Genomic markers analysis associated with resistance to Alternaria alternata (fr.) keissler-tomato pathotype, Solanum lycopersicum L.

Alternaria alternata, the causal pathogen of early blight (EB) disease, is one of the most important diseases in tomato, and other solanaceae family. We analyzed 35 tomato genotypes for quantitative/qualitative traits and biomass growth parameters, as well as the extent and structure of genetic variation associated with EB resistance. Phenotypic comparisons displayed significant differences in leaf blade width (24.95%), stem thickness (30.28%), foliage density (18.88%), and plant size (18.89%), with significant positive correlations with EB resistance (0.18-0.75). Correlation analysis showed that mature fruit size, thickness of fruit pericarp, and leaf type were significantly and negatively correlated with EB resistance (up to -0.41). The susceptible tomato seedlings represented significant reductions in biomass parameters. According to ISSR analysis, the highest resolving power (≥0.79) and heterozygosity (≥0.24) values revealed the presence of high genetic variability among the tomato genotypes. Bayesian model-based STRUCTURE analysis assembled the genotypes into 4 (best ΔK = 4) genetic groups. Combined phenotypic and molecular markers proved to be significantly useful for genetic diversity assessment associated with EB disease resistance.

Overexpression of plastid transketolase in tobacco results in a thiamine auxotrophic phenotype.

To investigate the effect of increased plastid transketolase on photosynthetic capacity and growth, tobacco (Nicotiana tabacum) plants with increased levels of transketolase protein were produced. This was achieved using a cassette composed of a full-length Arabidopsis thaliana transketolase cDNA under the control of the cauliflower mosaic virus 35S promoter. The results revealed a major and unexpected effect of plastid transketolase overexpression as the transgenic tobacco plants exhibited a slow-growth phenotype and chlorotic phenotype. These phenotypes were complemented by germinating the seeds of transketolase-overexpressing lines in media containing either thiamine pyrophosphate or thiamine. Thiamine levels in the seeds and cotyledons were lower in transketolase-overexpressing lines than in wild-type plants. When transketolase-overexpressing plants were supplemented with thiamine or thiamine pyrophosphate throughout the life cycle, they grew normally and the seed produced from these plants generated plants that did not have a growth or chlorotic phenotype. Our results reveal the crucial importance of the level of transketolase activity to provide the precursor for synthesis of intermediates and to enable plants to produce thiamine and thiamine pyrophosphate for growth and development. The mechanism determining transketolase protein levels remains to be elucidated, but the data presented provide evidence that this may contribute to the complex regulatory mechanisms maintaining thiamine homeostasis in plants.

Over-expressing the C(3) photosynthesis cycle enzyme Sedoheptulose-1-7 Bisphosphatase improves photosynthetic carbon gain and yield under fully open air CO(2) fumigation (FACE).

BACKGROUND: Biochemical models predict that photosynthesis in C(3) plants is most frequently limited by the slower of two processes, the maximum capacity of the enzyme Rubisco to carboxylate RuBP (V(c,max)), or the regeneration of RuBP via electron transport (J). At current atmospheric [CO(2)] levels Rubisco is not saturated; consequently, elevating [CO(2)] increases the velocity of carboxylation and inhibits the competing oxygenation reaction which is also catalyzed by Rubisco. In the future, leaf photosynthesis (A) should be increasingly limited by RuBP regeneration, as [CO(2)] is predicted to exceed 550 ppm by 2050. The C(3) cycle enzyme sedoheptulose-1,7 bisphosphatase (SBPase, EC 3.1.3.17) has been shown to exert strong metabolic control over RuBP regeneration at light saturation. RESULTS: We tested the hypothesis that tobacco transformed to overexpressing SBPase will exhibit greater stimulation of A than wild type (WT) tobacco when grown under field conditions at elevated [CO(2)] (585 ppm) under fully open air fumigation. Growth under elevated [CO(2)] stimulated instantaneous A and the diurnal photosynthetic integral (A') more in transformants than WT. There was evidence of photosynthetic acclimation to elevated [CO(2)] via downregulation of V(c,max) in both WT and transformants. Nevertheless, greater carbon assimilation and electron transport rates (J and J(max)) for transformants led to greater yield increases than WT at elevated [CO(2)] compared to ambient grown plants. CONCLUSION: These results provide proof of concept that increasing content and activity of a single photosynthesis enzyme can enhance carbon assimilation and yield of C(3) crops grown at [CO(2)] expected by the middle of the 21st century.

Bio-genetic analysis of resistance in tomato to early blight disease, Alternaria alternata.

