فصلنامه علوم زراعی ایران
سال ششم شماره 2 (پیاپی 22، تابستان 1383)

In order to determine, source of grain yield limitation under different enviromental conditions, as well as indentifying the rate of restrication caused by terminal heat stress on development and growth of wheat, this research was conducted with twenty wheat genotypes using Randomized Complete Block Design (RCBD) with three replications, in two separate experiments in two years(1998-2000). The experiments were sown in late of december and january to stimulate favoarable and unfavourable conditions, respectively. Five to seven days after anthesis flag leaf and spikelets from one side of spike were removed to stimulate, sink and source limitation respectively. Aftert harvest, source and sink restrication percentage were calculated according to the mean of remaining grains in treated spike and control (without removal of flag leaf and spikelets). Results indicated that all genotypes had not sink restrication and the contribution of flag leaf to grain dry weight was 12%. However, some genotypes showed source restrication. This restrication was estimated from 0 to 34% (mean: 12.6%) and 5.7 – 41.2% (mean:17.2%) for favourable and unfavourable conditions, respectively. Therfore, source restrication caused by exposure to terminal heat stress was greater by 6%. Likewise, results indicated that source restrication was higher in genotypes with large grain size. Grain weight had not significant effect in the determination of final yield. Reduction in grain yield must be sought in other yield components, such as grain number per spike and spikes number per sqaure meter.

In order to evaluate the tolerance level and identification of tolerance mechanism to salinity, response of five genotypes of wheat (Zagros, Tajan, Opata/Bow, Pgo/Seri and Rayon) to six salt treatments including 0, 25, 50, 75, 100 and 150 mM NaCl was studied in hydroponic culture in growth chamber under control condition. Pgo/Seri and Opata/Bow in comparison to the other genotypes, showed less reduction in growth under salinity. Pgo/Seri inhibited high Na+ accumulation in shoots and absorbed less Cl-. Opata/Bow accumulated high Na+ and Cl- in shoots and roots which probably were compartmented these toxic ions in the vacuole or apoplast to result a better osmotic adjustment and less toxicity of the ions. Tajan, Zagros and Rayon also accumulated high level of Na+ and Cl- that increased toxic effect of the ions. Results also indicated that Opata/Bow, in spite of high Na+ and Cl- accumulation, had higher salt tolerance in comparison to the other genotypes. Further field experiments are necessary for confirmation and application of the result.

To determine the most suitable sowing date for rapeseed cultivars this study was carried out in Busheshr Agriculture Research Center, Borazjan in 1997-1998 cropping season using a strip plot design with four replications. Rapeseed cultivars were: Global, Regent, Tower, Pf7045/91, Pf5045/88 and Maluka which were sown on four different dates with fifteen days interval (oct.20, nov.5, No. 20 and dec.5). Each plot was four row (3m), with 50cm row distances. Results showed that mean seed yield was highest (1509 kg/ha) when sown on oct.20. Interaction between sowing date and cultivars indicated that Pf7045/91 and Pf5045/88 sown on oct. 20, produced the highest mean seed yield of 2010 and 1840 kg/ha, respectively. Results of correlation studies indicated that grain yield had a positive and significant relation with oil yield, plant height and height of first pod. The heighst correlation was determined between seed yield and oil yield(r=0.99) and there was no significant correlation between the other traits.

Sainfoin (Onobrychis sativa) is a soft forage plant with high protein content. It has some characteristics such as: resistance to unfavorable environmental conditions as:low soil fertility, very low temperature, resistance to drought in dryland farming with acceptable yield, resistance to overgrazing in rangelands, and suitable for direct grazing. To study the effect of various levels of nitrogen and phosphorous on forage yield of Sainfoin a field experiment was conducted, using a randomized complete block design with four replications and two factors, nitrogen fertilizer with three levels (N0, N60 and N120 kg/ha) and phosphorous fertilizer with four levels (P0, P30, P60 and P90 kg/ha). The main purpose of this study was to introduce scientific strategies to safe and less harmful use of chemical fertilizers to produce acceptable yield with sustainable approach to environment conservation. In this research, dry matter yield (kg/ha), wet weight yield (kg/ha) and shoot height (cm) were measured. Except shoot height and dry matter of roots, other characteristics were significantly affected (P ≤ 1%) by various levels of nitrogen and phosphorous fertilizers. The interaction between these two types of fertilizers was not significant. Results of this study implies that N60P60 was the best fertilizer recommendation considering the economical aspects and acceptable forage yield.

