Ryegrass Populations Research Articles

Snow mould resistance under controlled conditions and winter survival in the field in populations of perennial ryegrass, meadow fescue, andFestuloliumare partly dependent on ploidy level and degree of northern adaptation

Pink snow mould caused by Microdochium nivale is a serious cereal and grass disease in several temperate regions. In this study, resistance to snow mould was evaluated under controlled conditions i...

Markers associated with heading and aftermath heading in perennial ryegrass full-sib families

BackgroundHeading and aftermath heading are important traits in perennial ryegrass because they impact forage quality. So far, genome-wide association analyses in this major forage species have only identified a small number of genetic variants associated with heading date that overall explained little of the variation. Some possible reasons include rare alleles with large phenotypic affects, allelic heterogeneity, or insufficient marker density. We established a genome-wide association panel with multiple genotypes from multiple full-sib families. This ensured alleles were present at the frequency needed to have sufficient statistical power to identify associations. We genotyped the panel via partial genome sequencing and performed genome-wide association analyses with multi-year phenotype data collected for heading date, and aftermath heading.ResultsGenome wide association using a mixed linear model failed to identify any variants significantly associated with heading date or aftermath heading. Our failure to identify associations for these traits is likely due to the extremely low linkage disequilibrium we observed in this population. However, using single marker analysis within each full-sib family we could identify markers and genomic regions associated with heading and aftermath heading. Using the ryegrass genome we identified putative orthologs of key heading genes, some of which were located in regions of marker-trait associations.ConclusionGiven the very low levels of LD, genome wide association studies in perennial ryegrass populations are going to require very high SNP densities. Single marker analysis within full-sibs enabled us to identify significant marker-trait associations. One of these markers anchored proximal to a putative ortholog of TFL1, homologues of which have been shown to play a key role in continuous heading of some members of the rose family, Rosaceae.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0844-y) contains supplementary material, which is available to authorized users.

Competitive Ability of Lettuce with Ryegrass1

ABSTRACT The objective of the study was to evaluate the competitive ability of summer crisp and butterhead lettuce types in coexistence with populations of ryegrass. The experimental design was completely randomized in a factorial 2 x 7 scheme, with four replications. On the A factor the lettuce types (summer crisp and butterhead) were allocated and, on B, the densities of ryegrass (0, 2, 4, 8, 16, 32 and 64 plants per pot). The number of leaves, chlorophyll content, leaf area, green mass and dry mass of the lettuce types and ryegrass were evaluated, and the diameter of the culture stem and the tiller number of the weed were determined. Differences in competitive ability between the lettuce types in competition with ryegrass were found, and butterhead was the most competitive when compared with summer crisp for all variables studied. There was an average loss of leaf area in lettuce types of up to 80% when it competed with ryegrass in the populations involved. Ryegrass is a very competitive weed to infect lettuce, and its handling is necessary, even at low densities to avoid productivity losses. The butterhead type of lettuce supports longer competition with ryegrass compared to summer crisp.

Influence of Management on Long-Term Seedbank Dynamics of Rigid Ryegrass (Lolium rigidum) in Cropping Systems of Southern Australia

A field study was undertaken to investigate the influence of different management strategies on rigid ryegrass plant density and seedbank dynamics over 4 yr. Even though weed seedbank declined by 86% after oaten hay in year 1, the residual seedbank enabled rigid ryegrass to reinfest field peas the next year, and the population rebounded sharply when weed control relied solely on PPI trifluralin. However, use of POST clethodim followed by crop-topping for seed-set prevention of rigid ryegrass in field pea was highly effective and caused a further decline in the weed seedbank. Integration of effective management tactics over 3 yr significantly reduced rigid ryegrass weed and spike density (90 and 81%) in the final year of the 4-yr cropping sequence. Use of oaten hay in year 1, followed by effective weed control in field pea and wheat crops, depleted the high initial seedbank (4,820 seeds m−2) to moderate levels (< 200 seeds m−2) within 3 yr. Effective weed-management treatments depleted the rigid ryegrass seedbank, reduced in-crop weed infestation, and returned higher grain yields and profitability. The results of this study clearly show that large rigid ryegrass populations can be managed effectively without reducing crop productivity and profitability provided multiyear weed-management programs are implemented effectively.

