scholarly journals Plant resistance and strategies for breeding resistant varieties

2002 ◽  
Vol 38 (SI 1 - 6th Conf EFPP 2002) ◽  
pp. S9-S14 ◽  
Author(s):  
D.A.C. Pink ◽  
P. Hand
Keyword(s):  
Plant Transformation ◽  
Marker Assisted Selection ◽  
Specific Resistance ◽  
Durable Resistance ◽  
Resistance Breeding ◽  
R Gene ◽  
R Genes ◽  
Resistant Varieties ◽  
Plant Phenotype ◽  
The Impact

An explanation of the ‘boom-bust’ cycle of resistance breeding was provided by the gene-for-gene relationship between a pathogen and its host. Despite this understanding, most R genes continued to be deployed singly and resistance has been ephemeral. The reasons for breeding ‘single R gene’ varieties are discussed. Alternative strategies for the deployment of R genes and the use of quantitative race non-specific resistance have been advocated in order to obtain durable resistance. The feasibility of both of these approaches is discussed taking into account the impact of technologies such as plant transformation and marker-assisted selection. A change in focus from durability of the plant phenotype to that of the crop phenotype is advocated.

Leptosphaeria maculans isolates reveal their allele frequency in western Canada

Plant Disease ◽  
2020 ◽  
Author(s):  
Fei Liu ◽  
Zhongwei Zou ◽  
Gary Peng ◽  
W. G. Dilantha Fernando
Keyword(s):  
Leptosphaeria Maculans ◽  
Resistance Breeding ◽  
Western Canada ◽  
R Genes ◽  
Pathogen Population ◽  
Pcr Assay ◽  
Differential Host ◽  
Resistant Varieties ◽  
Disease Resistance Breeding ◽  
Avr Genes

Blackleg, caused by Leptosphaeria maculans, is a major disease of canola in Canada, Australia, and Europe. For effective deployment of resistant varieties and disease management, it is crucial to understand the population structure of L. maculans. In this study, we analyze L. maculans isolates from commercial fields in western Canada from 2014 to 2016 for the presence and frequency of avirulence (Avr) genes. A total of 1, 584 isolates was examined for the presence of Avr genes AvrLm1, AvrLm2, AvrLm3, AvrLm4, AvrLm6, AvrLm7, AvrLm9, AvrLepR1, AvrLepR2, and AvrLmS using a set of differential host genotypes carrying known resistance genes and a PCR assay. Several Avr genes showed a higher frequency in the pathogen population, such as AvrLm6 and AvrLm7, which were present in >90% of isolates; while AvrLm3, AvrLm9 and AvrLepR2 showed frequencies of <10%. A total of 189 races (different combinations of Avr genes) were detected, with Avr-2-4-6-7-S, Avr-1-4-6-7 and Avr-2-4-6-7 as the three predominant races. When the effect of crop rotation was assessed, only a three-year rotation showed a significantly higher frequency of AvrLm2, relative to shorter rotations. This study provides the information for producers to select effective canola varieties for blackleg management, and for breeders to deploy new R genes in disease resistance breeding in the western Canada region.

scholarly journals Resistance Gene Analogs (RGA) as a tool in fruit tree's breeding

2009 ◽  
Vol 15 (1-2) ◽  
Author(s):  
A. Gutermuth ◽  
A. Pedryc
Keyword(s):  
Molecular Markers ◽  
Marker Assisted Selection ◽  
Resistance Breeding ◽  
Resistance Gene Analogs ◽  
R Gene ◽  
Fruit Traits ◽  
Major Objective ◽  
Fruit Species ◽  
Marker Design ◽  
Breeding Application

Breeding for pest and disease resistance comes as a major objective behind the fruit traits. To increase the effectiveness of fruit resistance breeding application of the Marker Assisted Selection ( MAS) is advantageous. For generating molecular markers which enable the following of interesting traits basically two methods are available: targeted marker design based on conservative region of already known Resistance ( R) gene sequences or randomly generated markers. The creation  and the application  of  these homology  based  markers  are the object of this review in  the main  temperate zone  fruit species.

