Apical stem culturing offers an alternative approach of manipulating cell sap for wheat grain carbon and nitrogen metabolism in a near in vivo conditions. Employing this technique, role of sucrose and glutamine in transport stream on sucrose metabolism, ammonia assimilation and aminotransferase activities were assessed towards starch and protein accumulation in two wheat genotypes PBW 343 (low yield) and PBW 621 (high yield). At mid-milky stage, detached tillers were cultured in complete liquid medium containing varied concentration of glutamine and sucrose for seven days during year 2012–13 and 2013–14. Increasing glutamine concentration from 17 to 25 mM in the culture medium having 117 mM sucrose enhanced activities of nitrate reductase, glutamate synthase, glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) at 4 days after culturing (DAC) in correspondence with an increase in soluble protein content. However, at 7 DAC content of soluble protein decreased whereas starch accumulation increased showing, thereby a compensatory effect on carbon and nitrogen metabolism. Apparently, activities of sucrose synthase, soluble acid and neutral invertase significantly decreased. Increasing sucrose concentration from 117 to 125mMled to an increase in transformation of sugars to starch in grain but protein content decreased. PBW621 showed high protein content due to higher activities of GOT, GPT at 4 DAC which subsequently increased carbon skeleton of proteins towards starch synthesis at 7 DAC. Grain filling processes in terms of soluble sugars/starch were strongly correlated to invertase activities whereas proteins to aminotransferases.
The present investigation was carried out to study the distinct salt tolerance mechanism in two sets of material, Gly II transgenics and Kharchia landraces. The Gly II transgenics were developed for glyoxalase II (osglyII) gene (GenBank accession no. AY054407) from Oryza sativa through Agrobacterium mediated method in the background of wheat cultivar PBW 621. Kharchia 65 is a salt tolerant landrace derivative developed from Kharchia local which is native to saline soils of Rajasthan. The six wheat genotypes, viz. Kharchia local, Kharchia 65, PBW 621, G-2-2, G-3-4 and G-1-13 were evaluated for growth parameters, antioxidant enzymes and contents of glutathione, ascorbic acid, malondialdehyde (MDA), H2O2, sugars, chlorophyll, carotenoid, electrolyte leakage (EL) and Na+, K+ under control and two salt treatments (150 mM and 250 mM NaCl). The activities of antioxidant enzymes, glutathione, sugar content increased in both GlyII and Kharchia genotypes as compared to PBW 621. The GlyII activity increased (77–84%) in GlyII genotypes alongwith content of reduced glutathione (GSH) to maintain redox homeostasis. Apparently, GlyII and Kharchia genotypes exhibited minimum oxidative stress due to low content of MDA, H2O2, diminished EL and thereby causing less growth reduction and maintaining high chlorophyll and carotenoid level as compared to PBW 621. In addition, Gly II transgenic material and Kharchia lines showed less Na+ accumulation, greater seedling biomass and sugar content due to its salt tolerance mechanism. We infer that GlyII activity enhances GSH which play significant role in detoxifying ROS to establish stress homeostasis. The route for generation of GSH is via ascorbate-glutathione pathway mediated by glutathione reductase. Hence, GlyII transgenics and Kharchia genotypes can diminish salt stress following above mechanism.
Effect of different doses of nitrogen (N) (90, 120, 150 and 180 kg Nha–1) on the activities of aminotransferases and alkaline inorganic pyrophosphatase (AIP) in relation to the accumulation of proteins, amino acids and sugars in roots and internodes at 15 and 40 days post anthesis (DPA) stages was studied in six wheat genotypes namely HD 2967, GLU 1101, PBW 343, BW 9022, PH-132-4840 and PBW 550. Supra-optimal N doses (150 kg Nha–1 and 180 kg Nha–1) accentuated glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT) and alkaline inorganic pyrophosphatase activities in correspondence with an increase in amino acid, protein and sugar content in both roots and internodes in all the six genotypes. Activities of analyzed enzymes were significantly high at 15 days post anthesis (DPA) stage and thereafter declined at maturity (40 DPA) in parallel with decrease in amino acid contents. Maximum activity of GOT, GPT and AIP was observed in HD 2967 and GLU 1101 genotypes along with higher build up of proteins and amino acids which resulted in higher grain yield. Activity of GPT was comparatively high over GOT, indicating its major role towards protein synthesis. Grain filling processes in terms of proteins and amino acids were positively correlated with GOT and GPT activities while sugars were correlated to AIP. Thus, nitrogen acquisition and assimilation resulted in favoured utilization of N in form of amino acid and proteins accumulation while sugar content was also stimulated. Due to immense activities of aminotransferases and higher contents of amino acids and proteins in GLU 1101 and HD 2967 genotypes at optimal dose and higher dose of N, these genotypes hold future potential for developing new cultivars with better grain quality characteristics.
