فصلنامه علوم زراعی ایران
سال بیست و دوم شماره 4 (پیاپی 88، زمستان 1399)

Association mapping is a technique with high resolution for QTL mapping based on linkage disequilibrium and has shown more promising for describing genetically complex traits. In addition, it is a powerful tool for describing complex agronomic traits and identifying alleles that can contribute to enhance the desired traits. In this study, whole genome association mapping was used in a set of 148 spring barley cultivars. Phenotypic evaluation was conducted at Zahak Agricultural Research Station, Iran, using alpha-lattice design with two replications, for two croppinhg cycle (2014-2015 and 2015-2016). Traits such as days to anthesis, days to physiological maturity, grain filling period, flag leaf length, flag leaf width, grain number per main spike, thousand grain weight and grain yield were measured. Association analysis between the markers and phenotypic traits was performed with a mixed linear model (MLM with K+Q). In total 28 QTLs were identified which were related to the measured traits. A stable QTL was detected on chromosome 5H (74.76 cM) for days to anthesis. Three QTLs were detected on chromosomes 4H (125.08 cM and 120.64 cM) and 5H (74.76 cM) for grain filling period. One QTL on chromosome 2H (10.87 cM) was associated with days to anthesis, grain filling period and 1000 grain weight. One QTL on chromosome 4H (125.08 cM) was also associated with days to anthesis, grain filling period as well as flag leaf length and 1000 grain weight. Common genetic locations for these traits could be due to pleiotropic effects or genetic linkage.

For sustainable rice production in Iran the optimum use of production resources and the reduction of production costs are the two important issues. In this situation, water availability is a major limiting factor in sustainable rice production. Hence, changing of rice production system from lowland irrigated to aerobic production system, which is based on dry-seed sowing in non-puddled and non-satuared soil, is main goal in the national research plan. Six selected aerobic rice genotypes from preliminary yield trials together with two local checks of rice including; Neda, as tolerant and Tarom, as susceptible cultivars to aerobic conditions were evaluated using randomized comlete block design with three replications in Mazandaran and Golestan, Iran, provinces for three years from 2013-2015. Simple analysis of variance for each location showed significant differences among rice genotypes for all traits. Combined analysis of variance for grain yield was performed. There were highly significant differences for main effect of genotype, year × location and year × location ×genotype interactions effect. Grain yield stability analysis through AMMI and GGE bioplot methods indicated that aerobic rice cv. Vandana with an average grain yield of 2760 kg.ha-1 over all environments had high and grain yield with yield stability. This cultivar was also close to ideal rice genotype with lower plant height (98.8 cm) and phenology (97.0 days to 50% flowering), followed by the other two  aerobic rice genotypes; G2 (IR78908-193-B-3-B) and G6 (IR80508-B-194-3-B) with high grain yield over all environments. Therefore, these aerobic rice genotpes were selected and could be used in the national rice breeding programs or recommended for being grown in aerobic rice production system in Mazandaran and Golestan province under water-shortage conditions.

To investigate the effect of cover crops on soil physical properties, weed control and yield of white radish, a filed experiment was carried out using randomized complete block design with three replications in 2017 and 2018 in the research field of Mohaghegh Ardabili University, Ardabil, Iran. Experimental treatments included: cultivation of barley (Hordeum vulgare L.) and hairy vetch (Vicia villosa L.) cover crops as monoculture and dual mixed crop 50:50 ratio and without cover crops (control). The results showed that the highest biomass (5172 kg.ha-1) of cover crops over two years from mixed barley + vetch and the lowest (3396 kg.ha-1) obtained from monoculture of hairy vetch. The barley monoculture reduced dry weight of common lambsquarters (59.1%), wild mustard (54.7%), Anchusa italica (73.1%) and reduced the total weeds (64.9%) as compared to the control. The soil bulk density, soil porosity percentage and time required for water infiltration were 1.32 g.cm-3, 50.21%, 7.21 second, respectively, and improved by monoculture of hairy vetch. The highest white radish yield (46100 kg.ha-1) obtained from monoculture of barley cover crop treatment which increased by 25.97% as compared to control. Based on the results of this experiment, monoculture of barley as cover crop could effectively control weeds and increase white radish yield. However, monoculture of hairy vetch was more effective in improving soil physical properties as compared to other treatments.

