سهیل کرم نیا

In order to determine the nitrogen requirement of rice (cv. Guilaneh) using the nitrogen nutrition index and chlorophyll meter, an experiment was conducted as a randomized complete block design with three replications in the research field of the Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran in 2016. Experimental treatments consisted of six nitrogen fertilizer levels (0, 60, 120, 180, 240, and 300 kg N. ha-1; Urea source). Evaluation of the relationship between nitrogen nutrition index and chlorophyll-meter readings at three stages of plant growth (maximum tillering, booting, and heading) to predict grain yield in response to nitrogen fertilizer showed that the equation of the critical nitrogen concentration in Guilaneh was Nc = 3.99W -0.36. The correlation between chlorophyll-meter readings and nitrogen nutrition index was positive and significant at each plant growth stage. The results showed that the mature lower leaves were more sensitive than the younger higher leaves in response to nitrogen fertilizer and were more suitable for detecting plant nitrogen status, especially during the booting and heading stages. The highest correlation was found between the nitrogen nutrition index and chlorophyll-meter (r=0.95*) and relative chlorophyll-meter (the ratio of chlorophyll-meter readings in each treatment to nitrogen saturated treatment) (r=0.96**) in the third leaf and booting stage. The overall results of this experiment showed that the nitrogen nutrition index and chlorophyll meter may consider reliable indicators for evaluating the nitrogen status of rice (cv. Guilaneh) during the growing season.

Global warming has increased the earth's average temperature, and the tensions resulting from extreme heat have increased in different regions. Heat stress occurs in the form of an increase in temperature beyond the critical threshold for a certain period of time in different stages of the growth of crop plants. Therefore, the quantitative and qualitative changes in crop plants, including rice, as a result of heat stress caused by the global increase in temperature is one of the most critical concerns in many rice-growing regions of the world, including our country. Plants were adapted to heat stress by changing physiological, biochemical, and molecular metabolism. A stable photosynthetic system can reduce heat damage and increase grain yield under heat-stress conditions. The damage caused by high temperatures can be different in different rice growth stages, from germination to seedling stage, flowering, and seed ripening. The flowering and seed-filling stages are heat-sensitive stages in rice plants. Thermal damage in these stages can cause significant economic losses to rice production. In this article, an attempt has been made to review the physiological changes of rice under the influence of heat stress. The studied changes include the biochemical reaction of the plant during heat stress (electrolyte leakage, lipid peroxidation level and antioxidant enzyme activity), photosynthesis, membrane changes, plant changes to tolerate or escape from heat stress, changes in metabolism at the physiological, biochemical and molecular levels, adaptation to heat, regulating the activity of transcription factors related to heat stress response and changes in the expression pattern of genes under the influence of heat stress. Also, the relationship between heat stress and the biochemical characteristics that determine the quality of rice and the factors affecting the efficiency of rice grain quality, including the metabolic activities of sugar and starch and the gene expression of quality traits of rice under the influence of heat stress, were studied. Finally, the ability of rice breeding to deal with heat stress was reviewed. In the discussion of breeding for heat tolerance in rice, heritability and genetic diversity of traits related to heat stress tolerance, the results of studies conducted in the field of identifying QTLs for heat tolerance, the use of classical crossing to introduce varieties resistant to heat stress, induced mutation in breeding rice was evaluated for increased heat stress tolerance. The results have shown that rice can tolerate non-lethal heat stress by avoiding, escaping, or physical changes at the cellular level, such as changing the physical state of the membrane, synthesis of specialized heat shock proteins, and enhancing anti-oxidative defense. Changes in the physical state of the membrane and its compounds, the production of heat shock proteins, transcription factors, osmolytes, and increasing the level of antioxidant defense are the key processes to maintain the cellular oxidation-reduction balance in heat stress. Investigating the quality changes of rice under heat stress showed that the decrease in the level of enzymes in the synthesis of sucrose and starch causes significant damage to the yield and quality of the grain in hot weather. Also, the identification of several QTLs for heat tolerance, induction mutation, classical breeding using the crossing of a high-quality variety and a heat stress-resistant variety had favorable results in the identification and introduction of heat stress-resistant cultivars. Based on the reviewed results, it can be concluded that heat stress is an inevitable condition in rice cultivation; therefore, identifying and reviewing its physiological changes can be very important and provide appropriate breeding goals.

To identify genotypes tolerant to drought stress in rice germplasm, a factorial pot experiment was carried out in the form of a completely randomized design with three replications and 70 rice genotypes originating from Central and West Asian countries in non-stress and drought-stress conditions at the Rice Research Institute of Iran, Rasht, north of Iran, in 2019. Based on the results of this year (i.e. 2019), 19 genotypes selected and cultivated in the form of randomized complete block design with three replications in two environments (normal and drought stress) in 2020. Based on tolerance and sensitivity indices and the results of cluster analysis, rice genotypes were divided into two groups, and based on the comparison of means and deviations from the total mean, genotypes of the second group (Shirodi and Neda (Iran), Sela-Zodras and Shisham-Bagh-2014 (Afghanistan) and Dijla (Iraq) recognized as stress-tolerant genotypes. Also, six genotypes (Nada and Shiroudi (Iran), D3 (Iraq), Sela-Zodras, Jalal-Abad Indica-2014, and Shisham Bagh-2014 (Afghanistan)) were identified by biplot analysis and the ranking method of seven genotypes (Shirodi, Neda and Gilaneh (Iran) Sela-Zodras, Jalal Abad Indica-2014 and Shisham Bagh-2014 (Afghanistan) and D3 (Iraq) were recognized as drought stress tolerant genotypes. Altogether, based on the methods of cluster analysis, biplot, and ranking, the genotypes of Shiroudi and Neda (Iran), Sela-Zodras, and Shisham Bagh-2014 (Afghanistan) were recognized as drought tolerant genotypes. The mentioned selected genotypes can be used in advancing breeding programs for developing new rice genotypes with higher tolerance to drought stress.