Advances in breeding techniques for durable resistance to spot blotch in cereals

2021 ◽  
pp. 435-474
Author(s):  
Ramesh Chand ◽  
◽  
Sudhir Navathe ◽  
Sandeep Sharma ◽  
◽  
...  
Keyword(s):  
Durable Resistance ◽  
Resistance Breeding ◽  
Spot Blotch ◽  
Wheat Breeding ◽  
Economic Importance ◽  
Molecular Approaches ◽  
Genome Wide ◽  
Resistant Varieties ◽  
Necrotrophic Effector ◽  
Breeding Techniques

This chapter reviews advances in breeding techniques for durable resistance to spot blotch in cereals. It starts by highlighting the spread, economic importance and the disease cycle of spot blotch. The chapter then goes on to examine the diversity of the pathogen and physiological specialization. This is then followed by a discussion on the identification of resistance sources, as well as the histological, biochemical and morphological components of resistance. The chapter also reviews molecular approaches for resistance breeding, specifically focusing on quantitative trait loci (QTL and genome-wide association mapping (GWAS) studies. Resistance genes and their possible deployment are also discussed, along with a section on low molecular weight toxins and their possible role in pathogenicity. The chapter also examines necrotrophic effector triggered susceptibility and associated genes and breeding for spot blotch resistance in wheat. Breeding for spot blotch resistance in barley is also discussed, before concluding with a discussion on farmers participatory research in the release of spot blotch resistant varieties.

scholarly journals Airborne nomadic pathogens: does virulence accumulate along the way from Paris to Beijing?

2002 ◽  
Vol 38 (SI 1 - 6th Conf EFPP 2002) ◽  
pp. S60-S64 ◽  
Author(s):  
E. Limpert ◽  
P. Bartoš ◽  
H. Buchenauer ◽  
W.-K. Graber ◽  
K. Müller ◽  
...  
Keyword(s):  
Population Genetics ◽  
Leaf Rust ◽  
Western Europe ◽  
Specific Resistance ◽  
Framework Programme ◽  
R Genes ◽  
The Impact ◽  
Cereal Rusts ◽  
The Way

It is well established that race-specific resistance selects for the specifically matching genes effecting virulence in the pathogen. As well, the use of different R-genes in time makes virulence complexity, VC (the number of virulences per pathogen genotype), to increase. Moreover, it becomes obvious here that the wind-dispersed cereal rusts and mildews are obligate nomads and highly mobile. As a consequence of these points and as a result of modelling, VC was expected to increase in the direction of predominant winds, e.g. from west to east across Europe, and it did by approximately one or more virulences per 1000 km. Starting from the barley mildew pathogen, comprehensive evidence is also available from leaf rust on wheat covering some 5000 km from Western Europe into Siberia. The impact of our findings for population genetics across Europe and Asia is supposed to be considerable and worth further elucidating, e.g., within the 6<sup>th</sup> EU Framework Programme.

scholarly journals Qualitative and Quantitative Late Blight Resistance in the Potato Cultivar Sarpo Mira Is Determined by the Perception of Five Distinct RXLR Effectors

2012 ◽  
Vol 25 (7) ◽  
pp. 910-919 ◽  
Author(s):  
Hendrik Rietman ◽  
Gerard Bijsterbosch ◽  
Liliana M. Cano ◽  
Heung-Ryul Lee ◽  
Jack H. Vossen ◽  
...  
Keyword(s):  
Late Blight ◽  
Quantitative Resistance ◽  
Durable Resistance ◽  
Potato Cultivar ◽  
Field Resistance ◽  
R Gene ◽  
R Genes ◽  
Qualitative And Quantitative ◽  
Rxlr Effectors ◽  
Sarpo Mira

Potato defends against Phytophthora infestans infection by resistance (R)-gene-based qualitative resistance as well as a quantitative field resistance. R genes are renowned to be rapidly overcome by this oomycete, and potato cultivars with a decent and durable resistance to current P. infestans populations are hardly available. However, potato cultivar Sarpo Mira has retained resistance in the field over several years. We dissected the resistance of ‘Sarpo Mira’ in a segregating population by matching the responses to P. infestans RXLR effectors with race-specific resistance to differential strains. The resistance is based on the combination of four pyramided qualitative R genes and a quantitative R gene that was associated with field resistance. The qualitative R genes include R3a, R3b, R4, and the newly identified Rpi-Smira1. The qualitative resistances matched responses to avirulence (AVR)3a, AVR3b, AVR4, and AVRSmira1 RXLR effectors and were overcome by particular P. infestans strains. The quantitative resistance was determined to be conferred by a novel gene, Rpi-Smira2. It was only detected under field conditions and was associated with responses to the RXLR effector AvrSmira2. We foresee that effector-based resistance breeding will facilitate selecting and combining qualitative and quantitative resistances that may lead to a more durable resistance to late blight.

scholarly journals Assessment of powdery mildew (Blumeria graminis f. sp. hordei) resistance genes in Turkish barley varieties

2009 ◽  
Vol 89 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Ahmet Zeybek ◽  
Şahin Dere ◽  
Gülay Gök ◽  
Asude Çallak ◽  
Mahinur S. Akkaya
Keyword(s):  
Hordeum Vulgare ◽  
Powdery Mildew ◽  
Resistance Genes ◽  
Blumeria Graminis ◽  
Leaf Segment ◽  
R Gene ◽  
R Genes ◽  
Resistant Varieties

