فصلنامه علوم زراعی ایران
سال بیست و یکم شماره 4 (پیاپی 84، زمستان 1398)

To estimate required parameters of phenology sub-model in SSM-Wheat model (cardinal temperatures, critical photoperiods and photoperiod sensitivity coefficient) and to determine of the biological day for eight bread wheat genotypes (Morvarid, Tajan, Kohdasht, Darya, Gonbad, Arta, N-87-20 and N-87-19) in Golestan province of Iran in 12 sowing dates, an experiment was carried out using randomized complete block design with four replications during 2012 and 2013 cropping cycles. Beta-quadratic model was used to explain the relation of stem elongation rate of the wheat genotypes in response to temperature and photoperiod. The bread wheat genotypes did not have significant differences in critical photoperiod and cardinal temperature. However, they were significantly differ for biological day and photoperiod sensitive coefficient. Therefore, cardinal temperatures including; base, optimum and ceiling temperatures were used in 0, 28 and 40 °C, respectively, for all of genotypes in the model. In addition, the critical photoperiod fixed on 21 hours in this model. Coefficient of sensitivity to photoperiod varied from0.00272 to 0.0091 for genotypes. The bread wheat genotypes did not show significant differences in terms of biological days (bd) in phenological stages including; sowing to emergence (6.2 bd), tillering to stem elongation (7.9 bd), booting to heading (3.4 bd), heading to anthesis (6.4 bd) and physiological maturity to harvest maturity (6.8 bd). However, significant differences observed in phenological stages emergence to tillering (6.5-8.8 bd), stem elongation to booting (4.7-5.9 bd) and anthesis to physiological maturity (21.1-24.8 bd) among genotypes. Model evaluation indicated that root mean square error for biological days to anthesis and days to physiological maturity was 7.7 (with coefficient of variation 10.3%) and 1.7 (with coefficient of variation 2.5%), respectively. Therefore, parameters of cardinal temperatures, critical photoperiods, photoperiod sensitivity coefficient and biological day were estimated reasonably for bread wheat genotypes of Golestan province.

Floral transition through vernalization has a large influence on cold tolerance and agronomic traits in winter cereals. It is now apparent that in many plants small RNAs play critical roles in determination of the flowering time. There is evidence suggesting that the miR156 and miR172 families play a key role in the flowering transition of plants. In this study, the expression of two temporally regulated miRNA (miR156 and miR172) and their targeted genes (SPL3, AP2) were investigated in the winter bread wheat cv. Norstar and the spring bread wheat cv. Baj in 2017-2018 cropping season. The vernalization was exposed to the cold treatments (4°C) for 2 and 14 days at seedling stage. Time to flowering was estimated using the final leaf number (FLN), which significantly decreased under vernalization treatments, only in winter cultivar 'Norstar'. Moreover, analysis of variance showed that vernalization treatments × cultivarsv interaction effect was significant on FLN. Comparison of gene expression using bootstrapping method showed that the expression of miR172 was significantly down-regulated only in Norstar under vernalization treatments. Similarly, the expression of miR156 was completely different under vernalization treatment in two cultivars. Increased expression of miR156 in Baj cultivar was not significant, but vernalization treatment significantly decreased the expression of this gene in cv. Norstar. Although the induction of AP2 expression during vernalization (14 days) was observed in both cultivars, but, the expression levels of SPL3 were only significantly decreased in cv. Norstar, and this reduction was more in two-day vernalization. Unexpectedly, in this experiment, there was no relationship between up-regulation of both miRNA and down-regulation of their targeted genes in two bread wheat cultivars. These results demonstrated that molecular mechanism of flowering time in bread wheat is complex and still largely unknown.

