Iranian Journal of Crop Sciences
Year:2002 | Volume:4 | Issue:1|Papers Count:8

Increasing plant density is often associated with lodging, hence decreasing photosynthesis efficiency and grain yield. A field experiment was conducted to evaluate the effect of three plant densities 30, 50 and 70 p/m2 and three different chlormequat chloride concentrations:0, 1.4 and 2.8 l/ha on some morphological characteristics and grain yield of winter rape seed (cv.Talayeh). The study was conducted under Bajgah agroclimatic conditions in a silty clay loam soil, Shiraz, Iran. The experimental design was a randomized complete block with four replications. The results indicated that, increasing plant density from 30 to 70 p/m2caused a significant increase in plant height (p<5%). When chlormequat chloride was applied at the rate of 1.4 l/ha at plant density of 70 p/m2 plant height was significantly decreased. Meanwhile the stem diameter and grain yield of plants treated with 2.8 l/ha chlormequat chloride at plant density of 70 p/m2 increased significantly. Although, the inter-nodes length and plant dry weight of the chlormequat -treated plants were smaller than control, their differences were not significant. It was conducted that under similar conditions to the present study, cv. Talayeh with plant density of 70 p/m2, and foliar application of chlormequat chloride at the rate of 2.8 l/ha can be used to achieve the highest grain yield.

The objective of this research was to study the genetic variation for total dry matter yield and three quality characteristics: digestible organic matter in dry matter (DOMD), water soluble carbohydrate (WSC) and crude protein content (CP) in perennial ryegrass (Lolium perenne) under spaced plants and swards conditions. A polycross nursery containing 24 genotypes were established. Prior to planting, each parent was vegetatively propagated to give 8 clones. At harvest, seeds of propagated clones of each genotype was combined. Both seed of half sib families and their clone propagated parents were grown as spaced plants and sward over two years. Near Infrared Spectroscopy (NIR) was used to estimate the quality parameters. The broad sense heritability estimates (h2b) were relatively high for quality traits (h2b= 0.48-0.80), but moderate for dry matter yield (h2b= 0.25-0.49). Narrow sense heritability (h2n), was low for dry matter yield (h2n=0.03-0.26)and high for quality traits (h2n=0.03-0.92). Genetic analysis indicated that non-additive genetic variance was the major component controlling DM yield, while, additive genetic variance was more significant for quality traits. The genotypic correlation of DOMO and WSC was significantly positive, while the relationship of CP with WSC was significantly negative. These results were consistent over two years. None of the phenotypic or genotypic correlation estimates of DOMD and CP were significant. OM yield and DOMD were negatively correlated under swards. The genetic correlation of DM yield with WSC was positive, however, its relationship with CP was negative.

Seeds of six rice cultivars (Binam, Domsiyah, Shahpasand, Sepidrud, Khazar and Valed 46) along with their diallel crosses progenies were sown in a randomized compelete block design with 3 replications in Rasht in 1990. 10 quantitative traits (grain weight per plant, 1000 seeds weight, no. of filled seeds per panicle, no. of deaf seeds per panicle, panicle length, no. of tillers per plant, plant height, transplantation to first panicle (days), transplantation to full maturity (days) and length to width ratio of rice grain were evaluated and measured on 10 plants. The ANOVA showed significant differences among genotypes for evaluated traits. The genotypic and phenotypic correlation coefficients for each pair of traits were estimated by genotypic variance and covariance analysis. In most cases, the sign of phenotypic and genotypic correlation coefficients were the same. However, in same cases phenotypic and genotypic correlation coefficients were close to each other. This implies that the .environmental variance and covariance were minimal. The genotypic correlation were used for path coefficient analysis. The genotypic correlation coefficient of grain yield per plant with 1000 grain weight (rG=0.31**), no. of filled grains per panicle (rG=0.61**) and no. of tiller per plant (rG=0.37**) were positive and significant. However, genotypic correlation coefficients of grain yield per plant with no. of deaf seeds per panicle (ro=-0.65**), plant height (rG=-0.26**) and days from transplantation to full grain maturity (rG=-0.52**) were significantly negative. The result of path analysis indicated that using traits such as no. of filled grain per panicle and days from transplantation to full grain maturity (earliness of genotypes), can lead the selection for high grain yield per plant. Using traits such as high no. of tillers per plant and short stature of plant, because of their genotypic correlations with grain yield, may be also useful for increasing grain yield per plant in rice.

