Yazar "Vahdati, Kourosh" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • [ X ]
    Öğe
    Characterization of plant growth-promoting rhizobacteria (PGPR) in Persian walnut associated with drought stress tolerance
    (Nature Portfolio, 2022) Lotfi, Naser; Soleimani, Ali; Cakmakci, Ramazan; Vahdati, Kourosh; Mohammadi, Parisa
    There is a lack of information on the rhizosphere of nut-bearing trees where microbial populations can benefit roots and tree growth. The current research aimed at discovering plant growth-promoting rhizobacteria (PGPR) in the rhizosphere of soil samples from around the root zone of six walnut trees, each of which was considered as a genotype, i.e. 'TT1', 'TT2', 'SS2', 'ZM1', 'Chandler' and 'Haward'. The trees grew in different arid and semiarid regions of Iran and Turkey. The strains were isolated and identified based on different morphological and biochemical markers. Drought-stress tolerance was assessed in the case of each isolate through their transfer to culture medium, containing polyethylene glycol (PEG(6000)) at 0 and 373.80 g L-1. Resilient strains were analyzed for measuring their ability to produce siderophore, hydrogen cyanide (HCN), Indole-3-acetic acid (IAA) and Gibberellic acid (GA(3)). In sum, 211 isolates were identified, of which a large number belonged to the Bacillus genus and, specifically, 78% of the strains were able to grow under drought stress conditions. The genus Arthrobacter was only detected in the rhizosphere of 'ZM1', 'Haward' and 'TT1' genotypes. In 4% of the strains, IAA production exceeded 53 mg L-1, while a high level of phosphorus solubility was verified in 6% of the strains. No strain was found to have the capability of producing HCN. The strains were screened for drought-tolerance, which resulted in the discovery of two promising strains, i.e. ZM39 and Cha43. Based on molecular identification through amplification and sequencing of the 16S rDNA gene, these two strains seemed to belong to Bacillus velezensis and Bacillus amyloliquefaciens, respectively. The discovery of new PGPR strains could probably assist walnut trees in improving their mechanisms of adaptation to drought stress.
  • [ X ]
    Öğe
    Comprehensive biochemical insights into the seed germination of walnut under drought stress
    (Elsevier, 2019) Lotfi, Naser; Soleimani, Ali; Vahdati, Kourosh; Cakmakci, Ramazan
    The evaluation of physiological and biochemical aspects is essential to identify clues that can assist breeders in selecting Persian walnut genotypes with considerable tolerance to drought stress. This objective can be obtained by analyzing seed biochemical compounds from different genetic resources, e.g. seeds from individual trees that are commonly exposed to drought stress. In the current research, we evaluated the effects of drought stress, as induced by PEG(6000), on the germination of walnut seeds collected from six promising genotypes (i.e. 'SS2', 'TT2', 'TT1', 'ZM1', 'Haward' and 'Chandler'). A photoperiod of 12 h was provided during the experiments, along with an average temperature of 25 +/- 1 degrees C. According to the different indexes of germination, a greater tolerance was observed among three genotypes, namely, 'ZM1', 'Haward' and 'Chandler'. In response to drought stress, the contents of proline and total soluble sugars increased, especially at intense levels of stress, whereas the amount of starch decreased. The levels of antioxidant activity significantly increased by POD, APX, CAT, SOD and LOX enzymes in the radicle and plumule tissues as the water potential reached -1.5 MPa. Three genotypes, namely, TT2', 'TT1' and 'SS2' were susceptible to cell wall damage (i.e. by lipid peroxidation). High levels of Spd and Spm in tolerant genotypes were accompanied by significant increases in the zeatin, endogenous IAA, zeatin riboside and ABA in the seeds. Our results suggest that, under drought stress, seed germination in walnuts can benefit from the accumulation of free Spd in seeds during the phases of germination. However, the accumulation of free Put appeared to be an inhibitory factor which suppressed the germination of walnut seeds.