In vitro embryogenic callus is a critical factor for genetic transformation of rice, especially for indica varieties. In this study, we investigated the relationship between polyamines, including putrescine (Put), spermidine (Spd) and spermine (Spm), and callus browning, and we studied the effect of exogenous Put on callus regeneration and on the content of endogenous polyamines. In addition, the expression levels of arginine decarboxylase gene (Adcl) and S-adenosylmethionine decarboxylase gene (Samdc) in embryogenic callus were studied by quantitative Real-time PCR analysis. The results showed that the contents of endogenous Put and Spd in the browning callus were significantly lower than those in normal callus. Exogenous Put could effectively improve the growing state of callus of indica rice and enhance the development of embryogenic callus. The content of endogenous polyamines in embryogenic callus, especially Spd and Spm, was increased after addition of exogenous Put. Additionally, exogenous Put also had an obvious impact on the expression levels of Adcl but partial effect on the expression levels of Samdc gene. This study could increase the knowledge of both embryogenic callus induction and polyamine catabolism in callus in indica rice.
Weed competition in southern Brazil is one of the main limiting factors for Oryza sativa L. (flooded rice) yield. Echinochloa spp. (barnyardgrass) occurs at a high frequency. Although the potential for weed interference in this cereal is well known, there is little information available about the impact of nutrient competition on rice. Thus, this study aimed to evaluate the relationship between the increase of the barnyardgrass population and the development and nutrition of flooded rice plants at different stages of development. The treatments consisted of growing populations of barnyardgrass competing with the crop from stage V4, which were: 0, 1, 6, 13, 100 and 200 plants · m−2. The experimental design was randomized blocks with two replications, and the experimental units were plots 1.53 m wide by 5 m long. Plant biomass, nutrient uptake and loss of productivity were determined with three replications. An increase in the barnyardgrass population reduced the dry mass of rice leaves and stems, regardless of the evaluation period and the vegetative or reproductive period. Barnyardgrass plants had a significant impact on the reduced grain yield of a flooded rice crop, mainly due to high nutrient competitiveness, especially N in the vegetative period and K in the reproductive period. Barnyardgrass caused a loss of yield by unit · m−2 of 1.13%. The competition for N between rice and barnyardgrass plants was higher in the vegetative period, while for K, Ca and Mg the highest competition occurred in the reproductive period.
The paper presents the results of the Ti10V2Fe3Al alloy crack resistance assessment using the Rice’s J-integral technique as a function of morphology and volume fraction of α-phase precipitates. Titanium alloys characterized by the two-phase structure α + β are an interesting alternative to classic steels with high mechanical properties. Despite the high manufacturing costs and processing of titanium alloys, they are used in heavily loaded constructions in the aerospace industry due to its high strength to density ratio. The literature lacks detailed data on the influence of microstructure and, in particular, the morphology of α phase precipitates on fracture toughness in high strength titanium alloys. In the following work an attempt was made to determine the correlation between the microstructure and resistance to cracking in the Ti10V2Fe3Al alloy.
Rice blast is one of the most destructive rice diseases known to cause considerable yield losses globally. Plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) are closely associated with rice plants and improve plant growth and health. To determine how isolated bacteria trigger rice growth, an assessment of phosphate solubilization and auxin production mechanisms was carried out in vitro and in vivo. In this study, the interactions between PGPR and Rhizophagus irregularis were evaluated in wildtype and CYCLOPS mutant plants to provide a sustainable solution against blast disease and reduce the amount of yield loss. Importantly, Bacillus subtilis UTSP40 and Pseudomonas fluorescens UTSP50 exhibited a suppressive effect on AMF colonization which shows the probable existence of a functional competition between AMF and PGPR to dominate the rhizosphere. On the other hand, R. irregularis decreased the biocontrol activity of B. subtilis UTSP40 in wild type, although this reduction was not significant in mutant plants. Results showed that the same defense-related genes were induced in the roots of wild type colonized by B. subtilis UTSP40 and R. irregularis. Therefore, plant cell programs may be shared during root colonization by these two groups of beneficial microorganisms.
