Effects of aerial pollutants on the growth and yield of spring barley

Open-topped chambers were used to determine the effect of field concentrations of aerial pollutants on the growth and yield of spring barley. Experiments were conducted in the Marston Valley, Bedfordshire, where sulphur dioxide and fluoride are the major pollutants. The charcoal filtered chambers enabled pollutant concentrations to be reduced by 60–70%. Cleaning the air increased straw and grain yields. The filtration was non-selective and did not identify the injurious agent. The chambers were found to accelerate the crop's development by 7–8 days and reduce yield by suppressing tillering.     

Effects of small air ions on net blotch disease of barley

Small positive air ions significantly reduced the number of lesions and percentage of leaf area covered by lesions of net blotch disease of barley. Appearance of disease symptoms was delayed by three days when plants were exposed to an atmosphere of positive ions. No such effect was observed for negative air ions. Height and dry weight were significantly stimulated by unipolar ions.     

Genome-wide association studies of net form of net blotch resistance at seedling and adult plant stages in spring barley collection

Net form of net blotch (NFNB) of barley (Hordeum vulgare L.), caused by Pyrenophora teres f. teres (Ptt) Drechsler (anamorph: Drechslera teres [Sacc.] Shoem.), is considered one of the major constraints of successful barley production in major barley growing regions of the world. Resistance to NFNB was evaluated in a barley collection of 336 genotypes (AM-2014), at seedling stage using isolates LGDPtt.19 and TD10 in the USA, and adult stage in seven hotspot environments in Morocco. The AM-2014 panel was genotyped with 9K SNP markers and genome-wide association studies (GWAS) were carried out using mixed linear model (MLM: Q?+?K) accounting for population structure (Q) and kinship (K) as covariates. Significant (P?<?0.001) marker trait associations were corrected for false discovery rate (FDR) at the q?<?0.05. Four genotypes showed an average infection response (IRs ≤ 2) to both isolates, LGDPttt.19 and TD10, at the seedling stage, and 30 genotypes showed resistance in all environments in the field while three genotypes exhibited the highest resistance at both stages. The GWAS of NFNB identified 31 distinct QTLs on all seven barley chromosomes, of which 8 with resistance at seedling stage, 21 were associated with resistance at the adult stage, and two QTLs, QRptt.2H-132.15 and QPtt.6H-54-55, conferred resistance at both stages. Of 31 resistance QTLs reported in this study, 10 QTLs coincided with previously mapped QTL while 21 are novel, thereby validating the GWAS approach used in this study. The resistance sources identified in AM-2014 and QTL mapped in this study are valuable resources for marker-assisted breeding for NFNB resistance in the future.     

Effects of mildew on the growth and yield of spring barley: 1969-72

Mildew decreased grain yield by decreasing ear number and grain size (but not grain number/ear), the damage depending on the earliness and severity of mildew. In 1971 when mildew was early and severe, ethirimol seed dressings at 0.22 kg a.i./ha, which gave only early protection, increased yield more than did ethirimol sprays applied to protect the flag leaf and ear. In 1972 sprays were better than seed dressings at this rate because mildew was less severe during the seedling stages.     

Field screening for resistance to barley net blotch

Inoculation with barley net blotch from infested straw debris was compared with that from diseased plants after sowing infected grains. The straw debris had a high, uniform inoculation potential which gave an early, continuing infection and easily reproducible results that were effective for screening barley cultivars in the field for resistance against a natural population of the pathogen. Further, it minimises an eventual influence from other leaf pathogens coming from the surroundings. Irrigation was decisive for the success of the method - especially in the initial phase. Ten m separation with an immune crop was insufficient to completely prevent infection in the uninoculated plots. The tested 25 cvs were differentiated in six categories of resistant and susceptible on the basis of disease development and final level of attack. None of them was free of symptoms. The most resistant cvs kept a constant, low level of attack during the whole growing season, whereas the most susceptible cvs showed an early and rapidly increasing attack. Intermediate cvs were characterised with more or less slow increase of the attack. The size and proportion of the brown necrotic spots and the surrounding yellow halo varied greatly from one cultivar to the other. The grain yield reduction was due solely to an effect on the thousand grain weight which decreased linearly with the squared point score for net blotch. Further, the disease affected the quality of the grains as less nitrogen was transported from straw to grain in the severely diseased plants.     

