نشریه نهال و بذر
سال بیست و سوم شماره 1 (بهار 1386)

Effect of genotype × environment interaction (GE) is created by different responses of genotypes to different environmental conditions. Effect of GE interaction limits the accuracy of grain yield estimation and identification of specific genotypes for specific environments. Therefore, consideration of that is essential in progress of plant breeding. To determine yield stability and genotype× environment interaction effects, 20 barley genotypes were evaluated during 2000–2002 cropping seasons in seven moderate research stations including Karaj, Kerman, Isfahan, Birjand, Zarghan, Neishabour and Yazd. Combined analysis of variance on grain yield showed significant differences in years, locations, year × location, genotypes and genotype × location × year interaction. Since the genotype × location × year interaction was significant, different stability analysis methods were used to determine stable genotypes. Stability parameters such as Si 2, CVi, Sdi2, Wi2, di2, MS(Y/L)i, Ri2, R, SDR, SS(HV)I and SS(IC)i were estimated for each genotype. Overall, genotypes no. 4(Trompillo/L.Moghan), 13(Rihane–03) and 15 (Gustoe/Arar) showed the highest stability in most of methods of stability analysis, therefore, these genotypes were recommended for on-farm trials and release.

Two spotted spider mite (Tetranychus urticae complex) is an important pest of egg-plant in Iran. In the present study, population of eggs and active stages and amount of losses of the spider mite were determined on upper and lower leaves of nine egg-plant cultivars in Varamin during 2001-2002. The experiment was in a randomized complete block design with three replications. Each plot consisted of four rows and on each row ten egg-plants were cultivated. Spider mite population on all cultivars was checked at weekly samplings, from July to October. Number of mites (eggs and active stages) on upper and lower leaves were then counted by stereo binocular microscope. Loss percent of mite was assessed by measuring the weight of ten randomly selected fruits of each cultivar in three replications at fifteen day intervals during fruiting period. Analysis of variance on data showed significant differences of mite population on upper and lower leaves of different cultivars and also among the cultivars. In 2000, the highest mean populations of active mites on lower leaves, 37.80 and 46.87, and on upper leaves, 27.19 and 38.08 were recorded on Borazjan cv. in naturally and artificially infested treatments, respectively. In 2001, egg and active mite populations on cultivar were significantly different only in artificially infested treatment. The maximum numbers of eggs (63.47) and active stage (107.94) were recorded on Imami 905 cultivar. Maximum and minimum losses of 69.42% and 12.86% were recorded on Imami 905 and Ghalami Varamin cultivars. These cultivars were determined as the most susceptible and resistant cultivars to mite damage, respectively

Black root rot of chickpea (Cicer arietinum L.) is prevalent in Fars province of Iran. Using resistant or tolerant cultivars are the best measures of control. Three years studies were conducted to evaluate the reactions of 126 genotypes of chickpea from gene bank and 26 collections from the province to an isolate of Fusarium solani. Results of the greenhouse studies, by planting seeds in the artificially infested soil, indicated that all the genotypes and collections were susceptible. To investigate the possibility of field tolerance among the genotypes, seeds were planted in two separate locations, Fasa and Zarghan, as augmented design in double rows, 2 m long 60 cm distant, in a field naturally infested with F. solani. Genotypes no. 25, 41, 50, 51, 72, 90, 101 and 125 in Fasa and 9, 10, 13, 14, 25, 50, 51, 62, 78, and 79 in Zarghan were assessed as tolerant genotypes. In the third year, the reactions of these genotypes were revaluated in a naturally infested field in Zarghan where all the genotypes showed susceptible reactions. It is therefore concluded that 126 gene bank genotypes and 26 local collections were all susceptible to F. solani the cause of black root rot, in the Fars province.

