Drought stress-induced changes in redox metabolism of barley (Hordeum vulgare L.).

In the present investigation, influence of water stress on redox metabolism was evaluated in the flag leaf and grains of four barley (Hordeum vulgare L.) genotypes viz DWRB 101, 432 ICARDA, Jyoti and 430 ICARDA at 10th, 20th and 30th days after anthesis (DAA). Relative water content, electrolyte leakage, antioxidative enzymes and their related metabolites were studied during drought stress. Relative water content was well maintained in both the tissues of DWRB 101 and 432 ICARDA. The upregulation of catalase at 20th DAA while ascorbate peroxidase, glutathione reductase and dehydro reductase at 30th DAA in the flag leaf and grains of DWRB 101 and 432 ICARDA may be responsible for lesser increase in H2O2 content as compared to other genotypes. Moreover, the downregulation of superoxide dismutase was comparatively higher in Jyoti and 430 ICARDA. The redox homeostasis was well established during the stress in DWRB 101 and 432 ICARDA by maintaining comparatively higher ratios of ascorbate/dehydroascorbate and reduced/oxidized glutathione. Therefore, scrutiny of data indicated that DWRB 101 and 432 ICARDA may perform better under drought stress in comparison with Jyoti and 430 ICARDA.

Inheritance and biochemical basis of yellowing of apical leaves: a unique trait in chickpea (Cicer arietinum L.).

A unique trait, i.e. yellowing of apical/young leaves in response to low temperature and high relative humidity was identified in a chickpea genotype, ICCX110069. To determine inheritance pattern of this trait, ICCX110069 was crossed to four other genotypes, GL14050, GL14049, GL14059 and SAGL152117, that exhibited normal green apical leaves under similar environmental conditions. The F1, F2, F3, BC1F1 and BC1F2 generations were generated. A ratio of 13 normal green leaf: three yellow leaf was found to be the best fit, indicated digenic gene action with suppressor effect of normal green leaf over the expression of yellowing of apical/young leaf trait. The chlorophyll content was significantly lower, while guaiacol peroxidase activity was significantly higher in yellow leaves of ICCX110069 as compared to green leaves of the same genotype and of GL14049, indicating the competence of antioxidative defence mechanism involved with the expression of this trait.

Metabolic adjustments during compatible interaction between barley genotypes and stripe rust pathogen.

Stripe rust is a fungal disease that has devastated the barley production for a long time. The present study focused on the role of ß-glucan, PR proteins, diamine oxidase (DAO), polyamine oxidase (PAO), key enzymes and metabolites of phenol and proline metabolism in the stripe rust resistance of barley. RD2901 with resistant behavior against stripe rust showed increased levels of PR proteins, phenylalanine ammonia lyase (PAL), tyrosine ammonia lyase (TAL) along with the accumulation of ß-glucan and lignin which strengthen the plant cell wall during plant-pathogen interaction. It also depicted the enhanced activities of glutamate dehydrogenase (GDH) and ornithine aminotransferase (OAT) coupled with the increased amounts of proline, glycine betaine and choline after infection with M-race of P. striiformis f. sp. hordei. On the contrary, the sensitive genotype Jyoti was unable to enhance the activities of most of these enzymes except PAL and OAT so that it showed an increase in lignin and choline contents only. Secondly, the increase in lignin content was less as compared to the tolerant genotype. Hence, it can be inferred that these key metabolites and enzymes of various metabolic pathways may contribute to the resistance of barley against stripe rust pathogen. This study suggested that these key enzymes and their metabolites could serve as markers for the characterization of plant defensive state that is essential for crop protection.

Water deficit stress tolerance in chickpea is mediated by the contribution of integrative defence systems in different tissues of the plant.

Drought induces heavy yield losses in chickpea (Cicer arietinum L.). Besides understanding the physiological and biochemical parameters contributing to drought tolerance, we need to understand the importance of one tissue in combatting drought stress-induced oxidative stress and influencing the antioxidative defence system in other tissues. The study was conducted to examine the influence of drought stress conditions on the antioxidative defence system and physiology in different tissues such as roots, leaves, nodules, pod walls and seeds at various vegetative and reproductive growth stages in two chickpea cultivars differing in rooting behaviour: ICC4958 (deep rooted) and ILC3279 (shallow rooted). The traits contributing to drought tolerance in ICC4958 were increased root area, decreased leaf area index or increase in root area, decreased leaf area; ILC3279 displayed a decrease in root area and an increase in LAI. The adaptation of ICC4958 was also accompanied by biochemical adjustments, like increases in antioxidative enzymes (superoxide dismutase, peroxidase, ascorbate peroxidase, glutathione reductase and catalase) and nonenzymatic antioxidants (ascorbic acid, proline and stress-induced proteins). However, increases in antioxidant enzymes, nonenzymatic antioxidants and proteins in ILC3279 were lower than in ICC4958. The lower malondialdehyde content and membrane permeability index in ICC4958 might be responsible for reduced damage under drought stress. Increased H2O2 content in ICC4958 was related to enhanced antioxidative defence, emphasising its role as a signalling molecule under stress. This is the first study conducted on drought stress-induced enzymatic and nonenzymatic antioxidative defence systems in underground, aboveground vegetative and reproductive tissues in chickpea cultivars differing in rooting behaviour.