Journal of Plant Molecular Breeding
Volume:8 Issue: 1, Winter and Spring 2020

Salicylic acid (SA) is a phenolic phytohormone that acts as a key regulator of the signaling network in plants under biotic and abiotic stresses. SA exerts stimulatory effects on various physiological processes to plant growth and development. In this research, valerian, chicory, withania, and purple coneflower plants were transferred into an aeroponic system where the effects of SA were investigated on some plant characteristics under greenhouse conditions. The plants were foliar sprayed with SA (0, 50, 100, and 150 mg l-1) at 20, 40, and 60 days after transplanting (DAT). Results showed that the highest chlorophyll a+b, carotenoid, plant height, root length, root volume, number of leaves per plant, root fresh weight, root dry weight, shoot fresh weight, and shoot dry weight were obtained from 150 mg l-1 SA in all the studied medicinal plants. The results revealed that the exogenous application of SA in the aeroponic system increased the root fresh weight, root dry weight, shoot fresh weight and shoot dry weight of chicory, withania, valerian, and purple coneflower plants. Also, the studied medicinal herbs grew well in the aeroponic system.

Barley is an important feed grain in many areas such as Canada, Europe and in the U.S. It has also so important for animal feed and has several other usages such as alcohol industry, malt productive and biomass-fuels. The characteristics of physiological and biochemical events during leaf senescence either flag leaf or other leaves have been investigated in field-grown barley (Hordeum vulgare cv. Hordea). The traits included grain yield, chlorophyll and protein levels, CO2 assimilation rate, fluorescence, α-tocopherol and carotenoid levels, cellular oxidative level and chloroplast-encoded gene expression. The result showed significant role of flag leaf in grain yield. The chlorophyll and protein levels decline dramatically during senescence particularly in other levels. This result was quite similar for net CO2 assimilation rate and maximal efficiency of PSII photochemistry (Fv/Fm). This suggests that PSII apparatus remains functional in senescent flag leaf. Two main lipid-soluble antioxidant agents (α-tocopherol and carotenoid) showed significant increase particularly in flag leaf at late senescence stage around 25 days after anthesis, the level of lipid and other macromolecular-derived peroxidation has been measured by TBARM assay. The TBARM levels increased gradually during flag leaf and particularly other leaves senescence. The transcript levels of the chloroplast-encoded psbA decrease during senescence especially in other leaves. However, the transcript level was significantly higher in flag leaf leading to high level of photosynthesis capacity at the molecular level.

To evaluate the genetic diversity and the effect of drought stress on grain yield of wheat, 56 wheat genotypes were evaluated for terminal drought stress tolerance in field environments in the Kermanshah of Iran during the 2010-2011 cropping season. The experiments were conducted at the Campus of Agriculture and Natural Resources, Razi University using alpha-lattice design with two replicates under two different water regimes included non-stress (normal irrigation at all stages of growth) and drought stress (end-season after flowering stage) conditions. Several new stress tolerance indices were evaluated. So that, ten drought tolerance indices including stress tolerance index (STI), relative drought index (RDI), yield index (YI), yield stability index (YSI), drought resistance index (DI), abiotic tolerance index (ATI), stress susceptibility percentage index (SSPI), sensitive drought index (SDI), modified stress tolerance index in normal irrigation (K1STI), and modified stress tolerance index in stress irrigation (K2STI) were calculated based on grain yield under drought (GYs) and irrigated (GYp) conditions. The result of analysis of variance indicated high significant differences among genotypes for grain yield trait. In general, terminal drought stress reduced 27.2% of grain yield. The Shiroudi, Rassoul, Darab-2, Marvdasht, Argh, and Shiraz genotypes which are high reduction of grain yield (61.1, 51.3, 48.4, 44.1, 43.1, and 43.0%, respectively) and also genotypes 318, Ghohar, 330, Mahdavi, and Alamout which are low reduction of grain yield with drought stress (4.1, 4.7, 7.0, 7.5, and 10.2%, respectively). Furthermore, results showed that wheat genotypes can be classified as normal and stress situations using cluster analysis. The correlation analysis among grain yield under non-stress and drought stress conditions with different drought tolerance indices showed that STI, YI, K1STI, and K2STI indices were appropriate indicators to identify the high grain yield genotypes. Based on these indicators, Mughan-1, Golestan, Navid, 330, Darab-2, and Bahar genotypes had the highest grain yield under both experimental conditions. Therefore, these wheat genotypes are suitable for cultivation in Mediterranean regions that are constantly exposed to drought stress at the end of the growing season, and areas with similar climatic conditions. Also, they are recommended to be used as parents for the improvement of drought tolerance in other wheat genotypes.

