فصلنامه علوم زراعی ایران
سال بیست و چهارم شماره 3 (پیاپی 95، پاییز 1401)

Rice provides food for more than half of the world's population. Unlike other cereals used in the form of processed, rice is mostly consumed directly with removal of paddy and brown husks. Therefore, considering rice grain quality is one of the main factors in product marketability and consumption. Rice grain quality can be considerd and evaluated by assessment of four properties: physical, chemical, sensory and nutritional value. Physical properties such as grain shape, chalky grains, transparency and uniformity of grains. Grain size, chalkiness and color are important features that affect consumer choice. Grain cooking properties (chemical factors) mainly include apparent amylose content, gelatinization temperature, and gel consistency. Also, the viscosity properties of starch grains are considered as an important secondary difference in cultivars with similar amylose content. Sensory characteristics include aroma, grain hardness after cooking, color and taste which are important and favorite characteristics for rice consumers in the world. Major nutrients in rice include; starch, protein, fats, and non-starch polysaccharides. The key period for the formation of grain quality characteristics of rice is early and mid-grain filling stages. In addition to genetic factors, the cooking quality of rice is strongly influenced by environmental conditions, as the rice garin quality may vary from year to year or even from field to field. Rice grain quality prediction requires the association of genetic information with grain quality phenotypes in different environments. Despite the negative relationship between quality properties and grain yield in rice, targeted cross-breeding to transfer the quality related traits of local rice cultivars to improved commercial cultivars with reasonable levels of tolerance to environmental stresses as well as optimum crop management practices, are among the promising strategies for improving the rice grain quality.

Inclusion of cover crops in crop rotations has several benefits such as supplying nitrogen for the next crop. To investigate the effect of cover crops and different levels of nitrogen fertilizer on tuber yield, yield components, and different nitrogen efficiency indices of potato, a filed experiment was conducted as split plots arrangements in randomized complete block design with three replications in 2018-19 and 2019-20 growing seasons at the agricultural research farm of Faculty of Agriculture and Natural Resources, Razi University, Kermanshah, Iran. The main plots was assigned to cover crop at four levels including; rye, vetch, mixed (vetch + rye) and control (no cover crop) and the sub-plots was nitrogen fertilizer application at four levels including; 0 (control), 33, 66, and 100 percent of the recommended fertilizer level based on the soil test. The results showed that treatments had significant effects on tuber yield and yield components, plant height, the number of main stem per plant, nitrogen use indices and tuber nitrate content. Vetch and mixed treatments along with application of 66 percent of nitrogen fertilizer led to the 13 and 8 percent increases in potato yield when compared with application of 100 percent of nitrogen fertilizer without cover crop, respectively. Maximum tuber yield obtained in vetch with application of 66 percent of nitrogen fertilizer (35.42 ton.ha-1) and the least tuber nitrate (31.92 mg.kg-1) wasmeasured in control (without nitrogen fertilizer). Application of nitrogen fertilizer had a significant negative effect on nitrogen use efficiency as the highest nitrogen use efficiency (94.78 kg.kg-1) was obtained by inclusion of vetch as cover crop and without application of nitrogen fertilizer. In conclusion, our findings showed the positive effect of cover crops along with application of optimum level of nitrogen fertilizer on tuber yield potato, plant height and number of main stem per plant. This can be considered as a crop management package that leads to the reduction of application of chemical fertilizers, prevents its adverse effects on environment and more economic benefits for farmers.

To evaluate the effect of seed pre-soaking on forage yield and quality and water productivity in late planting of two forage sorghum cultivars, a field experiment was conducted was conducted as split factorial arrangements in randomized complete block design with three replications in 2017 and 2018 growing seasons at the research field of Seed and Plant Improvement Institute, Karaj, Iran. Four planting dates; July 1st, July 10th, July 23rd, and August 1st were assigned to the main plots, and factorial arrangement of seed treatments (without pre-soaking as control and seed pre-soaking) and sorghum cultivars (Peghah and Speedfeed) were randomized in sub-plots. The results showed that days from planting to the emergence of sorghum cultivars were reduced by four to six days, at different sowing dates, as affected by seed pre-soaking treatment. Late planting significantly reduced forage production, dry matter yield, protein yield, and digestible dry matter yield but improved crude protein content and dry matter digestibility. The highest fresh and dry forage yields (147.79 and 32.82 ton ha-1, respectively) and the maximum digestible dry matter and protein yield (18498 and 2904 kg.ha-1, respectively) were obtained in seed pre-soaking treatment of cv. Speedfeed in July 1st planting date. The highest water productivity for dry matter production (7.22 kg.m-3) was recorded in seed pre-soaking treatment of cv. Speedfeed in July 23rd planting date. Although seed pre-soaking reduced the digestibility of dry matter by 0.64% compared to without pre-soaking treatment, but significantly increased digestible dry matter yield and protein content. Peghah cultivar was superior for crude protein content and dry matter digestibility, and cv. Speedfeed for forage yield and water productivity. Based on the results of this experiment, seed pre-soaking treatment could compensate for the delay planting of two forage sorghum cultivars by increasing forage yield. The results of this experiment also showed that seed pre-soaking and July 1st planting date were more effective on the performance of cv. Speedfeed.

