Iranian Journal of Crop Sciences
Year:2003 | Volume:5 | Issue:1|Papers Count:8

Leaf area distribution which determines the interception of radiation for photosynthesis is affected by environmental conditions, specially drought stress and nutrients contents. The shape of the polynomial reflected the bell shape of individual leaf area versus leaf number curves, with the highest leaf area in the mid-portion of the canopy. A third-order polynomial accurately described the relationship between leaf area index (LAI) and plant height at tasseling stage. This study was conducted as a split-factorial in Randomized Complete Block Design with four replications. Drought treatments were the plant irrigation after soil water reached 70% (without stress), 60% (medium stress), and 50% (high stress) of field capacity (FC) as main plots. Zn (0, 10 and 20 kg/ha) and P (0 and 150 kg/ha P2O5) were randomly assigned to sub-plots. The results showed that all traits were affected by drought stress. By increasing in drought stress, PAR interception increased at the bottom of the canopy. Increasing had also similar effects on all characteristics but with lower severity than drought stress. No significant effects of Zn were seen. Interactions between treatments were not significant. The results of this experiment showed that grain yield increased linearly with increase in total LAI, LAI above ear, and LAI below ear; but decreased linearly by increase in PAR interception at the bottom of the canopy.      

In order to study light competition in mixed canopy of wheat and weeds, two experiments were conducted in Ferdowsi University of Mashad, Iran during 2000-2001 cropping season (field study), and Guelph University, Ontario, Canada (2002), (growth cabinet study). The treatments of the field study included three levels of Cruciferous weeds (wild mustard, turnip weed and flix weed) and five levels of weed density (0,4, 8, 16 and 32 plants/m2 for wild musturd and turnip weed, and 0, 16, 32, 64 and 128 plants/m2 for flix weed). Randomized complete block design with four replications in an additive series technique with fixed no. of 450 wheat per square meter was employed as the experiment design. In growth cabinet study, is used a model system of annuals to examine how canopies of species having differing morphologies differed in light-interception. Wheat, wild mustard and flix weed were grown as "targets", surrounded by neighbours of a single species. Neighbours could be anyone of the target species. Plants were grown in pots, with one target plant and three neighbors plants. Results of experiment indicated that wild mustard and turnip weed (in comparison to flix weed) had more effect on PPFD and R: FR. In addition, with increase in leaf area of mixed canopy, the quality and quantity of light changed.      

In order to determine the most important morphological and physiological traits associated with wheat grain yield. The study was conducted during 1999 and 2000 growing season in Koohdasht, with 10 spring bread wheat (Triticum aestivum L.) genotypes. A Complete Randomized Block Design with four replications was used. The results showed that varieties were different in grain yield, straw yield, biological yield, spike weight, 1000 kerna1 weight and GDD needed to complete their phenological stages. However, there was significant difference in no. of spike. M-2. The Zagros with 560 and the Pik/Opata with 360 g/m-2 produced the highest and lowest dry matter among genotypes, respectively. The Kasyan/ Genaro 81 line with maximum LAI (3.26) at anthesis produced the maximum grain yield (1583 kgha-1), but Maya74"s" and Seri82/Vee"s" genotypes with minimum LAI (2.4) at anthesis stage produced lowest grain yield. Crop Growth Rate pattern was low in initial stage, then increased after receiving 500 GDD and maximum the CGR achieved after receiving 800-900 GDD at athesis stage. The maximum CGR belonged to Descenocido-7 and Dovin-1 genotypes (1.3 gm-2, GDD-1)and minimum CGR was related to Kvz/Bjy"s" and Maya 74"s" genotypes (0.89 gm-2, GDD-1) at anthesis stage. Strong relationship (r-90**) was established between maximum CGR and grain yield. The results showed that genotypes No.3, 4 and 10 performed better than the other in some physiological and agronomical charactristics.      

