The genetic relatedness analysis of male sterile and their maintainer lines of onion (Allium cepa L.) by using RAPD primers

RAPD markers analysis was performed to investigate genetic relatedness among nine sterile (A), maintainer lines (B), and male parents (C) of onion. Initially, 180 arbitrary decamer primers were screened; of these 20 primers were selected which yielded 812 bands, 45.34% of which were found to be polymorphic. Squared-Euclidean Distance matrix revealed a minimum genetic distance between the genotypes MS 48A and MF 65C and a maximum genetic distance between the genotypes MLT 84C and MF 65B. Cluster analysis grouped the nine onion genotypes into two major clusters. The first cluster consisted of two male sterile groups, i.e. MS-65 (Arka Lalima) and MS-48 (Arka Kirthiman) of single bulb onions. The second cluster consists of MLT (Multiplier) group. PCA re-confirmed the results of the dendrogram, revealing the precision in estimation of genetic relatedness among the genotypes tested. None of the primers produced unique banding patterns to distinguish all nine genotypes. This information about genetic relatedness among the nine genotypes would be better utilized in further onion breeding programs.     

Simulated long-term nitrogen losses for a midwestern agricultural watershed in the United States

Adequate knowledge on the movement of nutrients under various agricultural practices is essential for developing remedial measures to reduce nonpoint source pollution. Mathematical models, after extensive calibration and validation, are useful to derive such knowledge and to identify site-specific alternative agricultural management practices. A spatial-process model that uses GIS and ADAPT, a field scale daily time-step continuous water table management model, was calibrated and validated for flow and nitrate-N discharges from a 365 ha agricultural watershed in central Iowa, in the Midwestern United States. This watershed was monitored for nitrate-N losses from 1991 to 1997. Spatial patterns in crops, topography, fertilizer applications and climate were used as input to drive the model. The first half of the monitored data was used for calibration and the other half was used in validation of the model. For the calibration period, the observed and predicted flow and nitrate-N discharges were in excellent agreement with r² values of 0.88 and 0.74, respectively. During the validation period, the observed and predicted flow and nitrate-N discharges were in good agreement with r² values of 0.71 and 0.50, respectively. For all 6 years of data, the observed annual nitrate-N losses of 26 kg ha⁻¹ for the entire simulation were in excellent agreement with predicted nitrate-N losses of 24.2 kg ha⁻¹. The calibrated model was used to investigate the long-term impacts of nitrate-N losses to changes in the rate and timing of fertilizer application. Results indicate that nitrate-N losses were sensitive to rate and timing of fertilizer application. Modeled annual nitrate-N losses showed a 17% reduction in nitrate-N losses by reducing the fertilizer application rate by 20% and switching the application timing from fall to spring. Further reductions in nitrate-N losses require conversion of row cropland to pasture and/or replacement of continuous corn or corn–soybean rotation systems with alternative crops.     

Effects of changes in N-fertilizer management on water quality trends at the watershed scale

In this study, the ADAPT (Agricultural Drainage and Pesticide Transport) model was calibrated and validated for monthly flow and nitrate-N losses, for the 2000-2004 period, from two minor agricultural watersheds in Seven Mile Creek (SMC-1 and SMC-2) in south-central Minnesota. First, the model was calibrated and validated using the water quality data from the SMC-1 and again independently validated with the SMC-2 dataset. The predicted monthly flow and associated nitrate-N losses agreed reasonably with the measured trends for both calibration (r² = 0.81 and 0.70 for flow and nitrate-N losses, respectively) and validation (r² = 0.85 and 0.78 for flow and nitrate-N losses from SMC-1, and 0.89 and 0.78 for flow and nitrate-N losses from SMC-2, respectively) periods. The model performed less satisfactorily for the snowmelt periods than it did for the entire simulation period. Using the calibrated model, long-term simulations were performed using climatic data from 1955 to 2004 to evaluate the effects of climatic variability and N application rates and timing on nitrate-N losses. The predicted nitrate-N losses were sensitive to N application rates and timing. A decrease in the fall N application rate from 179.3 to 112 kg/ha decreased nitrate-N losses by 23%. By changing application timing from fall to spring at a rate of 112 N kg/ha, nitrate-N losses decreased by 12%. The predicted nitrate-N losses showed a linear response to precipitation with larger losses generally associated with wet years. A 25% increase in mean annual precipitation would offset reductions in nitrate-N loss achieved using better N fertilizer management strategies described above.     