To study the effects of tillage system, planting method and of nitrogen fertilizer rate on the agronomic characteristics and seed yield of rapeseed (Brassica napus L.) Dalgan oilseed rape cultivar, as the second crop after rice, a split factorial experiment in complete randomized block design with three replications was carried out in two cropping seasons (2016-2018) at paddy fields of Rice Research Institute of Iran, Rasht, Iran. In this experiment, three tillage systems (conventional tillage, minimum tillage, and no-tillage) were considered as main plots and two planting methods (direct and transplanting) and four rates of nitrogen (N) fertilizer (0, 100, 200 and 300 kg.ha-1) as factorial arrangement in sub plots. The results showed that conventional and minimum tillages in the transplanting method had the maximum seed yield (with the averages of 3458 and 3360 kg.ha-1, respectively). Transplanting method with 300 kg.ha-1 of nitrogen level had higher number of auxiliary branches per plant, number of siliques per plant, seed yield, and oil yield. Minimum tillage system with 200 kg.ha-1 of nitrogen with an average seed yield of 4144 kg.ha-1 had the highest seed yield. Based on the results of this experiment, minimum tillage system with 200 kg.ha-1 of nitrogen in both planting methods, direct seeding and transplanting, would be more suitable for oilseed rape production in Guilan region.

Information on genetic variability and heritability of plant attributes and their correlation with lint yield and fiber quality is important for planning breeding and selection strategies for prediction of genetic gains in cotton breeding programs. For these purpose, a field experiment was carried out using randomized complete block design with four replications in 2016 and 2017 at Hashem-Abad cotton research station, Gorgan, Iran.  Variability and heritability and genetic improvement for sixteen quantitative and qualitative traits were evaluated in 40 cotton genotypes including; 31 recombinant inbred lines (F7) and nine parental genotypes.in. The analyisis of variance as well as phenotypic, genotypic and environmental variances revealed high variation among cotton genotypes.  Cotton genotpeswere grouped in three distinct classes using cluster analysis. In general, phenotypic coefficient of variation (PCV) estimates were higher than genotypic coefficients of variation (GCV) for all the studied attributes, implying the environment effect on the studied traits. The highest PCV and GCV were estimated for seed cotton yield, sympodial and monopodial branch numbers. High heritability and genetic improvement was observed in lint percentage (76.7% and 15.2%, respectively), boll number (72.6% and 23.5%, respectively), boll weight (67.9% and 19.7%, respectively) and sympodial number (56.8% and 79.3%, respectively), indicating the effect of additive gene action and favorable response of these traits to selection. Also, the above mentioned traits had significant positive correlation with seed cotton yield and reaffirmed to be the main cotton yield components. The results indicated that selection for boll number per plant, boll weight, lint percentage and sympodial branch number per plant are desirable selection indices for indirect selection for lint yield and fiber quality improvement of cotton at early generations.

This study was conducted to quantitatively evaluate selfed (S1, S2 and S3) and open pollinated (OP1, OP2 and OP3) generations of alfalfa in terms of inbreeding depression and general combining ability of S2 families of alfalfa ecotypes. Selfing of selected plants to produce three generations of S1, S2 and S3 generations were performed under the field conditions and the clones of each selfed- generations were used for producing of open pollinated- generations.  For comparison of dry forage yield and plant height of selfed (S1, S2, S3) and open pollinated (OP1, OP2, OP3) generations randomized complete block design with three replications was employed in 2015 and 2016 growing seasons at Plant and Seed Improvement Institute, Karaj, Iran.. The results revealed significant differences among ecotypes, generations and growing seasons and their two- way and three-way interactions for dry forage yield. Alfalfa ecotypes reacted differently to selfing, and the highest rate of vigor depression was observed in the S1 generation tropical ecotypes. However, vigor recovery observed in all ecotypes with continuing selfing and vigor remarkably increased in S3 generation. Vigour recovery was observed more in OP2 than OP3. The highest general combining ability for dry forage yield observed for Yazdi and Nikshahri ecotypes which are tropical ecotypes. Therefore, crossing of these ecotypes with ecotypes originated from different climatic conditions could be more effective in improvement of forage yield of synthetic and hybrid (semi or free hybrid) varieties in alfalfa.

To study the adaptability and seed yield stability, in this experiment, ten quinoa genotypes including; Red Carina, Titicaca, Giza1, Q12, Q18, Q21, Q22, Q26, Q29, Q29 and Q31 were evaluated using randomized complete block design with three replications in 2017 and 2018 in four locations; Karaj, Shahr-e-Kord, Kashmar and Urmia for their adaptability and grain yield stability. The results showed that quinoa genotypes had significant differences for most of the studied traits. However, genotype × location × year interaction effects on plant height, inflorescence length and days to flowering was not significant. Q26 genotype had the highest grain yield (2007 kg.ha-1) in Shahr-e-Kord. The lowest yield (338.33 kg.ha-1) was related to Q21 genotype in Karaj. The results of AMMI stability analysis showed that Q29 genotype had the highedt grain yiled stability with the shortest distance from the center of the graph. Cv. Giza1, cv. Red Carina, Q31 and Q26 genotypes also ranked next in terms of grain yield stability. Also, Q12, Red Carina and Q22 genotypes had specific adaptation in Karaj and Kashmar, and Giza1 and Q18 genotypes showed high specific adaptation in Urmia. In general, the results of this experiment showed that all quinoa genotypes were compatible with spring cultivation in experimental sites.