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

Ten combinations of diallel crosses of five maize inbred lines and their parents were evaluated for grain yield and yield components using randomized complete block design in four replications at Karaj and five other locations including Gorgan, Kerman, Shiraz, Esfehan and Hamadan in year 2000. Combined analysis of variance over locations revealed significant differences among genotypes for all traits, except kernel depth. Environmental effect was significant, showing differences among environments. Significant genotype×environment effect for all traits(except for number of kernels per ear row) was observed, indicating genotypic control of number of kernels per ear row and environmental effects on other traits. Diallel analysis for grain yield and yield components indicated presence of dominance effects for grain yield, for additive effects 1000 kernel weight and number of rows per ear, and dominant and additive effects for number of kernels per ear row. However, the additive effects were more important than dominant effects in controlling number of kernels per ear row.

In the past, fertilizer trials conducted on nitrogen rate have not considered OC and TN in soil. Thus, in many trials, nitrogen fertilizer could not increase wheat yield under rainfed condition even with supplementary irrigation or high rainfall. In this investigation, those factors especially OC & TN that cause non-response to N application on Sardari variety were studied. Statistical results for five out of 12 experiments conducted for nine years showed that nitrogen fertilizer up to 30 kg/ha significantly increased grain yield in comparison with control. Mean of grain yield was enhanced up to 393 kg/ha in Kermanshah province. Increased application of nitrogen (N45) caused an increase in grain yield but wasn’t significant. More than this rate (N45) not only didn’t increase grain yield but also decreased grain yield in some years with low rainfall. In the remaining experiments, due to high amount of OC and NT in sites of the experiment, nitrogen fertilizer not only did not increase grain yield, but in two experiments, grain yield decreased. Therefore, critical level of OC and TN in soil with the Cate-Nelson procedure for 95% percent of maximum yield is equal to 1 percent and also critical level of mineral-N in soil is equal to 0.12 percent. In general, based on conducted field trials application of 30 kg/ha of net nitrogen in soil of containing less than 1 and 0.12 percent of OC and TN, respectively, for dryland wheat (Sardari cv) in Kermanshah province are recommended.

The necessary condition for a good crop is good seed quality, but unfortunatly this subject has not been adequately addressed in Iran. The recognition of good seed quality requires knowledge of physiological relations in seed development period. In this respect, study of limiting factors is necessary. This investigation recognizes how water deficit affects seed development and seedling growth in maize reproductive period. Therefore, duration of water deficit effects on seed dry weight, embryo weight, endosperm weight in seed filling period, germinability initiation, % germination and seedling dry weight were evaluated. Field experiment was conducted in the agronomy field of Azad university, Fasa campus in summer of 2000 using a randomized complete block design with 3 replications. Water deficit treatments included three levels that consisted of control or normal situation of moisture in soil, early water deficit (carried out from the second day after pollination), and late water deficit (carried out from the eighteenth day after pollination). The linear regression between % germination with % kernel moisture and embryo dry weight and endosperm dry weight with seedling dry weight were determined. Results showed that seed, embryo and endosperm weight differences were significant from middle filling period for all treatments. Maximum seed dry weight, embryo weight and endosperm weight was achieved with control. Percent kernel moisture was not significantly affected by water deficit in stages of seed growth. Germinability initiation difference was not significant for all treatments, but % germination and seedling dry weight was affected significantly. Germinability of maize seed began from 35 to 42 days after pollination. The relationships between % kernel moisture with % germination, embryo dry weight with % germination, and endosperm dry weight with seedling dry weight for one to three levels was significant.

Domsiah which has a high quality characteristics is a local rice variety in Iran but it is tall and sensitive to lodging. This study was conducted to induce short culm character in Domsiah rice from 1995 to 1998. Seeds were irradiated with gamma rays at 100,200 and 300 Gray; and DMA at 0.1%, 0.2% and 0.3% (for 24 hrs, in room temperature), separately. The irradiated seeds were seeded in nursery and then transplanted in main land. At the end of the first season, main panicle of some randomly selected plants were harvested and planted in M2 generation as a panicle-to-row. Results showed no significant variation among the DMS treatments, hence these treatments were removed from the experiment. A short culm mutant line was obtained from 300 Gray gamma rays in M2 generation. This mutant line showed no segregation in M3 generation. In order to study some morphological characters in M3 generation, the mutant line and control were planted. Then, 15 plants were collected from the short culm line separately and were planted in M4 generation, in 15 distinct rows. There was no significant difference in panicle length among short culm mutant lines and control. However, there were significant differences among culm mutant lines for plant height, tiller no., length and width of flag leaf. Meanwhile, the intra-variation in short culm mutant lines were negligible. The height of short culm mutant lines were about 60 cm shorter than the control (165 cm) but tiller number was significantly more than the control. The reduction of internode 2 through 5 caused the height reduction in short culm mutant lines.

In order to obtain a sustainable agriculture and environment protection, there have been many efforts in recent years to reduce herbicide uses. This research was conducted in 1379 (year 2000) at Sari agricultural college experimental station as a randomized complete block design with 11 treatments and four replications to investigate the effects of reduced Bentazon rate application on weed control and the corresponding soybean growth and yield. The treatments were: reduced bentazon rates of 0.84 (recommended rate), 0.75, 0.58, 0.24 and 0.25 kg ai/ha for one-stage spraying, (0.25+0.58), (0.25+6.42) and (0.42+0.42) kg ai/ha for split-application of two-stage spraying, and (0.25+0.25+0.25) for split - application of three-stage spraying and two control treatments of weed-free check and weedy check. Based on soybean yield (number of pod and production rate), it was concluded that bentazon use could be reduced up to 30 percent to control velvetleaf (Abutilon teophrasti), which is important in reducing production costs and environmental pollution. Use of reduced bentazon rate and split-application could control velvetleaf as much as 90 percent which is equal to the effect of the recommended rate. Comparison of reduced bentazon rate using a split application at three stage spraying (0.25+0.25+0.25) with normal to recommended rate did not significantly differ in velvetleaf control percentage and soybean yield.

Twenty two Iranian and foreign varieties of alfalfa (Medicago sativa L.) were studied with respect to total amount of saponins (quantitative analysis) and kinds of saponins (qualitative analysis). Quantitative analysis was conducted by spectrophotometer method. Varieties showed high significant differences for total amount of saponins. Total amount of saponins showed no significant correlation with alfalfa weevil (Hypera postica Gyll.) larval damage. Qualitative analysis was conducted by TLC method. Eight types of saponins were recognized in the varieties. The comaprison of saponin banding patterns with standard patterns showed that bands 3,4, and 7 (saponins) were Medico side J, Soyasaponin I and Medico side A, respectively. Other five saponins could not be recognized with available standard saponins. The 1st, 2nd, and 8th Saponin bands showed significant negative correlations with weevil larval damage, 3rd and 4th Saponin showed significant positive correlations, and 5th, 6th and 7th Saponin bands showed no correlation with larval damage.