Iran Agricultural Research
Volume:38 Issue: 1, Winter and Spring 2019

The relationship between canopy temperature and soil moisture is particularly important because of using canopy temperature as an indicator of crop water stress. A field experiment was conducted to calculate crop water stress index (CWSI) of two canola cultivars including RGS and Sarigol at College of Agriculture and Natural Resources of Darab, Shiraz University, Iran during 2013-2014 growing season. Irrigation regimes consisted of well watered [Irrigation equal to 100% field capacity (FC)], light drought (75% FC), moderate drought (50% FC), and severe drought (25% FC) stresses which were arranged in a randomized complete block design (RCBD) with three replications. In RGS and Sarigol, CWSI values showed an increasing trend from March (0.066 and 0.093 in well watered) to June (0.711 and 0.821 in severe drought) respectively, as a result of higher vapor pressure deficit (VPD) and increase in canopy-air temperature differences (Tc-Ta).In both cultivars, when the air temperature increased from March to June, Tc-Ta increased. The highest monthly average value of CWSI for all treatments was obtained in June. By increasing the drought stress, the color grading score decreased from 6 to 2 sharply in May and June. An acceptable color quality (6 -5) was sustained in May, under light drought condition. Also, a negative relationship was observed between CWSI with color quality (R2=0.94**) and grain yield (R2=0.97**). It could be concluded that in semi-arid areas, light drought is the best option for canola production while mean seasonal CWSI being ranged about 0.198 to 0.294 without any loss in visual color quality of canola.

This study aimed to investigate the effects of nitrogen fertilizer and a bioherbicide on Egyptian broomrape in a tomato research field at College of Agriculture, Shiraz University, Shiraz, Iran in 2014. Treatments consisted of several levels of nitrate ammonium including 0, 100, 200 and 300 kg ha-1 and a biofertilizer as the first factor and how to use the bioherbicide including soaking seedling roots in bioherbicide, bioherbigation and no bioherbicide application (control) as the second factor. Application of 200 kg ha-1 nitrate ammonium reduced broomrape height and biomass up to 18.7 and 33.7 %, respectively. It increased tomato yield up to 26.8%. Bioherbigation also caused a significant decrease in broomrape height and dry biomass by 44.5 and 58.6 %, respectively. Our results showed that application of 200 kg ha-1 nitrate ammonium along with the bioherbicide can be a promising strategy to decrease the detrimental impact of broomrape and to increase tomato yield.

Zeolite application to clayey soils may change potassium (K) pools distribution and its release rate. To test this hypothesis, two heavy-textured calcareous soils with different mineralogy (smectitic and mixed by XRD) from southern Iran were selected. Experiment was a completely randomized factorial arrangement. Treatments consisted of two soils and two zeolite levels (0 and 5%) and wetting-drying treatment. Soil samples were incubated in 50% of saturation percentage for 90 days. Then, three wetting-drying cycles were done on samples. Different forms of K and K release to 0.01 M CaCl2, HCl and CH3COOH by 12 successive 15 min extractions of soil samples were determined. Zeolite increased the content of different K forms in soil 1 (smectitic), while it increased soluble and exchangeable K and decreased non-exchangeable K in soil 2 (mixed mineralogy). This may be due to the high CEC (189 cmol(+)/kg) and K content (2.13% K2O) of the used zeolite. Wetting-drying cycles increased non-exchangeable K in soil 1 and exchangeable K in zeolite treated soils. CaCl2 extracted more K than HCl and CH3COOH solutions (682, 281 and 292 mg kg-1, respectively) because Ca ions are more efficient than H ions in replacing K from surface sites in the K-bearing minerals. Zeolite and wetting-drying had no effect on K release from soil 1 while they significantly decreased K release rate from soil 2.

Determining of chilling and heat requirements of olive cultivars growing in Fars Province is important for the selection of cultivars that will exhibit satisfactory growth and development. The purposes of this study were determining the chilling and heat requirements of olive and comparison of Utah and Positive Utah Chill unit (PCU) models for determining the chilling requirements of olive cultivars. In this regard, chilling requirement of flower buds of ‘Fishomi’, ‘Dezful’, ‘Zard’, ‘Dehghan’ and ‘Shiraz’ cultivars were determined. Cuttings of these cultivars were taken during autumn when the mean temperature fell below 12ºC. Cuttings were kept at 5 ºC for periods of 0, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700 and 1800 h. Results indicated that the chilling requirements of ‘Fishomi’, ‘Dezful’, ‘Zard’, ‘Dehghan’ and ‘Shiraz’ were  900, 1000, 900-1000, 1000-1100 and 900 h, respectively. Results also showed that the PCU unit model was more efficient than the Utah for estimating chilling requirements under subtropical field conditions. Heat requirements from the end of dormancy to full bloom stage of these five olive cultivars were estimated as 199.2, 272.1, 245.2, 245.2, 321 growing degree days (GDDs), respectively. It was observed that ‘Fishomi’ had the lowest chilling requirement and ‘Dehghan’ obtained the highest one. Hence, ‘Fishomi’ can be recommended for cultivation in subtropical regions.