Early blight disease (EB), Alternaria alternata, is destructive on Solanum lycopersicum Mill. The responses of 35 domestic and exotic commercial tomato genotypes to early blight were examined at transplanting and maturing stages using genetic diversity analysis, with 15 Inter Simple Sequence Repeat (ISSR) primers, total phenolic content (TPC), and enzymatic activity of catalase (CAT), phenylalanine ammonia lyase (PAL), peroxidase (POD) and superoxide dismutase (SOD) assays. The disease severity ranged from 18 to 87.5%. Eleven of 15 ISSR primers generated 68 loci of which 63 (90%) were polymorphic. Polymorphism information content value varied from 0.3 to 0.5 with an average of 0.4. Nei's measure of the average gene diversity ranged from 0.06 to 0.5. The Tomato genotypes were divided into five clusters in Un-weighted Pair Group Method with Arithmetic Mean (UPGMA) analysis, showing a considerable similarity between resistance level and molecular classification pattern. Antioxidant analysis indicated a significant increase in TPC and CAT, POD, PAL and SOD activities in most inoculated tomato genotypes at both growth stages. The highest increase in activity was seen in PAL (5-fold) and TPC (4-fold) at transplanting stage, whereas the highest TPC (2 to 3-fold) and POD activity (3-fold) were found at maturing stage in all the inoculated resistant genotypes in comparison with controls. Esfahan Local and H. a.s 2274 showed the highest level of activity in POD (2.5- and 3- fold, respectively) and TPC (2.5- and 4-fold, respectively). Our results suggest that using both genetic diversity and enzymatic diversity as markers, it is possible to discriminate resistant from susceptible tomato genotypes to early blight disease.

Genetic defense analysis of tomatoes in response to early blight disease, Alternaria alternata.

Early blight disease of tomato is one of the most devastating biotic stresses worldwide, and in Iran, Alternaria alternata is one of the most predominant species causing the disease. In the current study, a diverse collection of 35 tomato genotypes and implication of 5 SlWRKYs and 7 PR genes as well as enzymatic activity were evaluated on resistant and susceptible cultivars through real-time polymerase chain reaction at transplanting and maturing stages and by measuring product formation using spectrophotometry. The results indicated that the expression of these antifungal genes in 14 genotypes at two growth stages after inoculation with A. alternata highly enhanced by 1-50-fold. There was also significant upregulation of WRKYs and PRs genes among the resistant tomato varieties in comparison to susceptible and control varieties at both stages. These findings demonstrate the varieties that showed increased or decreased SlWRKY1 expression also displayed similar changes in the expression of PR1 and PR2 genes. Furthermore, the differential expression patterns of SlWRKY1 and SlWRKY11 were consistent with PR7 and PDF1.2 expression patterns. The analysis of enzymatic activity of PR2 and PR3 proteins, ß-1,3-glucanase, and chitinase showed the highest level of activity in resistant inoculated genotypes against A. alternata. Therefore, the current findings suggest the possible involvement of these transcription factors in the increased expression of PR genes in response to A. alternata infection.

Effect of salt levels and cropping methods on wheat agronomic characteristics.

The purpose of this study was to evaluate the effect of Salt levels and Cropping methods on wheat agronomical characteristics. A Split plot layout within Randomized Complete Block Design with four replication was used. Irrigation water quality were in main plots, it consists in 4, 8 and 12 dS m(-1) and Cropping methods were in sub plots that inclusive of traditional cropping, 60 cm furrow, 80 cm furrow and aside sloping 80 cm furrow with double row planting. The results shows the effect of salinity stress on 1000 grain weight, grain yield, sum of tiller, amount of germinated tiller, amount of kernel per spikelet and amounts of spikelet were measured decreased significantly. Effect of cropping methods on LAI, TDW and grain yield were more significantly. The greatest amount of LAI, TDW and grain yield were in 60 cm furrow where as, the lowest of LAI and grain yield were in a side sloping 80 cm furrow in case, the lowest of TDW obtained in traditional cropping method. Effect of cropping method on other measured factors were not significant. Interaction of salt treatments and cropping methods on LAI, TDW and grain yield were more significant where as, the highest amount of LAI, TDW and grain yield in 4 dS m(-1) belong to traditional cropping method with exceptional of TDW that was in 60 cm furrow the traits declined significantly in a side sloping 80 cm furrow with the rising salinity stress in 12 dS m(-1). According to this study the suitable method with the highest traits agronomy in low salinity (4 dS m(-1)) and high salinity (12 dS m(-1)) were traditional cropping method and 80 cm furrow method, respectively.