Genetic analysis and selection for wheat yield in drought-stressed and irrigated environments

Summary Wheat (Triticum aestivum L.) cultivars grown in the southern Great Plains of the U.S.A. are exposed to a wide range of moisture conditions due to large fluctuations in the amount and frequency of rainfall. Yield stability under those conditions is therefore a desirable trait for wheat breeders. Our primary objective was to quantify various genetic parameters for grain production in drought-stressed and irrigated environments. We also attempted to predict and measure yield responses when selection is practiced in either drought-stressed or irrigated environments, or both. Seventy F₂-derived lines from the cross, TAM W-101/Sturdy, were evaluated at Goodwell, OK, under irrigated and naturally drought-stressed conditions in 1987 and 1988. Genetic variance and heritability estimates were higher in the irrigated environment than in the drought-stressed environment. The genetic correlation coefficient for yields in the two environments was 0.20±0.16, indicating that selection of widely adapted genotypes requires testing in both environments. Based on the genetic variance/covariance structure of this particular population, the linear index which maximized the combined expected gain in both environments was 0.66Y₁ + 0.34Y₂, in which Y₁ and Y₂ are yields in the irrigated and drought-stressed environments. This index is not expected to apply across all populations; rather, it further supports the hypothesis that testing in either environment alone (drought stressed or irrigated) may not be most effective for increasing either mean productivity or yield under drought stress.     

Performance of different filter combinations with surface and subsurface drip irrigation systems for utilizing municipal wastewater

Large volumes of wastewater (WW) are being generated worldwide as a consequence of rapid urbanization and growth of industries. The reuse of WW finds increased application in irrigation but the presence of toxic elements and microorganisms limits its use for irrigation purpose. To reduce the contamination of WW for irrigation, drip system is seen as an appropriate choice due to restricted quantity of water application. Emitter clogging is viewed as the main problem associated with drip system for its large-scale use with WW. Physical and chemical characteristics of WW were determined and compared with groundwater (GW). Higher EC, pH, Mg, and CO₃ were observed in the GW but higher turbidity, total solids, HCO₃, and Ca were observed in the WW. The population of total coliforms (2.72 × 10⁴ to 5.2 × 10⁷) and E. coli (1.8 × 10³ to 2.64 × 10⁶) were detected in WW. The hydraulic performance of drip emitters was studied for 2 years with WW and GW using sand media filter (F1), disk filter (F2), and combination of both filters (F3). Higher removal efficiency for turbidity, total solids, Ca, Mg, CO₃ total coliforms, and E. coli was observed with combination filter. Emitter discharge exponent was also close to 0.5 with combination filter. Emitter flow rate decreased (in the sequence of F1 > F2 > F3) with increase in time of operation. After 2 years of operation under F3, coefficient of variation was less than 4 % with both WW and GW. Thus, it showed good performance in surface placed emitters but it was 7.2 % with WW and 9.5 % with GW under subsurface (15 cm) placed emitters. Clogging of emitters was controlled by flushing. Flushed emitters placed at 30 cm depth resulted in 3.7 % reduction in discharge as compared to 8.7 % reduction in the absence of flushing, under filter F1. Emitters with F2 produced least improvement in discharge.     

Short communication

Papillomaviral has been identified in peripheral blood cells of both cattle and humans with and without associated disease and it has been suggested that such cells may act as sites of viral latency. In order to investigate the possibility of latent papillomaviral infection in the aetiopathogenesis of the equine sarcoid, peripheral blood derived DNA samples from 20 healthy and 34 sarcoid-affected donkeys were subject to polymerase chain reaction ( ) using papillomaviral specific primers. Analysis of blood derived samples failed to demonstrate the presence of papillomaviral in any animal. Screening of 37 matched sarcoid derived samples confirmed the presence of BPV in 34 diseased donkeys. This study supports the hypothesis of as an aetiological agent in the equine sarcoid and suggests that latent virus in circulating peripheral blood cells does not play a role in the pathogenesis and epidemiology of the equine sarcoid.     

Genomic prediction in a numerically small breed population using prioritized genetic markers from whole-genome sequence data

The objective of this study was to investigate the accuracy of genomic prediction of body weight and eating quality traits in a numerically small sheep population (Dorper sheep). Prediction was based on a large multi-breed/admixed reference population and using (a) 50k or 500k single nucleotide polymorphism (SNP) genotypes, (b) imputed whole-genome sequencing data (~31 million), (c) selected SNPs from whole genome sequence data and (d) 50k SNP genotypes plus selected SNPs from whole-genome sequence data. Furthermore, the impact of using a breed-adjusted genomic relationship matrix on accuracy of genomic breeding value was assessed. The selection of genetic variants was based on an association study performed on imputed whole-genome sequence data in an independent population, which was chosen either randomly from the base population or according to higher genetic proximity to the target population. Genomic prediction was based on genomic best linear unbiased prediction (GBLUP), and the accuracy of genomic prediction was assessed according to the correlation between genomic breeding value and corrected phenotypes divided by the square root of trait heritability. The accuracy of genomic prediction was between 0.20 and 0.30 across different traits based on common 50k SNP genotypes, which improved on average by 0.06 (absolute value) on average based on using prioritized genetic markers from whole-genome sequence data. Using prioritized genetic markers from a genetically more related GWAS population resulted in slightly higher prediction accuracy (0.02 absolute value) compared to genetic markers derived from a random GWAS population. Using high-density SNP genotypes or imputed whole-genome sequence data in GBLUP showed almost no improvement in genomic prediction accuracy however, accounting for different marker allele frequencies in reference population according to a breed-adjusted GRM resulted to on average 0.024 (absolute value) increase in accuracy of genomic prediction.     

