فصلنامه علوم زراعی ایران
سال پنجم شماره 2 (پیاپی 18، تابستان 1382)

An experiment was conducted in 1994 in Karaj, Seed and Plant improvement Institute to study the effects of irrigation intervals and methods of N application on the yield and some qualitative and quantitative characteristics of forage sorghum (Sorghum bicolor (L) Moench var. speed feed). A split plot in time & site design with four replications was used; the irrigation intervals (every 7, 12, 17 and 22 days) were the main plots. Each main plot was sub-divided into three sub-plots for assigning the methods of N application. i. e. M1 = 1/2 of N applied when the plants had 5 to 7 leaves and the other half after the first harvest. M2 = 1/3 of N at 5 to 7 leaves stage, 1/3 of N when the plants had 30 - 40 cm height and the last 1/3 of N after the first harvest. M3 = 1/3 of N at 5 to 7 leaves stage, 1/3 of N after the first harvest and 1/3 of N when the height of regrown was about 30-40 cm. Results showed that 7 and 12 days intervals for imigation and M2, M3 methods of N application provided better conditions for crop development and growth, because the crop used environmental factors better than the other treatments. The most characteristics in M2 and M3 distribution of N were better than M1. It was concluded that, if the crop is sown in time, the 10 - 12 days of irrigation intervals and splitting nitrogen applications at two growth stages (M2 or M3) of sorghum is recommended for Karaj region.

In this study a field experiment was conducted in 1997-98 at two locations (Kooshkak and Bajgah). Twenty five bread wheat (Triticum aestivum L.) genotypes were studied in a randomized complete block design with replications in each location. Agronomic and physiological traits were measured in five developmental stages [tillering (S1), stem elongation (S2), spike emergence (S3), dough stage (S4) and maturity (S5)]. The significant traits were distinguished and their genotypic correlation coefficient with grain yield, heritability, genotypic and phenotypic coefficient of variation were determined. Number of spikelet per main spike and spike to main stem dry weight ratio (at S3) had the highest (h2= 80.14%) and the lowest (h2=1.05%) heritability, respectively. The heritability of grain yield was estimated 21.54%. Most of the measured traits had significant genotypic coefficient of variation. Grain yield had significantly positive genotypic correlation coefficient, with spike to stem dry weight ratio of main stem at S5, number of grains per main spike, number of spikelet per main spike, spike to stem dry weight ratio of tillers at S5, number of kernels per tiller, number of spikelet per tiller, number of spike per square meter, harvest index, number of tiller per plant, stem diameter (1st. internode), stem diameter (2nd internode), culm density, spike length, including awns net assimilation rate at third sampling (NAR3), leaf area duration at third sampling (LAD3) and leaf area duration at fourth sampling (LAD4) and had significantly negative correlation, with 100 grain weight, plant height, percentage of infertile tillers, spike length, without awns crop growth rate at second sampling (CGR2), net assimilation rate at second sampling (NAR2), and relative growth rate at second sampling RGR2. Overall, increasing grain yield through indirect selection, is effective. In this experiment the most important traits for increasing grain yield were number of grains per main and tiller stems, number of spikelet per spike, stem diameter and culum density. It was also determined that decreasing in plant height and percentage of infertile tillers could be suitable for improuing grain yield. Among physiological indices, NAR3, LAD3 and LAD4 were the most effective criteria for increasing grain yield.

In order to study combining ability and gene action for quantitative traits in intra and interspecific hybrids, three genotypes of G.hirsutum with three genotypes of G.barbadense were intercrossed in a half-diallel pattern. Fifteen hybrids with six parents (21 genotypes) were studied in a randomized complete block design (RCBD) with three replications at Gorgan(Karkandeh) Cotton Research Station. Some quantitative and morphological traits (yield, boll weight, boll number, plant height, monopod and sympod length, monopod and sympod number) were measured and recorded in hybrids and parents. Results showed significant differences among genetypes for all traits, except for sympod number. Based on mean yield Siokra 324Tabladila (intraspecific hybrid) and Termez14Siokra324 (interspecific hybrid) were superior, in comparison to the other hybrids. Combining ability analysis showed that additive and non-additive variances were effective on cotton yield, boll number, boll weight, plant height, and sympod length, however, additive gene action may be important for the monopod number and monopod length. The siokra324 (G.hirsutum) and Termez14(G.barbadense) were identified as best parents for GCA. Siokr324Tabladila (intraspecific hybrid) and Termez14 Tabladila (interspecific hybrid) had best specific combining ability. Estimates of the genetic parameters according to Hyman and Jinks method supported the results. Average degree of dominance at each locus and graphical analysis indicated partial dominance for boll weight and monopod length, and over dominance effects for other traits. Dominant genes had positive and increasing effects on the yield, boll number, plant height and sympod length.

