Jalal A. Aliyev

Photosynthesis, photorespiration and productivity of wheat and soybean genotypes†

The results of the numerous measurements obtained during the last 40 years on gas exchange rate, photosynthetic carbon metabolism by exposition in ¹⁴CO₂ and activities of primary carbon fixation enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC/O), in various wheat and soybean genotypes grown over a wide area in the field and contrasting in photosynthetic traits and productivity are presented in this article. It was established that high productive wheat genotypes (7-9 t ha⁻¹) with the optimal architectonics possess higher rate of CO₂ assimilation during the leaf ontogenesis. Along with the high rate of photosynthesis, high values of photorespiration are characteristic for the high productive genotypes. Genotypes with moderate (4-5 t ha⁻¹) and low (3 t ha⁻¹) grain yield are characterized by relatively low rates of both CO₂ assimilation and photorespiration. A value of photorespiration constitutes 28-35% of photosynthetic rate in contrasting genotypes. The activities of RuBPC and RuBPO were changing in a similar way in the course of the flag leaf and ear elements development. High productive genotypes are also characterized by a higher rate of biosynthesis and total value of glycine-serine and a higher photosynthetic rate. Therefore, contrary to conception arisen during many years on the wastefulness of photorespiration, taking into account the versatile investigations on different aspects of photorespiration, it was proved that photorespiration is one of the evolutionarily developed vital metabolic processes in plants and the attempts to reduce this process with the purpose of increasing the crop productivity are inconsistent.

Genome diversity and evidence of recombination and reassortment in nanoviruses from Europe

The recent identification of a new nanovirus, pea necrotic yellow dwarf virus, from pea in Germany prompted us to survey wild and cultivated legumes for nanovirus infections in several European countries. This led to the identification of two new nanoviruses: black medic leaf roll virus (BMLRV) and pea yellow stunt virus (PYSV), each considered a putative new species. The complete genomes of a PYSV isolate from Austria and three BMLRV isolates from Austria, Azerbaijan and Sweden were sequenced. In addition, the genomes of five isolates of faba bean necrotic yellows virus (FBNYV) from Azerbaijan and Spain and those of four faba bean necrotic stunt virus (FBNSV) isolates from Azerbaijan were completely sequenced, leading to the first identification of FBNSV occurring in Europe. Sequence analyses uncovered evolutionary relationships, extensive reassortment and potential remnants of mixed nanovirus infections, as well as intra- and intercomponent recombination events within the nanovirus genomes. In some virus isolates, diverse types of the same genome component (paralogues) were observed, a type of genome complexity not described previously for any member of the family Nanoviridae. Moreover, infectious and aphid-transmissible nanoviruses from cloned genomic DNAs of FBNYV and BMLRV were reconstituted that, for the first time, allow experimental reassortments for studying the genome functions and evolution of these nanoviruses.

Detection of ‘Candidatus Phytoplasma brasiliense’ in a new geographic region and existence of two genetically distinct populations’

Abstract‘Candidatus Phytoplasma brasiliense’, a phytoplasma taxon associated with hibiscus witches’ broom disease was first described in 2001 in Brazil. In September 2007, a peach tree (Prunus persica) displaying yellowing symptoms reminiscent of phytoplasma infection was sampled in Guba region of Azerbaijan. A phytoplasma was detected in the diseased peach tree by nested PCR amplification of its 16S rDNA with universal primers for phytoplasmas. Phylogenetical analyses of the amplified 16S rDNA showed that the phytoplasma infecting the peach tree corresponded to ‘Ca. P. brasiliense’, a species never reported in Euro-Mediterranean area. To set up a detection assay, cloning of a ‘Ca. P. brasiliense’ DNA fragment was undertaken by comparative RAPD. The amplified dnaK-dnaJ genetic locus was used to design a nested PCR assay able to amplify all ‘Ca. P. brasiliense’ isolates of the subgroup 16SrXV-A without amplifying the related members of the group 16SrII. This assay also allowed confirming the first detection of ‘Ca. P. brasiliense’ in diseased basil collected in south Lebanon.

