Iranian Journal of Crop Sciences
Year:2002 | Volume:4 | Issue:2|Papers Count:8

A set of 108 durum wheat accessions, selected from different origins; Turkey, Italy and Mexico, were evaluated for genetic variation for some morphological and physiological characteristics. A field experiment was conducted at Karaj in 1997-1998. The characteristics under investigation were spike yield, awn length, number of grain number per spike, peduncle length, plant height, spike length, spikelet number per spike and 1000 kernel weight. Analysis of variance showed that durum wheat from different origin was significantly different for most of the characteristics. Significant correlations were found between mean spike yield and number of grain no. per spike, 1aaa-kernel weight and number of spikelt per spike. The results of multiplot linear regression and path analysis indicated that 94% of variation in spike yield is explained by 1000kernel weight, grain number per spike and spikelet number per spike. The direct effect of number of grain number per spike and 1aaa-kernel weight on mean spike yield were positive and significant, but the effect of number of spikelet per spike on mean spike yield was indirectly through number of grain per spike. Therefore, number of grain per spike and 1000-kernelweight were the most important components measured and it is concluded that yield improvement in durum wheat would be possible by selection for these characteristics.  

To evaluate the yield loss of potato crop caused by weeds in the Ardebil potato fields and to compare the efficiency of the traditional hand weeding and chemical control, an experiment, using a randomized complete block, was conducted in two main potato producing regions of Ardebil (Niar and Agbilagh) in 1997. Three treatments that were included in the experiment were: no control (check), three time hand weeding during the growing season, and chemical control using Sencor (Metribuzin WP 70%) as pre-emergence herbicide. Analysis of variance indicated that there was a significant difference at I% level between the treatments in both regions. The tuber yield of chemical control treatment was 32% and 10% lower than hand weeding in Niar and Agbilagh, respectively. The tuber yield of no control (check) treatment was also 63% and 43% lower than hand weeding in Niar and Agbilagh, respectively. Combined analysis of variance revealed that there was a significant difference between two locations, treatments and the interaction of treatments locations. The mean tuber yield of hand weeding, chemical control and no control (check) were 29.8, 23.46 and 13.90t/ha, respectively. It was also found that the tuber yield of hand weeding and chemical control treatments were higher by 15.90 and 9.56 t/ha respectively in comparison with no control (check). The mean tuber yield in no control (check) was 53% lower than the hand weeding treatment.    

Domsiah is one of local rice cultivar with best quality in Iran, but it is nearly late with long awn. This study was conducted to induce earliness and awnless characterstics in Domsiah cultivar from 1995 to 1999. The seeds were irradiated with gamma rays at 100, 200 and 300 Gray, and Dimethyl Sulfate (DMS) at 0.1%, 0.2% and 0.3% (for 24 hrs. in room temperature), separately. At the end of first year of study, main panicels of some randomly selected plant were harvested and planted at M2 generation as a panicle-to-row. Results showed no sigificant varition among the DMS treatments; hence these treatments were removed from the study. Four early mutant populations (E1 to E4) were obtained from treatments of gamma rays at M2 generation. These mutant populations showed segregation for maturity. Meanwhile, the E1 population showed segragation for awnless. The plant height, culm number, maturity and panicle length were studied in mutant lines at M3generation. The E3line was 15 days earlier than control at M4 generation. The plant height of this line was significantly different compared to control, the awnless mutant line was also shorter and earlier. In order to study some morphological characteristics and yield at M 5generation, the E3and awnless mutant lines were planted in randomized completed block design with three replications in Rasht and Tonekabon in 1999 and 2000. The characteristics under study were included: plant height, culm number, peduncle, second internode length, flag leaf length and width, days to panicle emergence (DPE), days to maturity (DMA), panicle length, grain length and width, spikelet fertility, grain no. per panicle, grain yield, 100-grainweight, amylose (%), gel consistency and gelatination temperature. There were no significant differences in second internode length, DPE, spikelet fertility, amylose %, gel consistency and gelatination temperature. Generally, the correlation coefficient between DPE and DMA in rice is positive and significant, however, it was found non significant in this study. Because of highly significant correlation (r =0.7**) between yield and l00-grainweight, it is possible to improve grain yield through 100-grainweight. Although, there was not a significant difference between early mutant and awnless lines in DMA, however, 100 grain weight and no. of grain per panicle in awnless mutant line were higher than in early mutant line. These two mutant lines has significant difference for DMA compared to control i.e. they were 13 days earlier than control.    