Characterization of Multiple Herbicide-Resistant Italian Ryegrass (Lolium perennessp.multiflorum) Populations from Winter Wheat Fields in Oregon

Many Italian ryegrass populations in Oregon are resistant to more than one herbicide; therefore, the resistance patterns of these populations must be determined to identify alternative herbicides for management. Two suspected resistant Italian ryegrass populations (R2 and R4) survived flufenacet plus metribuzin applications under typical winter wheat production conditions. Populations R2 and R4 were resistant to clethodim, pinoxaden, quizalofop, mesosulfuron-methyl, flufenacet, but not to acetochlor, dimethenamid-p, metolachlor, pyroxasulfone, imazapyr, sulfometuron, or glyphosate. R4 was resistant to diuron, but R2 was not. The estimated flufenacet doses required for 50% growth reduction (GR50) were 438 g ai ha−1(R2) and 308 g ai ha−1(R4). Both populations were controlled by pyroxasulfone at rates greater than 15 g ai ha−1. An Asp-2078-Gly substitution in the ACCase gene was found in both populations, while an Ile-2041-Asn was found only in the R4 population. A Ser-264-Gly substitution inpsbA gene was found in the R4 population. These mutations previously have been reported to provide resistance to ACCase and photosynthetic inhibitors, respectively. No resistance mutations were identified in the acetolactate synthase (ALS) gene of either population. The addition of the P450 inhibitor, chlorpyrifos, increased the injury resulting from mesosulfuron-methyl on both resistant populations providing indirect evidence that the ALS resistance may be metabolic. Multiple herbicide-resistant Italian ryegrass populations were identified in this study with both target site and nontarget site based mechanisms likely involved. However, several herbicides were identified including pyroxasulfone, a herbicide in the same group as flufenacet, which could be used to control these two populations.

Salt and water stress of ACCase herbicides resistant and susceptible populations of rigid ryegrass (Lolium rigidum)

Salt and water stress of ACCase herbicides resistant and susceptible populations of rigid ryegrass (Lolium rigidum)

Crop rotation and tillage system effects on reducing ryegrass occurrence in spring wheat

Under the Mediterranean climatic conditions of the Western Cape province, the Swartland region is intensively cropped, producing spring wheat (Triticum aestivum L.), but due to ryegrass competition, yield is reduced. In addition, ryegrass has developed resistance to herbicides. This necessitates the use of integrated weed management practices for suppressing ryegrass in wheat fields. The objectives were to quantify and qualify the impact of crop rotation and tillage systems used in combination with reduced herbicide input and to determine whether these could reduce ryegrass population numbers. Analyses of variance of data were used to determine crop rotation×tillage system response in field and shade-netting experiments. Wheat monoculture, in both tillage systems, was associated with the highest ryegrass population increase in both years. The results of both the field and shade-netting experiments showed that there was no significant difference between minimum-tillage and no-tillage in reducing ryegrass numbers. Results obtained from the shade-netting experiment indicated that the three crop-rotation treatments under minimum-tillage differed significantly from the control. In the field wheat–medic–wheat–medic rotations under no-tillage out-performed all other rotations, followed by wheat–lupin–wheat–canola under minimum-tillage. It is essential to use competitive crop sequences that decrease particular weed population numbers.

Windrow Burning Eliminates Italian Ryegrass (Lolium perenne ssp. multiflorum) Seed Viability

Windrow burning is one of several harvest weed seed control strategies that have been developed and evaluated in Australia to address the widespread evolution of multiple herbicide resistance in annual weeds. Herbicide-resistant Italian ryegrass populations are common in the Palouse region of eastern Washington and northern Idaho. Field and greenhouse studies were conducted to evaluate the effects of burning standing stubble and narrow windrows on the survival of Italian ryegrass seed on the soil surface and to determine the amount of crop residue remaining after both practices. Italian ryegrass emergence was 63, 48, and 1% for the nonburned check, burned standing stubble, and burned windrow treatments, respectively. Crop-residue dry weights were 9.94, 5.69, and 5.79 Mg ha−1 for these same treatments. Windrow burning can be an effective tactic in an integrated weed management strategy for Italian ryegrass control in the Palouse region of eastern Washington and northern Idaho.