Hydrogen peroxide generation and antioxidant enzyme activities in the leaves and roots of wheat cultivars subjected to long-term soil drought stress

The dynamics of the activity of catalase, ascorbate peroxidase, guaiacol peroxidase, and benzidine peroxidase, as well as the level of hydrogen peroxide in the vegetative organs of durum wheat (Triticum durum Desf.) cultivars was studied under long-term soil drought conditions. It was established that hydrogen peroxide generation occurred at early stages of stress in the tolerant variety Barakatli-95, whereas in the susceptible variety Garagylchyg-2 its significant amounts were accumulated only at later stages. Garagylchyg-2 shows a larger reduction of photochemical activity of PS II in both genotypes at all stages of ontogenesis under drought stress than Barakatli-95. The highest activity of catalase which plays a leading role in the neutralization of hydrogen peroxide was observed in the leaves and roots of the drought-tolerant variety Barakatli-95. Despite the fact that the protection system also includes peroxidases, the activity of these enzymes even after synthesis of their new portions is substantially lower compared with catalase. Native PAGE electrophoresis revealed the presence of one isoform of CAT, seven isoforms of APX, three isoforms of GPO, and three isoforms of BPO in the leaves, and also three isoforms of CAT, four isoforms of APX, two isoforms of GPO, and six isoforms of BPO in the roots of wheat. One isoform of CAT was found in the roots when water supply was normal and three isoforms were observed under drought conditions. Stress associated with long-term soil drought in the roots of wheat has led to an increase in the heterogeneity due to the formation of two new sedentary forms of catalase: CAT2 and CAT3.

Virus-induced changes in photosynthetic parameters and peroxidase isoenzyme contents in tomato (Solanum lycopersicum L.) plants

Tomato samples were collected from the field of Absheron peninsula in Azerbaijan in order to evaluate the incidence of main Tobamoviruses. According to results of serological and molecular tests, Tomato mosaic virus (ToMV), Tobacco mosaic virus (TMV), and Pepper mild mottle virus (PMMoV) were detected as single and mixed infections (TMV + PMMoV; ToMV + PMMoV) in various tomato samples. It was found that Tobamovirus infection caused an increase in the content of malondialdehyde, alterations in the activities of peroxidase enzymes and quantitative and qualitative changes in their molecular isoforms. A comparison of thylakoid membrane polypeptides from virus-infected leaves indicated a decrease in the content of the thylakoid membrane polypeptides with molecular masses of 123, 55, 47, 33, 28–24, 17, and 15 kD. PSII efficiency and the content of chlorophylls (a and b) were significantly lower in the virus-infected leaves.

Photosynthesis, Photorespiration and Productivity of Wheat Genotypes (Triticum L.)

The results of the numerous measurements obtained during the last 40 years on gas exchange intensity using of infrared gas analyzer URAS-2T (Germany), photosynthetic carbon metabolism by exposition in 14CO2 and activities of enzyme of primary carbon fixation, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC/O) in various wheat genotypes grown over a wide area in sowings and contrasting on photosynthetic traits and productivity are presented in this paper. It was established that high productive wheat genotypes with the best architectonics (7—9 t ha−1) possess higher intensity of CO2 assimilation and high values of photorespiration in leaf ontogenesis. Genotypes with moderate (4–5 t ha−1) and low (3 t ha−1) grain yield are characterized by relatively low intensity both of CO2 assimilation and photorespiration. Activities of RuBP carboxylase and RuBP oxygenase were changing in a similar way in the course of the flag leaf and ear elements development. The rates of sucrose (the main transport metabolite in plants) biosynthesis and products of glycolate metabolism also correlate with the CO2 assimilation rate and the activity of RuBP oxygenase. Hence, taking into account the versatile investigations on different aspects of photorespiration it was proved that photorespiration is one of the evolutionary developed vital metabolic processes in plants.