Thirty-four Turkish barley (Hordeum vulgare) varieties were tested for the presence of resistance genes (R-genes) to powdery mildew (Blumeria graminisf. sp.hordei) using the “leaf segment test” with nine isolates of the fungus. The most commonly found R-gene wasMla8, while a combination of R-genesMlgandMl(CP)was found in three varieties (Tokak 157/37, Beysehir 98, Konevei 98). The geneMlhwas found in four varieties (Obruk 86, Anadolu 86, Çıldır 02, Özdemir 05), while no R-gene was found in three varieties (Hamidiye 85, Yesevi 93, Bülbül 89). No clear inferences could be made for the partly-resistant varieties Gemici 7243, Yea 793.12 and Akhisar 98 using the test isolates selected, which suggests the presence of still unidentified R-genes. Overall, 10 previously characterized R-genes for powdery mildew (Mla8,Ml(La),Mlg,Ml(CP),Mlh,Mlat,Mla1,Mlh,Mla7,Mlra) were present in Turkish barley varieties, along with some other(s) still to be identified.

scholarly journals SNPs, InDels, and Microsatellites within and near to Rice NBS-LRR Resistance Gene Candidates

Agronomy ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2297
Author(s):  
Mark J. Quinton-Tulloch ◽  
Katherine A. Steele
Keyword(s):  
Indica Rice ◽  
R Gene ◽  
R Genes ◽  
Rice Varieties ◽  
Sequence Comparisons ◽  
Bioinformatic Tools ◽  
Genome Wide ◽  
Resistant Varieties ◽  
Resistance Gene Candidates ◽  
Bioinformatics Study

Plant resistance genes (R-genes) drive the immune responses of crops against specific pathotypes of disease-causing organisms. Over time, genetic diversity in R-genes and R-pseudogenes has arisen among different rice varieties. This bioinformatics study was carried out to (i) predict the full sets of candidate nucleotide-binding site leucine-rich repeat (NLR) R-genes present in six rice genomes; (ii) detect variation within candidate R-genes; (iii) identify potential selectable markers within and near to LRR genes among 75 diverse indica rice genomes. Four high quality indica genomes, plus the standard japonica and indica reference genomes, were analysed with widely available bioinformatic tools to identify candidate R-genes and R-pseudogenes. They were detected in clusters, consistent with previous studies. BLAST analysis of cloned protein sequences of 31 R-gene loci gave confidence in this approach for detection of cloned NLR R-genes. Approximately 10% of candidate R-genes were located within 1 kb of a microsatellite (SSR) marker. Sequence comparisons among indica rice genomes detected SNPs or InDels in 334 candidate rice R-genes. There were significantly more SNPs and InDels within the identified NLR R-gene candidates than in other types of gene. The genome-wide locations of candidate R-genes and their associated markers are presented here for the potential future development of improved disease-resistant varieties. Limitations of in silico approaches used for R-gene discovery are discussed.

scholarly journals Isolation and Characterization Of Rice R Genes: Evidence for Distinct Evolutionary Paths in Rice and Maize

Genetics ◽  
1996 ◽  
Vol 142 (3) ◽  
pp. 1021-1031 ◽  
Author(s):  
Jianping Hu ◽  
Beth Anderson ◽  
Susan R Wessler
Keyword(s):  
Gene Family ◽  
Gene Families ◽  
Chromosome 1 ◽  
R Gene ◽  
R Genes ◽  
Helix Loop Helix ◽  
Isolation And Characterization ◽  
Undetermined Function ◽  
Evolutionary Paths

Abstract R and B genes and their homologues encode basic helix-loop-helix (bHLH) transcriptional activators that regulate the anthocyanin biosynthetic pathway in flowering plants. In maize, R/B genes comprise a very small gene family whose organization reflects the unique evolutionary history and genome architecture of maize. To know whether the organization of the R gene family could provide information about the origins of the distantly related grass rice, we characterized members of the R gene family from rice Oryza sativa. Despite being a true diploid, O. sativa has at least two R genes. An active homologue (Ra) with extensive homology with other R genes is located at a position on chromosome 4 previously shown to be in synteny with regions of maize chromosomes 2 and 10 that contain the B and R loci, respectively. A second rice R gene (Rb) of undetermined function was identified on chromosome 1 and found to be present only in rice species with AA genomes. All non-AA species have but one R gene that is Ra-like. These data suggest that the common ancestor shared by maize and rice had a single R gene and that the small R gene families of grasses have arisen recently and independently.

