sami jalali

Rice is one of the most important summer crops in Khuzestan Province. Due to the severe water limitation, the effect of using strip drip system in the method of direct seeded rice in dry bed was monitored on the yield of common rice cultivars of the province and changes in soil salinity. This research was conducted during 2019-20 and 2020-21, at the Ahvaz Agricultural Research Station on three adjacent plots of land, using split-plot design and randomized complete blocks in three replications. The main factor was irrigation including three levels: daily irrigation, every two days, and three days; and the secondary factor included three cultivars (Red Anbori, Champa, and Daniyal) and one salt tolerant rice line (S2). In the first year, due to the allocation of water outside the cultivation date, the yield of the crop was very low, so, the analysis was done based on the second year. The average volume of irrigation water in the field was measured as 14,800, 15,200, 15,700 and 16,100 m3/ha for, respectively, line S2, Red Anburi, Daniyal, and Champa. The results showed that, in the daily irrigation, the "Red Anburi" local cultivar had the highest yield with 3767 kg/ha and S2 line had the lowest 2541 kg/ha, so that when the irrigation changed from every day to three days, the yield decreased by 56% on average. The highest water productivity was obtained by the "Red Anburi" cultivar (0.25 kg/m3) in the daily irrigation. The reason for this problem can be shown in the monitoring of soil salinity, so that with daily irrigation, the salinity of the saturated extract in all soil layers showed a decreasing trend from 3.77 to 1.8 dS/m. According to the results, use of drip irrigation system would significantly reduce the volume of irrigation water compared to "conventional puddled transplanted rice". This has been an effective strategy in reducing the stress on the water resources of the province and saving the available water to preserve the ecosystem, although significant reduction of rice cultivation area in this province is recommended.

Heat and its effects are considered one of the serious threats and damages to the production of agricultural and horticultural crops in many regions of the world. Therefore, it has led to pervasive changes in terms of morphological, physiological, anatomical, and molecular, which causes a sharp decrease in the economic performance of agricultural products. Nowadays, in order to reduce these inhibitory effects, in addition to classical and conventional breeding methods, modern and molecular methods can be used to identify heat-tolerant genes and use them in breeding programs to improve plant tolerance to environmental stresses.

The selection for heat tolerance among four local cultivars Hovyzeh, Hamar, Red-Anbori, Champa and three promising heat tolerant lines V1, V2 and V3 obtained from the international breeding programs of Khuzestan Agricultural Research and Training Center and Natural Resources were evaluated by osHATS and HSP70 genes qPCR on two experimental cultivation dates: May 20 (unfavorable) and June 20 (favorable) 2022 in Ahvaz.

The results obtained from the analysis of gene expression by qPCR on the date of the first cultivation confirmed the presence of the osHTAS gene in rice varieties and lines so that the local variety Champa, Hovyzeh, and line V2 has a high relative gene expression compared to other varieties and lines studied and they were significantly different from each other. The analysis of the osHTAS gene expression on the second planting date (June) in Ahvaz also shows the presence of the high-temperature tolerance gene in Hovyzeh, Hamar and V2 lines; therefore, the mentioned varieties could be used as parental lines for transfer heat tolerance gene to be used in multi-breeding programs and terms of the relative expression level of the gene, they showed a statistically significant difference with each other. The results of the relative gene expression of the HSP70 gene in the cultivation date of May showed that the local cultivars Champa, Red-Anbori and Hovyzeh had a remarkable superiority over the others. Examining the HSP70 gene expression pattern of rice cultivars and lines on the second planting date also revealed that the local cultivars Red-Anbori, Champa, Hovyzeh, and Hamar showed superiority. The tolerance of local cultivars to heat stress is due to their rapid growth and the creation of a large green cover in the early stages of growth, and their great adaptation to the region's environmental conditions.

Local cultivars can withstand heat stress well with rapid growth and creating much vegetation due to their high adaptability to environmental conditions and the presence of heat stress tolerance genes. They could be used as parental lines in breeding programs.

To investigate the weed response to ecosystems of local and high-yield rice cultivars at different planting dates in direct cultivation by dry-bed seeding, an experiment was conducted in the form of a split-plot in a randomized complete block design with three replications in the research farm of Shavor Research Station. The main plot of planting date in three levels (June 15, June 25, and July 5) and four rice cultivars including two local cultivars Champa and Red-anbori and cultivars High-yielding and improved Danial and Shafagh was grown as a subplot at each planting date. According to the results, the highest and lowest number of weeds in the sampling on the first and second planting dates were obtained with an average of 123 and 61 plants, respectively. Among rice cultivars, the lowest weed density was observed in sample in Danial cultivar. In this experiment, the predominant species in the samples were two weeds barnyard grass and chinese lantern. The rate of weed emergence was around 0.56 to 0.63 number per day. in all three planting dates in the range of 20-40 days after planting. Therefore, weed control and field care during this period is essential to achieve optimal grain production.

