نشریه نهال و بذر
سال هجدهم شماره 3 (تابستان 1381)

A Field experiment was conducted to study drought tolerance indices in corn genotypes for two years (1996 and 1997) at Seed and Plant Improvement Institute Experimental Station, Karaj, Iran. Three hybrids (SC704, SC711, and SC704M) and four parent lines (B73, B73 x R84, M017 and L105) with four stress treatments (without stress, stress at vegetative period, at an thesis period, and during kernel filling period) were studied in RCB design with three replications. Among four estimated indices, i.e. mean productivity (MP), tolerance index (TOLl), stress susceptibility index (SSI), and stress tolerance index (STI), the last index was more efficient than other indices in selection ,of genotypes under stress and non-stressed conditions. Among the genotypes, hybrid SC704 was more suitable for non-stressed conditions because of its high yield potential and hybrid SC704M was more adapted to stress condition. Hybrid SC711 showed the average performance of "other -two hybrids. Except parent B73 x B84, with high potential yield, the most tolerant line in this study was M017. Correlation between hybrids and their parents for yield and tolerance indices under optimum condition, were negative and weak, however, under stress conditions, there were positive and stronger correlations.

Intercropping of two cultivars of soybean, especially those of different growth types, may cause increase in production, mainly due to better use of required sources for growth. In a field experiment, seed yield of two soy bean cultivars which differed in some morphological characteristics were investigated at Khoy Agricultural Research Station. A split plot design with 3 replications was used. Main plots were consisted of 3 plant densities of 20, 33 and 50 plants m-2, sub-plots were allocated to 5 intercropping ratios of Williams and Clark cultivars. The results indicated that plant height, number of sub branches and first pods height were affected by plant density and intercropping ratio of 2 cultivars. Pod number per plant and 1000 seed weight were the most important yield components and showed a positive correlation with plant density and intercropping ratios, but number of seeds per plant was not affected. The highest seed yield (4615 kgha-l) was obtained from 50:50 ratio of two cultivars in 50 plants m-2 density which had a land equivalent ratio (LER) above 1.10.

A Field experiment was conducted to determine the effect of five plant densities (10, 15, 20, 25 and 30 plants m-2) on yield and yield components of three sorghum cultivars (Local, Payman and Kimyia) in Sistan region in South East of Iran, using a split design based on randomized complete block design. The results showed that the plant density had a significant effect on number of seeds per panicle, 1000 kw, grain yield and grain yield per plant. The highest grain yield (3830 kg ha-1) was obtained from the density of 30 plants m-2. Grain yield per plant, number of seeds per panicle and 1000 kw were significantly decreased by increase in plant density. Local cultivar produced the highest number of panicles and number of seeds per panicle than other cultivars. The interaction effects of treatments on measured traits were not significant. According to the obtained results, density of 30 plants m-2 are more appreperiate and recommendable for the region.

Two experiments were conducted to find out the best grafting date and best bed system to induce enough callus in grafting :::union:::. Both experiments were run in the greenhouse of Department of Horticulture, Faculty of Agriculture, the University of Tehran during year 2001. Two methods of grafting i.e. side-grafting and saddle-grafting were applied in two separate experiments. In the first experiment, using side-grafting technique, one-year old Persian walnut seedlings with diameter of 2-4 cm were used. In the second experiment, using saddle-grafting technique, thin (1-2 cm.) one year old seedlings were used. In these experiments, effects of date of grafting (22nd December and 22nd January), and kind of callusing bed (hot bed and normal bed without heating system at the bottom) were studied as a factorial in completely randomized design with three replications of 20 plants/ plot. Results showed that in the first experiment, using side-grafting technique, date of grafting had highly significant effect on grafting success in a way that first date was much more successful than the second date. Kind of callusing bed had no significant effect. However, in this experiment, the best result was obtained by grafting at the first date and using hot bed. In the second experiment, using saddle-grafting technique, first date was more successful than the second date but the differences did not reach significant level. Kind of callusing bed had also no effect.

To investigate the effect of Citrus species and harvesting time on the quantity and quality of hesperidins, a falconoid used in medicine industries, an experiment was conducted at Citrus Research Institute located in Ramsar. The experiment was started in 1997 and repeated in 1998. The treatments consisted of four citrus species included Local orange (Citrus sinensis [L] Osbeck), Thomson Navel orange (Citrus sinensis [L] Osbeck), Clementine mandarin (Citrus reticulate Blanco) and Satsuma mandarin (Citrus unshiu Marcovitch), and four harvest times, as the fruits harvested from June drop every ten days. Three trees were selected for each species as three replications in the base of two-factor completely randomized design. According to the results, harvest time had significant effect on hesperidin content. As the highest hesperidins content was obtained 50 to 60 days after full bloom. Results also showed that fallen fruits at June drop or due to drought and high temperature season can be used for extracting of hesperidins. Hesperidin yield was higher in Local orange and Clementine mandarin than the other cultivars. Because of the Local orange cultivated in large scale in the north of Iran, therefore it is a suitable source for production of hesperidin.