The effect of rotation speed on the power consumption and cutting accuracy of guided circular saw: Experimental measurement and analysis of saw critical and flutter speeds

ABSTRACT

This paper investigates the effect of rotation speed and vibration response of a circular saw on the sawing process of Douglas-fir wood. An idling test was conducted on a guided circular saw to determine its stable operation speeds and vibration behavior. Short-time Fourier transform analysis was performed on saw idling test data, and variation of excited frequencies of the blade as a function of rotation speed was obtained. The saw blade critical speeds and the rotation speeds that correspond to saw flutter instability were identified. Then experimental cutting tests were conducted at different cutting conditions and the effect of rotation speed and saw vibration response on cutting power consumption and sawing accuracy was investigated. The results showed that conducting a saw idling test and vibration response analysis can identify the saw critical and flutter speeds, which is essential for identifying the optimum rotation speed of circular saw. There was a significant increase in power consumption when cutting at super-critical and super-flutter speed. The effect of rotation speed on sawing accuracy is complex and nonlinear. This effect interacts with feed speed, which makes it difficult to generalize sawing accuracy versus rotation speed in the circular sawing process.     

Control of fruit-flies (Dacus spp.) by attractants of plant origin

Four dominating species of fruit-fliesDacus zonatus, D. cucurbitae, D. dorsalis andD. ciliatus are widely distributed throughout Pakistan. They cause heavy damage to ripe and semi-ripe fruits and vegetables annually in our country. A natural attractant of plant origin, i.e., from Tulsi (Ocimum sanctum L.) was isolated and extracted in PCSIR Laboratories Complex, Karachi, with a view to applying for the control of fruit-flies. Different extracts of roots, stems, flowers, seeds, bark, and leaves were prepared in chloroform, acetone, ethylene chloride, ethanol, and ethyl acetate; and were tested for trapping fruit-flies in specially designed traps under different field conditions. A cotton pad (0.3 mg) treated with 0.25 ml of leaves extract in ethyl acetate is found to be a potent attractant for luring and trapping the fruit-flies (Dacus spp.) from a distance of 0.8 km. Methyl eugenol used as a standard attractant also gave the same results.     

Effect of amplitude and frequency on soil break-up by an oscillating tillage tool in a soil bin experiment

Experiments were conducted in a soil bin to study the effect of amplitude and frequency of an oscillating tillage tool on fragmentation of Kharagpur sandy clay loam soil. It was observed that the maximum utilization of energy occurs at an oscillation frequency close to the natural frequency of the soil. Therefore, optimum values of frequency and amplitude of oscillation were determined on the basis of maximum clod surface produced per unit of energy input. The oscillating tillage tool produced smaller soil aggregates than a non-oscillating one. At a given amplitude of oscillations, increase in frequency above the natural frequency of soil did not increase soil break-up further. At any frequency, soil break-up increased with increase in amplitude. At a tool oscillation frequency equal to the natural frequency of soil the equation MWD = A₀exp(−K₀r), where MWD is the mean weight diameter of soil aggregates, r is the amplitude of the oscillations, A₀ is MWD of soil aggregates produced by an identical rigid tool and K₀ is a constant, described the data on soil break up adequately.     

Comparing two methods of sequential fractionation in the study of copper compounds in Haplic chernozem under model experimental conditions

Purpose

It is very important to obtain the information on the soils capacity to immobilize HMs and distribute them among soil components. The aim of this work was to study the fractional composition of Cu compounds in Haplic chernozem under model contamination conditions using different fractionation methods.

Materials and methods

The fractional composition of copper compounds in Haplic Chernozem artificially contaminated with copper acetate has been studied under model experimental conditions. General regularities and differences in the distribution of Cu forms in soils at the use of sequential fractionation by the Miller method modified by Berti and Jacobs (1996) and the Tessier method (Tessier et al. 1979) are revealed.

Results and discussion

The differences are related to the metal affinity for specific carrier phases, as well as to the selectivity and extraction capacity of the reagents used in these methods. A significant increase in the most mobile exchangeable Cu fraction is observed in contaminated soils. Aluminosilicates and soil organic matter make the largest contribution to the adsorption and retention of Cu.

Conclusions

The Tessier method is more suitable for the separation of the total technogenic component from contaminated soils. The Miller method is more informative at the determination of loosely bound HM compounds because of the use of weaker extractants.

     

Influence of PAH contamination on soil ecological status

Purpose

The purpose of this paper is to study the responses of soil biological parameters as indicator of ecological status on PAH-contaminated soil.

Materials and methods

Studies are conducted on the soils and natural grassy vegetation of monitoring plots subjected to Novocherkassk power station (NPS) emissions. Monitoring plots were established at different distances from the NPS (1.0–20.0 km).

Results and discussion

The level of polycyclic aromatic hydrocarbons (PAHs) around NPS is the highest at the monitoring plot located at distance 1.6 km to the northwest through the prevailing wind direction. Gradually, decrease of PAHs was observed while increasing the distance from the NPS through the prevailing wind direction. Calculation of correlations between PAH level and biological activity parameters of soils showed lack of dependence with total and every PAH content in all 12 studied monitoring plots. The most significant correlations were found between PAH content and enzyme activity in the monitoring plots situated through the prevailing wind direction from NPS.

Conclusions

The main pollution source in the studied area is NPS. It was found that contamination of soil by PAHs has a direct dependence on the activity of all biological communities in chernozems, as well as the activities of dehydrogenase and the phytotoxicity of soils. Inverse correlations have been revealed between the PAH contamination and abundance of soil bacteria.