Rhizobacteria modify soil biological indices and induce tolerance to osmotic stress in tomato depending on the salinity level and bacteria species.

Salinity is a major abiotic stress that impacts crop productivity globally. Plant growth-promoting rhizobacteria (PGPRs) exploit several mechanisms to not only decrease soil salinity but also improve the systemic tolerance of plants to osmotic stress. In this work, the effect of five PGPR strains was investigated on the growth and physiological responses of tomato plants, including stomatal closure, proline, and K+ and Na+ content under a range of salt stress, 0, 2.5, 5, 7.5, and 10 dS m-1. The effect of PGPR strains and salinity levels on the soil biological characteristics was also investigated. Salt stress affected the plant growth and physiological factors and soil biological factors in a dose-dependent manner. The highest saline stress, 10 dS m-1, reduced shoot and root dry weight and root volume up to 51.3, 41.5, and 51.8%, respectively. It also increased stomatal resistance and proline content 2.01- and 3.66-folds and decreased K+/Na+ ratio 4.16-folds, respectively. It also reduced basal respiration, substrate-induced respiration, and microbial biomass carbon up to 2.25-, 4.83-, and 6.7-folds and increased qCO2 3.18-folds, respectively. PGPR strains were able to modulate salt tolerance mechanisms, improve plant growth factors, and improve soil biological indicators. Bacillus megaterium P2 was the best strain in the balancing K+/Na+ uptake at least at 10 dS m-1. However, the efficiency of strains was dependent on the magnitude of salt stress. Therefore, it is possible to introduce PGPR strains based on soil salt level or exploit rhizobacteria consortia to manage salt stress in different conditions.

Genetic diversity of bread wheat genotypes in Iran for some nutritional value and baking quality traits.

Genetic variation among 78 irrigated bread wheat genotypes was studied for their nutritional value and baking quality traits as well as some agronomic traits. The experiment was conducted in a randomized complete block design with three replicates under normal and terminal drought stress conditions in Kermanshah, Iran during 2012-2013 cropping season. The results of combined ANOVA indicated highly significant genotypic differences for all traits. All studied traits except grain yield, hectoliter weight and grain fiber content were significantly affected by genotype × environment interaction. Drought stress reduced grain yield, thousand kernel weight, gluten index, grain starch content and hectoliter weight and slightly promoted grain protein and fiber contents, falling number, total gluten and ratio of wet gluten to grain protein content. Grain yield by 31.66% and falling number by 9.20% attained the highest decrease and increase due to drought stress. There were negative and significant correlations among grain yield with grain protein and fiber contents under both conditions. Results of cluster analysis showed that newer genotypes had more grain yield and gluten index than older ones, but instead, they had the lower grain protein and fiber contents. It is thought that wheat breeders have bred cultivars with high grain yield, low protein content, and improved bread-making attributes during last seven decades. While older genotypes indicated significantly higher protein contents, and some of them had higher gluten index. We concluded from this study that it is imperative for breeders to pay more attention to improve qualitative traits coordinated to grain yield.

Investigation of different concentrations of MS media effects on gene expression and steviol glycosides accumulation in Stevia rebaudiana Bertoni.

Stevia rebaudiana Bertoni is one of two species that contains steviol glycosides. Among steviol glycosides that extracted from leaves, stevioside and rebaudioside A are the two major and the sweetest glycosides that are about 200-300 times sweeter than sucrose with zero calories. The best method for stevia propagation is tissue culture. So, for investigation of nutrients in medium, we studied the effect of different concentrations of MS media (MS, 0.5 MS, 0.25 MS, 0 MS) on morphological traits, UGT74G1 and UGT76G1 genes expression and accumulation of steviol glycosides in stevia leaves. The best growth rate (0.472 mm/d) has occurred in plants grown in MS media. Also, the highest gene expression of UGT74G1 gene (1.000 Total lab unit) was seen under MS treatment. However, the highest expression level of UGT76G1 gene (1.701 Total lab unit) was observed at plants grown in 0 MS. The highest amount of both Stevioside and Rebaudioside A (14.23 and 8.12, respectively) were accumulated in plants under MS treatment. Obviously, dilution of MS media associated with decreasing in both expression of the intended genes and accumulation of steviol glycosides.

Morphological and molecular genetic variations of oat genotypes grown in Kermanshah, Iran.

Morphological traits and molecular markers are two common methods for genetic variation studies. Molecular markers, morphological traits methods and relationship between the two were used to study genetic variation among 43 oat genotypes and varieties. For this purpose, an augmented design was conducted in three replicates at 2008-2009 cropping season in the experimental field of Campus of Agriculture and Natural Resources of Razi University, Kermanshah, Iran. Four wild oat accessions (Avena sterilis) were added to evaluated genotypes in molecular experiment. Results showed a significant variation among genotypes for all morphological traits and they were classified based on this variation in four groups by WARD cluster analysis. In molecular experiment, 28 inter simple sequence repeat (ISSR) primers amplified 206 polymorph bands. Based on Jaccard similarity matrix, similarity among genotypes was varied from 0.23 to 0.66 and cluster analysis classified genotypes in seven groups by complete linkage method. The correlation between ISSR marker and morphological traits classifications was not significant. ISSR showed to be a helpful marker for genotype identity and separation as it put wild accessions in a group.