Biochemical and Molecular Aspects of Drought Tolerance in Wheat Triticum L. Genotypes

Wheat (Triticum aestivum L.) cultivars contrasting in genetic makeup and differing in drought-resistance were grown in field conditions in a wide area under normal water supply and severe water deficit. One of the genotypes (Azamatli-95) was short-stemmed, with vertically oriented small leaves and drought-tolerant while the other genotype (Giymatli-2/17) was short-stemmed, with broad and drooping leaves and drought-sensitive. It was found out that the content of CP I (Mr 115 kD) and apoprotein of P700 with Mr 63 kD, also LHC II polypeptides insignificantly increased in the drought-resistant cv. Azamatli-95 under extreme water supply condition while their content decreased in drought-sensitive cv. Giymatli-2/17. The intensity of synthesis of α- and β-subunits of CF1 (55 and 53.5 kD) and 33–30.5 kD proteins also decreased in the sensitive genotype. The intensity of short wavelength peaks at 687 and 695 nm sharply increased in the fluorescence spectra (77 K) of chloroplasts from Giymatli-2/17 under water deficiency and there was a stimulation of the ratio of fluorescence band intensity F687/F740. After exposure to drought, cv Giymatli-2/17 showed a larger reduction in the actual PS II photochemical efficiency of chloroplasts than cv. Azamatli-95. Activities of catalase, ascorbate peroxidase, superoxide dismutase and glutathione reductase, as well as photochemical activity of photosystem I and photosystem II were studied in leaves of durum and bread wheat genotypes in ontogenesis. It was found out that dynamics of catalase and ascorbate peroxidase functioning in well-watered plants through ontogenesis practically did not change both among durum and among bread wheat cultivars. Functioning of these enzymes during ontogenesis under water deficit differed. Catalase activity increased in all stressed genotypes: in durum wheat cultivars maximal activity was observed in the milk ripeness and in bread wheat cultivars at the end of flowering. Ascorbate peroxidase activity also increased under water deficit: in tolerant wheat genotypes maximal activity occurred at the end of flowering, and in the sensitive ones at the end of ear formation. The maximum activity of glutathione reductase both as in the control, as well as in drought-subjected plants was observed in the anthesis stage. Superoxide dismutase activity was lower than the control during ontogenesis, except in the last stages. It should be noted that PS I and PS II photochemical activities were also high in genotypes subjected to drought both at the end of ear formation and flowering stages. Drought resistance was checked by RAPD-PCR as a quick and easy method for durum (Triticum durum L.) and bread (Triticum aestivum L.) wheat genotypes contrasting in tolerance. P6 primer (5′ TCGGCGGTTC 3′) produced 920 bp band mainly in drought tolerant genotypes. It was found that P7 (5′ TCGGCGGTTC 3′) primer produced 750 bp band was not absolutely universal for Triticum L. genotypes. In order to identify DREB1 genes in these genotypes PCR-analysis was carried out using functional markers specific for A, B, and D genomes. It was found that DREB 1 gene was located on chromosome 3A in all genotypes, excepting one semi-tolerant genotype Tale-38. In comparison with other genotypes, a 717 bp PCR product of DREB -B1 gene was located on B genome in drought-tolerant Barakatli-95. The results reported here provide an entry point and a reference to future analysis of gene expression during drought. In addition, these results can suggest possible targets for the enhancement of stress tolerance in crops by genetic engineering. The data presented here might be used for monitoring environmental stresses in field-grown plants and selecting stress-resistant varieties for growth under unfavorable conditions.

