Genetic variation inMeloidogyne incognita virulence against the tomatoMi resistance gene: evidence from isofemale line selection studies

1994 ◽  
Vol 88 (6-7) ◽  
pp. 749-753 ◽  
Author(s):  
P. Castagnone-Sereno ◽  
E. Wajnberg ◽  
M. Bongiovanni ◽  
F. Leroy ◽  
A. Dalmasso
Keyword(s):  
Genetic Variation ◽  
Resistance Gene ◽  
Isofemale Line ◽  
Line Selection

The coevolution of host resistance and parasitoid virulence

Parasitology ◽  
1998 ◽  
Vol 116 (S1) ◽  
pp. S29-S45 ◽  
Author(s):  
A. R. Kraaijeveld ◽  
J. J. M. Van Alphen ◽  
H. C. J. Godfray
Keyword(s):  
Genetic Variation ◽  
Artificial Selection ◽  
Host Resistance ◽  
Genetic Basis ◽  
Isofemale Line ◽  
Fitness Costs ◽  
Geographical Patterns ◽  
Wide Range ◽  
Great Scope ◽  
Fertile Area

SummaryHost-parasitoid interactions are abundant in nature and offer great scope for the study of coevolution. A particularly fertile area is the interaction between internal feeding parasitoids and their hosts. Hosts have evolved a variety of means of combating parasitoids, in particular cellular encapsulation, while parasitoids have evolved a wide range of countermeasures. Studies of the evolution of host resistance and parasitoid virulence are reviewed, with an emphasis on work involvingDrosophilaand its parasitoids. Genetic variation in both traits has been demonstrated using isofemale line and artificial selection techniques. Recent studies have investigated the fitness costs of maintaining the ability to resist parasitoids, the comparative fitness of flies that have successfully defended themselves against parasitoids, and the degree to which resistance and virulence act against one or more species of host or parasitoid. A number of studies have examined geographical patterns, and sought to look for local adaptation; or have compared the traits across a range of species. Finally, the physiological and genetic basis of change in resistance and virulence is being investigated. While concentrating onDrosophila, the limited amount of work on different systems is reviewed, and other possible areas of coevolution in host-parasitoid interactions are briefly discussed.

Application of DNA markers in determination of fusarium resistance and genetic diversity in chickpea

2018 ◽  
Author(s):  
S. M. Babayeva ◽  
J. A. Nasibova ◽  
Z. I. Akparov ◽  
K. B. Shikhaliyeva ◽  
A. D. Mammadova ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Resistance Gene ◽  
Dna Markers ◽  
Rapd Markers ◽  
Molecular Characterisation ◽  
Fusarium Resistance ◽  
Low Genetic Diversity ◽  
Screening For Resistance

Genetic diversity and fusarium resistance of 50 cultivated chickpea genotypes was studied using ISSR and RAPD markers. The results of both marker systems were consistent with each other, but was somewhat higher for RAPDs. A total of 48 fragments were obtained with both markers together, 32.7% of which were polymorphic. Molecular characterisation through ISSR and RAPD data indicated low genetic variation (GDI=0.39; PIC=0.21) among local and introduced chickpea accessions. The genetic distance values ranged from 0 to 0.134, with a mean of 0.05. The low genetic diversity indicated that new genotypes must be introduced to increase the variability of chickpea germplasm in Azerbaijan. As a result of screening for resistance to fusarium most of genotypes were found to have 600 bp fragment of OPJ20 linked with Foc01 resistance gene, while none of them had resistance gene to Foc4. The results could provide information for future chickpea breeding activities and conservation.

scholarly journals Resistance Gene Carriage Predicts Growth of Natural and ClinicalEscherichia coliIsolates in the Absence of Antibiotics

2018 ◽  
Vol 85 (4) ◽  
Author(s):  
Richard C. Allen ◽  
Daniel C. Angst ◽  
Alex R. Hall
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Genetic Variation ◽  
Resistance Gene ◽  
Resistance Genes ◽  
Bacterial Pathogens ◽  
Antibiotic Resistance Genes ◽  
Resistant Bacteria ◽  
Content Type ◽  
Free Growth

