نشریه نهال و بذر
سال سی و چهارم شماره 2 (تابستان 1397)

Tolerance to the disease is defined as the plant's ability to reduce damage caused by a pathogen attack and yield is good even when the plant is infected by pathogen. The concept of tolerance arises from the fact that in conditions of severe disease infection, in some cultivars, yield reduction is less than the other cultivars. In this study, the tolerance of 20 wheat cultivars was evaluated against yellow rust. The effect of stripe rust in Neishabour on grain yield under conditions of severe disease (stress) and protected from disease (non- stress) were analysed. The mean reduction (%) in grain yield in all cultivars infected by yellow rust was 18.2%. Damage by stripe rust varied from 3.5 to 57 percent. Based on the results of two years of disease stress, Kavir, Neishabour and Inia (with 16%, 14% and 13% yield loss, respectively) were more tolerant to yellow rust. In moderately susceptible cultivars, Tajan with 5.71% yield reduction was identifiect as the most tolerant cultivar. Sirvan among the cultivars with moderate infection (5MS) had highest resistance reaction. The average yield reduction of Sirvan in disease condition was about 15%, and its 1000 grain weight reduced by 9% as compared with protected condition.

Charcoal rot is one of important disease of soybeans. In this study, 130 different soybean genotypes were evaluated in a simple lattice design with two replications in 2014 and 2015 in Karaj, Iran. Grain yield and disease-related indices including lesion length, lesion length: plant length ratio, percentage of infected plants and number of microsclerota on stem were measured. The results showed that the lowest (1.11 percent) grain yield reduction was observed for genotype 45 whereas genotype 11 had the highest (60.96 percent) grain yield reduction. The results of this study also showed that genotypes 1, 3,4, 5, 10, 12, 20, 24, 30, 31, 32, 40, 41, 43, 45, 46, 50, 53, 54, 63, 64, 66, 74, 76, 77 and 115 were resistant with low percentage of grain yield reduction and were free of disease symptoms. Genotypes 6, 11, 13, 18, 25, 33, 35, 42, 55, 57, 58, 59, 62, 70, 72, 73, 78, 86, 93, 97, 109, 111, 113, 123, 124, 129 and 130 were identified as susceptible genotypes with high percentage of grain yield reduction and disease symptoms on stem. The correlation between percentage of grain yield reduction and lesion length (r = 0.62**) and percentage of infected plants (r = 0.53*) were positive and significant. The results of stepwise regression analysis showed that lesion length and percentage of infected plants could explain more than 61 percent of the variations observed in the performance of genotypes under disease stress conditions.

To evaluate some fruit characteristics and yield of seven promising olive genotypes a field experiment was carried out- using randomized complete block design with three replications in 2016 in Dallaho research station, Sarepol Zahab, Iran. Fruit yield and some fruit characteristics including; fruit weight, stone weight, drymatter (%), oil content were measured. Results showed that genotypes were significantly different for fruit yield and fruit characteristics. Genotype × year interaction effect was significant on fruit weight, fruit flesh weight, stone weight, flesh percentage, fruit yield and oil yield. Dd1 genotype with mean of 7.87 g had the heighest and Ps1 genotype with 3.31 g had the least fruit weight. Genotype, year and genotype × year interaction effects were significant on fruit yield and oil yield. The highest fruit and oil yield belonged to Bn6 with 17653 kgha-1 and 2362.1, respectively. Cultivar Sevillano had the lowest fruit yield (3000 kgha-1) and oil yield (218.9 kgha-1). Considering fruit and oil yield, Bn6 and Dd1 were identified as superior genotypes.

Thirteen karyotypic parameters in clones from 10 accessions of alfalfa (Medicago sativa L.) from geographical sources in lake regions of Turkey were studied by using multivariate analysis. Root tips meristems stained with aceto-iron-hematoxylin. All clones of accessions were tetraploid (2n=4x=32) and the chromosomes were very small, ranging from 1.69 to 5.92 µm. The existences of heterogeneity in clones of alfalfa accessions of lake regions, Turkey were demonstrated due to B chromosomes and heteromorphic phenomena, and significant differences were observed among populations for most of the evaluated traits. On the basis of karyotypic formula, the clones had two types of chromosomes (m and sm), categorizing them in eight different classes. Assessment of karyotype symmetry and asymmetry were carried out, using various indices e.g. DRL, DI, TF%, CV%, Stebbins and Romero-Zarco categories. Correlation coefficient showed that the long arm had the highest correlation with total length of chromosomes, and the short arm had the lowest correlation with arm ratio. In principal components analysis, about 82.37% of the variance and variability among the clones of accessions were explained by variations in chromosomal length, the location of the centromere in the karyotype and karyotype asymmetry index. In cluster analysis based on the UPGMA method, the distances were determined by Euclidean square distance method Dendrogram demonstrated four groups.

To estimate genetic parameters of agronomic traits in tobacco, six oriental-type tobacco varieties were crossed based on diallel mating system without reciprocals in 2013. F1 populations and six parental lines were planted using randomized complete block design with three replications in 2014 at research field of Urmia Tobacco Research Center, Urmia, Iran. Some charectristics including number of leaves, leaf length and width, plant height, stem diameter, internodes length, fresh leaf and dry weight were measured and analyzed using Griffing method II and mixed effect model B. Analysis of variance revealed significant differences (P≤0.01) between varieties for plant height, leaf number and fresh weight and for leaf dry weight (P≤0.05). General combining ability of varieties for all aforementioned traits was significant at the 1% probability level. Specific combining ability was also significant at the 1% probbaility level for plant height, leaf number and fresh weight. Both additive and non-additive (dominance) gene effects were involved in controlling of plant height, leaf number and fresh weight, however, additive gene effect controlled leaf dry weight. In general, the ratio of GCA to SCA was significant for all of the studied traits except leaf fresh weight which emphasizes the importance of additive effect in inheritance of this trait.

Ber and jujube (Ziziphus spp.) are tropical and subtropical fruits. Seventy two accessions from five Ziziphus species including: Z. jujuba, Z. nummularia, Z. spina-christi, Z. mauritiana and Z. oxyphylla collected from different parts of Khoozestan and Ilam proviences were evaluated using leaf and fruit characteristics. The primary results of morphological characteristics showed that there were high variability for some of the evaluated traits such as fruit weight, pulp:seed ratio, leaf size and TSS/TA ratio. The highest and lowest fruit weight were recorded in Z. mauritiana and Z. nummularia species. In the second experiment, 30 accessions from evaluated germplasm which had higher fruit weight were selected and their genetic diversity was investigated using 15 ISSR primers. A total of 166 alleles were identified by the 15 ISSR primers with their sizes ranging from 170 to 1500 bp. The number of observed alleles for each locus ranged from 6 (LBMB-B) to 15 (HB14, HB12) with an average of 11.06 alleles per locus. Polymorphic information content (PIC) was highest (0.81) in the HB14 and UBC-826 loci, while the LBMB-B locus had the lowest value (0.65), with an average of 0.76 among all ISSR loci.