Drought stress as the most important abiotic stress plays an important role in yield reduction of crop plant worldwide. Considering physiological indices to improve drought resistance, is of major importance.In order to evaluate Chromosomal Locations of physiological indices for drought tolerance in wild species of rye a complete series of disomic addition lines of rye, donor parents (Secale cereale L.cv. Imperial) and recipient (Triticum aestivum L.cv. Chinese Spring) were studied under field, greenhouse and laboratory conditions in College of Agriculture at Razi University in 1998. Disomic addition lines showed significant differences for relative water content (RWC), relative water loss (RWL), water use efficiency (WUE), and stomatal resistance (SR), implying genetic variation and possibility of selection for improving drought tolerance in disomic addition lines. Physiological indices of stomatal resistance, relative water loss and water use efficiency played an important role in determination of regression equation of grain yield under stress condition. Based on the physiological multiple selection index (MSI), it is interperated that quantitative traits loci (QTLs) controlling physiological characteristics for drought tolerance in rye are most likely located on chromosomes 3R and 7R. Assessment of disomic addition lines based on stress tolerance index (STI) and germination stress index (GSI) also indicated that QTLs controlling drought tolerance in rye are associated to chromosomes 3R and 7R.

In order to simulate light intercepted by wheat and wild oat and turnip weed, two field experiments were conducted in agricultural research station of Mashhad University in 2000-2001. The experiments were carried out as factorial in a Randomized Complete Block design with four replications.In the first experiment, the factors included wheat densities at 3 levels (300, 450 & 600 p/m2) and wild oat densities at 5 levels (0, 20, 40, 80 & 160 p/m2). The factors of the second experiment consisted of the same wheat densities as the first one, and turnip weed densities at 5 levels (0, 4, 8, 16 & 32 p/m2). The INTERCOM model with triangular leaf area density function was used, instead of parabolic function. The results indicated that leaf area distribution around the canopy has a triangular function and the height of maximum leaf area density depends on the weed species, weed and wheat densities. Either weeds intercepted more radiation than wheat in the upper layer of canopy. Sensivity analysis of model showed that: height, leaf area index, height of maximum leaf area density and light extinction coefficient are imporant parameters in light interception by each species.

To study seed yield and some associated characteristics in chickpea under drought stress conditions and to identify tolerant lines, an experiment was conducted in Kurdistan Agricultural Research Station during 1998 cropping season. In this study twenty-one Desi type chickpea genotypes including twenty entries originated from International Crops Research Institute for Semi Arid Tropics (ICRISAT), as well as a local check (Pirouz) were sown in tow separate RCB design with 3 replications under stress and non-stress conditions. Drought Susceptibility Index (DSI) was estimated based on seed yield of chickpea genotypes under stress and non-stress conditions. Simple correlation coefficients and path analysis were also calculated and performed. Results showed that, there were considerable genotypic variations for yield and yield components among chickpea genotypes. Relationships between number of secondary branches, 100seeds weight, plant height and seed yield was positive. Correlation between days from sowing to flowering and seed yield was negative (r = -0.821**). Number of secondary branches had the highest direct effect on seed yield. Thus, early maturity and more secondary branches implied to be more associated with higher seed yield under drought prone climates in Kurdistan province.

This experiment was conducted in 2000 at Lordegan experimental station in Shahrekord. The experiment was carried out using a split plot design with three replications. Three levels of row speacing (35, 50, 60 cm) as the main plot and three levels of plant distances (5, 10, 15 cm) as the sub plot. Plant density were between 111000 until 570000 plant per hecatare. Each plot included five rows ten meter long. The mean of pod number in row spacing and plant distances increased as plant density decreased. The pod dry weight was significantly affected by row and plant spacing at 1% level, however, their interaction was not significant. Row spacing and row spacing × plant distance had not significant effect on number of seeds in pods but plant spacing had significant effect at 1% level on this traits. Row and plant spacing affected the 100 seed weight. The effect of row spacing and plant distances and their interactions on seed yield was significant at 1% level. The highest yield (5562.53 kg/ha) was harvested at 50× 10 (cm) with 200000 plant per hectare and the lowest yield (3726. 1 kg/ha) at 60 ×15 (cm) with 111000 plant per hectare.