Comportamento agronômico de azevém anual (lolium multiflorum lam.) no estado do Rio Grande do Sul

Os objetivos deste trabalho foram avaliar a produção de forragem e o número de dias até o florescimento em 15 populações de azevém da cultivar Comum, uma população das cultivares KLM 138 (Uruguai) e Fepagro São Gabriel e uma população local, visando à seleção de germoplasma com potencial produtivo. O delineamento experimental adotado foi o de blocos ao acaso com três repetições e medidas repetidas no tempo (cortes). A produção de forragem foi avaliada por meio de cortes de uma amostra de 2 m lineares por parcela. As amostras de forragem de cada parcela foram secas e pesadas para a determinação da matéria seca total. Uma subamostra de matéria seca total de cada parcela, em cada corte, foi utilizada para estimar a porcentagem de folhas. Os dados foram submetidos à análise de variância através de modelos mistos e as médias comparadas pelo Teste de Tukey (P<0,05). Uma quarta repetição (bloco) com todas as populações não recebeu cortes, tendo sido utilizada para estimar o número de dias até o florescimento. Considerou-se florida quando mais de 50% das plantas das parcelas apresentavam inflorescências. Com exceção do primeiro corte, em todos os demais a produção de matéria seca total não teve variação (P>0,05), refletindo a existência de pouca variabilidade para esse caráter nas populações avaliadas durante o ciclo de crescimento. As populações avaliadas diferiram de forma significativa em relação à porcentagem de matéria seca de folhas (P=0,0002). A cultivar KLM 138 apresentou as maiores porcentagens de folhas durante o ciclo de crescimento, todavia as populações da cultivar Comum Uruguaiana, Dom Pedrito e Vacaria também apresentaram boa produção de folhas e poderiam ser utilizadas para a seleção inicial de novos materiais promissores, em razão da maior participação de folhas promover maior qualidade da dieta ofertada aos animais. A variação no número de dias até o florescimento possibilita a seleção para diferentes ciclos de maturação do azevém comum.

Target Enzyme-Based Resistance to Clethodim inLolium rigidumPopulations in Australia

Clethodim resistance was identified in 12 rigid ryegrass populations from winter cropping regions in four different states of Australia. Clethodim had failed to provide effective control of these populations in the field and resistance was suspected. Dose–response experiments confirmed resistance to clethodim and butroxydim in all populations. During 2012, the LD50of resistant populations ranged from 10.2 to 89.3 g ha−1, making them 3 to 34–fold more resistant to clethodim than the susceptible population. Similarly, GR50of resistant population varied from 8 to 37.1 g ha−1, which is 3 to 13.9–fold higher than the susceptible population. In 2013, clethodim-resistant populations were 7.8 to 35.3–fold more resistant to clethodim than the susceptible population. The higher resistance factor in 2013, especially in moderately resistant populations, could have been associated with lower ambient temperatures during the winter of 2013. These resistant populations had also evolved cross-resistance to butroxydim. The resistant populations required 1.3 to 6.6–fold higher butroxydim dose to achieve 50% mortality and 3 to 27–fold more butroxydim for 50% biomass reduction compared to the standard susceptible population. Sequencing of the target-site ACCase gene identified five known ACCase substitutions (isoleucine-1781-leucine, isoleucine-2041-asparagine, aspartate-2078-glycine, and cysteine-2088-arginine, and glycine-2096-alanine) in these populations. In nine populations, multiple ACCase mutations were present in different individuals. Furthermore, two alleles with different mutations were present in a single plant of rigid ryegrass in two populations.

Population Structure, Genetic Variation, and Linkage Disequilibrium in Perennial Ryegrass Populations Divergently Selected for Freezing Tolerance.