Utilization of plant residues has led to identification of natural methods of crop protection. One of such method is using the knowledge of allelopathy. A field study was conducted to determine the response of corn to different rates and ages of sunflower residues in Sari, Iran, using a randomized complete block design with seven treatments and four replications. Treatments included the age of plant residues (6, 8, and 10 week-old), plant residue rates (8 and 16% soil weight), and control (no plant residue). Seedling emergence (two weeks after planting), plant height and dry weight of corn (two, four, and six weeks after planting) and final plant height and dry weight and grain yield of corn plant were measured. Results showed that seedling emergence, height, and dry weight were reduced in comparison with control. Increasing the age of residues did not significantly affect on these traits for 6 and 8 weeks old residues, but 10 weeks old residue reduced all measured traits. Residues rate did not significantly affect these traits. The most reduction in final plant height and dry weight were observed in older residue (I0 weeks old) mixed with soil treatment (22 and 52%. respectively). In these study residues from older plants found to be more phytotoxic.    

In order to evaluate the competitive effects of wild oat on winter wheat in different densities, a field experiment was conducted in Mashad in 2001 .The experiment was carried out as factorial in a randomized complete block design with four replications. The factors included wheat densities at 3 levels (300,450,600 plants/m2) and wild oat densities at 5 levels (0, 20, 40, 80,160 plants/m2). Results indicated that wild oat plant height was lower in the early stages of growth but increased in the latest stages compared to wheat. Wheat plant height increased with increases in wheat plant density. Increase in wheat plant density led to decrease in wild oat LAI and biomass. Time of canopy closure in wild oat reached faster than winter wheat (nearly 15 days).The average wheat and wild oat relative growth rates during the growth period were 0.027 and 0.034 g-l g-1 day-l, respectively. The maximum amount of wheat yield loss was nearly 47% in 160 wild oat and 300 wheat plants/m2 and in the presence of wild oat, wheat yield loss decreased as wheat plant density increased.    

Black stem disease caused by Phoma macdonaldii is one of the most important diseases of sunflower. Development of resistant cultivars is one of the useful approaches to control this disease. For this purpose, reaction of 10 sunflower cultivars to the disease was studied in controlled environmental conditions in growth chamber using a randomized complete block design with 3 replications, (each replication consisted of 10 seedlings). Twelve days-old seedlings were inoculated with pycniospore suspension of Phama macdonaldii (106 pycniospore/ml). Ten days after inoculation, the two cotyledon petioles of each seedling were scored on a I to 9 rating scale for the percentage of necrosis on petiole area. The most tolerant cultivars were DK3825 and Argos (scored 4 and 4.4 respectively) and the most susceptible cultivar was Andora (scored 8.70). For comparison of the resistance of cultivars at the seedling and adult plant stages, two other experiments were carried out on four cultivars (resistant and susceptible) at the fifth pair leaves and flowering stages under the same conditions. In both growth stages, the classification of cultivars at the seedling stage was confirmed. Positive and significant correlations between the reaction of cultivars at the fifth pair leaves (r =0.97) and flowering stage (r =0.99) were observed.  

In order to evalute the effects of planting date on yield and yield components of spring safflower cultivars, this study was carried out in Arak, Iran, in year 2000 . A split-plot arrangment of treatment in a randomized complete block design with four replications was used. Planting date were assigned in the main plots and cultivars were arranged in the subplots. Seed were sown by hand (whitout preplanting irrigation) on April 24, May 9 and May 24, 2000. Five cultivars of spring safflower including Gila, UC - 1, Nebraska - 10, Arak -2811 and Esfahan local cultivar were used. Each subplot consisted of 4 rows, 7 m long with 50 cm between rows and 5 cm between plants on the rows. In this study, grain yield and it"s related characteristics such as: date of emergence, plant height, branching height, number of branches, number of bolls per plant, number of infertile bolls per plant, number of seed per boll, 1000 seed weight, biological yield, seed oil percentage, oil yield and harvest index were assessed. Results indicated that Arak - 2811 and Esfahan local cultivars were significantly superior to the other cultivars. Considering the earliness of Gila cultivar, it could be included in a crop rotation after barley without concern of unsuitable weather of autumn, and an acceptable grain yield could be harvested.