Citrus bacterial blast disease is one of the prevalent diseases in most citrus-growing regions in the world. Plants use a wide range of mechanisms to defend against pathogens, and the plant-pathogen interaction induces the expression of genes involved in the plant resistance. Furthermore, symbiotic association between plant and mycorrhizal fungi could effectively promote growth and protect the plant against adverse environmental conditions. In the present study, Serendipita indica-root colonized sour orange seedlings were infected by Pseudomonas viridiflava and the expression patterns of PR1, PR2, PR3, PR4, PR5, PAL, POX, and LOX genes in the early stages of citrus blast disease were investigated using the qRT-PCR at different sampling times. According to the results, the response of defense genes to bacterial infection was time dependent. In the S. indica-colonized sour orange plants, the highest level of PR1, PR4, PAL, POX, PR3, and PR5 genes expression was observed at 48 h after infection, but the expression of PR2 and LOX genes was increased at 72 h after infection compared to the control plants. It seems that S. indica can induce systemic effects and prepare the host plant to increase the expression of defense genes more rapidly once it receives a signal for the presence of the pathogen.

Plant karyotyping provides ordering and pairing all the chromosomes that can be used to determine the origin and genetic background of accessions. In this study, the karyotyping of 28 Iranian Falcaria vulgaris Bernh. accessions were evaluated for the first time. All accessions detected with the same number of chromosomes (2n=2x=22). However, in all samples, differences were found in the position of the centromere on chromosome pair 11. Our results demonstrated that the all chromosomes mainly have metacentric and sub-metacentric morphology. Karyotype asymmetry (F19) was observed among the accessions with 2A and 3A for F. vulgaris. So that the maximum asymmetry index (AsK) was related to F19 accession (74.95 %). Among the studied accessions, differences were found in chromosomes lengths, symmetry of karyotypes, relative length of chromosome (RL%), total form percentage (TF%), coefficient of variation of chromosome length (CVcl), average arm ratio (AR), centromeric index (CI), and ideogram chromosomes. The results indicated high cytological diversity of Iranian F. vulgaris accessions, suggesting that the geographical and environmental factors might have an effective role in the genetic structure and evolution of F. vulgaris chromosomes.

Fusarium wilt caused by the fungus Fusarium oxysporum f. sp. lycopersici (FOL) is one of the major devastating diseases of tomato plants throughout the world. There is no information on the molecular response of tomato line, Early Urbana-Y to FOL. The present study was performed to study the line response to FOL using phytopathological (disease severity and shoot fresh weight) as well as molecular methodologies. The transcription of several genes responsive to jasmonic acid (JA; Pin2), salicylic acid (SA; Chi3, Chi9 and PR1), the regulatory genes responsive to the signaling hormone JA (MYC2 and WRKY33) and ethylene (ET; ERF1) were studied by qRT-PCR technique at different time points after FOL inoculation (6-96 hour after inoculation). Disease symptoms development and reduced shoot fresh weight of the inoculated plants despite up-regulation of SA-dependent defense genes at different time points after pathogen infection indicated that SA signaling pathway is involved in the susceptibility of the Early Urbana-Y line to FOL. In contrast, JA and ET pathway genes were not strongly induced in response to the pathogen suggesting the involvement of JA/ET-mediated defense responses in reducing disease susceptibility. However, to gain a better understanding of enhanced resistance to fusarium wilt, more detailed molecular mechanisms underlying susceptibility of Early Urbana-Y line to FOL need to be further investigated in the future.