Supplemental irrigation under prolonged drought conditions has a key role in providing water for transpiration of rain-fed fig trees. The effect of different times and amounts of supplemental irrigation at different distances from the tree trunk on quantity and quality of Estahban rain-fed fig production was evaluated during two years. A randomized complete block design with four replications on fig cultivars of Sabz was used to conduct the experiment. Treatments of supplemental irrigation included three different application positions including: close to tree trunks (NT); 1-1.1 m from tree trunk (UT) and outside of tree canopy (OT), using three different quantities of irrigation water as no supplemental irrigation (control), 1000 and 2000 liters irrigation water per tree, and with two different supplemental irrigation times in early spring and mid-summer. Results showed higher soil water content for irrigation during early spring, near tree trunk with 2000 liters irrigation water per tree. Despite the reduction in total soluble solids (TSS), supplemental irrigation improved the yield, size and skin color of fruits compared to the control. In both years, fig yield was higher in NT and OT treatments compared to UT. Irrigation out of canopy produced more fruits with higher quality. A non-significant difference between yields in irrigation water amount treatments during the second year indicated the adequacy of 1000 liters per tree. Application of 1000 liters, out of canopy in mid-summer would be recommended to fulfill marketing goals and sustainable use of regional water resource under drought conditions in rain-fed fig orchards.

The occurrence of viral co-infection is a common phenomenon in cultivated and native plant species and can alter the dynamics of virus infection. In this study, disease progress was examined in single and mixed infections of Cucumber mosaic virus (CMV) and Bean yellow mosaic virus (BYMV) by measuring the rate of symptom development, disease severity and area under disease progress curve on infected bean and broad bean. Simultaneous infection of bean to CMV and BYMV caused higher disease severity; however, no significant differences in disease severity were found on broad bean. In this study, a novel statistical approach (Abbott's approach) was used to recognize virus joint action in bean and broad bean hosts. Abbott's approach indicated synergistic effect between CMV and BYMV on bean only while the interaction was antagonistic when growth responses were considered on the same host. In broad bean plants inoculated with CMV+BYMV, CMV and BYMV, the two viruses affected disease severity and growth responses in an additive manner. Taken together, Abbott's approach was an appropriate method to determine synergistic interaction in these pathosystems.

The effect of different nitrogen levels on plant growth, phenol content, antioxidant and Nitrate reductase )NR) activity of cucumber (Cucumis sativus cv. Super) inoculated with mycorrhiza was studied. A factorial experiment based on a completely randomized design (CRD) with 6 replicates was designed. Treatments were three levels of nitrogen (NO3-50, NO3-75 and NO3-100) and two mycorrhiza inocula (1000 spore (AM1), 2000 spore (AM2) and no mycorrhiza treatment (AM0) as the control. Results showed that the root fresh weight increased by mycorrhiza inoculation at all nitrogen levels, while it was unaffected by nitrogen levels and mycorrhiza inoculation. FV/FM was higher in NO3-75 mycorrhizal inoculated plants compared to that of AM0 ones. Antioxidant activity of plants increased due to mycorrhiza symbiosis in nitrogen deficiency treatments, so that AM1 and AM2 increased antioxidant activity in NO3-50 and NO3-75 treatments, respectively, as compared to the AM0 plants. The highest NR activity was observed in the NO3-50 treatment. However, mycorrhiza inoculation decreased NR activity of the plants at all nitrogen levels. Therefore, it can be concluded that mycorrhiza inoculation, especially the 1000 spores treatment (AM1), and a moderate level of NO3 (NO3-75) can be used and these application levels can be very effective for greenhouse cucumber production.

Chemical control is one of the important strategies in agricultural pest management because of easy operation, availability and fast control of pests. On the other hand, the environment has been exposed to various types of pesticides and pollutants which are growing daily. The persistent effects of residual pesticides commonly used cause numerous problems for non-target organisms especially parasitoids and predators. In this research, the effects of pyriproxyfen and imidacloprid on Cheilomenes sexmaculata (F.) (Coleoptera: Coccinellidae) were studied. The eggs of the ladybird beetle were treated with each pesticide in three concentrations by dipping method. Maximum field recommended concentration (MFRC=50 mg/L), 2/1 MFRC (to simulate multiple treatments) and 1/2 MFRC (to test the sublethal effects) were used for pyriproxyfen and 1/1 MFRC (140 mg/L), 1/2 MFRC (70 mg/L) and 1/4 MFRC (35 mg/L) were used for imidacloprid. The highest mortality of the first instar larvae was observed in imidacloprid at MFRC and pyriproxyfen at 2/1 MFRC. Also, maximum influence on fertility was observed at 2/1 MFRC of pyriproxyfen and MFRC of imidacloprid with 55% and 44% reduction compared to the control, respectively. Moreover, pyriproxyfen caused significant retardation on larval development at concentrations higher than 1/2 MFRC. Both insecticides initiated a significant effects on adult eclosion compared to the control and the greatest influence was observed by imidacloprid at 1/1 MFRC with 89% reduction in adult eclosion. Although results revealed that imidacloprid has higher acute toxicity to C. sexmaculata, further results obtained from the analysis of on the life cycle parameters of C. sexmaculata also indicated that pyriproxyfen also had toxic effects on this predator.

