Iranian Journal of Crop Sciences
Year:2019 | Volume:21 | Issue:3|Papers Count:7

Intensified salinization of water and soil resources has promoted interest for research and approaches of improving crop yield under saline conditions. Reviewing the literature showed that the records on understanding of different aspects of salt stress and enhanced salinity tolerance in the world goes back to more than a century. Different approaches have been suggested to increase crop yield under saline conditions, among which one is using plant growth regulators (PGRs). Application of PGRs has begun since 1930s and their global annual sales are about US$ 1. 2 billion. Nearly 40 active ingredients og PGRs are now in use, applied either as a single or combined treatments, among which the most important are auxins, cytokinins, gibberellins, ethylene, abscisic acid, brassinosteroids, salicylic acid, chlormequat chloride, paclobutrazol, jasmonic acid, ascorbic acid, triacontanol, strigolactones, nitric oxide, polyamines and plant peptide hormones. There have been large body of reports showing quantitative and quality improvement of crops as well as salinity tolerance as the consequences of PGRs application. However, most of these studies were conducted under controlled conditions (i. e. out of field conditions), as one season experiments, and this makes the results unreliable. In this paper, with having in mind the applicability for the field conditions, crop yield improvement as the result of using PGRs has been reviewed.

Study of heritability and gene action to improve agronomic and physiological traits, especially under drought stress conditions, are very important. The objectives of this study were to investigate heritability for important agronomic traits and some physiological characters in a cross between two spring wheat cultivars. The experiment was carried out using different generations (BC1, BC2, F3, RF3) derived from crosses between two cultivars, Arg (tolerant to salinity and drought) and Moghan3, under drought stress conditions using randomized complete block design with two replications in 2014 cropping season at the University of Tabriz research station, Iran. In all plots, irrigation was withheld after antesis until the end of season. Generation mean and generation variance analyses were used to estimate gene action and genetic variance components, respectively, for agronomic and physiological traits of wheat under water deficit conditions. Based on the analysis of variance, significant differences were observed between generations for peduncle length, spike length, flag leaf width, flag leaf area, number of fertile tillers, leaf chlorophyll content, days to heading, spike weight, straw weight, biomass, grain yield and harvest index which revealed the presence of genetic differences between two parents. The generation mean analysis for the flag leaf width and flag leaf area showed that the three-parameter model was the best fit. However, for other traits chi-square of the three parameter model was significant, indicating the presence of non-allelic interactions in the inheritance of these traits. Although both types of additive and dominance effects were significant in control of the studied traits, but dominance component was larger than the additive effect. The dominance × dominance epistasis was also more important than other epistasis components for the studied traits. The broad-sense and narrow-sense heritability of the traits ranged from 0. 754 to 0. 941 and from 0. 144 to 0. 579, respectively. Estimates of variance components revealed that dominance variance was greater than additive variance for peduncle length, spike weight, straw weight, biomass, grain yield and harvest index. While, the additive genetic variance was higher than the dominance genetic variance for spike length, flag leaf width, flag leaf area, fertile tiller number, chlorophyll content and days to heading. The average degree of dominance was more than one for all of the traits which indicated the presence of over-dominance gene action in controlling these traits. Presence of non-additive genetic effects in controlling the traits showed the necessity of selection in advanced segregating generations, when populations are relatively fixed line, using bulk-pedigree method or for development of hybrid varieties in wheat, should the pollination and male sterility barriers will be overcome.

Sorghum is an important forage crop used as silage, fresh forage and dry forage. To evaluate the yield stability of 16 genotypes; cultivars, lines and hybrids, of forage sorghum, experiments were conducted using randomized complete block design with three replications during 2016-17 at Karaj, Isfahan, Gorgan, and Mashhad field stations, Iran. The results of combined analysis of variance showed that the effect of location, year, genotype and their interactions were significant on forage yield. Mean comparison showed that hybrids No. 8 (Siloking) and 12 (FGCSI12) were superior to other genotypes with 130. 6 and 127. 5 t. ha-1 of fresh forage yiled, and 26. 97 and 27. 17 t. ha-1 of dry forage yield, respectively. The hybrid No. 2 (Speedfeed), No. 9 (PHFS-27), No. 5 (Juicy Sweet BMR SSH. 1) and No. 13 (Sucarose-Photo-BMR) had also high fresh forage yield of 105. 6, 107. 8, 108. 2 and 107t. ha-1, respectively. The analysis of variance by AMMI method and fitting of principal components to the interaction effects of genotype and environment showed that the two principal components were significant for fresh and dry forage yield. According to the AMMI model and AMMI stability value (ASV), genotypes No. 8 (Siloking) and 12 (FGCSI12) with the high yield and stability were identified as suitable genotypes.