Genetic variation for high temperature tolerance exists in wheat cultivars. Identifying key metabolic steps in this regard will help in improving grain yield. Effect of high temperature on activities of sucrose metabolizing enzymes and aminotransferases in relation to transformation of free sugars to starch and protein in developing grains of four wheat cultivars PBW 343, PBW 550, C 306, C 273 was studied by raising the crop under normal (October) and late planting (December) conditions. Significant reduction in chlorophyll content and increase in membrane injury index and lipid peroxidation were observed in all the cultivars. C 306 and C 273 showed higher membrane stability over PBW 343, PBW 550. High temperature accentuated sucrolytic enzymes and aminotransferases while activities of sucrose synthase/phosphate synthase got repressed. Higher build up of sugars and starch in PBW 343, PBW 550 cvs over C 306, C 273 resulted in higher yield in the former but their lower membrane integrity under heat stress leads to yield reductions. Disruption of starch biosynthesis resulted in their favoured utilization in nitrogen metabolism leading to higher amino acid and protein accumulation. Results indicated that sustainability for yield enhancement under stress could be possible by cross-breeding high yielding cvs PBW with increased membrane stability C ones for increasing thermotolerance. Grain filling processes in terms of sugars/starch were strongly correlated to sucrose synthase/phosphate synthase activities while protein to aminotransferases.
Authors:A. Adugna, A. Adugna, G. S. Nanda, G. S. Nanda, N. S. Bains, and N. S. Bains
-based) and chemically induced (CH9832- based) male sterility systems were compared for hybrid performance in wheat. A total of 40 genotypes including 10 CMS-based hybrids, 10 CHA-based hybrids, 10 B lines and 10 R lines were included in the experiment. analysis of variance revealed significant differences between the genotypes for all the characters studied. Differences between the hybrids and their parents were significant for all the characters. There were also significant differences between the hybrids resulting from the two systems of sterility. This study of 10 comparable hybrids showed, on average, midparent heterosis of 30.2 and 7.3% for CMS- and CHA-derived hybrids, respectively. Generally, the CMS-based hybrids were superior to their CHA-based equivalents for grain yield performance. In spite of the incomplete fertility the higher grain yield in CMS-based hybrids was attributed to the profuse tillering and high thousand-grain weight. On the other hand, the CHA-based hybrids had lower yield performance due to the lower thousand-grain weight and tillering. The lower grain weight and tillering in these hybrids compared with their CMS-based equivalents might be due to the toxic effect of the CHA, which was carried over to the hybrid and affected vigour. As a whole the CMS system was found to be better than the CHA system (based on the particular CHA used in this study) for hybrid performance in wheat.
Authors:I. Sharma, N. Bains, V. Sohu, and R. Sharma
Loose smut of wheat is a disease of world wide significance. Resistant cultivars constitute a potentially useful and environmentally benign method of controlling this disease. The genetic basis of resistance in 20 wheat genotypes with resistance to Ustilago tritici race T11 was studied in crosses with the widely grown but susceptible Indian cultivar, PBW 343. These lines were also involved in 10 ‘resistant × resistant’ crosses, to infer diversity for resistance genes in this set. All 30 crosses were developed to the F3 stage. Fifteen parents were inferred to carry dominant genes for resistance to race T11. Ten of these resistant lines (ML 521, W 59, W 1616, W 2484, W 2531, W 5915, W 6202, WL 1786, WL 2956 and WL 3450) had resistance controlled by 2 dominant genes acting in a complementary manner whereas in 4 lines (W 4461, W 5100, W 2615 and WL 3951), there was a single dominant gene and in a single genotype, WL 5907, there were 2 dominant genes with duplicate gene action governing the resistance. In lines W 2139, W 3899, W 4985, W 5450 and W 5792 a single recessive gene conferred resistance. Inheritance in two crosses, one derived from a line possessing a single dominant gene and the other from a line possessing a single recessive gene was re-analyzed and successfully confirmed in F5 generation. The segregation of most of the ‘resistant × resistant’ crosses conformed to the inferences drawn about the parents in the ‘resistant × susceptible’ crosses.
Six wheat cultivars, namely PBW 343, PBW 550 (stress susceptible), PBW 621, PBW 175 (drought tolerant), C 306 and HD 2967 (heat tolerant), were used in this study to evaluate the effect of heat and drought stress on the activities of peroxidases (POXs), diamine oxidase (DAO), polyamine oxidase (PAO) and arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) in relation to contents of polyamines (PAs), lipid peroxide and lignin. High temperature (HT) elevated activities of syringaldazine peroxidase (SPX), guaiacol peroxidase (GPX) and coniferyl alcohol peroxidase (CPX) in heat tolerant cultivars while, drought stress accentuated ADC/ODC activities in drought tolerant cultivars. Both heat and drought stress enhanced activities of DAO and PAO alongwith contents of H2O2 in PBW 175 and C 306. Amongst studied POXs, SPX activity was relatively more and coincided well with lignin content under HT stress while, the levels of ADC/ODC paralleled with putrescine and spermidine contents under drought stress. Higher build up of thiobarbituric acid reactive substances in cultivars PBW 343 and PBW 550 indicated their membrane instability during both the stresses. Our results revealed that SPX mediated lignification leading to higher cell wall rigidity under heat stress and drought increased PAs involved in ROS scavenging due to presence of positive charges which can bind strongly to the negative charges in cellular components such as proteins and phospholipids and thereby stabilize the membranes under stress conditions.