Drought is a major limitation for rice production in rainfed ecosystems. Identifying quantitative trait loci (QTLs) linked to drought resistance provides opportunity to breed high yielding rice varieties suitable for drought-prone areas. Although considerable efforts were made in mapping QTLs associated with drought-resistance traits in rice, most of the studies involved indica × japonica crosses and hence, the drought-resistance alleles were contributed mostly by japonica ecotypes. It is desirable to look for genetic variation within indica ecotypes adapted to target environment (TE) as the alleles from japonica ecotype may not be expressed under lowland conditions. A subset of 250 recombinant inbred lines (RILs) of F₈ generation derived from two indica rice lines (IR20 and Nootripathu) with contrasting drought-resistance traits were used to map the QTLs for morpho-physiological and plant production traits under drought stress in the field in TE. A genetic linkage map was constructed using 101 polymorphic PCR-based markers distributed over the 12 chromosomes covering a total length of 1,529 cM in 17 linkage groups with an average distance of 15.1 cM. Composite interval mapping analysis identified 22 QTLs, which individually explained 4.8–32.2% of the phenotypic variation. Consistent QTLs for drought-resistance traits were detected using locally adapted indica ecotypes, which may be useful for rainfed rice improvement.
Chromium is a heavy metal; this element is considered as an environmental hazard. Toxicity effects of chromium on growth and development of plants including inhibition of germination process decrease of growth and biomass of plant. The aim of this research is to study accumulation of Chromium along with nutrients and its effect on the growth of Paddy plant (Oryza sativa L). Thus, paddy seedlings grown in petriplates lined with filter paper undergoing, different treatments of Cr (0, 2.5, 5, 10, 25, 50, 75, 100 and 200 mg/L). After one week seedlings were removed and morpho physiological parameters like root length, shoot length and dry weight of plants and Biochemicals ,accumulation of nutrients along with Cr in roots and shoots were determined. The results indicated that the concentrations more than 100 mg/L chromium cause the reduction of morphophysiology parameters in the treatment plants rather than control plant and Cr addition in the cultures caused enhancement of chromium content in roots and shoots of plant seedlings. Similarly the biochemicals and nutrient accumulation also affected by increasing concentrations of chromium. It was also noted that accumulation of chromium in the roots was much higher than the shoots of the seedlings under treatment.
A number of morphological, physiological and phenological traits are known to improve the performance of rice challenged by drought. Root morphological traits and stress-induced response form important components of drought tolerance. Enhancing grain yield remains the principal objective of most breeding programs. Interaction between primary traits poses a formidable challenge while dealing with grain yield under stress. The evaluation of root morphology at three different growth stages and grain yield along with related characteristics under contrasting moisture regimes was made using nine backcrosses along with their parent and standard checks. The backcrosses invoved transgressant double haploid lines derived from IR64 and Azucena with IR64. Marked genotypic differences were observed for all root morphology as well as grain yield related characteristics across the sampling dates as revealed by individual and combined ANOVA. Among the nine backcrosses studied in this experiment, the BC1F2 population of P124 x IR64 were evaluated for forwarding based on their performance with respect to maximum root length and grain yield under both well-watered and low-moisture stress conditions. Sixtynine plants - ten percent of the backcross population - were selectively genotyped using RAPD primers. Under well-watered conditions two RAPD markers showed strong linkage to QTLs for maximum root length evaluated under ww conditions. Two other markers could explain the considerable amount of variation in MRL under LMS. One of the markers identified under low-moisture stress conditions was also able to explain variability in maximum root length in the mean environment.
A study was conducted at the Department of Horticulture, KNUST, Kumasi from June to November, 2015 with the objectives to (i) determine the rate of ATONIK plant growth regulator (PGR) suitable for high yield of two varieties of hybrid rice (ii) determine the combined effects of PGR rates and varieties on the growth and yield performance of hybrid rice. A 2 x 5 factorial arrangement in randomized complete block design with three replications was used. The factors were varieties at two levels: Agra Rice and Jasmine 85 and PGR at five levels: ATONIK at 450 ml/ha, ATONIK at 500 ml/ha, ATONIK at 550 ml/ha, ATONIK at 0 ml/ha and GA3 at 60 ml/ha. Comparing the ATONIK rates with the GA3, ATONIK at 450 ml/ha resulted in a 14.3 % increase in the number of rice panicles. Application of ATONIK at 450 ml/ha, 500 ml/ha and 550 ml/ha resulted in 14.4%, 10.7% and 4.4% higher percentage of productive tillers, respectively, than that produced by GA3 at 60 ml/ha. ATONIK at 450 ml/ha application led to a 17.8 % increase in grain yield. For the harvest index, application of ATONIK at 450 ml/ha resulted in the highest harvest index of 45 %, significantly greater than the other PGR treatments. In conclusion, the study clearly demonstrated that ATONIK PGR was superior to GA3 in the vegetative and productive performance of rice. The most suitable rate of ATONIK for increased rice productivity was 450 ml/ha.