To study the response of Hashemi (local) and Gilaneh (improved) rice cultivars to the application of different sources and levels of organic fertilizers, a field experiment was conducted using a randomized complete block design with three replications in 2018-2019 and 2019-2020 cropping seasons in research field of Rice Research Institute of Iran (Rasht), Iran. Experimental treatments include poultry manure (2.5, 5 and 10 ton.ha-1), cow manure (5, 10 and 20 ton.ha-1), sheep manure (10, 20 and 40 ton.ha-1), and two control treatments including chemical fertilizers and no-fertilizer. Traits measured included plant height, number of tiller.plant-1, number of fertile tiller.plant-1, number of panicle.m-2, grain yield as well as amylose content and gelatinization score. The results showed that the effect of organic fertilizers was significant on yield components and grain yield of rice cultivars. Application of 20 ton.ha-1 of cow manure increased plant height (142 cm), number of fertile tillers (14), number of panicle.m-2 (240) and grain yield (3643 kg.ha-1) in Hashemi cultivar and also increased plant height (134 cm), number of fertile tillers (17), number of panicle.m-2 (252) and grain yield (4760 kg.ha-1) in Gilaneh cultivar. Experimental treatments had a significant effect on the gelatinization score of rice grains. The highest grain yield obtained in the treatments of 20 ton.ha-1 of cow manure and Hashemi cultivar (3670 kg.ha-1). The results of this study showed that the application of 20 ton.ha-1 of cow manure increased grain yield by 60 and 64%, in comparison to control treatment of no-fertilizer, and compensated of 86 and 88% of grain yield in Hashemi and Gilaneh rice cultivars, respectively, as compared to the treatment of chemical fertilizers.

Legumes are the most important source of plant protein and Mung bean has a high nutritional value for humans, as it produces seeds containing high protein percentage. The major problem of salinity in seed germination of higher plants is due to excessive amounts of sodium chloride, osmotic pressure, disruption of nutrient uptake and transport, and direct effects of ionic toxicity on the membrane and enzymatic systems that in turn reduce germination. External use of methyl jasmonate can modulate the effects of various stresses, such as salinity and drought, by increasing the antioxidant activity of the seed. Therefore, the purpose of this research was to evaluate the effect of methyl jasmonate and salinity stress on germination and enzymatic properties of Mung bean.

This study was conducted as factorial based on a completely randomized design with three replications during 2015-16 at the laboratory of Department of Agronomy, Tarbiat Modares University. The experimental treatments included four methyl jasmonate solution (0, 50, 100 and 150 mM) and four salinity stress levels (0, 2, 4 and 6 dS/m salinity from NaCl). Petri dishes were placed in a germinator at 25 ° C and in full darkness for 14 days. In this experiment, germination rate and percentage, time to reach 50% germination, alpha and beta amylase, catalase and peroxidase were measured.

The results of the experiment showed that the lowest rate of slope and final germination percentage were obtained in 50 and 100 mM solutions of methyl jasmonate. In terms of T50, an increase of 4.7 days was observed per one dS/m increase in salinity stress and the lowest T50 was estimated at a methyl jasmonate solution concentration of 78.68 mM. In terms of the activity of germination enzymes, reduction of 0.031 μmol/ml/min per 1 dS.m increase in salinity stress and the highest amount of α-amylase were estimated 72.6 μmol/ml/min at a methyl jasmonate solution concentration of 73.33 mM. Also, the lowest activity of β-amylase enzyme was 0.79 μmol/ml/min at a concentration of 5.6 dS/m salinity stress and the highest activity of β-amylase enzyme was estimated to be 1.7 μmol/ml/min at a methyl jasmonate solution concentration of 86.67 mM. The highest activity of catalase (25.7 ∆A/mg protein/min) was observed at 14.72 dS/m salinity stress and the lowest activity of catalase enzyme (8.9 ∆A/mg protein/min) was estimated at 5.88 mM methyl jasmonate solution. The highest activity of peroxidase enzyme (22.06 ∆A/mg protein/min) was at 24.3 dS/m salinity stress and the lowest activity of the enzyme peroxidase (2.5 ∆A/ mg protein/min) was determined at a methyl jasmonate solution concentration of 266.66 mM.

In general, pre-treatment of methyl jasmonate can reduce the germination time, increase the rate of germination and reduce the oxidative stress in salt stress conditions by improving the activity of germination enzymes, increasing the activity of enzymes, increasing the activity of hydrolyzing enzymes and increasing the easy availability of seedlings to nutrients during germination. Highlights: 1- Germination rate and percentage and morpho-physiological changes of Mung bean seed as affected by methyl jasmonate were investigated. 2- The role of alpha and beta amylase germination enzymes in accelerating the production of Mungbean seedlings under saline conditions were estimated. 3- Methyl jasmonate- induced catalase and peroxidase enzymes activity in resistance to salinity stress were estimated.