An Herbicide-Susceptible Rigid Ryegrass (Lolium rigidum) Population Made Even More Susceptible

Weed Science ◽  
2012 ◽  
Vol 60 (1) ◽  
pp. 101-105 ◽  
Author(s):  
Sudheesh Manalil ◽  
Roberto Busi ◽  
Michael Renton ◽  
Stephen B. Powles
Keyword(s):  
Genetic Variation ◽  
Phenotypic Variation ◽  
Recurrent Selection ◽  
Wild Population ◽  
Rapid Evolution ◽  
Differential Susceptibility ◽  
Variable Cross ◽  
Lolium Rigidum ◽  
Rigid Ryegrass ◽  
Low Rate

A wild population of a plant species, especially a cross-pollinated species, can display considerable genetic variation. Genetic variability is evident in differential susceptibility to an herbicide because the population can show continuous phenotypic variation. Recent, recurrent selection studies have revealed that phenotypic variation in response to low herbicide rates is heritable and can result in rapid evolution of herbicide resistance in genetically variable cross-pollinated rigid ryegrass. In this study, the heritable genetic variation in an herbicide-susceptible rigid ryegrass population was exploited to shift the population toward greater herbicide susceptibility by recurrent selection. To enhance herbicide susceptibility, herbicide-susceptible rigid ryegrass plants were divided into two identical clones, and one series of cloned plants was treated with a low rate of herbicide (diclofop). The nontreated clones of individuals that did not survive the herbicide treatment were selected and bulk-crossed to obtain the susceptible progeny. After two cycles of selection, the overall susceptibility to diclofop was doubled. The results indicate that minor genes for resistance are present in an herbicide-susceptible rigid ryegrass population, and their exclusion can increase susceptibility to diclofop.

scholarly journals Inheritance of glyphosate resistance in rigid ryegrass (Lolium rigidum) from California

Weed Science ◽  
2005 ◽  
Vol 53 (5) ◽  
pp. 615-619 ◽  
Author(s):  
Marulak Simarmata ◽  
Suleiman Bughrara ◽  
Donald Penner
Keyword(s):  
First Generation ◽  
Recurrent Selection ◽  
Maternal Inheritance ◽  
Glyphosate Resistance ◽  
Segregation Ratio ◽  
Lolium Rigidum ◽  
Response Curves ◽  
Mendelian Segregation ◽  
Rigid Ryegrass ◽  
Homozygous Resistant

Glyphosate resistance was found in a rigid ryegrass population in northern California. A sample of the resistant plants were collected and grown under greenhouse conditions. The objective of this study was to evaluate glyphosate resistance in the progeny of the collected plants by recurrent selection, obtain the homozygous resistant and sensitive lines to establish dose-response curves, and to determine the inheritance of glyphosate resistance in rigid ryegrass. Diverse levels of resistance were observed in the first generation with survival of 89, 59, 45, and 9% from glyphosate at 1x, 2x, 4x, and 8x respectively, where x = 1.12 kg ha−1isopropylamine salt of glyphosate. Clones of plants that died from 1x were allowed to produce seed and were further subjected to recurrent selection to generate the most sensitive plants (S lines), which died from 0.125x glyphosate. The most resistant plants (R lines) were generated from the survivors receiving 8x glyphosate. The ratio between I50rates for the glyphosate resistant and the glyphosate sensitive plants was > 100-fold. The R and S lines were crossed reciprocally and F1progeny of both (R × S) and (S × R) showed intermediate resistance. These survived up to 2x glyphosate. The F2progeny were generated by intercrossing of F1plants. The ratio of sensitive, intermediate, and resistant plants in the F2population before the treatment of glyphosate at 0.125x followed by 8x was 1 : 16, 14 : 16, and 1 : 16 respectively, which corresponded to the Mendelian segregation ratio of two genes. The results indicated that the inheritance of glyphosate resistance in rigid ryegrass from California appeared to be nuclear, incompletely dominant, multigenic, and pollen-transmitted with no indication of maternal inheritance.