Rapid screening of plant germplasm in the early stages of growth and determining the genetic basis of wheat leaf wilting index at the seedling stage is necessary for wheat breeding programs. In the present research, leaf wilting index for 290 Iranian bread wheat genotypes, including; 90 cultivars and 200 landraces were studied under drought stress conditions at the seedling stage in 2021 in research greenhouse of faculty agriculture of Urmia University, Urmia, Iran. The results showed that there was variation between the studied genotypes for leaf wilting index, and the landraces had significantly 12% more wilting scores than cultivars. This can be attributed to direct or indirect selection by breeders. The leaf wilting index of about 9% of cultivars and 3% of landraces were identified in drought stress tolerant group. GWAS had nearly the same results as general lineare model and MLM methods. Chromosomes 3B, 2A, 7B, 1A, 3A, 4B, 5B, 6A and 6B, respectively, had the highest number of marker-trait associations in the entire population which explained the phenotypic variation of the trait from 6 to 20%. Annotation of significant markers confirmed the results of GWAS analysis and showed that five markers on chromosomes 1A, 2A, 3A and 7B were aligned with different genes involved in drought stress tolerance. An integral component of membrane, protein phosphorylation, methyltransferase activity and zinc ion binding were part of the molecular functions and biological processes of the identified genes. The findings of this research provide a deep insight into the variation of leaf wilting traits in Iranian bread wheat germplasm under drought stress conditions, which can be used as selction criterium in the national bread wheat improvement programs.

Determination of optimum sowing date plays an important role in crop management and achieving the higher yield. To study the effectof sowing date on seed yield of canola cultivars, a filed experiment was carried out as strip split plot block arrangement in randomized completed block design with three replications in 2017-18 and 2018-19 cropping seasons at Safiabad Agricultural and Natural Resources Research and Education Center of Dezful, Iran. Vertical factors consisted of six levels of sowing date (23rd September, 07th October, 22nd October, 06th November, 21st November  and 06th December), and horizontal factors were seven canola cultivars (Agamx, Hyola4815, Hyola50, Hyola401, Safi6, Zabol9 and Zabol13). Results showed that high temperature, due to the delay in sowing date, during the silique stage and grain filling period led to a reduction in the number of silique per plant and seed yield. In 2017-18, mean comparison of sowing date × cultivar interaction effect revealed that the highest number of siliques per plant (513.5 silique.plant-1) belonged to Zabol-13 in 23rd September sowing date , and the lowest (88.5 silique.plant -1) to Zabol13 in sowing date 06th December. In 2018-19, the highest number of siliques per plant (713.67 silique.plant-1) was counted in 22nd October sowing date and Safi6, and the lowest (126.24 silique.plant-1) belonged to Hyola401 in 06th December sowing date. The highest seed yield (3244 kg.ha-1) belonged to Agamax in 22nd October sowing date in2017-18 cropping season. Hyola50 had the highest seed yield (2888 kg.ha-1) in 7th October sowing date in 2018-19 cropping season. Seed yield stability anlysis showed that Hyola50 had the lowest mean rank and identified with thehighest seed yield and yield stability in all sowing dates (except .22nd October) followed by Agamax and Zabol9, respectively. In conclusion, 23rd September - 06th November can be recommended as optimum sowing date window for canola production in the north Khuzestan conditions in Iran.

To investigate the effect of foliar application of micronutrients and salicylic acid on seed and oil yield of canola under drought stress conditions,  a field experiment was carried out as spilt factorial plots arrangemnts in randomized complet block design in 2016-17 and 2017-18 cropping seasons in Lorestan University, Khorramabad, Iran. Experimental treatments included; irrigation at two levels: (A1) irrigation at 80% of field capacity (non- stress) and (A2) irrigation at 30% of field capacity (drought stress) assigned to main plots and foliar application of combination of iron, zinc and manganese elements at two levels: (B1) zero, and (B2) concentration of 2‰ and salicylic acid foliar application at four levels: (C1) zero, (C2) 0.5, one (C3) and (C4) 1.5 mM were randomized in sub-plots. The results showed that water deficit stress decreased total chlorophyll content (12%), Silque number per plant (20.4 silique.plant-1) and increased peroxidase enzyme activity (22%). Application of micronutrients increased chlorophyll content (13%) and carotenoids (10%). Salicylic acid foliar application with concentration of 0.5 mM had the highest seed oil content (40.9%). The highest water productivity (1.26 kg.m-3) was obtained in irrigation at 80% of the field capacity, foliar application of two per thousand concentration of iron, zinc and manganeze, and foliar application of 1.5 mM salicylic acid (A1B2C4). In 2016-17, the highest seed yield (4427 kg.ha-1) was obtained from the application of irrigation at 80% of the field capacity, foliar application of 2‰ micronutrients and foliar application of 1.5 mM salicylic acid (A1B2C4). In 2017-18, the highest seed yield (4955 kg.ha-1) was obtained irrigation at 80% of the field capacity, foliar application of 2‰ micronutrients and foliar application of one mM salicylic acid (A1B2C3). The results showed that under drought stress conditions, simultaneous application of micronutrients and salicylic acid increased seed yield and significantly increased oil yield (1449 kg.ha-1) as compared with control treatment (803 kg.ha-1). Based on the results of this experiment, foliar application of iron, zinc, and manganese micronutrients together with 1.5 mM salicylic acid improved seed and oild yield of canola under drought stress conditions.