Low temperature is one of the abiotic stresses seriously affecting the growth of perennial ryegrass (Lolium perenne L.), and freezing tolerance is a complex trait of major agronomical importance in northern and central Europe. Understanding the genetic control of freezing tolerance would aid in the development of cultivars of perennial ryegrass with improved adaptation to frost. The plant material investigated in this study was an experimental synthetic population derived from pair-crosses among five European perennial ryegrass genotypes, representing adaptations to a range of climatic conditions across Europe. A total number of 80 individuals (24 of High frost [HF]; 29 of Low frost [LF], and 27 of Unselected [US]) from the second generation of the two divergently selected populations and an unselected (US) control population were genotyped using 278 genome-wide SNPs derived from perennial ryegrass transcriptome sequences. Our studies investigated the genetic diversity among the three experimental populations by analysis of molecular variance and population structure, and determined that the HF and LF populations are very divergent after selection for freezing tolerance, whereas the HF and US populations are more similar. Linkage disequilibrium (LD) decay varied across the seven chromosomes and the conspicuous pattern of LD between the HF and LF population confirmed their divergence in freezing tolerance. Furthermore, two Fst outlier methods; finite island model (fdist) by LOSITAN and hierarchical structure model using ARLEQUIN, both detected six loci under directional selection. These outlier loci are most probably linked to genes involved in freezing tolerance, cold adaptation, and abiotic stress. These six candidate loci under directional selection for freezing tolerance might be potential marker resources for breeding perennial ryegrass cultivars with improved freezing tolerance.

Fructan synthesis, accumulation and polymer traits. II. Fructan pools in populations of perennial ryegrass (Lolium perenne L.) with variation for water-soluble carbohydrate and candidate genes were not correlated with biosynthetic activity and demonstrated constraints to polymer chain extension.

Differences have been shown between ryegrass and fescue within the Festulolium subline introgression family for fructan synthesis, metabolism, and polymer-size traits. It is well-established that there is considerable variation for water-soluble carbohydrate and fructan content within perennial ryegrass. However there is much still to be discovered about the fructan polymer pool in this species, especially in regard to its composition and regulation. It is postulated that similar considerable variation for polymer traits may exist, providing useful polymers for biorefining applications. Seasonal effects on fructan content together with fructan synthesis and polymer-size traits have been examined in diverse perennial ryegrass material comprising contrasting plants from a perennial ryegrass F2 mapping family and from populations produced by three rounds of phenotypic selection. Relationships with copy number variation in candidate genes have been investigated. There was little evidence of any variation in fructan metabolism across this diverse germplasm under these conditions that resulted in substantial differences in the complement of fructan polymers present in leaf tissue at high water-soluble carbohydrate concentrations. The importance of fructan synthesis during fructan accumulation was unclear as fructan content and polymer characteristics in intact plants during the growing season did not reflect the capacity for de novo synthesis. However, the retention of fructan in environmental conditions favoring high sink/low source demand may be an important component of the high sugar trait and the roles of breakdown and turnover are discussed.

Multiple Resistance to Acetyl Coenzyme A Carboxylase and Acetolactate Synthase Inhibiting Herbicides in Tunisian Ryegrass Populations (Lolium rigidum)

Multiple Resistance to Acetyl Coenzyme A Carboxylase and Acetolactate Synthase Inhibiting Herbicides in Tunisian Ryegrass Populations (Lolium rigidum)

A survey of Lolium rigidum populations in citrus orchards: Factors explaining infestation levels

The presence of herbicide‐resistant Lolium rigidum in Mediterranean (Spanish) citrus orchards was reported in 2005 and it poses a serious threat to crop management. The main objective of this research was to investigate which components could be responsible for the persistence of annual ryegrass populations in Mediterranean mandarin and orange orchards. This is the first study regarding L. rigidum populations in Mediterranean citrus orchards. Surveys were conducted in 55 commercial citrus orchards in eastern Spain in 2013 by interviewing technicians who were working in cooperatives about crop management. The level of infestation by L. rigidum and the presence of harvester ants (Messor barbarus) then were estimated in the same orchards. The variables were subjected to a two‐dimensional analysis and both univariate and multivariate logistic regression models were fitted for each of the three L. rigidum density levels that had been established. The multivariate models showed the significant factors that were associated with various L. rigidum densities: (i) at a low density, the herbicides that were applied, the number of applications in 2013 and the type of irrigation (flood or drip); (ii) at a medium density, the presence of harvester ants; and (iii) at a high density, the herbicides that were applied in 2013. The results indicated that drip irrigation and one application of glyphosate mixed with other herbicides (or herbicides other than glyphosate) were associated with a lower L. rigidum density. The alternative management options that are presented here should help farmers to reduce weed problems in Mediterranean citrus orchards. Future research is required to better understand the presence of herbicide‐resistant populations, as well as the possible beneficial presence of granivorous ant species.