Resistance to bixlozone and clomazone in cross-resistant rigid ryegrass (Lolium rigidum) populations from southern Australia

Weed Science ◽  
2021 ◽  
pp. 1-6
Author(s):  
David J. Brunton ◽  
Gurjeet Gill ◽  
Christopher Preston
Keyword(s):  
Recurrent Selection ◽  
Selection Process ◽  
Resistance Mechanism ◽  
Fold Increase ◽  
Elevated Risk ◽  
Cross Resistance ◽  
Lolium Rigidum ◽  
Rigid Ryegrass

Abstract Three resistant (R) rigid ryegrass (Lolium rigidum Gaudin) populations from southern Australia (EP162, 375-14, and 198-15) with cross-resistance to thiocarbamate, chloroacetamide, and sulfonylisoxazoline herbicides displayed reduced sensitivity to the isoxazolidinone herbicides bixlozone and clomazone. Each of these R populations was exposed to two cycles of recurrent selection (RS) in which plants were treated with the field rate of bixlozone, survivors were bulk crossed, and seed was collected. After the first cycle of recurrent selection (RS1), the LD50 to bixlozone in population 198-15 increased to 17.5-fold compared with the S population and increased further to 26.9-fold after a second cycle of recurrent selection (RS2). The recurrent selection process also increased the level of resistance to bixlozone in populations EP162 and 375-14 (7.8- to 18.4-fold) compared with the S population. Phorate antagonized bixlozone and clomazone in SLR4 (34.6- and 28.1-fold increase in LD50) and both herbicides in populations EP162 (36.5- to 46.6-fold), 375-14 (71.4- to 73.9-fold), and 198-15 (86.4- to 91.5-fold) compared with the absence of phorate. The increase in LD50 of all L. rigidum RS populations when treated with phorate suggests a lack of herbicide activation is not the likely resistance mechanism to these herbicides. This research highlights the elevated risk of thiocarbamate-resistant L. rigidum populations to rapidly evolve resistance to the isoxazolidinone herbicides bixlozone and clomazone.

Inheritance of evolved thiocarbamate resistance in Rigid Ryegrass (Lolium rigidum) populations from Australia

Weed Science ◽  
2021 ◽  
pp. 1-19
Author(s):  
David J. Brunton ◽  
Peter Boutsalis ◽  
Gurjeet Gill ◽  
Christopher Preston
Keyword(s):  
Recessive Allele ◽  
Recessive Trait ◽  
Dominant Allele ◽  
Lolium Rigidum ◽  
Dominant Trait ◽  
Susceptible Parent ◽  
Rigid Ryegrass

Abstract Populations of rigid ryegrass (Lolium rigidum Gaudin) from southern Australia have evolved resistance to the thiocarbamate herbicide prosulfocarb. The inheritance of prosulfocarb resistance was explored by crossing R and S individuals. In all families within each cross, except 16.2, the response of the F1 were intermediate between the parents, suggesting that resistance is inherited as a single, partially dominant trait. For 16.2, the response of the F1 was more similar to the susceptible parent, suggesting resistance may be a recessive trait in this population. Segregation at the discriminating dose of 1200 g a.i. ha−1 prosulfocarb in populations 375-14 fitted the ratio (15:1) consistent with two independent dominant alleles; 198-15 fitted a ratio (13:3) for two independent alleles, one dominant and one recessive; and EP162 fitted a ratio (9:7) for two additive dominant alleles. In contrast segregation of population 16.2 fitted a (7:9) ratio consistent with two independent recessive alleles contributing to prosulfocarb resistance. Four different patterns of resistance to prosulfocarb were identified in different resistant populations, with inheritance as a dominant allele, dominant and recessive, additive dominant and as an independent recessive allele. This suggests there are several different mechanisms of prosulfocarb resistance present in L. rigidum.

scholarly journals Recurrent Selection with Glufosinate at Low Rates Reduces the Susceptibility of a Lolium perenne ssp. multiflorum Population to Glufosinate