Isozymes are useful and important markers for studying genetic structure and breeding of rice. The level of polymorphism is an important character of each marker that represents its validation and relative importance. Allelic frequencies represent genetic structure of populations. Therefore, this investigation was conducted for evaluation of genetic structure and identifying of relative importance of isozyme loci in Iranian landraces of rice. One hundred twenty rice accessions were selected from National Plant Gene Bank of Iran (NPGBI). In each sample, enzyme extract was extracted from 4-6 seedlings. Separation and visualization of isozymes was carried out using Glaszman et al. (1988) protocol, with some minor modifications. In most isozymic loci, allelic frequencies of Iranian landraces had significant differences with average of other Asian rices. Also in each locus, one or two alleles were frequent. Five loci including Amp3, Pgi2, Est2, Amp1 and Amp2 with 60, 55.3, 54.8, 51 and 48 percent were more polymorphic, respectively. Three loci, Amp4, Est5 and Est9 were monomorphic and they are not useful markers for rice. Genetic diversity of Iranian landraces and Asian rices on Cat1, Pgi2, Amp3, Amp4 and Est5 loci have not significant diffrences, however, Pgi1, Est9, Est1 and Amp1 were reverse. Genotypic diversity index was 3.46, which is high in comparison with other Asian rices. These results showed a very high genetic variability and special genetic structure in Iranian landraces of rice. These can be due mainly to independent evolution of Iranian land races in unique ecological region of Iran which differes with the ecological conditions in the origin of rice in Southeast of Asia, India and China.

Increasing of yield is the most important objective of plant breeders in breeding programs. However, yield is a complex trait and includes several quantitative components. Its inheritance is polygenic, hence studying and improving the associated components to yield would promote yield. The objective of this study was to study the inheritance of quantitative traits in bread wheat using generations mean analysis (GMA). Sardari cultivar and inbred line 14, with different characteristics were crossed to develop the F1 generation. The F1 plants were selfed and backcrossed to both parents to produce F2 and backcross generations, respectively. All generations (F1, F2, BC1 and BC2) along with relevant parents were planted in field experimental station, Faculty of agricultural Tehran University, using a randomized complete block design (RCBD) with three replications. Generation mean analysis was performed using scaling test which asseses all generations simultaneously. The generations mean squares of the following traits: spike weight, plant height, number of kernel per spike, kernel weight per spike, 1000-kernel weight, awn length, spike length, awn status, spikelet compactness, kernel color, and number of tillers, were significant. The minimum number of genes controlling these traits, were 2, 2, 2, 2, 5, 1, 2, 4, 2, 2, 2 and 1, respectively. The average of broadsense and narrowsense heritabilities were 62% and 33%, respectively. Gene effects including mean, additive, dominance, epistasis effects as well as additive × additive, additive × dominance and dominance × dominance were observed for all traits. For awn length and number of tillers, additive and dominance effects and for other traits except awn status and glume color, the epistasis effects (specially additive × dominance and dominance × dominance) were determined as the most important effects in controlling the heritability of these traits. For spike weight, spike length, kernel weight per spike, awn length, plant height, spikelet compactness, and kernel color additive effect was more important than dominant effect. However, for number of kernel per spike dominant effect was more important than additive effect.

Sorrel [Rumex acetosa L. (Polygonacea)] is a dioecious perinnial species which is being used as a model plant in sex determination molecular genetic studies. In this study for determination of the most suitable explant and medium for regeneration in this species, explants from different organs such as leaf, petiol, cotyledon, hypocotyle and root were cultured on Murashing and Skoog (MS) medium supplemented with vitamins, 2% sucrose, 0.8% agar and different compositions of hormons. Auxins; IAA, NAA and cytokenins; Zeatin, BAP, TDZ and Kinetin as well as IAA and BAP with Gibberllic Acid were added to culture media. Experiments were carried out as factorial in completely randomized design. Callus induction and regeneration from explants were evaluated. The most suitable explants and medium for regeneration were leaf and MS medium supplemented with 0.75 mgl-1 IAA and 1.5 mgl-1 BAP, respectively. The highest callus induction and regeneration was obtained from the leaf explants at the rate of 100% and 81%, respectively. Regenerates from the leaf explants on this medium had proliferated status. Histological studies confirmed that the origin of regeneration was from active and condensed cells that had developed from central parts of callus followed by marginal cells to form single or proliferated primordial. These results suggest new, simple, short and efficient regeneration method in this model species which can be used in genetic studies and gene transformation.