Breeding and production of drought tolerant cultivars for arid and semi-arid area is very important. The present experiment was carried out to evaluate the effects of drought stress on seed yield and yield components of oilseed rape as well as identification of high yielding and drought stress tolerant genotypes. Eighteen new winter oilseed rape lines and commercial cultivars were evaluated under three moisture conditions in two cropping seasons (2014-2016) in agricultural research station of Islamabad-e-Gharb, Kermanshah, Iran. The three moisture conditions included: full irrigation, irrigation withhold from the flowering and from silique development stages. Results showed that among the yield components, numbers of seeds per silique and 1000-seed weight were significantly affected by drought stress. The reduction in 1000-seed weight under irrigation cut off from silique development stage and flowering stage was 12.8% and 24.4%, respectively. Cumulative reduction in yield components under drought stress conditions caused a significant decrease in grain yield by 32.3% and 41.3%, under irrigation cut off from silique development and flowering stage, respectively. Correlation analysis showed that there was a weak relationship between yield in full irrigation and drought stress conditions, therefore, using drought tolerance indices to screen genotypes with high yield potential and drought stress tolerant is essential. Three dimensional diagrams based on seed yield in full irrigation condition, irrigation cut off condition from silique development stage and STI showed that genotypes GKH2624, GKH3705, Nima, Neptune, GKH0224 and HW118 were located in group A, while under irrigation cut off condition from flowering stage genotypes GKH2624, GKH3705, Nima, Neptune, GKH0224, HW118, Wpn6 and L155 were classified in group A. In general, according to biplot derived from principal components analysis and 3-D graphs, under severe drought stress (irrigation cut off from flowering stage), genotypes WPn6, HW118, Nima and GKH2624 were identified as drought tolerant genotypes with high yield potential.

A factorial experiment (based on completely randomized design) with three replications was conducted in faculty of agriculture of Urmia University, Iran in 2016 to investigate the effect of soil Zn deficiency on the expression of genes encoding bZIP4, bZIP79 and bZIP97 transcription factors in Zn-efficient and Zn-inefficient bread wheat cultivars. Cv. Bayat (Zn-efficient) and cv. Hirmand (Zn-inefficient) were grown under soil Zn deficient and Zn sufficent conditions. The expression levels of three above-mentioned transcription factors were measured using Real time PCR technique in leaf and root of the cultivars at two growth stages; beginning of stem elongation (vegetative) and 30% of heading (reproductive). Analysis of variance showed that the interaction effect of cultivar × tissue × sampling time was significant on the expression of three studied genes. The mean comparison revealed that the highest expression level of bZIP4 (more than 65 fold change) in the leaf of Zn-efficient cultivar (Bayat) at vegetative stage under Zn deficiency conditions. The highest expression of bZIP79 and bZIP97 genes (more than 31 and 60 fold change, respectively) observed in the root of Bayat cultivar at vegetative stage under Zn deficiency conditions. No significant difference was found between Zn-efficient and Zn-inefficient cultivars for the expression level of three studied genes at the vegetative stage. Considering the significant increase in expression of all studied genes at vegetative stages, it may be concluded that the mRNA transcription of the transporter genes involved in Zn uptake and translocation (ZIP genes), are activated at the heading stage of the two bread wheat cultivars. Moreover, according to the increased expression of bZIP4 in leaf, and bZIP79 and bZIP97 in root, the possible role of bZIP4 and bZIP79, and bZIP97 might be the transcriptional activation of ZIP genes involved in Zn translocation within the plant and Zn uptake from soil, respectively, under soil Zn deficiency conditions.

To study the effect of sowing time and nitrogen levels on growth, yield and nitrogen efficiency of quinoa cv. Titicaca, a field experiment was conducted at in 2017-2018 growing season research farm of Agricultural and Natural Resources Sciences University of Khuzestan, Ahvaz, Iran. The experiment was conducted in split plot arrangement in randomized complete block design with four replications. Experimental factors were four sowing dates (23 Sep., 12 Oct., 1 Nov. and 21 Nov.) assigned to main plots and five nitrogen rates (0, 80, 160, 240 and 320 kg.ha-1) randomized in sub plots. Analysis of variance showed that the effect of sowing date and nitrogen rate and their interaction effect were highly significant on all traits. Mean comparison showed that the highest number of seed.plant-1 (16915), biological yield (20064 kg.ha-1) and seed nitrogen content (3.67%) was observed in the sowing date of 23 Sep. and 320 kg.ha-1 nitrogen fertilizer. Also, the highest seed yield (8657 kg.ha-1), 1000 grain weight (4.26 g), harvest index (56.7%) and plant nitrogen content (2.80%) were observed at sowing date of 12 Oct. and 320 kg.ha-1 nitrogen. The lowest seed yield (381 kg.ha-1) was observed in sowing date of 21 Nov. and and no-application of nitrogen. With increasing nitrogen application from 80 to 320 kg.ha-1, nitrogen efficiency indices decreased. The highest seed yield of quinoa in Ahvaz can be achieved by sowing on 23 Sep. and 320 kg.ha-1 nitrogen.