Agronomy ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1288 ◽  
Author(s):  
Maor Matzrafi ◽  
Sarah Morran ◽  
Marie Jasieniuk
Keyword(s):  
Lolium Perenne ◽  
Recurrent Selection ◽  
Cross Resistance ◽  
Susceptible Population ◽  
Selection Cycle ◽  
Herbicide Resistant ◽  
Repeated Applications ◽  
Resistance To Herbicides ◽  
Rate Selection ◽  
Low Rate

Repeated applications of herbicides at the labelled rates have often resulted in the selection and evolution of herbicide-resistant weeds capable of surviving the labelled and higher rates in subsequent generations. However, the evolutionary outcomes of recurrent herbicide selection at low rates are far less understood. In this study of a herbicide-susceptible population of Lolium perenne ssp. multiflorum, we assessed the potential for low glufosinate rates to select for reduced susceptibility to the herbicide, and cross-resistance to herbicides with other modes of action. Reduced susceptibility to glufosinate was detected in progeny in comparison with the parental population following three rounds of selection at low glufosinate rates. Differences were mainly observed at the 0.5X, 0.75X, and 1X rates. Comparing the parental susceptible population and progeny from the second and third selection cycle, the percentage of surviving plants increased to values of LD50 (1.31 and 1.16, respectively) and LD90 (1.36 and 1.26, respectively). When treated with three alternative herbicides (glyphosate, paraquat, and sethoxydim), no plants of either the parental or successive progeny populations survived treatment with 0.75X or higher rates of these herbicides. The results of this study provide clear evidence that reduced susceptibility to glufosinate can evolve in weed populations following repeated applications of glufosinate at low herbicide rates. However, the magnitude of increases in resistance levels over three generations of recurrent low-rate glufosinate selection observed is relatively low compared with higher levels of resistance observed in response to low-rate selection with other herbicides (three fold and more).

scholarly journals Recurrent selection with glufosinate at low rates reduces the susceptibility of a Lolium perenne ssp. multiflorum population to glufosinate

2020 ◽  
Author(s):  
Maor Matzrafi ◽  
Sarah Morran ◽  
Marie Jasieniuk
Keyword(s):  
Lolium Perenne ◽  
Recurrent Selection ◽  
Cross Resistance ◽  
Susceptible Population ◽  
Selection Cycle ◽  
Herbicide Resistant ◽  
Repeated Applications ◽  
Resistance To Herbicides ◽  
Rate Selection ◽  
Low Rate

ABSTRACTRepeated applications of herbicides at the labelled rates have often resulted in the selection and evolution of herbicide-resistant weeds capable of surviving the labelled and higher rates in subsequent generations. However, the evolutionary outcomes of recurrent herbicide selection at low rates are far less understood. In this study of an herbicide-susceptible population of Lolium perenne ssp. multiflorum, we assessed the potential for low glufosinate rates to select for reduced susceptibility to the herbicide, and cross-resistance to herbicides with other modes of action. Reduced susceptibility to glufosinate was detected in progeny in comparison with the parental population following three rounds of selection at low glufosinate rates. Differences were mainly observed at the 0.5X, 0.75X, and 1X rates. Comparing the parental susceptible population and progeny from the second and third selection cycle, the percentage of surviving plants increased to values of LD50 (1.31 and 1.16, respectively) and LD90 (1.36 and 1.26, respectively). When treated with three alternative herbicides (glyphosate, paraquat, and sethoxydim), no plants of either the parental or successive progeny populations survived treatment with 0.75X or higher rates of these herbicides. The results of this study provide clear evidence that reduced susceptibility to glufosinate can evolve in weed populations following repeated applications of glufosinate at low herbicide rates. However, the magnitude of increases in resistance levels over three generations of recurrent low-rate glufosinate selection observed is relatively low compared with higher levels of resistance observed in response to low-rate selection with other herbicides (three fold and more).

scholarly journals Evaluating indirect genetic effects of siblings using singletons

