فصلنامه علوم زراعی ایران
سال هجدهم شماره 2 (پیاپی 70، تابستان 1395)

This experiment was conducted to determine the effects of defoliation intensity at different sowing dates on quantitative and quality characteristics of sugar beet at Motahari Research Field Staiton of Sugar Beet Seed Institute, Karaj, Iran, in 2010 and 2011. The experiment was arrangemed as split plot using randomized complete block design with four replications. Main plot were assigned of two levels of sowing date (sowing on time, in early spring, and late, about one month later) and subplots consisted of combination of four growth stages, initial (germination till six-leaf), canopy development (six-leaf till canopy closure), mid-season (canopy closure) and late season (reduction of canopy closure till harvest time), with four levels of defoliation intensity (25, 50, 75 and 100 percent of leaf blade). In each main plot, four treatments including the control treatment (without defoliation) and three sowing dates, simultaneous with defoliation at the first three stages of defoliation times, were considered. After harvesting, root yield and other main quality properties was measured. Results showed that root and white sugar yields with a delay of about 26 days reduced by 11 and 7 percent, respectively. Late season sever defoliation reduced sugar content, white sugar content and extraction coefficient of sugar beet. Defoliation in mid-season and late stages of crop life-cycle significantly reduced sugar yield. It was concluded that when leaves of sugar beet are damaged, by any mean, re-sowing is not recommended and the filed could be preserved.

Triticum and Hordeum are two genera of Triticeae family with important cultivated species. Analysis of phylogenetic relationships of cultivated species and wild relatives of these genera is essential for their efficient use in breeding programs. In the present study, phylogenetic relationships of four Triticum and three Hordeum species were assessed using 150 barley microsatellite primer pairs. In total, 49 primer pairs amplified products in the both genera and 19 only in Hordeum species. Out of the 49 amplified markers, 21 were only polymorphic in Triticum species and in total, 59 alleles ranging from 2 to 5 with an average of 2.80 alleles per locus were amplified. In Hordeum genus using 43 polymorphic markers, 123 alleles with an average of 3.02 allele per locus and range of 2 to 14 were obtained. In two genera species, 18 polymorphic primer pairs amplified 91 alleles ranging from 2 to 19 with an average of 5.05 and gene diversity varied from 0.14 to 0.85 with a mean value of 0.59. Cluster analysis using Neighbor-Joining algorithm and Kimura-2-parameter distance coefficient and principal coordinate analysis separated the species of the two genera. In a cluster of Triticum genus, species were grouped based on their ploidy levels and bread wheat cultivars were separated from its wild relatives, and species with A genomes were grouped together. In Hordeum genus, cultivated barley was also separated from their wild relatives. Results of the present study show the efficiency of barley SSR markers in analysis of phylogenetic relationships of Triticum and Hordeum genera. In addition to reasonable transferability and polymorphism of the used markers in the species of both genera, they could also group the species based on their genomic constitution and evolutionary relationships.

To assess the effects of different cropping systems of sesame and cowpea on cotton productivity, six cropping systems including; fallow-cotton, sesame-cotton, cowpea-cotton, 50-50 sesame/cowpea-cotton, 75-25 sesame/cowpea-cotton and 25-75 sesame / cowpea-cotton were experimented and evaluated using randomized completed block design with Three replications in Fasa, Iran, in 2014 and 2015. Results showed that in 2014 intercropping of 50:50 sesame-cowpea compared to monocultured was highly superior in terms of land equivalent ratio (1.03), area time equivalent ratio (1.04) and land use efficiency (155%). These findings suggest that specific function of each crop within the intercropping could increase the total productivity of the system. However, in 2015, results showed that planting cotton after cowpea and 75-25 sesame/cowpea intercrop were more productive than other cropping systems and when compared with fallow-cotton system, and cotton yield increased by 29.9 percent. Harvest index was higher in 75-25 sesame/cowpea-cotton system. The assessment of cropping systems economic value showed that the highest economic value was related to cowpea-cotton which this is due to high yield of cowpea in monoculture (3772.4 kg.ha-1) and higher yield of cotton (3406 kg.ha-1) following cowpea and the lowest belonged to fallow-cotton system. Therefore, it was concluded that cowpea-cotton rotation increased the cotton productivity.