Two bactericidal chemicals including copperoxychloride in three concentrations (3000, 1500 and 1000 ppm) and Bordeaux mixture in three concentrations (1 %,0.75% and 0.50%) separately and in combination with pruning application were evaluated on . Citrus aurantifolia for control of citrus bacterial canker disease in tv,. J Citrus aurantifolia orchards in Kahnoj and Jiroft. Two compounds were applied in three different times in the growing season, winter, budding stage and after petal fall. Complete randomized block design and four replicates per treatment were applied and SAS software used for data analysis. Results showed that in general and under equal condition, Bordeaux mixture was more effective than copperoxychloride for control of citrus bacterial canker disease. Best control of disease was resulted from application of Bordeaux mixture in three stages including 1% in winter, 0.75% in budding stage and 0.5% after petal fall .

Genetic and geographical variation in 600 Iranian local bread wheat lines were studied in Agricultural College at Karaj in 1998/99 cropping season. A systematic design and multivariate techniques were used. To study morpho-thecnological traits. Principal component analysis reduced 22 variables down to eight components with 80.5% proportional cumulative variance. Factor analysis using maximum likelihood estimation method with varimax rotation was performed on 21 variables and reduced them down to six common factors with 63.6% proportional cumulative variance which were economic yield production and partitioning (17.4%), dry matter production (15.2%), tillering (10.3%), productivity (8.2%), height-related factors (6.9%) and preheating phase length (5.6%). Common and specific variances of revealed that proportional common variances of grain yield, 100-kernel weight, No. of kernels/ Spike and No. of fertile tillers/ plant were 98%, 93%, 93% and 84%, respectively. According to the results, consideration of the 6-common factor model is very suitable and determinable for yield and yield components. With cluster analysis using UPGMA method and based on 65% within group similarity, locations were classified into six clusters. Cluster analysis using WARD method classified the 600 landraces into six clusters. One-way ANOV A on all traits was performed using clusters membership as subscript to prove 6-cluster model statistically. The results showed that these 6 clusters had significant differences (?= 0.001). Genetic variability did not follow the same pattern as geographical variability.

Experiments were conducted to study the in vitro propagation of nine improved Asian pear cultivars namely "KS6", "KS7", "KS8", "KS9", "KS10", "KS11", "KS12", "KS13" and "KS14" and the effects o("culture media and plant growth regulators on the micropropagation. Single-node explants, harvested from current season"s growth shoots, were disinfected and cultured on three basal media, murashige and Skoog (MS), halfstrength MS salts (1/2 MS) and woody plant medium (WPM)," supplemented with 1 mg 1-1 benzylaminopurine (BAP). Growth and proliferation of Asian pear explants at the stablishment phase were obtained only in five cultivars ("KS7", "KS8", "KS12", "KS13" and "KS14"), and WPM was the best medium for their growth. In the multiplication phase, shoots obtained from in vitro conditions were subcultured four times, each with one-month interval, on the fresh media, supplemented with various concentrations of BAP (0, 1 and 2 mg 1-1 The highest shoot proliferation rate was obtained at 2 mg 1-1 BAP. Meanwhile, with increase of BAP concentration in this stage, proliferated shoots height was decreased and vitrified shoots percentage, increased. The best medium for proliferation of "KS7" shoots was WPM, but there was not any significant difference among the various media for the other cultivars (excepting "KS14", proliferated in WPM better than 1/2 MS). Moreover, with increase of subculture number, proliferation rate was increased, too. For rooting, 1/2 MS medium with different concentrations of indolebutyric acid (IBA) were used. Shoots were transferred on mentioned medium for different durations before transfering on the hormone-free MS medium. Micro propagated shoots failed to produce roots in all cultivars, after two months.

To identify races of T. laevis, 20 infected samples of wheat were collected from important wheat grown areas. Seeds of the differential monogenic and oligogenic lines were artificially infected with teliospores of different samples and grown in the field. At harvesting time, percentage of infected spikes was assessed for each line, and races of each sample were determined, using standard method for race identification. According to the results, five isolates being virulent on Bt7 was determined as race L-1, four isolates being virulent on Ba and Bt? as race L-3, two isolates being virulent on Btl and Bt? as race L-4, eight isolates being virulent on Bt2, Bt3 and Bt7 as race L-1 0 and one isolate being virulent on Bt2, Bt3, Bt4, Bt6 and Bt7 as race L-17. Genes Bt2, Bt3 and Bt7 were susceptible to most of the isolates, therefore these genes are not recommended for using in breeding programs, Bt8, Bt9 and Btl3 were susceptible to some isolates. Genes Bt1, Bt4, Bt6 (except one race), Bt5, Bt10, Bt11, Bt12, Bt14 and BtP were resistant to all identified races, these genes are effective for development of resistant cultivars in different parts of the Iran.

Line No. 4 was selected from local Champ a rice of Lord Egan, based on pure line selection method, during 1992 to 1995. The mean yield of this line was 6342 and 6829 kgha-l in two regions of Lord Egan in 1996 to 1997. The yield of this line was 700-1500 kgha-l more than that of Lord Egan local rice. Line 4 is more early maturing than the local rice with better marketability and quality. Amylase content of the grain is 21.4 24.6% and its white rice length is 6.1-6.3 mm. The grain are aweless, the color of pale a is brown furrow on straw, Panicle execution from pod of flay leaf is well, the plant height is 115-120 cm, and the growth period (days from planting to harvest) is 135-140 days. The panicle length is 21-24 cm, the seed number per panicle is 90-120 but its percentage of unfilled grains is less than local rice. Line 4 was introduced in Iran as Kohrang cultivar in 1999.