scholarly journals Recent Findings Unravel Genes and Genetic Factors Underlying Leptosphaeria maculans Resistance in Brassica napus and Its Relatives

2020 ◽  
Vol 22 (1) ◽  
pp. 313
Author(s):  
Aldrin Y. Cantila ◽  
Nur Shuhadah Mohd Saad ◽  
Junrey C. Amas ◽  
David Edwards ◽  
Jacqueline Batley
Keyword(s):  
Brassica Napus ◽  
Genetic Factors ◽  
Quantitative Resistance ◽  
Genetic Resistance ◽  
Leptosphaeria Maculans ◽  
Gene Interaction ◽  
R Gene ◽  
R Genes ◽  
Blackleg Resistance ◽  
Avr Gene

Among the Brassica oilseeds, canola (Brassica napus) is the most economically significant globally. However, its production can be limited by blackleg disease, caused by the fungal pathogen Lepstosphaeria maculans. The deployment of resistance genes has been implemented as one of the key strategies to manage the disease. Genetic resistance against blackleg comes in two forms: qualitative resistance, controlled by a single, major resistance gene (R gene), and quantitative resistance (QR), controlled by numerous, small effect loci. R-gene-mediated blackleg resistance has been extensively studied, wherein several genomic regions harbouring R genes against L. maculans have been identified and three of these genes were cloned. These studies advance our understanding of the mechanism of R gene and pathogen avirulence (Avr) gene interaction. Notably, these studies revealed a more complex interaction than originally thought. Advances in genomics help unravel these complexities, providing insights into the genes and genetic factors towards improving blackleg resistance. Here, we aim to discuss the existing R-gene-mediated resistance, make a summary of candidate R genes against the disease, and emphasise the role of players involved in the pathogenicity and resistance. The comprehensive result will allow breeders to improve resistance to L. maculans, thereby increasing yield.

scholarly journals Multiyear Evaluation of the Durability of the Resistance Conferred by Ma and RMia Genes to Meloidogyne incognita in Prunus Under Controlled Conditions

2013 ◽  
Vol 103 (8) ◽  
pp. 833-840 ◽  
Author(s):  
Samira Khallouk ◽  
Roger Voisin ◽  
Ulysse Portier ◽  
Joël Polidori ◽  
Cyril Van Ghelder ◽  
...  
Keyword(s):  
Meloidogyne Incognita ◽  
Economic Losses ◽  
R Gene ◽  
R Genes ◽  
Tomato Plants ◽  
Controlled Conditions ◽  
Meloidogyne Spp ◽  
Resistance Breakdown ◽  
Susceptible Tomato ◽  
Prunus Spp

Root-knot nematodes (RKNs) (Meloidogyne spp.) are highly polyphagous pests that parasitize Prunus crops in Mediterranean climates. Breeding for RKN-resistant Prunus cultivars, as an alternative to the now-banned use of nematicides, is a real challenge, because the perennial nature of these trees increases the risk of resistance breakdown. The Ma plum resistance (R) gene, with a complete spectrum, and the RMia peach R gene, with a more restricted spectrum, both provide total control of Meloidogyne incognita, the model parthenogenetic species of the genus and the most important RKN in terms of economic losses. We investigated the durability of the resistance to this nematode conferred by these genes, comparing the results obtained with those for the tomato Mi-1 reference gene. In multiyear experiments, we applied a high and continuous nematode inoculum pressure by cultivating nematode-infested susceptible tomato plants with either Prunus accessions carrying Ma or RMia R genes, or with resistant tomato plants carrying the Mi-1 gene. Suitable conditions for Prunus development were achieved by carrying out the studies in a glasshouse, in controlled conditions allowing a short winter leaf fall and dormancy. We first assessed the plum accession ‘P.2175’, which is heterozygous for the Ma gene, in two successive 2-year evaluations, for resistance to two M. incognita isolates. Whatever the isolate used, no nematodes reproducing on P.2175 were detected, whereas galls and nematodes reproducing on tomato plants carrying Mi-1 were observed. In a second experiment with the most aggressive isolate, interspecific full-sib material (P.2175 × [‘Garfi’ almond × ‘Nemared’ peach]), carrying either Ma or RMia (from Nemared) or both (in the heterozygous state) or neither of these genes, was evaluated for 4 years. No virulent nematodes developed on Prunus spp. carrying R genes, whereas galling and virulent individuals were observed on Mi-1-resistant tomato plants. Thus, the resistance to M. incognita conferred by Ma in Prunus material in both a pure-plum and an interspecific genetic background, or by RMia in an interspecific background, appears to be durable, highlighting the value of these two genes for the creation of Prunus rootstock material.

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