Water scarcity is a major constraint in the development of rice farming in some parts of the world. In many areas, the volume of water consumed in the field and during the growing season of rice is usually more than the actual requirement due to traditional flood irrigation. In the province of Khuzestan, irrigation water requirement is potentially high due to the coincidence of rice cultivation with the beginning of hot months of the year. In traditional irrigation management, regular water entry and exit from the basins is commonly used to reduce water temperature and create a cool environment for plant development. This system causes a lot of water losses. It seems that a change in the irrigation method of rice fields is necessary. The application of new technologies, such as pressurized irrigation systems, can be an appropriate approach to reduce future problems related to increasing water shortages. In this regard, the study of pressurized irrigation systems has been considered as one of the strategies for reducing water consumption and increasing water productivity in rice cultivation in the research program. Result of a research in Pakistan about water use efficiency and economic feasibility of growing rice with sprinkler irrigation showed that the application of this system increased the yield of rice by 18%, while the water consumed was 35% less than the traditional irrigation system (McCauley, 1990).

An experiment was carried out to study of heat stress on assimilate remobilization of rice in north of Khuzestan province in a split-plot arrangement using randomized complete blokes design with three replication in 2006 and 2007 at Shavoor Agricultural Research Station, Dependent in Research Center of Agricultural and Natural Resources of Khuzestan. For exposing rice cultivars to different higher temperature regimes, main plot were assigned to three sowing dates from 5 May, 26 May and 16 Jun and cultivars were; Hoveizeh, Hamar (heat tolerance) Ghermez Anbori, Champa (heat sensitive) and Danial (relatively heat tolerant) were in sub-plots. Results showed that the highest dry matter redistribution was in Ghermez Anbori and heat tolerant cultivars. The grain, stem and leaf portions were significant on sowing date and cultivars. The second and third planting dates and heat tolerant cultivars had higher content. The highest remobilization, current photosynthesis and the portion of organs in filling grain yield were 1140.8 kg.ha-1, 3923.3 kg.ha-1, and 22.5%, respectively, in 26 May planting. But the highest share portion of current photosynthesis in grain yield was in 5 may in the planting date.

Current research was conducted during 2006 and 2007 cropping seasons to assessment the anatomy of the flag leaf and yield of rice in the Khuzestan province according split plot experiment based on randomized complete block design with three replications. Main plot included different sowing dates at three levels (5 May, 26 May and 16 June). Hoveizeh, Hamar (Heat tolerance), Ghermez Anbori, Champa (Heat sensitive) and Danial (Relatively heat tolerant) cultivars at five levels were belonged to sub-plots. The results of combined analyses showed that was a significant different in planting date by variety interaction in all of trades. On the other hand, the related temperature condition, varieties had different reaction. Given that metabolic energy is needed to transfer sugar in this path, reduction of phloem cell surface can predispose the material preservation and shortening the transfer path by reducing the rate of respiration and transfer intervals. In the other hand, size of phloem depends on the size of source and reservoir and their relationships. Highest and lowest levels of large vascular bundles were related to 2nd and 1st planting dates; but highest and lowest levels of small vascular bundles, xylem and phloem obtained in 2nd and 1st planting dates respectively.

In order to evaluation of trend yield and physiological indices variation of some current Rice cultivars an experiment was carried out in split-plot arrangement using randomized complete blocks design with three replication. In 2006 and 2007 years at Shavoor Agricultural Research Station in Khuzestan province. For exposing rice cultivars to different higher temperature regimes, main plots were assigned to three sowing dates from 5 May with 20 days intervals and cultivars namely: Hoveizeh, Hamar (heat tolerance) Ghermez Anbori, Champa (heat sensitive) and Danial (relatively heat tolerant) were randomized in sub-plots. The results of combined analysis of variance showed that the highest grain yield was harvested from the second sowing date (26 May). It was the superior to first sowing date (5May) with 62.5 percentages. The reason of higher yield related to superior physiological indices in panicle exertion, LAD in ripening duration and also higher dry matter storage potential. In among cultivars, Hoveizeh was the superior to other cultivars and had higher yield related to Ghermez Anbori, Champa with 50.9 and 36.3 percentage respectively. In spite of heat sensitive cultivars had higher of Maximum leaf area index but their's crop growth rate, net assimilation rate and relative growth rate were lower.

This experiment was carried out to determine the effects of heat stress, due to different planting dates, on the peduncle anatomy of rice cultivars and their grain yields. It was performed in a split-plot experiment using randomized complete blocks design with three replications in 2006 and 2007 cropping seasons at the Shavoor Agricultural and Natural Resources Research Center of Khuzestan. Three planting dates (May 5th. with 20 days intervals), to expose rice cultivars to different tempratures, were assigned to main plots and cultivars (Hoveizeh, Hamar, heat tolerant, Ghermez Anbori, Champa, heat sensitive, and Danial, relatively heat tolerant) to sub-plots. The results of combined analysis showed that the effects of planting date× variety interactions were significant for all of traits, including air channel surface, large vascular bundles surface, xylem and phloem. This indicates that cultivars reacted differently to planting dates. Lowest and highest airchannels surface levels were related to 1st and 2nd planting dates (15492.23 and 21144.38 µm2) and to Hoveizeh and Champa cultivars (15492.23 and 23411.18 µm2) respectively. Lowest and highest xylem surface obtained in 3rd and 1st planting dates (741.37 and 898.03 µm2) respectively. But, lowest and highest level of large vascular bundles were optained in 2nd and 3rd planting dates (15514.20 and 15983.93 µm2)and for phloem (3121.68 and 3437.55 µm2)respectively. Based on these results it can be said that the reduction of large vascular bundles surface and phloem in 1st and 2nd planting date are mechanisms of water conservation and maintaining cell turgor pressure. Increasing xylem vascular bundle surface also, would facilitate availability of water to plant under drought stress conditions.