Effects of fungicide treatments and variety on development, grain growth and yield of spring barley

The effects of four fungicide treatments for the control of mildew on spring barley were assessed in three field experiments, one in each of the years 1981, 1982, 1983. The fungicide treatments (+/ - triadimenol seed treatment and +/ - triadimefon foliar spray applied during early booting) were chosen to control mildew, and hence affect yield determining processes, at different times in the life of the crop. Two of the experiments also tested different nitrogen amounts and the third tested four varieties differing in their degree of mildew resistance. Mildew appeared too late to affect the production and survival of spikelets and shoots, but reduced average grain weight by reducing the rate of grain growth. Grains in the upper part of the ear had a considerably lower growth rate and final weight than grains in central and basal positions but there was no evidence that the effects of mildew on grain size depended upon grain position within the ear. Mildew incidence increased with increasing nitrogen and varietal susceptibility but there were few significant interactions between these factors and fungicide treatment for grain yield. The degree of mildew control achieved by the seed treatment varied with barley variety. Use of the two successive fungicide treatments did not yield more barley than use of either alone. Amongst varieties, grain positions within the ear and fungicide treatments there was a close correlation between rate of grain growth and final grain weight. Duration of grain growth was not related to rate of grain growth or final grain weight but was inversely correlated with mean temperature during the period of rapid grain growth. The temperature sums during the period of rapid grain growth were similar for the three years and it is suggested that a more precise knowledge of the relationships between mildew incidence, varietal susceptibility and rate of grain growth may enable more accurate predictions to be made about likely yield responses to fungicide treatments.     

The relationship between leaf blotch caused by Rhynchosporium secalis and losses in grain yield of spring barley

Two methods were used to investigate the loss in grain yield associated with specific levels of leaf blotch. Yields from plots sprayed with fungicide were compared with those from unsprayed plots and yields of varieties of different susceptibility to the disease were compared with one another. A disease assessment key is presented, which was used to assess the percentage laminar area of the top two leaves affected by the disease. A linear relationship between disease on the upper two leaves and yield was established. Results from nine trials showed a consistent relationship between the disease level, at growth stage 11·1 (Feekes scale), and loss in yield. The loss in yield expressed as a percentage of the yield of an uninfected crop was equivalent to approximately two-thirds of the percentage of the flag-leaf area visibly infected, or one-half of the infected area on the second leaf. The predicted loss in yield is the average of these two estimates.     

Identification and mapping of net form of net blotch resistance in South African barley

Net form of net blotch (NFNB) caused by the fungus Pyrenophora teres f. teres is an economically important foliar disease of barley (Hordeum vulgare) in southern and eastern Africa. Little attention has been given to disease resistance breeding, and knowledge about the presence of NFNB resistance in breeding lines is limited. Deploying resistance into varieties used in this region is important for future control of the disease. We have identified NFNB disease resistance in existing South African breeders’ lines and have mapped the resistance in line UVC8. Six different trials, three conducted in South Africa and another three in Australia, were used to identify resistance QTL. A major QTL was identified on chromosome 6H having a LOD score of 40.5 and 55% of the phenotypic variance explained. Kompetitive Allele Specific PCR (KASP?) markers were designed for this QTL region. These and microsatellite markers can now be used to routinely select for NFNB resistance.     

Effects of defoliation at different growth stages and in different grain-filling environments on the growth and yield of spring barley

The yield of spring barley grown outside was little affected by the removal of all fully expanded leaves during late tillering or early stem extension but was decreased by defoliation either earlier or later. Removal of all except the top two leaves when 50% of the ears were fully emerged also had relatively little effect on yield but damage was increased if only the flag leaf was retained, especially if the leaves apart from the flag leaf were removed 10 days earlier when the first awns were visible. Defoliation treatments, including those which had little effect on barley grown outside, generally had proportionately greater effects if the plants were moved to a warm glasshouse at the start of grain filling.     

