Iranian Journal of Crop Sciences
Year:2000 | Volume:2 | Issue:3|Papers Count:6

In order to study genetic variation, protein yield and its related traits of spring wheat genotypes under optimum and post-an thesis drought stress conditions, sixteen wheat genotypes (four durum wheat and twelve bread wheat) were evaluated in two separate experiments using Completely Randomized Block Design with four replications in 1998 and 1999 in Ahvaz Ag. Research Station. Results showed that environmental effect was significant only for glucose equivalent harvest index at the 1% level. Difference for protein yield, nitrogen harvest index, total protein yield, protein concentration index, grain protein / straw protein ratio and glucose equivalent harvest index were significant at the 1% level. Nitrogen harvest index of durum genotypes was higher than that of bread wheat genotypes, but because of bread wheat high grain yielding, the highest protein yield was obtained from bread wheat genotypes. Except for nitrogen harvest index under drought stress condition, there was a significant difference in genetic variation coefficient for all the traits between durum and bread wheat genotypes at the 1% level. Different traits contribution in multiple linear regression analysis of grain protein, indicates that there are various adaptation mechanism or genotypes responses to environmental stresses.

In order to increase wheat yield components in Atrak cultivar this study was carried out for two years in Khuzistan Agricultural Research Center during 1997 and 1997-98. The design of the experiment was split plot with 3 replications. The main plots were consisted of 3 planting densities; (100, 300 and 500 seeds per m2) and sub plots were allocated to 4 tiller removal treatments (all tillers removed, removing all but one and two tillers remained and no tiller removed as control). Also based on two years results a trial was carried out in 1999-2000 in a box with Completely Randomized Design with three replications and three levels of row distance (20, 10 and 5 cm) and three tiller removal (all tillers removed, one tiller per plant and no tiller removed as control. In the treatments the sowing density was 400 seeds per m2. The results showed that as planting density increased, spike per m2 increased but seed per spike decreased. Planting density had no significant effect on 1000-gtain weight. However spike partial thinning caused an increase in 1000-grainweight, indicating a source limitation. The treatment in which all tillers were removed had the highest seed weight and seed number per spike. On the basis of these results, the highest planting density with lowest number of tiller per plant, produced the highest grain yield. The results of 1999-2000 experiment indicated that a uniform planting pattern has a positive effect on yield components. It was concluded that for Atrak cultivar, 400 seeds per m2density with 5x5 spacing is the best treatment and is recommended.

In order to determine the relationship between high density stress and drought stress, an experiment was inducted in research field of SPII (Karaj) in 1997. The experimental design was strip plot with Randomized Complete Block arrangement and with three replications. Vertical factor was allocated to four levels of density including optimum density (i.e. 70,000 pl/ha), 100,000pl/ha, 140,000 pl/ha and 70,000 pl/ha+drought stress treatment at flowering stage (cut off two successing irrigations). Horizontal factor was six commercial and promising cultivars of corn. The soil of experimental field was sandy loam with pH=8. For determination of relationship between density and drough stress, two indices i.e. stress susceptibility index (SSI) and stress tolerance index (STI) were estimated and simple and ranked correlation between them and yield were found. The highest plant density (140,000 plant/ha) showed the highest correlation coefficient with drought stress, and it seems that even higher densities could more effective in selection of tolerant cultivars to drought. STI was better related to drought and very high density (140,000 plants/ha) than SSI. However, it will be possible to remove the susceptible and select the tolerant cultivars by using SSI and STI in very high density (140,000 pl/ha or more). But it seems to be better to use high plant density only for elimination of drought susceptible cultivars, and for selection of tolerant cultivars more studies are needed to be done.

Twelve rapeseed (Brassica napus L.) cultivars and lines were evaluated at Fars Agricultural Experimental Station (Zarghan) for two cropping years (1995-1997). The experiment was conducted in Randomized Complete Block Design with 4 replications. Each variety and line planted in four rows of six meters each with 60 cm between the rows and four cm between the plants. Results showed that K16, among 0 group cultivars had the highest grain (2067 kg/ha) and oil (878 kg/ha) yields, and Cobra, a 00 group cultivar had also highest seed (1634 kg/ha) and oil (688 kg/ha) yields with no significant difference between Falcon and Global cultivars. There was a positive correlation between grain and oil yields, capsules number in the main stem and capsules number per plant, however there was a negative correlation between plant height and seeds number per capsule.

Coincidence of maize cultivation with other crops such as rice and summer cash crops causes the vegetative phase of maize being faced with moisture deficit stress. To investigate the effect of plant density and water deficit during vegetative phase on maize grain yield and its components, a field experiment was conducted in experimental farm at College of Agriculture, Shiraz University located at Kooshkak (longitude 520; 35" E, and latitude 300 4' N) during summer 1999. The treatments were two levels of plant density 6.67 and 13.34 plants m-2) and three levels of water stress (supply of 50, 75, and 100 percent crop water requirement) in a Randomized Complete Block Design arranged as factorial with three replicates. The results showed that water stress decreased husks dry weight and ear diameter, significantly. At higher plant density dry weight of ear, husk, ear with husk and cob decreased significantly. Water stress caused decreased in grain yield per unit area. In the present study, higher plant density increased the grain yield. Low water availability was associated with higher harvest index and water use efficiency. Water use efficiency was also increased at higher plant density. Considering the results of present study, it appears that in maize plant densites usually practiced, water stress occurred before tassel emergence may decrease grain yield up to 14%. The adverse effects of water deficit at higher densities may be alleviated by increased water use efficiency.

The objectives of this experiment was to study the effect of supplemented irrigation and chemical fertilizer application rainfed chickpea production. The experiment was implemented in a split split plots based on RCBD with 36 treatments and 3 replications at Sararood Dry land Research Station during 1991-1994. The supplemented irrigation as the main plot was provided at four levels of each with main irrigation water applicated preflowering (I1), rod initiative (I2) and seed development (I3), in the control (I0), no supplemented irrigation was given. In the subplots phosphorous and nitrogen fertilizer were given at four levels of P0, P30, P60 and NO, N20, N40 respectively. The results showed that supplemented irrigation increased grain yield through increase in biomass production and grain weight. This increase was 28, 40 and 56% at 11, 12 and 13 respectively. Supplementary irrigation at 13 had the highest effect on increasing the grain yield and for every mm irrigation water given then, there is 5.9 kg/ha. Increase in grain yield. phosphorous application did not have a significant effection the yield. The effect of nitrogen (N20) during 1994-1995 on grain yeild was significant. Therefore application of supplementary irrigation along with 20 kg/ha nitrogen and no phosphorous is recommended for chickpea production in Sararood.