Rice haploid plants can be produced in test tube by culturing of anthers and pollens of F1plants, Which are produced from crossing of pure lines. This is very important in rice plant breeding and development of new varieties in the world. In this study, the produced F1 plants were selected in the booting stage (mid-uninucleate stage) and treated in the cold condition at 8 °C for 8 days. Owing to the influence of N6 and B5 media on the callus induction, the anthers were cultured on the above media using factorial experiment which consisted of two factors including culture media and genotypes. Results showed that there was a significant difference among different genotypes for callus induction. The callus induction in the anthers of F1 plants had relative dominance in comprising to the other genotypes. There was also a significant interaction effect between the two factors of genotype and culture medium. The highest efficiency of the callus induction occurred in anthers of "Khazar" variety, with the average of about 30 percent on the N6 medium. The N6 medium with the average of 20 percent was better than B5 medium for callus induction for most of genotypes. In order to regenerate green plants, the produced cali were transferred on the SK-11 medium containing different levels of kinetin hormone. Results showed that the SK-11 medium (including 2 mg/1 kinetin) induced the highest efficiency of green  plantlets, with the average of 32 percent. In this study, IRRI 15/Nemat hybrid produced the highest efficiency of green plantlets with the average of 53.75 percent. In order to increase the root number and length, the green plantlets were transferred on the LS medium and then the produced plants were transferred to Yoshida solution to be adapted to the environmental conditions. The highest number of plants in this stage belonged to the IRRI 15/ Nemat hybrid with the average of 69 percent. In the final step of the study, the number of 141green plants were transferred to the vases in the greenhouse and the total haploid plants produced in this process was 23.4%.  

In order to study dry matter and nitrogen remobilization in rice genotypes under different transplanting dates and determination of their proportion in grain yield, a field experiment was carried out in Rice Research Institute (Amol, Iran) during 1998 cropping season. A factorial experiment was arranged in completely randomized block with three replications, in which transplanting date at three levels (including May 13,May 23 and June 1) and rice genotypes at four levels (Tarom, Nemat, Sahel and Fajr) were the factors. Results showed that different genotypes remobilized different amount of dry matter. Among the genotypes, Fajr and Tarom remobilized the highest and the lowest amount of dry matter from stem and flag leaf, respectively. However, Fajr was the lowest in case of other leaves. Stem and flag leaf remobilized different amount of dry matter under different transplanting dates, but other leaves were similar under different conditions. In terms of nitrogen remobilization, different genotypes also showed significant differences. In general, dry matter remobilization from stem to grain was more than other parts (flag leaf and other leaves) of the plant. However, nitrogen remobilization to grain, from leaves (flag leaf and other leaves) showed higher contribution than stem. Nitrogen remobilization showed a significantly positive correlation with grain yield while correlation between grain yield and dry matter remobilization was not significant.    

Virulence level of 7 isolates of Rhizoctonia solani belonging to Anastomosis Groups (AG) 4 and 2-2, were compared by inoculating them on cultivar le. Thereafter, the selected highly virulent isolate belonging to AG2-2 was used for evaluation of resistance in 20 selected sugar beet genotypes to R.solani. Ten-weeks-old plants of different sugar beet genotypes were inoculated with infected corn kernels. Experiment was conducted in completely randomized design with 3 replicates in greenhouse condition. Each replicate included 200 pots, one plant in each. The rate of infection for each plant was measured using 0-7 scale, and Disease Severity Index (DSI) was calculated for each treatment. The results showed that ETS, F-20278, EP2, and 41RT were  resistant to Rhizoctonia root and crown rot.    

In order to study the effects of sowing date and plant density on vegetative characters, yield and yield components of rapeseed varieties, an experiment was conducted at Agricultural Research Station of Gonbad during 2000 - 2002. The experiment was a split factorial arranged in a RCBD with 4 replications. Four sowing dates (Qct. 22 nd, Nov. 6th, Nov. 21st and Dec. 6th) were as main plots and two varieties (Sarigol and Hyola 401) and two row spacing (24 and 36 cm) were subplots in a factorial arrangement. The results of combined analysis for two year showed that plant height, the number of days from emergence to flowering and physiological maturity, duration of flowering and number of pod per plant decreased significantly with delay in sowing date. The number of grains per pod and 1000 grain weight of Hyola40I hybrid were more than those of Sarigol variety. The number of pod per plant and the number of grains per pod in 36 cm row spacing were more than those of 24 cm row spacing; however 1000 grain weight of 24 cm row spacing was greater than that of 36 cm. Generally grain yield of rapeseed decreased with delay in sowing date. The first sowing date had the highest grain yield (4513 kg/ha), whereas the fourth sowing date produced the lowest grain yield (3228 kg/ha). The grain yield of Hyola 401 hybrid (4139 kg/ha) was more than Sarigol variety (3550 kg/ha). The grain yield of 24 cm row spacing was more than that of36 cm row spacing .The grain yield of row spacing 24 and 36 cm were 4238 and 3451 kg/ha, respectively. The combination of first sowing date, Hyola 401 hybrid, and 24 cm row spacing treatment produced the highest grain yield (5169 kg/ha).