Mapping quantitative trait loci associated with barley net blotch resistance

Net blotch of barley, caused by Pyrenophora teres Drechs., is an important foliar disease worldwide. Deployment of resistant cultivars is the most economic and eco-friendly control method. This report describes mapping of quantitative trait loci (QTL) associated with net blotch resistance in a doubled-haploid (DH) barley population using diversity arrays technology (DArT) markers. One hundred and fifty DH lines from the cross CDC Dolly (susceptible)/TR251 (resistant) were screened as seedlings in controlled environments with net-form net blotch (NFNB) isolates WRS858 and WRS1607 and spot-form net blotch (SFNB) isolate WRS857. The population was also screened at the adult-plant stage for NFNB resistance in the field in 2005 and 2006. A high-density genetic linkage map of 90 DH lines was constructed using 457 DArT and 11 SSR markers. A major NFNB seedling resistance QTL, designated QRpt6, was mapped to chromosome 6H for isolates WRS858 and WRS1607. QRpt6 was associated with adult-plant resistance in the 2005 and 2006 field trials. Additional QTL for NFNB seedling resistance to the more virulent isolate WRS858 were identified on chromosomes 2H, 4H, and 5H. A seedling resistance QTL (QRpts4) for the SFNB isolate WRS857 was detected on chromosome 4H as was a significant QTL (QRpt7) on chromosome 7H. Three QTL (QRpt6, QRpts4, QRpt7) were associated with resistance to both net blotch forms and lines with one or more of these demonstrated improved resistance. Simple sequence repeat (SSR) markers tightly linked to QRpt6 and QRpts4 were identified and validated in an unrelated barley population. The major 6H QTL, QRpt6, may provide adequate NFNB field resistance in western Canada and could be routinely selected for using molecular markers in a practical breeding program.     

Effects of chemical treatments for mildew control at different times on the growth and yield of spring barley

Experiments in 1973 and 1974 tested the effects of ethirimol seed treatment and the timing of single sprays of ethirimol or tridemorph, on mildew control and the growth and yield of spring barley. These treatments were compared with selected combinations of two treatments designed to give longer protection. In 1973, combinations of seed treatment and spray, or two sprays, did not yield better than the best component treatment applied alone or the most effective single spray of tridemorph applied on 1 June. In 1974, mildew developed usually early and yields were increased by applying ethirimol to the seed plus a tridemorph spray or two tridemorph sprays. However, barley sprayed once with tridemorph on 20 May, the expected best date, yielded more than barley receiving a seed treatment of ethirimol plus a tridemorph spray applied on either 3 or 12 June. Sprays of captafol and tridemorph, applied as separate treatments, successively to the same plots on three occasions, gave the best yields in both years. Treatments most affected ear number but they did have some effect on all components of yield. In 1974 there was a significant relationship between ear number and the variance of the number of grains per ear.     

Mapping quantitative trait loci associated with spot blotch and net blotch resistance in a doubled-haploid barley population

Spot blotch and net blotch are important foliar barley (Hordeum vulgare L.) diseases in Canada and elsewhere. These diseases result in significant yield reduction and, more importantly, loss of grain quality, downgrading barley from malt to feed. Combining resistance to these diseases is a breeding priority but is a significant challenge using conventional breeding methodology. In the present investigation, an evaluation of the inheritance of resistance to spot and net blotch was conducted in a doubled-haploid barley population from the cross CDC Bold (susceptible)?×?TR251 (resistant). The population was screened at the seedling stage in the Phytotron and at the adult-plant stage in the field for several years. Chi-squared analysis indicated one- to four-gene segregation depending on disease, isolate, plant development stage, location and year. A major seedling and adult-plant resistance quantitative trait locus (QTL), designated QRpt6, was re-confirmed for net-form net blotch resistance, explaining 32?C61% of phenotypic variation in different experiments. Additional QTL for seedling and adult-plant resistance to net blotch were identified. For spot blotch resistance, a major seedling resistance QTL (QRcss1) was detected on chromosome 1H for isolate WRS1909, explaining 79% of the phenotypic variation. A highly significant QTL on 3H (QRcs3) was identified for seedling resistance to isolate WRS1908 and adult-plant resistance at Brandon, MB, Canada in 2008. The identification of QTL at only one location or from 1?year suggests spot blotch resistance is complex and highly influenced by the environment. Efforts are being made to combine spot and net blotch resistance in elite barley lines using molecular marker-assisted selection.     