Rice yield as a complex trait is the main target in most rice breeding programs. To map the main and epistatic QTLs controlling grain yield and yield components, an experiment was carried out using a 129 F6 recombinant inbred lines population (IRA population) originated from a cross between Alikazemi / IR67017-180-2-1-2, in 2015 growing season in two locations, Rasht and Tonekabon, Iran.  The experimental design was augmented design arrangment with five check cultivars in randomized complete block design with five replications. Analysis of variance showed that the linkage map consisted of 87 Single Sequence Repeats (SSRs) covering 1356.0 cM of rice genome in 12 linkage groups with an average distance of 15.58 cM spamming two markers. The results of combined analysis of variance for two locations, using composite interval mapping method, identified a total of 13 main QTLs on rice chromosomes for five measured traits. The qTN3 with 13.9% for tiller number per plant, the qFG4 with 11.6% for filled grain per panicle and the qGY6 with 15.6% for grain yield had significant positive additive effect. Furthermore, the qSG1 with 19.9% phenotypivc variation had a negative additive effect on the number of unfilled grain.panicle-1. These finding suggest that these QTLs can be used in rice breeding programs for improving grain yield. The interaction between additive effect (A) of QTLs and environment (E) was significant on grain yield and number of unfilled grain.panicle-1, but it was not significan on other traits. A total of 18 QTL pairs with significant additive × additive (AA) epistatic effect were identified for all traits. The highest epistasic effects were related to grain yield and number of unfilled grain.panicle-1 with six pairs of QTLs for each of these traits. Only one of the epistatic effects between qSG1-2 and qSG6 had significant AAE effect with a R2aae = of 3.4%. In addition, some QTLs were identified as three gene clusters controlling the grain yield, number of tiller.plant-1 and number of filled grain.panicle-1. Furthermore, five microsatellite markers including RM7551, RM8218-RM3417 and RM5302- RM283 0.2 to 5 cM distance from were identified as linked markers with qGY6, qFG4 and qSG1, respectively. These markers can be considered in the marker-assisted rice breeding program.

This experiment was carried out to investigate the effect of biopolymer coated urea under deficit irrigation on ear yield, nitrogen uptake, nitrogen recovery efficiency and nitrogen use efficiency, grain protein and plant nitrogen content in sweet corn (KSc 403). The experiment was carried out in strip plot arrangement based on randomized complete block design with four replications in Agricultural Sciences and Natural Resources University of Khuzestan, Iran in 2015. The experimental treatments included; three levels of irrigation (100%, 80%, and 60% of plant water requirement) assigned to vertical plots and six levels of urea fertilizer (uncoated urea, sulfur-coated urea, starch-coated urea, agar-coated urea, and chitin-coated urea) randomized in horizontal plots. The results revealed that coated urea fertilizer with chitin could increase ear yield and NUE by of 20.2% and 32.9%, respectively, in comparison with uncoated urea fertilizer. The highest water productivity and economic water productivity was obtained from chitin coated urea and highest native soil nitrogen from non-coated urea fertilizer. The highest N uptakes and recovery efficiency were obtained in chitin-coated urea fertilizer and 100% of water requirement treatments. However, no significant difference was observed between this treatment and agar coated urea in 100% of water requirement. Redudcing 40% in water requirement decreased ear yield and NUE by 40.3% and 41.1%, respectively. The highest ear yield of sweet corn were obtained from 100% of water requirement (10238 kg.ha-1) and chitin coated urea fertilizer (9853 kg.ha-1) that was not significantly different with other biopolymer coated urea treatments. In conclusion, the results of this experiment showed urea coated fertilizer with biopolymers increased ear yield and nitrogen uptake in sweet corn and enhanced agronomic nitrogen use efficiency, nitrogen recovery and water productivity.