To evaluate the effects of drought stress by withholding of irrigation during reproductive stages and foliar application of micronutrients (Zn, Mn and B) on seed yiled and oil quality, an experiment was carried out as split plot arrangements in randomized complete block design with three replications at Safiabad Agricultural and Natural Resources Research and Education Center, Dezful, Iran, in two growing seasons (2013-2015). Main plots consisted of three irrigation levels: full irrigation (control), withholding of irrigation from flowering stage, and withholding of irrigation from silique stage, and sub plots included 10 levels of foliar application of micronutrients (2, 4, 6‰ zinc, 2, 4, 6‰ manganese, 2, 4, 6‰ boron, and the foliar application of distilled water as control). Foliar applications were made during both budding and initiation of flowering stages. Results showed that withholding of irrigation significantly decreased seed yield and yield components. Withholding of irrigation from flowering and silique stages reduced the silique no. plant-1 by 40% and 8%, respectively. Mean comparison of withholding of irrigation and foliar application showed that the highest seed yield (4301 kg. ha-1) belonged to full irrigation and foliar application of boron (4‰ ) in both growing seasons. The lowest seed yield (1863 kg. ha-1) obtained in withholding of irrigation from flowering stage and no micronutrient. Withholding of irrigation from flowering stage led to decrease oleic and linoleic acids content. The highest oil content (45. 6%) measured in full irrigation and application of zinc (6‰ ) and boron (6‰ ). The lowest oil content (40. 3%) observed in severe moisture stress conditions and no micronutrients. The results of this experiment showed that withholding of irrigation from flowering stage imposed severe stress on crop and should be avoided. The highest seed yield belonged to application of manganese and boron (4‰ ) and zinc (6‰ ) under withholding of irrigation from silique stage. To obtain reasonable seed yield, full irrigation and foliar application of zinc (4‰ ) and boron (4‰ ) is possible.

To study the effect of zinc sulfate rates on response of bread wheat cv. Cahmran to terminal heat stress conditions in Ahvaz, Iran, this experiment was conducted at the research farm of Agricultural and Natural Resources Sciences University of Khuzestan, Iran in two cropping cycles (2015-2016 and 2016-2017). The experimental design was split plot arrangements in randomized complete block design with four replications. Experimental factors were three sowing dates (29 Nov., 14 Dec. and 30 Dec. ) assigned main plots and five zinc sulfate rates (0: Control, 10, 20, 30 and 40 kg. ha-1) randomized in sub plots. Combined analysis variance showed that year had a significant effect on measured traits. Mean comparison of traits in different sowing dates showed that grain yield decreased with delay in sowing date, due to occurrence of terminal heat stress. The highest (6726 kg. ha-1) and lowest (2884 kg. ha-1) grain yield were obtained in the first and last sowing dates, respectively. The results showed that grain yield increased with increasing zinc sulfate rates and the highest grain yield (6724 kg. ha-1) was obtained from application of 30 kg. ha-1 zinc sulfate. Mean comparison of interaction effect of sowing dates × zinc sulfate rate on studied traits showed that the highest grain yield (6508 kg. ha-1) was in the first sowing date and 30 kg. ha-1 of zinc sulfate application, and the lowest grain yield (2958 kg. ha-1) was in the last sowing date and no-zinc sulfate application (Control). In conclusion, the result of the experiment showed that delay in planting of bread wheat cv. Chamran imposed late heat stress and application of 30 kg. ha-1 zinc sulfate reduced heat stress effect and improved grain yield.

The rapid population growth and the need for more agricultural production necessitate more attention to water shortage and enhancing water productivity. To assess water productivity and supply: demand ratio index in sugar beet, this experiment was carried out using SUCROS growth simulation model. Long-term climatic data and collecting questionnaires from farmers were used to assessing water productivity in sugar beet agroecosystems in 10 counties of Khorasan Razavi province, Iran and investigating the role of water management in water productivity and drought stress conditions in sugar beet. Results of long-term simulations showed that the actual yield (33. 5 t. ha-1) by farmers was only one-third of the attainable yield (97. 3 t. ha-1) of sugar beet in the targted areas. Forty eight percent of this yield gap was due to water constraints. The results indicated the low productivity (1. 5-1. 8 kg root m-3) of sugar beet in the targeted areas. The results also showed that inappropriate irrigation management, despite the high water consumption in some counties, led to decrease in water productivity and occurance of drought stress during the growing season. Results also showed a positive and significant relationship between water productivity and supply: demand ratio index in different locations. The index, over growing season, in different counties was highly depended on water management, air temperature (particularly during warmer months of the year) and soil water holding capacity. These results indicated the need for a more scientific attention to appropriate irrigation schedules according to the plant water requirement and soil water retention capacity during the warm seasons to meet the moisture requirement of sugar beet.

To evaluate the effect of nitrogen sources on yield and quality of sweet basil and forage maize under intercropping (additive series), a field experiment was carried out at the experimental field of faculty of agriculture, Lorestan University, Khorramabad, Iran, in 2013-2014 and 2014-2015 growing seasons. Experimental treatments were arranged as factorial in randomized complete block design with three replications. Experimental treatments included: without fertilizer (Control), 100% chemical fertilizer (N), bio-fertilizer (Nitroxin), integration of bio-fertilizer + 50% chemical fertilizer, and cropping patterns consisted of; sole cropping sweet basil and forage maize and the additive intercropping of maize + 25% sweet basil, maize + 50% sweet basil, maize + 75% sweet basil and maize + 100% sweet basil. Mean comparisons showed that in the second year sole cropping of sweet basil with 100% chemical fertilizer in second harvest had the highest total dry weight (3921. 9 kg. ha-1). Among cropping systems the highest total dry weight (19220 kg. ha-1) was obtained from sole cropping of forage maize. Application of the integration of Nitroxin + 50% nitrogen chemical fertilizer in intercropping produced reasonable biological yield and essential oil yield, and did not show a remarkable difference with nitrogen chemical fertilizer. The highest LER (1. 566) belonged to maize + 100% sweet basil with bio-fertilizer. The results showed that using the integration of bio-fertilizer + 50% chemical fertilizer can be considered as an enviromnet-friendly approach to reduce the consumption of chemical fertilizers in support of sustainable agriculture.