Seedling and adult stage resistance to net form of net blotch (NFNB) in spring barley and stability of adult stage resistance to NFNB in Morocco

This study was conducted to identify stable resistance to net form of net blotch (NFNB) in spring barley in Moroccan environments. Seedling resistance to NFNB was evaluated by inoculating 336 barley genotypes with two NFNB isolates LDNH04Ptt-19 and TD-10 in the greenhouse. These genotypes were evaluated for adult plant resistance to NFNB under seven environments in Morocco in 2015 and 2016. The disease severity was estimated at GS 77–87 on barley leaves using a double-digit scale. To investigate stability of resistance, 149 barley genotypes were subjected to AMMI analysis. At the seedling stage, differential responses of barley genotypes to different NFNB isolates were identified, whereas genotypes had variable stability to NFNB resistance at the adult stages. Five genotypes, AM-68, AM-95, AM-250, AM-267 and AM-322, were resistant to both NFNB isolates at the seedling stage. There were significant (p < .001) effects of genotype (G) and G × E interaction on NFNB severity for barley genotypes at the adult stage. The principal components, IPCA1 and IPCA2, accounted for 48.4% and 18.7% variation for NFNB severity, respectively. The AMMI stability values (ASVs) ranged from 0.01 to 15.5, and fifty-nine barley genotypes had stable responses (ASV ≤ 0.05) across all seven environments. Specifically, two stable genotypes, AM-187 and AM-244, had lower mean NFNB severities across all environments, suggesting a quantitative resistance in these genotypes. Divergent environmental responses of NFNB severity were measured in Sidi El Ayedi 2015 and Sidi Allal Tazi 2016, suggesting that these environments may be suitable to capture resistance to diverse pathotypes. These stable genotypes are valuable resources for introgression of both qualitative resistance and quantitative resistance to NFNB in future.     

Association mapping utilizing diverse barley lines reveals net form net blotch seedling resistance/susceptibility loci

Key message

A diverse collection of barley lines was phenotyped with three North American Pyrenophora teres f. teres isolates and association analyses detected 78 significant marker-trait associations at 16 genomic loci.

Abstract

Pyrenophora teres f. teres is a necrotrophic fungal pathogen and the causal agent of the economically important foliar disease net form net blotch (NFNB) of barley. The deployment of effective and durable resistance against P. teres f. teres has been hindered by the complexity of quantitative resistance and susceptibility. Several bi-parental mapping populations have been used to identify QTL associated with NFNB disease on all seven barley chromosomes. Here, we report the first genome-wide association study (GWAS) to detect marker-trait associations for resistance or susceptibility to P. teres f. teres. Geographically diverse barley genotypes from a world barley core collection (957) were genotyped with the Illumina barley iSelect chip and phenotyped with three P. teres f. teres isolates collected in two geographical regions of the USA (15A, 6A and LDNH04Ptt19). The best of nine regression models tested were identified for each isolate and used for association analysis resulting in the identification of 78 significant marker-trait associations (MTA; ?log10p value?>3.0). The MTA identified corresponded to 16 unique genomic loci as determined by analysis of local linkage disequilibrium between markers that did not meet a correlation threshold of R ²?≥?0.1, indicating that the markers represented distinct loci. Five loci identified represent novel QTL and were designated QRptts-3HL, QRptts-4HS, QRptts-5HL.1, QRptts-5HL.2, and QRptts-7HL.1. In addition, 55 of the barley lines examined exhibited a high level of resistance to all three isolates and the SNP markers identified will provide useful genetic resources for barley breeding programs.

