative and qualitative traits and their relationships with grain yield in white bean genotypes under optimum and limited irrigation conditions, 15 white bean genotypes were studied in two experiments using randomized complete block design with three replications in experimental field, Faculty of Agricultural, The University of Tehran in 2004 cropping season. Combined analysis of variance showed high genetic variation for most of the traits. Some traits had high genetic variation under both conditions. Stress Susceptibility Index (SSI), Geometric Mean Productivity (GMP) and Stress Tolerance Index (STI) had positive correlation with yield under optimum and limited irrigated conditions. Thus genotypes with greater GMP, STI and lower SSI were identified as the tolerant genotypes. For further evaluation, biplot was used. Four genotypes including No. 1, 2, 3, 5 and 14 were identified as tolerant genotypes and STI, GMP, MP indices were determined as suitable indicas in screening for drought tolerance.

In order to determine the effects of water deficit and different nitrogen levels on seed quality, seed oil yield and seed yield in rapeseed, two field experiments were conducted using a factorial split-plot in randomized complete block design in, 2005-2006 and 2006-2007 growing seasons in Seed and Plant Improvement Institute, Kafaj, Iran. In this study, three water regimes (irrigation after 40, 60 and 80 percent depletion of soil water) and four nitrogen levels (0, 75, 150 and 225 Kg/ha) as factorial in main plots and two cultivars (Zarfam and Modena) as sub-plots, were studied. Results showed that increasing the nitrogen rate from 0 to 220 kg/ha and? ?? in soil water, increased the seed yield. Increase in seed yield was related to increasing the number of siliques in plant and number of seeds per silique in both conditions. In water stress condition the seed oil decreased, but the seed protein increased. Increasing nitrogen use decreased seed oil, but increased seed protein. Results also showed that in both conditions (normal irrigation and water stress), high levels of N application could produce higher seed yield and seed oil yield. Zarfam had a higher nitrogen uptake and mobilization under normal irrigation and severe water stress conditions, and also in higher and lower nitrogen conditions, hence, produced higher seed yield.

In order to study of oxidative stress caused by low temperature stress on three rice (Oryza sativa L.) genotypes, 2-week-old rice seedlings were subjected to 13/15oC and 22/29oC as control (night/day, respectively) in phytotrone for 14 days. This experiment was conducted as factorial using completely randomized design with four replications. Low temperature stress caused significant increases in ascorbate (total, oxide and reduce) and α-tocopherol levels in both roots and leaves. Both roots and leaves of cold tolerant genotype IRCTN33, ascorbate oxide was significantly higher than other genotypes. Leaf hydrogen peroxide in sensitive genotype Hoveizeh had significant increase, which had negative correlation with amount of chlorophylls content. Significant increase in MDA (malondialdehyde) in Hoveizeh leaves showed sever membrane phospholipids per-oxidation. In leaves the lowest amount of H2O2 was detected in cold tolerant genotype IRCTN34. Root ascorbate oxide form in IRCTN34 was significantly less than other genotypes. However, Hoveizeh had weak antioxidant mechanisem among studied genotypes, while it was highly efficient in low temperature tolerant genotypes (IRCTN33 and IRCTN34). Therefore, it is possible to suggest them as low temperature tolerant parents to be used in rice breeding programs.

Effect of row spacing on grain yield and variation in growth indices of rapeseed (Brassica napus L.) cultivars as second crop following rice was investigated in a paddy fields at Rice Research Institute of Iran (Rasht), in 2003-2004 and 2004-2005 growing seasons. The experiment was conducted as a split plot in randomized complete block design with four replications. The main plots consisted of four rapeseed cultivars: Hyola308, RGS003, PF7045/91(Sarigol) and Hyola401 and the sub-plots were three row spacing: 20, 25 and 30 cm at constant plant densities (40 plant/m2). Results showed that PF7045/91 (Sarigol) ranked the first in relative growth rate (4.29 g/g.10GDD), crop growth rate (9.25g/m2.10GDD), leaf area index (1.89) and net assimilation rate (15.89 g/m2.10GDD), grains yield(2043 kg/ha) and oil content (34.19%) was significantly different with the other cultivars. Hyola308 ranked the last among cultivars. Row spacing of 20 cm ranked the first in relative growth rate (4.28 g/g.10GDD), crop growth rate (6.98 g/m2.10GDD), leaf area index (1.706), net assimilation rate (10.25 g/m2.10GDD), grains yield (1777 kg/ha) and oil content (33.35%) and were significantly different from other row spacings in LAI and NAR indices. Results also showed that PF7045/91 (Sarigol) ranked the first in light interception (LI%) and Hyola308 ranked the last (75.5% and 61.5%, respectively). Row spacing of 20 cm ranked the first in light interception (68.5%). Therefore, PF7045/91 (Sarigol) ranked the first in relative growth rate, crop growth rate, leaf area index, and net assimilation rate, grains yield, oil content and light interception. Row spacing of 20 cm also ranked the first for these traits.

In order to investigate effects of water stress, nitrogen fertilizer and manure and mixed nitrogen fertilizer and manure on chlorophyll meter reading, grain yield and yield components of grain maize cv. SC 704, a field study was conducted in 2005 and 2006 cropping seasons. A randomized complete block design with factorial arrangement with three replications was used. Treatment consisted of four levels of nitrogen fertilizer (0, 92, 184 and 276 kg N ha-1), mixed nitrogen fertilizer and manure (46 kg N ha-1 + 2.5 tons ha-1 farm yard manure (FYM), 92 kg N ha-1 + 5 tons ha-1 FYM and 138 kg N ha-1 +7.5 tons ha-1 FYM) and Farm Yard Manure (5, 10 and 15 tons ha-1 FYM) three levels of irrigation (optimum irrigation (control), water stress 75% crop water requirement and water stress 50% crop water requirement). Results showed that decreasing in nitrogen with water stress reduced plant growth. Maximum growth was observed when nitrogen and adequate water for maize crop was applied. Chlorophyll meter readings were significantly higher when water stress and nitrogen increased, and had a linear relationship with kernel nitrogen percentage and was affected by water supply. The results also showed the maximum grain yield was obtained in 138 kg N ha-1 + 7.5 tons ha-1 FYM with an average of 7555 and 7912 kg ha-1 in the first and second years, respectively. Maximum grain yield was observed when optimum irrigation was applied with an average grain yield of 8756 and 9462 kg ha-1 in the first and second years, respectively. When water stress was applied at 50 and 75% of optimum irrigation, grain yield was decreased by 63 and 41% in first year and by 66 and 41% in second year. The maximum grain yield was obtained in 138 kg N ha-1 + 7.5 tons ha-1 FYM and optimum irrigation with an average grain yield of 11790 and 12360 kg ha-1 in the first and second years, respectively. Results indicated that adequate nitrogen fertilizer slightly increased grain yield under water stress. Integrated nitrogen and FYM application increased grain yield under water stress but optimum irrigation increased grain yield. Under severe water stress condition nitrogen applied as integrated nitrogen fertilizer and manure increased grain yield. Integrated nitrogen fertilizers and manure, reduced the needs for chemical fertilizers and produced higher grain yield. It is concluded that application of 138 kg N ha-1 + 7.5 tons FYM ha-1 at optimum irrigation decreased the needs for chemical N fertilizer by 50%. It also increased the grain yield and water productivity by 6.2 and 6%, respectively in the first year and by 4.1 and 4.2% in the second years, as compared to the 276 kg N ha-1.