Variability of Seed Components of Selected Populations of English Ryegrass

The examination was performed at research field and laboratories of Agricultural Institute of Republic of Srpska-Banjaluka in the period 2006 - 2008. The goal of this paper was to examine the components of seed yield offsprings of autochthonous populations of English ryegrass, and based on these results, to single out the materials that would later be used in a program of creation of domestic varieties. During the examination, the following properties were analyzed: seed yield (kg ha-1), mass of 1000 seeds (g), size of seed (seed/g) and hectoliter mass (kg). During a biennial examination, significant differences were determined between populations of English ryegrass in a seed yield. The examined populations of English ryegrass achieved a high average seed yield (903.9 kg ha-1). The largest biennial average seed yield was achieved with populationSarajevo. The seed quality of the examined populations was good, while the average mass of 1000 seed amounted to 2.1 g. During these examinations, the smallest seed was inSarajevo population, while the largest one was in Banjaluka population. The average hectoliter seed mass of seven examined popu­lations of English ryegrass amounted to 25.8 kg.

Uso de clomazone associado ao safener dietholate para o manejo de plantas daninhas na cultura do trigo

O uso intensivo e repetido do método químico de controle na cultura do trigo selecionou populações de nabo (Raphanus raphanistrum e R. sativus) e azevém (Lolium multiflorum) resistentes a alguns herbicidas, em especial aos inibidores das enzimas ALS, ACCase e EPSPs. Para manejar as populações de plantas daninhas resistentes, é importante rotacionar os mecanismos de ação de herbicidas, tanto na dessecação como nas aplicações realizadas após a implantação da cultura. Assim, objetivou-se com este trabalho avaliar a eficácia do herbicida clomazone no controle de azevém e nabo, associado ou não ao protetor dietholate, na cultura do trigo. Os experimentos foram conduzidos em delineamento inteiramente casualizado (DIC) com quatro repetições. No ensaio 1 foram testadas doses de dietholate (0, 120, 240, 360 e 480 g para 100 kg de sementes de trigo cultivar TBIO Itaipu) e de clomazone (0, 198, 396 e 594 g ha-1) aplicado em pré-emergência. No ensaio 2, instalado de modo simultâneo ao ensaio 1, os tratamentos foram constituídos pela testemunha infestada, testemunha capinada, clomazone + dietholate (396 g ha-1 + 240 g para 100 kg de semente) – aplicado em pré-emergência, iodosulfuron-methyl (5 g ha-1) e pyroxsulam (18 g ha-1) – aplicados em pós-emergência. O tratamento das sementes de trigo com dietholate não interferiu no controle de azevém e nabo pelo clomazone aplicado em pré-emergência. O clomazone, mesmo aplicado em baixas doses, apresentou controle de azevém acima de 80%, podendo ser utilizado para o controle de biótipos resistentes aos herbicidas inibidores da EPSPs, ALS e ACCase. O iodosulfuron-methyl e o pyroxsulam apresentaram excelente controle de nabo e satisfatório de azevém.

Endophyte-mediated disease resistance in wild populations of perennial ryegrass (Lolium perenne)

Abstract Twelve wild, endophyte-infected populations of perennial ryegrass were tested for resistance against artificial infection of Drechslera siccans and Fusarium spp. Plants with identified endophyte presence (E+), together with plants free from endophytes (E−), were inoculated with serious turf grass pathogens: D. siccans (cause of brown blight) and a mixture of Fusarium species (cause of Fusarium blight). For both diseases, the positive effect of endophyte presence on plant resistance was observed. In the case of a few ecotypes, endophyte infection increased resistance against both diseases, which is of practical importance for disease control.

Mechanisms of glyphosate resistance in two perennial ryegrass (Lolium perenne) populations.