     

播期对春小麦生长发育及产量的影响

为了给陇中半干旱区春小麦高产栽培提供依据,2010年在甘肃定西进行了春小麦分期播种试验,并对不同播期条件下春小麦生长发育及产量形成进行了分析。结果表明:随着播期的推迟,春小麦播种-抽穗期日数减少、全生育期明显缩短;5月下旬之前,越早播种的春小麦LAI越大,5月下旬之后,播种愈晚春小麦LAI越大。早播春小麦LAI峰值靠前,晚播峰值滞后;6月下旬之前,播期早的春小麦叶绿素含量高于播期晚的,6月下旬之后播期愈早叶绿素含量下降愈快;不同播期春小麦群体生长率和净同化率在孕穗-抽穗期后差异显著,表现为3月18日播期最大,4月7日播期最小。各播期干物质累积在拔节期后表现为快速递增趋势。在拔节期前,早播处理的干物质积累速率较慢。随着播期的推迟,单株干物质最大积累速率出现时间提前,籽粒最大灌浆速率出现时间推迟,千粒重表现为先升后降;灌浆3个阶段各参数受播期影响比较显著;早播春小麦产量最高。     

Effects of a short-term p-hydroxybenzoic acid application on grain yield and yield components in different tiller categories of spring barley

The aim of these experiments was to evaluate how thresholds for phytotoxic substances obtained in seedling bioassays relate to yield losses or changes in yield components of mature barley crops after a short-term exposure to p-hydroxybenzoic acid. Under laboratory conditions a treatment with 1.81 mM p-hydroxybenzoic acid significantly reduced the radicle length of barley, whereas coleoptile elongation was less sensitive. The inhibition of the radicle length and coleoptile elongation was greater if the pH of the test solution was not buffered at pH 5.5. In a glasshouse trial the effect of p-hydroxybenzoic acid on the radicle and coleoptile elongation of spring barley was compared with the yield response after a three day exposure either during germination or at the double ridge stage of apex development. Applications of 0.72 mM, 1.44 mM and 3.62 mM p-hydroxybenzoic acid averaged over the treatments during germination or at the double ridge stage of development caused a yield reduction in the single ear weight of 5%, 13% and 19% in comparison with the control, respectively. The higher tiller categories in general showed a greater sensitivity towards an application of p-hydroxybenzoic acid and, therefore, could not compensate for the yield decrease of the main stem tiller. A single application of p-hydroxybenzoic acid either at germination or at the double ridge stage may cause yield losses, as reported from no-till systems or cereal monocultures. The data have implications for the interpretation of seedlings bioassays in allelopathic research and their applicability in estimating yield losses caused by phytotoxic substances. ei]Section editor: R Merckx     

Linkage disequilibrium mapping of yield and yield stability in modern spring barley cultivars

Associations between markers and complex quantitative traits were investigated in a collection of 146 modern two-row spring barley cultivars, representing the current commercial germ plasm in Europe. Using 236 AFLP markers, associations between markers were found for markers as far apart as 10 cM. Subsequently, for the 146 cultivars the complex traits mean yield, adaptability (Finlay-Wilkinson slope), and stability (deviations from regression) were estimated from the analysis of variety trial data. Regression of those traits on individual marker data disclosed marker-trait associations for mean yield and yield stability. Support for identified associations was obtained from association profiles, i.e., from plots of P-values against chromosome positions. In addition, many of the associated markers were located in regions where earlier QTL were found for yield and yield components. To study the oligogenic genetic base of the traits in more detail, multiple linear regression of the traits on markers was carried out, using stepwise selection. By this procedure, 18-20 markers that accounted for 40-58% of the variation were selected. Our results indicate that association mapping approaches can be a viable alternative to classical QTL approaches based on crosses between inbred lines, especially for complex traits with costly measurements.