To determine the genotypes with high yield and tolerance to drought stress and find the best drought stress indices, a field experiment was carried out in a randomized complete block design with three replications. In this experiment six genotypes of sunflower Azargol, Allstar, Record, Mehr, CMS60/52*R82 and CMS19*R256 were evaluated at Islamabad Research Station in 2002-2003. Genotypes were planted in two separate experiments, one with normal irrigation and the other with three irrigations in planting, buding and flowering stages. Results showed that drought stress caused a severe reduction in leaf area index, grain and oil yield, stem diameter and plant height. Under normal irrigation condition the highest grain yield obtained from Mehr and Record with 3908 and 3901 kgha-1, respectively. In drought stress conditions, the highest grain yield obtained from Azargol and Record with 2850 and 2634 kgha-1, respectively. It appeared that stress tolerance index (STI) and geometrical mean (GMP) might be the best indices to evaluate the genotypes for drought stress tolerance

In order to study the effect of harvesting time on yield and yield components of oilseed rape, an split–plot experiment on the basis of randomized complete block design with three replications was conducted in Zahak Agircultural Research Station of Zabol during two cropping seasons (2002-2003 and 2003-2004). Two cultivars Sarigol (pf/7047) and (Hyola 308) were main plots and seven harvest times T1: harvest in 10% seed color change in siliques of main stem, T2: harvest three days after T1 stage, T3: harvest six days after T1 stage, T4: harvest nine days after T1 stage, T5: harvest twelve days after T1 stage, T6: harvest fifteen days after T1 and T7: harvest eighteen days after T1 stage were sub plots of the experiment. The Results showed significant differences on siliqua number in plant, 1000 seed weight, seed yield and oil yield from aspect of harvest time. Delay in harvest time caused decrease in seed yield, siliqua number in plant and 1000 seed weight. T3 had 33% and 32% higher yield than T6 and T7, respectively. Cultivars had significant differences for seed number in siliqua, seed yield, oil percent and oil yield. Hyola 308 with 3553 kgha-1 had 21% more yield than Sarigol. Oil percentage did not show significant difference in different harvest times. Oil yield changes in different harvest times followed the same manner as did seed yield. Other traits did not also show differences. Considering the results, harvesting 3-6 days after 10 percent seed color change in main stem siliques(30-40 % seed color change, approximately) and use of early maturity hybrids or cultivars are recommended for Sistan area and similar regions

In order to evaluate the relationship of nutritional balance index (NBI) with yield and quality characteristics of grape, a four year experiment was conducted in Kohgiluyeh-va-Boyerahmad province. The purpose of this study was to determine the nutritional elements balance status and its effect on yield and quality of grape in orchards. In this experiment, DRIS norms were established first for grape. The established norms were then used to calculate DRIS indices and nutritional balance index for those orchards having low yields. Beside, exponential regression analysis was used to evaluate relationship of NBI with yield and quality characteristics of grape. The results showed a negative and significant (at 1% probability level) relationship between NBI and yield. Relationships of NBI with sugar, TSS and TSS/TA were negative that the latest case was significant at 5% probability level. Relationship between NBI and TA was positive but not significant. Based on the obtained results, the amount of NBI was high that expressed the imbalanced status of elements the most important factor in reduced grape yield and quality in orchards

Ethylene as a plant hormone plays a major role in senescence and loss of fruit quality and shelf life of apples. In order to maintain quality and increase storability of Golab Kohanz apples, an experiment was conducted in split factorial design with four replications. Treatments were threee different storage temperatures (1, 4 and 20 °C), gas combinations with two levels (2% CO2 + 3% O2 and 4% CO2 + 1% O2) and two types of polymeric films (polyethylene and polypropylene). The flesh firmness, total soluble solids (TSS). Electrolyte conductivity (EC), pH, terrible acidity (TA), TSS/TA and rate of ethylene production were measured in 14 days intervals. The results showed that ethylene production rate at 1°C was lower and the packed fruits under 1°C with gas combination of 1% O2 + 4% CO2 and polypropylene film maintained TSS, TA, TSS/TA and tissue firmness values compared to other treatments. pH and TSS/TA of fruits showed an increased trend, while TSS and TA decreased through the storage of fruits. The changes of quality factors occurred with slower rate than controls. The results indicated that modified atmosphere packaging has led to extension of storability and retardation of softening rate in fruits compared to controls