In order to investigate the effects of different levels of soil compaction on yield, yeild components, and sucrose in sugarcane, cv. CP 48-103 an experiment was conducted during 2000-2001 in Khuzestan, Iran. The experimental design was a randomized complete block with 3 replications. The soil was compacted to different levels by a tractor. Penetrometer resistances of the soil were measured as 650, 1250, 2350 and 3250 kpa.The results of this study showed that compacting the soil to a penetrometer resistance of 650 kpa had no significant effect on cane yield. However, the yield of cane decreased as compaction of the soil was increased to a penetrometer resistance of 3250 kpa. A similar trend to that of cane yield was observed for plant height, number of tillers and total dry matter yield as soil compaction increased. Soil compaction to the rate of PR of 3250 kpa had no significant effect on purity and sucrose percentage, consequently, on sucrose yield. However, there was a decreasing trend in these qualitative characteristics. The results of this study also indicated physiological growth indices such as LAI, CGR, NAR and RGR decreased as the soil compaction increased was compacted from a penetrometer resistance of 650 kpa to 3250 kpa.

In order to study wet and dry planting effects on grain yield of spotted bean cultivars, an experiment was conducted on four bean cultivars in Khomein for two years (1995 and 1996). The experimental design was split block in randomized complete block design with four replications. Four spotted bean cultivars (Talash, Local Khomein, G-14088, COS-16) were assigned as factor A to vertical plots, and two sowing methods (wet planting, and dry planting) as factor B in horizontal plots. In this study planting arrangement was 20 cm x 14 cm. The results revealed that there were significant differences among bean cultivars in plant height, number of pods/plant and seeds/plant, 100-seedweight and grain yield. Local Khomein cultivar had the highest plant height. Number of pods/plant and yield in COS-16 were higher than the other cultivars. Study of sowing methods, indicated that plant height increased by wet planting, number of pods/plant and seeds/plant and yield was also higher in this method. Study of interaction between cultivar and sowing method showed that the highest pods/plant, seeds/plant and grain yield were associated to COS-16 in wet planting method.

In order to study effects of drought stress at different growth stages in potato, three cultivars: Marfona, Agria and Draga were planted in 20 lit. pots-using a completely randomized design (CRD) with five replications. Three levels of drought stress (40%, 60%, 80% of soil available water=SAW) and a control (100% SAW) were applied in three growth stages (Planting to emergence, emergence to stolon initiation and stolon initiation to tuber initiation) and were arranged in factorial combination together with potato cultivars. Results showed that drought stress decreased relative water content (RWC), water use efficiency (WUE), Tuber no./plant, dry matter percent (DM%) and tuber yield, but increased leakage from cell wall. Agria demonstrated the highest tuber yield and WUE but the lowest leakage from cell wall. However, Draga had the lowest tuber yield, RWC and Tuber no./plant, but the highest DM%. Drought stress at stolon initiation stage decreased tuber yield. Drought stress levels of 60% SAW severely affected the tuber yield, however the difference between 40% and 80% SAW was not significant. Differences of drought stress levels, were significant only for Agria. The result indicated that high RWC together with medium Tuber no./plant led to optimum assimilate partitioning among tubers, hence higher tuber yield.

In order to determine the suitable plant density and genotype of durum wheat (introduced by Agricultural Research Center of Khuzestan) in terms of qualitative and quantitative characteristics, an experiment was conducted in Ahvaz, Iran in 1977/98 cropping season. The recorded characteristics were included yellow berry, protein quality, protein percentage of grain, no. of spikes per m2 and grain yield. Among the five genotypes studied (Shwa/Mald,Chen/Altar, Altar84, Gediz and Aconchi 89) , Chen/Altar showed the highest percentage of yellow berry (11.53%) and Shwa/Mald the lowest (2.3 % ).Shwa/Mald had the highest protein quality with Zeleny number of35.3 and Altar 84 had the lowest protein quality with Zeleny number of 29.4. Shwa/Mald had also the highest protein percentage (13.7 %) among the five genotypes. Plant density of 400 and 500 plants/m2 resulted in the highest (8.5) and 200 plants/m 2 the lowest (3.2) percentage of yellow berry. Plant density of 200 and 500 plants/m 2 had the highest and the lowest grain protein with 13.1% and 12.3%, respectively. In spite of increase in protein quality at lower density there was no any significant differences among the plant densities. As density increased, grain yield also increased. The highest grain yield was obtained at 500 plants/m2(5678 kg ha-1) and Chen/Altar had the highest yield among the genotypes (4976 kg ha -1).There was significantly negative correlation between grain yield and protein quality (p<0.05) and protein percentage (p<0.0 1). However, significantly positive correlation (p<0.01) was observed between grain yield and yellow berry. This study showed that Shwa/Maid with 500 plant m-2 can be recommended for Ahvaz climatic conditions