پژوهشنامه اصلاح گیاهان زراعی
پیاپی 12 (پاییز و زمستان 1392)

In recent decade use of graphical approach or GGE biplot for study G×E interaction become popular in plant breeding programs. In this approach the effects of genotype and G×E interaction are not separated and selection is based on both of above effects. In this study GGE biplot has been used to study 9 spring rapeseed genotypes over four locations in two years and another location in one year (totally 9 environments). The results of analysis of variance showed that 79. 2 percent of total variation was due to environment، 9. 3 percent due to genotype and 11. 5 percent due to G×E interaction. The polygon-view of GGE biplot recognized six superior genotypes and two megaenvironments so that the best genotypes within each environment were determined. The three genotypes located in sectors that no environments were placed in it indicated that these genotypes were poor in most of the environments. Simultaneous evaluation of yield and stability through average environment coordinate biplot showed that Hyola401 hybrid with the highest seed yield was the most unstable genotype. Option500 and Kristina with high seed yield and relative high yield stability selected. These two were the nearest varieties to ideal genotypes. Biplot of correlation among environments revealed that environmental vectors of Sarpol-e-zahab and Pol-e-Dokhtar were near to 90◦ so، these locations were different environments. All environments had high discriminating ability so that could able to show differences between genotypes. Masjedsolyman and Pol-e-dokhtar (second year) were the nearest environments to ideal environment so، they had the highest discriminating ability and representativeness.

Salinity stress causes ionic and osmotic stress resulting in cell death، inhibition of growth and ultimate adverse reducing crop productivity. In present study mechanism of salinity tolerance of Aeluropus littoralis under treatment of sodium chloride in four levels of salinity (120، 250، 450 and 600 mM) were investigated by cDNA-AFLP profiling. Salinity reduced the shoot growth، shoot to root ratio and Chlorophyll content and gene silencing was raised with increasing salinity. In 250 mM of salinity the plants had the highest physiological growth and the maximum number of expressed TDFs and also the greatest quality variance than control comparing to other levels of salinity. The results indicated that plants have the best response to salinity in the 250 mM of salinity and this level is appropriate to reveal mechanism of salt tolerance in this halophyte. Seems to silencing of genes that are active in control level، activation of some genes that are silence in control level، reduction expressed TDFs، reduction in Shoot to root ratio and a subsequent reduction in plant growth by salinity treatment is the common mechanism for salinity tolerance in this halophyte so that induction of salinity tolerance by expression of these silenced genes cause increase of growth in stress condition even than control.

The objective of present research was investigating the effects of salinity stress on rice seedling characteristics in order to identify appropriate selection criteria for selecting genotypes in seedling stage under salinity stress conditions. A population of 150 F4 families derived from a cross between two Iranian cultivars، Sepidrood and Gharib has been evaluated in controlled conditions by electrical conductivity of 12 dS m-1 in seedling stage. Analysis of variance showed significant differences between all families for all of the studied traits that were implicated high genetic diversity among families. Calculation of the correlation coefficient revealed high correlation coefficient of phenotyping and genotyping between biomass and shoot dry weight and، therefore، root dry weight and shoot fresh weight had high correlation with biomass، but standard tolerance ranking that was tolerance indices to salinity stress had negative and significant correlation with biomass. Stepwise regression analysis indicated that shoot and root dry and fresh weight had the greatest effects in explanation of lines biomass changes، respectively، so that they canexplain 97% of phenotypic variation for biomass. Path analysis showed that shoot dry weight had high direct effect and thus، it can be introduced as an appropriate selection index to increase biomass and selectinglines for improved salt tolerance. Also، factor analysis revealed five main factors that can explain 84. 7% of the total variation among genotypes. Generally، the results of present study indicated that shoot and root dry and fresh weight were more important for producing higherbiomass in salt stress conditions at seedling stage and traits such as standard tolerance ranking، root length، chlorophyll، shoot Na+ concentration، K+ concentration، shoot Na+/K+ ratio and shoot lengthwere lower important for selecting salt tolerant lines at rice seedling stage.

One of the most important role of mutation breeding is the creation of genetic variability in quantitative traits in various crop plants. The variability، thus created and enhanced for selection of new genotypes with desired characteristics. In present study role of two chemical mutagens، Ethyl Methane Sulphonate (140 Mili molar)، Sodium Azide (2 Mili molar) for creating variability in Tarrom Mahali cultivar have been investigated. The measured agronomic characters were: Plant height، tiller number، panicle length، number of filled seeds per panicle، length and width of seed (Milimeter) and 100-grain weight (gr). Results indicated that plant height، number of filled seed per panicle and tiller number showed the best response to these mutagens because plant height decreased in all mutagen treatments compared with control and number of filled seeds was increased in the most lines in two mutagens in compared with control. Maximum heritability and genetic advances were belonged to treatment EMS in most traits، therefore it is indicated that the effects of this mutagen is higher than that of Sodium Azide mutagen. Maximum variability advances were belonged to both mutagen treatments in number of tiller and filled seeds that effects of EMS was higher than AZ.