In a five years experiment, the effect of crop rotation was examined on yield and soil physico-chemical properties in 200 hectares land of College of Agriculture- during 2010-2015 growing seasons Shiraz University, Shiraz, Iran,. Eight rotation systems consisted of 1: complete fallow (no planting), 2: continuous maize-wheat, 3: wheat rotation with alfalfa, 4: maize rotation with alfalfa, 5, 6, 7 and 8: fallow in one, two, three and four of ten growing seasons during five years using randomized complete block design with four replications. Shiraz wheat cultivar and SC704 maize hybrid were used. Results showed that the highest wheat grain yield (7706 kg.ha-1) and maize fresh forage (82100 kg.ha-1) obtained when sown in rotation with alfalfa. Fallow had positive effect on yield of both crops, up to four seasons for wheat and up to two seasons for maize. Continuous maize-wheat with higher soil salinity and lower amount of nitrogen (N), phosphorous (P), zinc (Zn), iron (Fe), copper (Cu) and manganese (Mn) led to significant reduction in yield compared to rotations with alfalfa or fallow for more than two seasons. Wheat and maize in rotations with alfalfa had higher soil nitrogen, phosphorous, iron and manganese which were associated with greater wheat grain yield and maize fresh forage. Micronutrients were greater in fallow systems and this might led to greater and stable wheat grain yield and maize fresh forage yield. It was concluded that rotation with alfalfa or 2-3 seasons fallow for maize and 4 seasons for wheat improved soil chemical conditions, and consequently had higher economical yield of wheat and maize.

Maize is a moderately salt-sensitive crop, but there is little information about its morpho-physiological and grain yield responses to sprinkling irrigation with saline waters. To evaluate the effect of irrigation with saline water with different levels of electrical conductivity of 2.9 (control), 3.5, 4.1, 4.7 and 5.3 dS.m-1 on grain yield and morpho-physiological traits of maize hybrid KSC704, a field experiment was carried out using randomized complete block design with three replications in Shahid Chamran University, Ahvaz, Iran, in summer of 2013. To apply salinity levels, a sprinkler irrigation system was used to establish minimum and maximum salinity levels on two parallel pipelines on both sides of the field. Overlapping sprinklers led to establish a linear salinity gradient. Result showed that increasing the electrical conductivity of water and soil salinization, especially at 4.7 and 5.3 dS.m-1 significantly decreased grain yield (17.75 and 25%, respectively), relative water content (13 and 17%, respectively), stomatal conductance (41 and 61%, respectively), chlorophyll index (10 and 10%, respectively), leaf area index (26 and 37%, respectively) and ratio of potassium to sodium (45 and 39%, respectively), and increased leaf sodium content (20 and 28%, respectively) when compared with the control. In sprinkler irrigation method, it seems that due to both root and foliar absorption of salt, via impairment in the physiological functions of the plant, it caused reduction in dry matter and grain yield. In conclusion, these findings showed that, in sprinkler irrigation the threshold of salinity was ~4.1 dS.m-1. With regard to the saline water resources in Iran, especially in warm areas of Khuzestan, sprinkler irrigation may be beneficial in row crops, such as maize, production.

Study of agronomic traits and their relationship with seed yield can identify appropriate ways led to high yielding varieties selection. This experiment was carried out to investigate the relationship between agronomic traits and seed yield of 118 recombinant inbred lines of lentil (derived from the cross L3685 × Qazvin) along with their parents using alpha lattice design with two replications in research farm of Shahrekord University, Shahrekord, Iran, in 2012-13 and 2013-14 growing seasons. Since the effect of incomplete blocks within each replication was not significant, combined analyisi of variance was performed as randomized complete block design. Results showed that effects of year, lines and line×year were significant for all traits except seed diameter. Lines 111, 82, 30 and 85, were superior for phenological characteristics and seed yield. Estimatied genetic parameters showed that the weight and number of pods per plant, biological yield and seed yield had the highest levels of genetic improvement, genetic and phenotypic coefficients of variation. High heritability was observed for weight of pods per plant (h2=0.70), days to maturity (h2=0.67) and days to flowering (h2=0.58). Pearson correlation coefficient showed positive and significant relationship between seed yield and biological yield, leaf width, number and weight of pods per plant as well as a significant negative relationship with days to flowering and maturity. Stepwise regression indicated the important role of these traits (except of weight of pods per plant) in yield detrmination. By performing path analysis based on stepwise regression, biological yield and leaf width had the most direct effect on seed yield, while the number of pods per plant through biological yield had the most indirect effect on seed yield. Cluster analysis based on all traits formed four groups and superior lines were grouped together. According to the results of this experiment, number of pods per plant, biological yield, leaf width, days to flowering and maturity can be recommended as selection criteria for developing of lentil cultivars with high seed yield.