In two field experiments, the effect of some weed control treatments (citric acid at the rate of 10, 15 and 20%, acetic acid at the rate of 20, 30 and 40%, oxadiargyl, oxyflurfen, rice straw mulch, hand hoeing and an unweeded check control treatment) on weed growth and onion productivity in sandy soils at the Agricultural Experimental Station of the National Research Centre, Egypt was studied. The results indicated that all weeded treatments reduced the dry weight of broadleaf, grassy and total weeds as compared with the weedy check. Oxadiargyl, followed by two hand hoeing, rice straw mulch and acetic acid 40% recorded the greatest weed control efficiency. Insignificant differences were noticed between these treatments. Applying rice straw mulch increased bulb length, bulb diameter, bulb weight and onion yield by 67.52, 57.55, 45.74 and 66.22% over the weedy check, respectively. The highest values of N, P and K were obtained from rice straw mulch treatment followed by hand hoeing, oxadiargyl and acetic acid 40% treatments. It may be concluded that farmers can certainly depend on mulching or acetic acid at 40% instead of using chemical herbicides especially in organic farm systems for controlling onion weeds.
Leaf scald, caused by the necrotrophic fungus Monographella albescens, is one of the main threats to rice (Oryza sativa L.) around the world. This disease decreases yields in rice by up to 30% because of dead leaf tissue, damaged seeds, and sterile flowers. Currently, there is limited knowledge about the molecular mechanisms involved in rice plant resistance against this pathogen. For this purpose, six commercial cultivars of rice were primarily screened for M. albescens infection and development. Dasht and Salari were found to be the most resistant and susceptible to M. albescens infection, respectively. The plants were kept in a greenhouse at 29 ± 2°C during the day and 26 ± 2°C at night with a relative air humidity of 85 ± 5%. Forty-five days after sowing, the plants with three biological replications were inoculated by transferring a PDA disc (0.3 cm2) containing M. albescens mycelia to the middle third of the 7th, 8th, and 9th completely open leaves. The leaves were collected 24, 48, 72, 96 and 120 hai. Leaf samples were also collected from the non-inoculated plants (0 h) to serve as controls. Real-time quantitative PCR (RT-qPCR) showed rapid induction and significant accumulation of jasmonic acid (JA) and ethylene (ET) responsive genes such as lipoxygenase (LOX), allene oxide synthase 2 (Aos2), jasmonic acid carboxyl methyltransferase 1 (JMT1) and ACC synthase 1 (ACS1) in the resistant Dasht cultivar after infection with M. albescens. Furthermore, the transcripts of salicylic acid (SA) responsive phenyl alanine ammonia lyase 1 (PAL1) and nonexpressor of pathogenesis-related genes 1 (NPR1) genes were induced in the incompatible interaction. The activities of the defense enzymes superoxide dismutase (SOD), peroxidase (POX) and glutathione reductase (GR) increased strongly in Dasht in response to M. albescens infection. In addition, there was an increase in the H2O2 levels in the leaves of the Dasht cultivar during the infectious period of M. albescens associated with the enhancement of catalase (CAT) activity as well as higher levels of malondialdehyde (MDA). This is the first study on the interaction between rice and M. albescens at the molecular level. It can contribute to understanding how rice responds to pathogen infection, as well as assist with future research plans of molecular breeding regarding the tolerance to leaf scald disease.
Arsenic is one of the most harmful pollutants in groundwater. In this paper, the Nepali bio sand filter (BSF) was modi-fied with different bio-adsorbents, and proved to be an efficient method for arsenic removal from groundwater. Three dif-ferent bio-adsorbents were used to modify the Nepali BSF. Iron nails and biochar BSF, ~96% and ~93% arsenic removal was achieved, within the range of WHO guidelines. In iron nails, BSF and biochar BSF ~15 dm3∙h–1 arsenic content water was treated. In the other two BSFs, rice-husk and banana peel were used, the arsenic removal efficiency was ~83% of both BSFs. Furthermore, the efficiency of rice-husk and banana peel BSFs can be increased by increasing the surface area of the adsorbent or by reducing the flow rate.
The concrete-filled section of columns has been widely in construction used due to its structural elements. As a result, the usage of composite columns has recently increased all over the world. However, using foamed concrete alone does not result in much improvements in strength. Therefore, this paper examines the use of foamed concrete containing fibre to improve the strength of composite columns. Specifically, this study aims to determine the bond strength of concrete-filled hollow section (CFHS) with modified fibrous foamed concrete. Two types of fibre are used in this work, namely, steel fibre and polypropylene fibre, with rice husk ash (RHA) as a sand replacement to improve the compressive strength of foamed concrete. The CFHS with modified fibrous foamed concrete is tested by using the push-out method, and the results show that CFHS with steel fibre has a highest bond strength.