2021 ◽  
Author(s):  
Laurence Howe ◽  
David Evans ◽  
Gibran Hemani ◽  
George Davey Smith ◽  
Neil Martin Davies
Keyword(s):  
Genetic Variation ◽  
Educational Attainment ◽  
Family Environment ◽  
Phenotypic Variation ◽  
Molecular Genetic ◽  
Genetic Effects ◽  
Polygenic Risk Score ◽  
Indirect Genetic Effects ◽  
Molecular Genetic Evidence ◽  
Older Siblings

Estimating effects of parental and sibling genotypes (indirect genetic effects) can provide insight into how the family environment influences phenotypic variation. There is growing molecular genetic evidence for effects of parental phenotypes on their offspring (e.g. parental educational attainment), but the extent to which siblings affect each other is currently unclear.Here we used data from samples of unrelated individuals, without (singletons) and with biological full-siblings (non-singletons), to investigate and estimate sibling effects. Indirect genetic effects of siblings increase (or decrease) the covariance between genetic variation and a phenotype. It follows that differences in genetic association estimates between singletons and non-singletons could indicate indirect genetic effects of siblings.We used UK Biobank data to estimate polygenic risk score (PRS) associations for height, BMI and educational attainment in singletons (N = 50,143) and non-singletons (N = 328,549). The educational attainment PRS association estimate was 12% larger (95% C.I. 3%, 21%) in the non-singleton sample than in the singleton sample, but the height and BMI PRS associations were consistent. Birth order data suggested that the difference in educational attainment PRS associations was driven by individuals with older siblings rather than firstborns. The relationship between number of siblings and educational attainment PRS associations was non-linear; PRS associations were 24% smaller in individuals with 6 or more siblings compared to the rest of the sample (95% C.I. 11%, 38%). We estimate that a 1 SD increase in sibling educational attainment PRS corresponds to a 0.025 year increase in the index individual’s years in schooling (95% C.I. 0.013, 0.036).Our results suggest that older siblings influence the educational attainment of younger siblings, adding to the growing evidence that effects of the environment on phenotypic variation partially reflect social effects of germline genetic variation in relatives.

Frost Reduces Clethodim Efficacy in Clethodim-Resistant Rigid Ryegrass (Lolium rigidum) Populations

Weed Science ◽  
2016 ◽  
Vol 64 (2) ◽  
pp. 207-215 ◽  
Author(s):  
Rupinder Kaur Saini ◽  
Jenna Malone ◽  
Christopher Preston ◽  
Gurjeet S. Gill
Keyword(s):  
Dose Response ◽  
Coenzyme A ◽  
Resistance Mechanism ◽  
Lolium Rigidum ◽  
Weed Species ◽  
Susceptible Population ◽  
Acetyl Coenzyme A ◽  
Survival Percentage ◽  
Rigid Ryegrass ◽  
Acetyl Coenzyme A Carboxylase

Rigid ryegrass, an important annual weed species in cropping regions of southern Australia, has evolved resistance to 11 major groups of herbicides. Dose–response studies were conducted to determine response of three clethodim-resistant populations and one clethodim-susceptible population of rigid ryegrass to three different frost treatments (−2 C). Clethodim-resistant and -susceptible plants were exposed to frost in a frost chamber from 4:00 P.M. to 8:00 A.M. for three nights before or after clethodim application and were compared with plants not exposed to frost. A reduction in the level of clethodim efficacy was observed in resistant populations when plants were exposed to frost for three nights before or after clethodim application. In the highly resistant populations, the survival percentage and LD50were higher when plants were exposed to frost before clethodim application compared with frost after clethodim application. However, frost treatment did not influence clethodim efficacy of the susceptible population. Sequencing of the acetyl coenzyme A carboxylase (ACCase) gene of the three resistant populations identified three known mutations at positions 1781, 2041, and 2078. However, most individuals in the highly resistant populations did not contain any known mutation in ACCase, suggesting the resistance mechanism was a nontarget site. The effect of frost on clethodim efficacy in resistant plants may be an outcome of the interaction between frost and the clethodim resistance mechanism(s) present.

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