Identification of molecular markers associated with quantitative and qualitative traits can facilitate selection for these traits in breeding programs. This study was designed to identify AFLP markers associated with agronomic and fiber traits using an F4 population derived from interspecific cross between Gossypium hirsutum and G. barbadense. Seeds were grown in the field and plants were scored for eleven agronomic and fiber quality traits. Correlation analysis between AFLP markers and traits indicated that 19 and 14 markers were significantly associated positively or negatively with fiber and agronomic traits. Only markers which have been correlated with a specific traits significantly were used for stepwise multiple regression analysis. Associated markers explained from 6. 2% (for lint weight، seed weight and micronaire) to 43% (for 2. 5% span length) of the total variation available for different individual traits. Results suggest that these AFLP markers could be used for predicting and selecting desirable cotton germplasm to improve these traits.

This study was undertaken with the objective to determine the association between grain yield and its components and identifying traits have the greatest effects on grain yield of 25 rice cultivars، in a randomized complete block design with three replications. Correlation coefficients between traits indicate that traits the number of grains per panicle، number of filled grains per panicle، ratio of grain length to width and number of productive tillers were significantly associated with grain yield. Stepwise regression method was applied to study the effect of each trait on yield and also to fit the best regression model. Results showed that the traits including number of grains per panicle، number of productive tillers and grain length explained 31، 35. 1 and 8. 1 percent of grain yield variation، respectively. Results of path analysis showed that maximum direct effects belonged to the number of reproductive tillers (0. 820) and the total number of grains per panicle (0. 714). Number of filled grains per panicle had the greatest indirect effect (0. 664) on grain yield. On the basis of results of this study suggested number of productive tillers and the number of total grains per panicle could be considered as selection criteria for grain yield improvement in rice.

Appropriate selection of donor parent for breeding purposes needs sufficient knowledge about genetic diversity and germplasm classification. In order to investigation and classification of genetic diversity in 35 wheat (Triticum aestivum L.) genotypes، an experiment was conducted in University of Shahed based on randomized complete block design with 2 replications in 2009. In persent study 15 morphological characteristics such as days to 50% of flowering، plant height، number of stems per plant، number of productive tiller، number of internode، length of flag leaf، width of flag leaf، leaves angle، peduncle length، flag leaf distance to spike، spike length، number of grain per spike، awn length، 1000 grain weight and grain yield per plant were evaluated. The analysis of variance for all the traits indicated significant difference between studied genotypes (P<0. 01). Range and correlation analysis between traits، showed considerable genetic variation among studied genotypes. Cluster analysis via Ward method for field data، classified all genotypes in four groups. The ANOVA analysis showed significant difference among the clusters for leaves angle. Factors analysis، extract 5 factors that be able to describe nearly %75 of total variance.

In order to evaluate quality characteristics of 30 rice genotypes including improved، traditional and promising lines، a field experiment was undertaken at Sari Agricultural Sciences and Natural Resources University during 2009 cultivation season. Experiment was arranged in a randomized complete block design with three replications and 13 quality characters were evaluated. Results showed significant difference among different genotypes for all evaluated traits. For all evaluated traits، cluster analysis between genotypes based on Ward،s method indicated that genotypes can be classified into five cluster so that cluster I had genotypes such as Tarom Mahalli، 8803 and 8802 promising lines، cluster II and Pi-1 and 8802 lines، cluster III and Ghaem cultivar and 8804 and 8223 promising lines. Cluster IV and 8811 and 64410 promising lines and Tarom Deilamani and cluster V had Bahar and 8209 and 8403 and 8228 promising lines. Mean camparison of clusters according to Duncan،s test showed that maximum yield performance (4. 9 ton. ha-1) was belonged to cluster V، then clusters I and IV had the best performance and the minimum head rice yield was recorded in cluster III. In terms of amylose content، the highest amount (26. 20%) was observed in cluster V. According to Iranian consumers which prefer 22 percent amylase content could be introduced genotypes in cluster I and II as a medium amylase and quality genotypes. Furthermore، genotypes of cluster III and cluster V showed the highest and lowest amount of gel consistency GC respectively. The optimum amount of GC (<60 nm) was recorded for genotypes in cluster II and III.

A field study was carried out in 2007 to determine the response of promising genotypes of Mung bean to late season drought stress at zabol climatic condition. The experiment was conducted in a randomized complete block design with three replications at two locations (with and without drought stress). Treatments were 6 different genotypes of Mung bean. All treatments in two fields were irrigated normally until 50% heading stage. The last irrigation in drought stress conditions was done at 50% heading stage and then plants were developed under stress conditions until harvesting. Comparisons of traits in both conditions showed that water stress have negatively affected plant growth. The stress conditions had the highest effects on yield and the least effects on number of slinked pod. For evaluation of drought stress tolerance indices such as mean productivity (MP)، geometric mean productivity (GMP)، stress tolerance index (STI)، tolerance index (TOL)، stress sensitivity index (SSI)، harmonic mean of productivity (HARM)، were used. According to these indices، genotype PUSA was the most tolerant and the genotypes MN22 and MN92 were the most sensitive genotypes to drought stress. Principal component analysis used to study the relationship between indices. Two first components could explain more than 99% of variations of indices. Also، biplot of PC1 and PC2 showed the genotype PUSA was the most tolerant and the genotypes MN22 and MN92 were the most sensitive genotypes to last season drought stress between evaluated genotypes of Mung bean in zabol climatic conditions.