DNA markers have provided valuable tools for plant breeding and beneficial for germplasm characterization and indirect selection. Marker-assisted selection has the potential to deploy favorable gene combinations for disease and pest control as well as the quality of some crop products. However, practical application of molecular marker revealed that a successful MAS program depends on inheritance of the trait, number of individuals subjected to analysis and the genetic background. In this study, microsatellite (SSR) markers linked to the Russian wheat aphid (RWA) resistant gene (Dn4) and glume-color gene (Rg2) in wheat using a population of F2–derived F3 families derived from F2 single plants originating from a cross between the susceptible line (synthetic hexaploid-11) and the resistance cultivar (Halt) are reported. Two flanking microsatellite markers Xgwm106 and Xgwm337 are linked with Dn4 on the short arm of wheat chromosome 1D at 5.9 cM and 9.2 cM, respectively. The accuracy (AMAS) and efficiency (EMAS) of marker-assisted selection were calculated for homozygous RWA resistant genotypes of Dn4 gene in the F2 generation. Dominant morphological marker, Rg2, was also used for marker-assisted selection of Dn4 gene individually and in combination with microsatellite markers. EMAS of 100% for Xgwm337 marker and AMAS of 100% for bracketing markers Xgwm337-Xgwm106 and Xgwm337-Rg2 and non-bracketing markers Xgwm106-Rg2 were obtained.

In order to determine the effect of source-sink limitation on yield and yield components of four rice cultivars, an experiment was conducted at Rice Research Institute of Iran, Deputy of Mazandaran (Amol) in 2003. The experiment was in factorial based on randomized completely block design with four replications. The studied factors were source-sink limitation in four levels (cutting of all leaves except flag leaf cutting of flag leaf cutting of 1/3 end of panicle control) and cultivars in four levels (Tarom Neda Shafagh Fajr). Some traits such as grain yield, harvest index, grain number per panicle, unfilled grain number per panicle, panicle length, panicle fertility and 1000 grain weight in different source-sink limitation treatments were investigated. Results showed that imposing of different source-sink limitation treatments had a positive effect on all mentioned traits. Interaction effect between cultivar and source-sink limitation was also significant. The control and cutting of 1/3 end of panicle treatments had the highest (5255.3 kgha-1) and the lowest (4055.1 kgha-1) grain yield, respectively. Among cultivars, Neda had the highest grain yield (5419.6 kgha-1). Cutting of 1/3 end of panicle and cutting of flag leaf treatments had the highest (88.55 %) and the lowest (76.4 %) panicle fertility, respectively. There were positive and significant correlations between grain yield and harvest index, panicle length and grain number per panicle, but 1000 grain weight had a negative correlation with grain yield that was not significant. Generally, results showed that cultivar Tarom had sink limitation and other cultivars (Neda, Shafagh and Fajr) had source limitation

To determine the effects of pre-germinating of tubers and plant density on yield and some agronomic traits of six commercial potato cultivars, an experiment was carried out in Ardebil Agricultural Research Station for two years (2001 and 2002). The experiment was in a split split splot on the basis of completely randomized block design with three replications. Pre-germination and non pre-germination treatments were used as the main plot, six potato cultivars Mondial, Draga, Agria, Arinda, Moren and Marfona as sub plots and plant densities of 75 ´ 25 and 75 ´ 20 cm as sub sub plots. The results showed that pre-germination significantly influenced tuber yield, number of tubers per plant, number of main stems and mean weight of single tubers. Cultivar Mondial with 35.688 tha-1 in pre-germination and 75 ´ 20 cm treatments produced the highest yield