ABSTRACTBacterial pathogens that carry antibiotic resistance alleles sometimes pay a cost in the form of impaired growth in antibiotic-free conditions. This cost of resistance is expected to be a key parameter for understanding how resistance spreads and persists in pathogen populations. Analysis of individual resistance alleles from laboratory evolution and natural isolates has shown they are typically costly, but these costs are highly variable and influenced by genetic variation at other loci. It therefore remains unclear how strongly resistance is linked to impaired antibiotic-free growth in bacteria from natural and clinical scenarios, where resistance alleles are likely to coincide with other types of genetic variation. To investigate this, we measured the growth of 92 natural and clinicalEscherichia coliisolates across three antibiotic-free environments. We then tested whether variation of antibiotic-free growth among isolates was predicted by their resistance to 10 antibiotics, while accounting for the phylogenetic structure of the data. We found that isolates with similar resistance profiles had similar antibiotic-free growth profiles, but it was not simply that higher average resistance was associated with impaired growth. Next, we used whole-genome sequences to identify antibiotic resistance genes and found that isolates carrying a greater number of resistance gene types grew relatively poorly in antibiotic-free conditions, even when the resistance genes they carried were different. This suggests that the resistance of bacterial pathogens is linked to growth costs in nature, but it is the total genetic burden and multivariate resistance phenotype that predict these costs, rather than individual alleles or mean resistance across antibiotics.IMPORTANCEManaging the spread of antibiotic resistance in bacterial pathogens is a major challenge for global public health. Central to this challenge is understanding whether resistance is linked to impaired bacterial growth in the absence of antibiotics, because this determines whether resistance declines when bacteria are no longer exposed to antibiotics. We studied 92 isolates of the key bacterial pathogenEscherichia coli; these isolates varied in both their antibiotic resistance genes and other parts of the genome. Taking this approach, rather than focusing on individual genetic changes associated with resistance as in much previous work, revealed that growth without antibiotics was linked to the number of specialized resistance genes carried and the combination of antibiotics to which isolates were resistant but was not linked to average antibiotic resistance. This approach provides new insights into the genetic factors driving the long-term persistence of antibiotic-resistant bacteria, which is important for future efforts to predict and manage resistance.

scholarly journals Standing genetic variation of the AvrPm17 avirulence gene in powdery mildew limits the effectiveness of an introgressed rye resistance gene in wheat

2021 ◽  
Author(s):  
Marion C. Mueller ◽  
Lukas Kunz ◽  
Seraina Schudel ◽  
Sandrine Kammerecker ◽  
Jonatan Isaksson ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Powdery Mildew ◽  
Qtl Mapping ◽  
Resistance Gene ◽  
Resistance Genes ◽  
Resistance Breeding ◽  
Avirulence Gene ◽  
Avirulence Genes ◽  
Immune Receptor ◽  
Wheat Powdery Mildew

AbstractIntrogressions of chromosomal segments from related species into wheat are important sources of resistance against fungal diseases. The durability and effectiveness of introgressed resistance genes upon agricultural deployment is highly variable - a phenomenon that remains poorly understood as the corresponding fungal avirulence genes are largely unknown. Until its breakdown, the Pm17 resistance gene introgressed from rye to wheat provided broad resistance against powdery mildew (Blumeria graminis). Here, we used QTL mapping to identify the corresponding wheat mildew avirulence effector AvrPm17. It is encoded by two paralogous genes that exhibit signatures of re-occurring gene conversion events and are members of a mildew sub-lineage specific effector cluster. Extensive haplovariant mining in wheat mildew and related sub-lineages identified several ancient virulent AvrPm17 variants that were present as standing genetic variation in wheat powdery mildew prior to the Pm17 introgression, thereby paving the way for the rapid breakdown of the Pm17 resistance. QTL mapping in mildew identified a second genetic component likely corresponding to an additional resistance gene present on the 1AL.1RS translocation carrying Pm17. This gene remained previously undetected due to suppressed recombination within the introgressed rye chromosomal segment. We conclude that the initial effectiveness of 1AL.1RS was based on simultaneous introgression of two genetically linked resistance genes. Our results demonstrate the relevance of pathogen-based genetic approaches to disentangle complex resistance loci in wheat. We propose that identification and monitoring of avirulence gene diversity in pathogen populations becomes an integral part of introgression breeding to ensure effective and durable resistance in wheat.Significance StatementDomesticated and wild wheat relatives provide an important source of new immune receptors for wheat resistance breeding against fungal pathogens. The durability of these resistance genes is variable and difficult to predict, yet it is crucial for effective resistance breeding. We identified a fungal effector protein recognised by an immune receptor introgressed from rye to wheat. We found that variants of the effector allowing the fungus to overcome the resistance are ancient. They were already present in the wheat powdery mildew gene pool before the introgression of the immune receptor and are therefore responsible for the rapid resistance breakdown. Our study demonstrates that the effort to identify new resistance genes should be accompanied by studies of avirulence genes on the pathogen side.

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