Pullulanase (EC 3.2.1.41) in non-germinating seeds was compared with that in germinating seeds. Moreover, pullulanase from the endosperm of rice (Oryza sativaL., cv. Hinohikari) seeds was isolated and its properties investigated. The pI value of pullulanase from seeds after 8 days of germination was almost equal to that from non-germinating seeds, which shows that these two enzymes are the same protein. Therefore, the same pullulanase may play roles in both starch synthesis during ripening and starch degradation during germination in rice seeds. The enzyme was isolated by a procedure that included ammonium sulfate fractionation, DEAE-cellulofine column chromatography, preparative isoelectric focusing, and preparative disc gel electrophoresis. The enzyme was homogeneous by SDS/PAGE. The molecular weight of the enzyme was estimated to be 100000 based on its mobility on SDS/PAGE and 105000 based on gel filtration with TSKgel super SW 3000, which showed that it was composed of a single unit. The isoelectric point of the enzyme was 4.7. The enzyme was strongly inhibited by β-cyclodextrin. The enzyme was not activated by thiol reagents such as dithiothreitol, 2-mercaptoethanol or glutathione. The enzyme most preferably hydrolyzed pullulan and liberated only maltotriose. The pullulan hydrolysis was strongly inhibited by the substrate at a concentration higher than 0.1%. The degree of inhibition increased with an increase in the concentration of pullulan. However, the enzyme hydrolyzed amylopectin, soluble starch and β-limit dextrin more rapidly as their concentrations increased. The enzyme exhibited α-glucosyltransfer activity and produced an α-1,6-linked compound of two maltotriose molecules from pullulan.
A pot culture was carried out with Oryza sativa L. vari-Co-39, to investigate the effects of supplementary calcium chloride on plants grown at NaCl (50mM) concentration. Treatments were: (1) Control: nutrient solution alone (C); (2) nutrient solution plus 50mM sodium chloride (NaCl); (3) nutrient solution plus 10mM calcium chloride (CaCl2); (4) nutrient solution plus 15mM calcium chloride (CaCl2); (5) nutrient solution and 50 mM NaCl plus supplementary 10 mM CaCl2 (NaCl + CaCl2); and (6) 50 mM NaCl plus additional mixture of 15 mM CaCl2 in nutrient solution (NaCl + CaCl2). The plants grown under salt stress produced low dry weight and relative water content than those grown in standard nutrient solution and in CaCl2 alone. Supplemental calcium chloride added to nutrient solution containing salt significantly improved growth and relative water content. Membrane permeability increased with high NaCl application and these increases in root membrane permeability were decreased with supplementary Ca. The concentration of chloride (Cl) increases highly for all treatments. Sodium (Na) concentration in plant tissues increased in both shoots and roots at high NaCl treatment. Application of supplementary Ca lowered Na concentration. Concentrations of Ca. K and N were at deficient ranges in the plants grown at high NaCl levels and these deficiencies were corrected by supplementary Ca. The ameliorating effect of Ca on growth and physiological variables could reduce the negative effect of salinity of Oryza sativa L., plants.
To explore new antifungal agents for rice blast control, the antifungal activity of a series of novel 1,2,4-triazole derivatives against Magnaporthe oryzae has been evaluated. The antifungal activity was determined by using in vitro mycelial growth inhibition tests. Among the 19 test compounds, we found that the compound 1-(4-phenoxymethyl-2-phenyl-[1,3]dioxolan-2-ylmethyl)-1H-1,2,4- triazole (Gj) displayed potent antifungal activity against M. oryzae. The IC50 value was found approximately 3.8±0.5 μM and the IC50 value of propiconazole was found to be approximately 3.7±0.2 μM, respectively. Structure-activity relationship studies on aromatic ring structures provided insight and information about the structural requirements for antifungal activity of this synthetic series against M. oryzae.
This paper reports on a hydroponics experiment that was conducted to investigate the effect of inorganic arsenics on the seedlings of the rice cultivar Shanyou63. The seedlings were subjected to two treatments, i.e., As(III) and As(V). The results showed that the morphological traits of the seedlings were significantly altered after the arsenic treatments. Analysis of nitrogen, phosphorus, potassium, and arsenic contents of the roots and leaves of the seedlings indicated that the absorption of phosphorus and potassium was mainly affected by As(III), while that of nitrogen was mainly affected by As(V). The expression of 12 genes involved in the absorption and utilization of nitrogen, phosphorus, and potassium were all observed to be down-regulated after the arsenic treatments. As(V) significantly affected the absorption and utilization of nitrogen, while As(III) significantly affected those of phosphorus and potassium. The result obtained by realtime FQ-PCR regarding the difference in the gene expressions agreed with that of our hydroponics experiment.
Lowland sawah farmers often puddle to improve soil hydrophysical conditions for rice, but the puddling intensity beyond which no extra yield increases occur is unknown. Agro- nomic effects of six mechanical puddling intensities were assessed in three Nigerian inland-valley bottoms. All puddled plots, irrespec- tive of intensity, produced similar effects at all three locations. At 10 days after transplanting, soil bulk density of all puddled plots re- presented mean decreases relative to control plots of about 22.4, 15.8, and 31.7% at Akaeze, Adani, and Ejeti, respectively. Soil bulk density and moisture content upon saturation were similar during 40-120 days after transplanting. All puddled plots consistently showed taller plants and greater tillering than control plots only at Ejeti. Grain yields were similar among treatments in Akaeze and Adani (mean, 3.71 and 6.42 Mg ha -1 , respectively), but one-pass puddling yielded numerically highest in both locations. At Ejeti, grain yields followed the trend for plant growth, with mean values of 4.36 and 1.81 Mg ha -1 for puddled and control plots, respecti- vely. One-pass puddling may be sufficient for sawah rice grown late particularly in less humid environments.
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