The emerging role of silicon (Si) has attracted a great deal of interest from researchers because of the numerous agronomic benefits of this element to plants. Indeed, silicon improves plant resistance to a range of biotic and abiotic stresses, with consequent yield increases. Furthermore, it enhances resistance in several crops of great economic importance to diseases and insect pests. Until recently, the exact nature of protective effects of silicon in plants is uncertain. To date, two major defense mechanisms due to silicon application have been documented: physical defense and biochemical defense. In this review, the interaction between silicon-treated- plants and reduced biotic stresses (disease and insect pests) incidence was explored. The current research presents the agronomic importance of silicon in plants, the control of fungal and bacterial pathogens and insect pests according to their lifestyle, and viral agents, and different mechanisms of silicon-enhanced resistance. By regrouping the data presented in this paper, a good knowledge of the association between silicon treatment, increasing plant resistance, and decreasing biotic stresses occurrence could be achieved.
Biotic and abiotic stresses induce
increased formation of reactive oxygen species (ROS) through distinct pathways:
pathogen infections activate specific ROS-producing enzymes (i.e. NADPH
oxidase, cell wall peroxidases), which results in accumulation of cellular or
intercellular ROS, such as superoxide or hydrogen peroxide. Abiotic stresses,
on the other hand, cause elevated ROS production principally through an
impairment of photosynthetic and respiratory electron transport pathways. Also,
these two types of stresses have diverse effects on the antioxidant system of
the plant. Results of experiments studying the interaction of abiotic and
biotic stresses largely depend on the degree of the applied abiotic stress
treatment, the compatible or incompatible host-pathogen interaction and the
timing of inoculation in relation to the timing of a preceding abiotic stress
Crop productivity is greatly influenced by various environmental stresses, of which insect herbivory-induced biotic stress assumes much significance. As a consequence of insect herbivory, a number of plant biochemical processes involved in the tolerance mechanism are affected. Different studies have demonstrated a diverse functional role of various plant oxidative enzymes in protecting plants against biotic stress induced by insect herbivory. Comprehensive profiling of stress-associated plant oxidative enzymes is most relevant to successful molecular breeding of stress-tolerant crop plants. Thus, better understanding of the biochemical basis of plant defense mechanisms is imperative, not only from a basic science perspective, but also for biotechnology-based pest control practice. In this review, we emphasize the potential role of various oxidative enzymes in plant defense against insect herbivory.
The resistance of
maize inbred lines and their hybrids to Western Corn Rootworm was investigated
in a 4 × 4 full diallel system. The most tolerant line against WCR
larvae was the inbred line P26. Four maize inbred lines and their 12 normal and
reciprocal crosses were investigated for resistance to Fusarium ssp. and
European Corn Borer under natural conditions in four replications in 1998-2000.
The highest GCA values were found for the inbred lines P26 and P50. Studies
were also made to determine the optimum concentration of imidazolinone in the
selective medium for the detection of resistant cell lines originating from
homozygous genotypes produced by irradiation.
The fluorescence imaging technique was elaborated primarily for the detection of the fluorescence traits accompanying changes in the physiological status of stressed plants. The paper summarises the conditions and technical background required for the use of multi-wavelength fluorescence imaging. Images of leaves were recorded at wavelengths of 440, 520, 690 and 740 nm. Possible applications are illustrated by studies on the leaves of stressed plants. An evaluation of the images is presented, including the necessary corrections and fluorescence ratios, examples of comparisons between imaging and functional activity measurements, and an evaluation of the diagnostic importance and reliability of imaging in detecting the effects of stressors in plants. The results demonstrate that the multi-wavelength fluorescence imaging of leaves is a useful method for detecting the presence of stress in plants and for determining the extent of the stress.
Hexaploid synthetic wheat, derived from crosses between durum wheat and Aegilops tauschii, is widely accepted as an important source of useful traits for wheat breeding. During 2015 and 2016, three groups of synthetics were studied in Azerbaijan (3 sites) and Russia (1 site). Group 1 comprised CIMMYT primary synthetics derived from eastern European winter durum wheats crossed to Ae. tauschii accessions from the Caspian Sea basin. Group 2 included lines derived from CIMMYT synthetics × bread wheat crosses. Group 3 consisted of synthetics developed in Japan by crossing durum variety Langdon with a diverse collection of Ae. tauschii accessions. Varieties Bezostaya-1 and Seri were used as checks. Group 1 synthetics were better adapted and more productive than those in group 3, indicating that the durum parent plays an important role in the adaptation of synthetics. Compared to Bezostaya-1 synthetics produced fewer spikes per unit area, an important consideration for selecting bread wheat parents for maintenance of productivity. Synthetics had longer spikes but were not generally free-threshing. All synthetics and derivatives had 1000-kernel weights comparable to Bezostya-1 and significantly higher than Seri. All primary synthetics were resistant to leaf rust, several to stem rust, and few to stripe rust. Superior genotypes from all three groups that combine high expression of spike productivity traits and stress tolerance index were identified.
Treatment with various concentrations (0, 5, 15 and 20%) of PEG was used to simulate water stress, followed by inoculation with
(DTR) at two different points of time (6 and 72 h after the PEG treatment) in two DTR resistant (M-3 and Mv Magvas) and two sensitive (Bezostaya 1 and Glenlea) wheat varieties. The reduction in biomass production due to the PEG treatments was more pronounced in the shoots than in the roots. While in the case of Bezostaya 1 5% PEG reduced the level of infection, 20% PEG treatment lowered the tolerance level of M-3. DTR infection may be more efficient in inducing antioxidative defence systems than water stress. However, there was no direct correlation between the activity of the individual antioxidant enzymes and the drought or DTR tolerance of wheat plants.