Establishment of arbuscular mycorrhizal symbiosis in plant roots can affect plant physiological and morphological characteristics and may induce tolerance to heavy metals in plants grown in polluted soils; therefore, it can play an important role in phytoremediation. In present study, to investigate the effect of mycorrhizae on alfalfa growth and Pb uptake, a factorial experiment was designed with two factor: (1) plants non-inoculated (NM) or inoculated with Rhizophagus intraradices (Ri) or Funeliformis mosseae (Fm) and (2) soil non-contaminated (Pb0) and contaminated with 200 (Pb1), 400 (Pb2) and 600 (Pb3) mg kg-1 Pb2+. All plants were evenly inoculated with Sinorhizobium meliloti. The results showed that at high levels of Pb2+, both fungi compared to the NM controls enhanced root nodulation and phosphorus nutrition. Moreover, the dry weight of shoots, leaf area and chlorophyll index of the leaves were significantly increased in mycorrhizal plants compared to the NM plants. Mycorrhizal dependency increased by four- and three-folds in Ri and Fm plants, respectively, at Pb3 level in comparison with the non-polluted condition (p < 0.05).  Moreover, Pb translocation from root to the shoot was significantly declined at Pb3 level in Ri plants by 1.75-folds as compared with NM plants (p < 0.05). The comparison of the results obtained by principal component analysis demonstrated that R. intraradices symbiosis was more efficient for host plant protection against the phytotoxic effect of Pb. These results highlight the assisting role of AM fungi in protecting plants from metal toxicity and in plant establishment in Pb polluted soils.

Spinach is one of the most important green leafy vegetables (Spinacia oleracea L.). The qualitative and quantitative trait of the spinach depends on the weather conditions. Screening the foreign accession compare with Iranian ones is necessary for breeding purposes. In order to study the vegetative characteristics of 44 endemic and foreign accessions, an experiment was conducted in a randomized complete block design (RCBD) with three replications and 18 observations in spring, 2018. Quantitative and qualitative parameters of spinach evaluated based on descriptors investigated by Bioversity International Plant Genetic Resources Institute. In general, the intensity of the green color in the leaf of foreign accessions was higher than of endemic spinach. In this study, the highest yield belonged to “Viroflay” (71.224 ton/ha) among foreign accessions and, “Varamin88” (52.6 ton/ha) among Iranian's accessions had the highest performance. Minimum and maximum yields from 71224 to 8870 (kg/ha) belonged to accessions “Viroflay” and “Virginia savoy blight”. “D’inverno” accession showed the longest period of spring growth (89.66 days) and among the Iranian accession, “Hamadan2” (77 days), “Varamin88” (72 days) and “Varamin Prickly” (69.66 days) showed the longest growth in Isfahan environmental conditions respectively. The highest percentage of female plants was observed in “Monatol” accession. Among the endemic accessions, “Lorestan5” showed the highest female plant percentage. The results of this study showed that Iranian's accessions such as “Kashan”, “Lorestan6” and “Varamin Advanced Prickly” are suitable for mechanical harvesting due to their plant form, leaf and petiole attitude and can be used for plant breeding purposes. According to the cluster analysis, the accessions in this study were divided into two large groups (I, II), which the “Varamin88” placed beside the foreign outstanding accession in cluster I.

The documentation process is very important for identifying yield constraint factors and yield gap. For this purpose, all managing practices were recorded by monitoring of paddy rice fields in Sari region, Iran from 2015 to 2016. Field identifications were undertaken in such a way that they included all the main production procedures with variations in management viewpoints. The results revealed that seed consumption varied from 40 to 95 kg ha-1 and the range of seedling age varied from 20 to 50 days. Planting density was 10 to 66 plants per m2. Nitrogen application by 30% of the farmers ranged from 46 to 83 kg ha-1, and 40% of the farmers applied 83 to 138 kg of nitrogen per hectare. In 73% of the fields, nitrogen was not used after flowering stage. The range of yield varied from 3100 to 5430 kg ha-1, and in 60% of the studied fields, the paddy yield varied from 4205 to 5200 kg ha-1. In the comparative performance analysis (CPA) model, the actual yield and the yield potential were estimated to be 4495 and 6337 kg ha-1, respectively, and the yield gap was 1841 kg ha-1. Among the five variables entered in the model, the effects of potassium application and biological fight were remarkable, which the paddy yield increase by these variables was 709 and 806 kg ha-1, respectively, and equal to 39% and 44% of the total yield variation. Therefore, since the calculated potential yield was achieved through actual data in each paddy field, it seems this yield potential is attainable.