Iranian Journal of Crop Sciences
Year:2001 | Volume:3 | Issue:4|Papers Count:8

Fusarium head blight (FHB) of wheat is an important yield reducing factor in warm and humid wheat growing areas of the world. In Iran, due to introduction and widely cultivation of a susceptible cultivar Falat in Caspian sea shore area (Zone I), the FHB caused major epidemics and resulted in crop losses. In some parts of the central and southern regions of Iran, fusarium has also been reported on a limited scale. During 1997 - 98 growing season, 121 and 217 lines cultivars of wheat were evaluated for reaction to FHB at Sari and Gorgan Research Stations, respectively. Studies were conducted to determine correlation between spike density, plant height, 1000 KW., days to heading, and disease severity. Correlation coefficients and multiple range regression coefficient at Sari Station indicated that there was a significant negative correlation between grain infection and 1000 KW and spike density. Also, there were significant and negative regression between infection severity and days to heading, spike density, and 1000 KW. Results at the Gorgan Station also indicated that there were negative and significant correlation and regression coefficient between infection severity and 1000 KW, spike density, and plant height. These results can be useful for identification of resistance sources to FHB.

Rice is an important crop and is cultivated in diverse geographical areas of Iran. The presence of genetic diversity is essential in breeding programs. We have used 113 Iranian rice accessions obtained from the Iranian National Gene Bank Collected from various geographical origins. A set of 14 oligonucleotide primers was used for RAPD analysis. A total 135 reproducihly scorahle RAPD markers were generated across all varieties. Scoring was carried out on the basis of presence (1) and absence (0) of a given band. This data was used to construct a resemblance matrix according to Jaccard coefficient. NTSYS program was used to perform cluster analysis and build the dendrogram according to the UPGMA clustering method. These accessions were grouped in seven clusters and similarity among them was 45 - 88%. "Fajr" and "Sahel" with an 80% similarity were the closest improved cultivars. This germplasm showed vast diversity even for accessions with the same names. They are desirable sources for future breeding purposes.

Wheat c.v. Sabalan nutrient requirement was estimated under rainfed and supplemental irrigation conditions. The experiment was conducted in RCBD (split plot factorial) design with three replications. Main plots included three levels of irrigation namely: I0 (rain fed), I1 (one irrigation at heading stage), and I2 (two irrigations at heading and milky stage). Subplots included fertilizer use in factorial combination, nitrogen levels of 0,60,120 kg N ha-1, and, phosphorus levels of 0 and 60 kg P205 ha-1. The experiment was carried for 4 years during 1992-1996 at Maragheh Dry land Station. Amount of water used in each irrigation was calculated based on moisture deficiency from F.C in 100 cm soil profile depth. Nitrogen was split applied as urea (1.2 at planting and 1/2 at first irrigation) and triple superphosphate was applied at planting time. Results showed that irrigation had significant effects on wheat grain, straw yield and T.K.W increase at the 1% probability level. Highest yield was obtained from I1 as 1843 kg ha-1. Decreasing soil moisture from F.C, increased the efficiency of supplemental irrigation. Regression equation showed that wheat nitrogen requirement in rain fed (I0) and supplemental irrigation (I1) was 48 and 63 kg N ha-1, respectively and phosphorus requirement in (I0) and (I1) was 20 and 28 kg P205 ha-I, respectively.

In order to have a healthy environment, high productivity and reduced costs, it is essential to use lower rates of herbicides in chemical weed control. To investigate the effects of reduced rates of herbicides on weed control and soybean yield, an experiment was carried out in a randomized complete design with 11 treatments and four replications at experimental station of Agriculture College of Sari, Iran, during the growing season of 2000. Three herbicides were used at three rates each, namely, the recommended rate, 50 and 75% of the recommended rate of trit10uralin (pre - plant incorporation), bentazon, and sethoxydim (post emergence). Eleven treatments were triflouralin (pre - plant incorporation) at 0.84 kgailha (recommended rate), 0.63 and 0.42 kgai/ha, sethoxydim (post emergence) at 0.224 kgai/ha (recommended rate), 0.168, 0.112 kgai/ha and bentazon (post emergence) at 0.84 kgai/ha (recommended rate), 0.63, and 0.42 kgai/ha and two control treatments of weed - free check and weedy - check. Considering soybean seed yield of weed free check, reduction of herbicide application is possible to 50 percent of recommended rate. All treatments could control velvetleaf (Abutilon teophrasti) and pigweed (Amaranthus retroflexus) more than ninety percent (90%). The best grass control was seen in 50% of the recommended rates of trit10uralin and sethoxydim. The herbicides had no adverse effect on soybean. With reduced herbicide rates, both weed control percentage and soybean yield did not show any significant difference in comparison to recommended rate.

There is a specific relation between accumulation of some organic micro molecules, which plays a role in cell osmotic regulation, and salinity tolerance in saline induced plants. To evaluate accumulation of some compounds on water relations of alfalfa cultivars, an experiment was conducted in factorial design, arranged in RCBD with 3 replicates and 5 salinity levels (0 as control, 50,100, 150 and 200 mM NaCl) in greenhouse. Four alfalfa varieties (Sistan and Bluchestan, Golestan (20313), FAO (2566) and Hamedani Ahar) were irrigated with Hougland nutrient solution in hydroponics culture. Salinity stress reduced plant water potential and tissues relative water content (RWC). Reduction in RWC was proportional to reduction in water potential under saline condition. Least and most reduction of.RWC and water potential were observed in "Golestan" and "Hamedan-Ahar; respectively. Results showed that major reason for reduction of water potential of varieties under saline condition was due to accumulation of adaptability metabolites especially soluble carbohydrates. The correlation between adaptability metabolites with RWC was significantly positive but with water potential was negative. Significant differences were observed for all traits. The most accumulation rate of proline and soluble carbohydrates concentrations were in Sistan and Baluchestan and Golestan (20313), and the least were in FAO (2566) and Hamedani Ahar. Stomatal resistance has a role on adaptive metabolites on water relations in Alfalfa because resistant varieties with the least stomatal resistance provided more energy for adaptive metabolites production.

The effect of different planting dates on yield and yield components of five soybean cultivars, as the second crop, was evaluated at Research Station of Chahar Mahal and Bakhteyari Agricultural center in 1997. For this purpose, five soybean cultivars, namely Williams, Zane, Harcure, Elgin and Karaj - 18 were evaluated at mid and late June and mid July planting dates in a split plot design with randomized complete block layout. Planting dates and cultivars were considered as main and sub - plot, respectively. Vegetative and reproductive growth durations, plant dry weight at flowering, pod - set, maturity, vegetative growth related traits, yield components, seed weight per plant and grain yield were evaluated. Delay in planting reduced the number of days from planting to t10wering and necessary growing degree days for all the cultivars, but the duration from germination and t10wering to physiological maturity increased and growing degree days from t10wering to maturity decreased. Harcure, Williams cvs. and Karaj - 18 reached maturity after 101, 117 and 117 days from planting respectively. The effect of planting date on growth and development lenght period were significant at 1% probability level. Delay in planting date reduced plant height, height of first pod from soil surface, number of secondary stem, harvest index and yield. Mean comparisons show that duration of growth and development reduced with delay in planting date. The first planting date (16 June) was better than other dates and had the highest yield (2942.2 kg/ha).