Photosynthesis, Antioxidant Protection, and Drought Tolerance in Plants

Drought stress usually leads to reductions in crop yield, which can result from many drought-induced morphological, physiological, and metabolic changes that occur in plants. In this chapter, we review the most recent reports on drought-induced responses in plants, focusing on the role of oxidative stress as well as on other possible mechanisms. A key sign of drought stress at the molecular level is the accelerated production of reactive oxygen species. Levels of leaf and root enzymatic antioxidants (peroxidase, catalase, and glutathione reductase), nonenzymatic antioxidants (glycine betaine), and stress parameters (hydrogen peroxide and malondialdehyde) were determined under watered and drought stress conditions in two durum wheat genotypes differing in drought resistance. The dehydration of wheat leaves and roots was accompanied by the accumulation of H2O2, MDA, and GB, a phase change in the activity of antioxidant enzymes, indicating the development of oxidative stress. Activities of antioxidant enzymes under drought stress were shown to relate de novo synthesis of some isoenzymes. The activity, some physicochemical and kinetic parameters of carbonic anhydrase were comparatively studied in the flag leaves, ear elements, and root systems of wheat genotypes during ontogenesis. TRAP markers linked to the QTL for the drought tolerance were used for the molecular assessment of drought tolerance of wheat genotypes.

Genotypic Variation for Drought Tolerance in Wheat Plants

Many natural disasters, including drought, result in crop production and quality losses worldwide and global climate change makes the situation worse. A wide range of strategies used to enhance the drought tolerance depend on the genetically determined plant capacity and sensitivity, as well as the intensity and duration of the stress. Understanding the physiological, biochemical, and molecular mechanisms of drought tolerance is very important in development of selection and breeding strategies. Among crop plants, wheat is the staple food for more than 35 % of world population and is often grown in water-limited conditions. Wheat anti-drought study is of importance to worldwide wheat production and biological breeding. For this purpose, a rich gene fund was created, comprising thousands of wheat genotypes with contrasting photosynthetic traits, productivity, and tolerance to drought stress, and both selected from the ancient, aboriginal varieties of national selection and introduced from the world gene pool, particularly from Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), International Centre for Agricultural Research in Dry Areas (ICARDA), and other international centers. All these genotypes are grown in the field conditions on a wide area at the Absheron Experimental Station of the Research Institute of Crop Husbandry (Baku, Azerbaijan) under normal irrigation and drought. Numerous winter durum (Triticum durum Desf.) and bread (Triticum aestivum L.) wheat genotypes were the main target of the research. The main parameters for selection of these genotypes were grain yield, plant phenotypic features (stem height, area and architectonics of the leaf surface, etc.), duration of the vegetation, and other morphophysiological traits, as well as drought resistance. Random amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR) spectra were analyzed in 220 bread (T. aestivum L.) and 46 durum (T. durum Desf.) wheat genotypes. Using primer P6 (TCGGCGGTTC), 920-bp fragment was revealed in 234 genotypes. Primer P7 (TCGGCGGTTC) produced a 750-bp band only in 203 genotypes. Results obtained by using both P6 and P7 primers match in 74 % of the analyzed genotypes: In 184 genotypes, specific loci were amplified by both markers. The obtained results show that these genotypes possess loci associated with drought tolerance. In 13 genotypes (total 5 %), none of the primers amplified specific fragments. So, the presented data could be used for monitoring the environmental stresses in field-grown plants and help in selection of stress-resistant varieties.

Biotic Stress and Crop Improvement

Biotic stress is one of the major environmental factors affecting plants. Viruses, fungi, bacteria, weeds, insects, and other pests and pathogens represent a major constraint to agricultural productivity and a serious threat to vegetable and grain crops. Plant protection against pathogens and pests is a commercially important issue and one of the main directions of researches. Almost half of new infectious diseases identified in plants during the past 10 years have a viral nature. The number and distribution areas of some plant viruses in Europe have been increasing rapidly during the past 35 years that caused big problems from an economic point of view. Viral diseases have also become a real threat for different cultivars of vegetables, grains, and other agricultural crops in our country. It causes extensive leaf yellowing, stem and leaf deformation, reducing the fruit quality, substantial yield loss, and shortening the lifecycle of crops. The probable cause of decay of virus-infected plants is not only the virus activity itself but also reduced tolerance to unfavorable environmental conditions. The identification of the viruses affecting plants and the study of the plant responses are very important for the better understanding of the plant–virus interactions and for developing the tendency to reduce the plant virus-associated risks in Azerbaijan. Therefore, the main goal of the present study is to identify the most widespread plant viruses in Azerbaijan using different molecular techniques and to evaluate some characteristics of plant response to viral stress.