Perennial ryegrass (Lolium perenne) has developed resistance to glyphosate within New Zealand vineyards following many years of herbicide application. The objectives of this work were to confirm resistance within two populations obtained from affected vineyards, and to determine the mechanism of resistance to glyphosate. Population O was confirmed to have a 25-fold resistance to glyphosate, whereas population J had a sevenfold resistance. Results of genotyping assays demonstrated a single nucleotide substitution at codon 106 of 5-enolpyruvylshikimate-3-phosphate synthase in population O but not population J. Glyphosate-resistant and glyphosate-susceptible populations did not differ in glyphosate absorption. However, in both resistant populations, much more of the absorbed (14) C-glyphosate remained in the treated leaf than occurred in the susceptible population. Significantly more glyphosate was found in the pseudostem region of susceptible plants compared with resistant plants. Both target-site and non-target-site mechanisms of glyphosate resistance were found in the perennial ryegrass population with 25-fold resistance, whereas only the non-target-site mechanism of resistance was found in the population with sevenfold resistance. This is the first study of the mechanism of glyphosate resistance in perennial ryegrass.

Identification of glyphosate-resistant Lolium rigidum and Raphanus raphanistrum populations within the first Western Australian plantings of transgenic glyphosate-resistant canola

Transgenic glyphosate-resistant canola was first commercially grown in Western Australia (WA) in 2010, providing an opportunity to obtain important baseline data regarding the level of glyphosate resistance in weeds following the exclusive use of glyphosate for in-crop weed control. In this study, two surveys (2010 and 2011) were conducted across the 14 Mha of the grainbelt of WA. The 2010 survey was carried out at the late-flowering stage of glyphosate-resistant canola, whereas the 2011 survey was conducted at an earlier growth stage (6–8 leaves), ~2–3 weeks after the second in-crop glyphosate application. During the surveys, 239 fields were visited, representing an estimated combined area of 24 000 ha. The 2011 survey alone represented a subsample of 23% of the total glyphosate-resistant canola planting in the WA grainbelt for that season. Glyphosate resistance was identified in one population of wild radish (Raphanus raphanistrum L.) and in eight annual ryegrass (Lolium rigidum L.) populations. None of the tested capeweed (Arctotheca calendula (L.) Levyns) populations were glyphosate-resistant. In this survey, no populations of barley grass (Hordeum spp.), brome grass (Bromus spp.), wild oat (Avena spp.) or small-flowered mallow (Malva parviflora L.) survived glyphosate application. Despite a long history of pre-seeding and fallow glyphosate use in WA, this survey found that glyphosate still provides excellent in-crop control of most species; however, some resistance is evident, requiring diverse weed control techniques to limit their spread.

Persistence of dry matter yield among New Zealand perennial ryegrass (Lolium perenne L.) cultivars: insights from a long-term data set

Persistence of herbage yield is an important productivity trait of grass species and cultivars in New Zealand pastures. However, relatively little is known about genetic variation in this trait, principally because few studies comparing yield have continued beyond 3 years. This paper reports results from a comparison of 25 perennial ryegrass cultivars representing a wide range of functional types and genetic backgrounds conducted under sheep grazing in a summer-dry environment. Dry matter (DM) yield was measured for the first 3 years after sowing, then again in years seven and eight post-sowing, and in year ten post-sowing. Endophyte DNA fingerprinting conducted mid-way through year seven confirmed that, with one exception, ryegrass populations remained true-to-type in the cultivars sown with novel endophyte strains. The cultivar effect on DM yield was statistically significant in all measurement periods. Differences in yields among cultivars in years seven and eight were significantly and positively correlated with yield differences in years one to three (r=0.685 to 0.831 depending on which year contrasts were used). Thus, high-performing cultivars in the early years of the trial were also generally highperforming cultivars in years seven and eight, and vice-versa, indicating a high degree of yield stability in perennial ryegrass cultivars. Yield differences did not appear to be related to differences in cultivar heading date, ploidy, endophyte status, or genetic background. The relationship between yield in year ten and yields in years one to three was much weaker (r=0.392) than the relationship in years seven and eight. Possible reasons for this are discussed. Keywords: Perennial ryegrass; traits; persistence