Identification and fine mapping of a new gene, <Emphasis Type="Italic">BPH31</Emphasis> conferring resistance to brown planthopper biotype 4 of India to improve rice, <Emphasis Type="Italic">Oryza sativa</Emphasis> L

Background

Rice (Oryza sativa L.) is the staple food for more than 3.5 billion people, mainly in Asia. Brown planthopper (BPH) is one of the most destructive insect pests of rice that limits rice production. Host-plant resistance is one of the most efficient ways to overcome BPH damage to the rice crop.

Results

BPH bioassay studies from 2009 to 2015 conducted in India and at the International Rice Research Institute (IRRI), Philippines, revealed that the cultivar CR2711–76 developed at the National Rice Research Institute (NRRI), Cuttack, India, showed stable and broad-spectrum resistance to several BPH populations of the Philippines and BPH biotype 4 of India. Genetic analysis and fine mapping confirmed the presence of a single dominant gene, BPH31, in CR2711–76 conferring BPH resistance. The BPH31 gene was located on the long arm of chromosome 3 within an interval of 475 kb between the markers PA26 and RM2334. Bioassay analysis of the BPH31 gene in CR2711–76 was carried out against BPH populations of the Philippines. The results from bioassay revealed that CR2711–76 possesses three different mechanisms of resistance: antibiosis, antixenosis, and tolerance. The effectiveness of flanking markers was tested in a segregating population and the InDel type markers PA26 and RM2334 showed high co-segregation with the resistance phenotype. Foreground and background analysis by tightly linked markers as well as using the Infinium 6 K SNP chip respectively were applied for transferring the BPH31 gene into an indica variety, Jaya. The improved BPH31-derived Jaya lines showed strong resistance to BPH biotypes of India and the Philippines.

Conclusion

The new BPH31 gene can be used in BPH resistance breeding programs on the Indian subcontinent. The tightly linked DNA markers identified in the study have proved their effectiveness and can be utilized in BPH resistance breeding in rice.

     

Determination of theanine in commercial tea by liquid chromatography with fluorescence and diode array ultraviolet detection

Two liquid chromatographic methods that involve precolumn derivatization with o-phthaladehyde (OPA) and phenylisothiocyanate (PITC) with fluorescence and diode array UV detection for the determination of theanine have been developed. The chromatographic separations were achieved by reverse-phase high-performance liquid chromatography using octadecyl columns and gradient elution. The methods were applied to evaluate the theanine content of commercial tea leaves. The coefficient of variation of the peak area repeatability for within day (n = 8) and between day (n = 8 over 10 days) was lower than 3% for both of the methods. The estimated limit of detection (LOD) and limit of quantitation (LOQ) for the OPA method was 0.12 and 0.35 microg theanine, respectively. The PITC method was 500-fold more sensitive with LOD and LOQ values of 0.25 and 0.75 ng, respectively. The theanine content of the commercial tea samples varied from 2-5 mg/g leaf. The overall % recoveries for these methods ranged from 93-99.3. The sensitivity and simplicity of the method render them suitable for use in quality control laboratories.     

Rust Resistance and its Stability in Lines of Varying Productivity in Groundnut (Arachis hypogaea L.)

Twenty six lines of groundnut (Arachis hypogaea L.) of varying productivity were tested for yield under four treatments involving fungicidal control of rust and leafspots. Disease severity was measured at two stages of growth, namely 70 days (stage 1) and 90 days after sowing (stage 2). Instead of pod yield, a score (based on an Isd test and grouping over pod yield, shelling %, 100-kernel weight and % residual green leaf area at stage 2) was used to define performance status of the lines. A study of various character combinations revealed the importance of % residual green leaf area at both stages 1 and 2 in predicting the relative yield performance of lines. This result was obtained by comparing the % agreement of the status of lines given by a particular character set with performance status and was confirmed by a multiple regression analysis of pod yield on all other traits. Seven lines and three progenitor parents showed stability of performance with respect to rust resistance. They included lines derived from crosses between the national check, ‘Robut 33—1’, as one parent and either a rust resistant genotype, NC Ac 17090 or an early Russian accession of (Spanish type) ‘Chico’, as the other. It was suggested that breeding programmes should take into account performance status based on yield and disease severity instead of pod yield alone.