scholarly journals Evolution of Compatibility Range in the Rice−Magnaporthe oryzae System: An Uneven Distribution of R Genes Between Rice Subspecies

2016 ◽  
Vol 106 (4) ◽  
pp. 348-354 ◽  
Author(s):  
Romain Gallet ◽  
Colin Fontaine ◽  
François Bonnot ◽  
Joëlle Milazzo ◽  
Christophe Tertois ◽  
...  
Keyword(s):  
Magnaporthe Oryzae ◽  
Ecological Factors ◽  
Blast Disease ◽  
R Genes ◽  
Host Genotype ◽  
Rice Varieties ◽  
Genetic Groups ◽  
Plant Variety ◽  
Plant Pathogen Interaction ◽  
The Impact

Efficient strategies for limiting the impact of pathogens on crops require a good understanding of the factors underlying the evolution of compatibility range for the pathogens and host plants, i.e., the set of host genotypes that a particular pathogen genotype can infect and the set of pathogen genotypes that can infect a particular host genotype. Until now, little is known about the evolutionary and ecological factors driving compatibility ranges in systems implicating crop plants. We studied the evolution of host and pathogen compatibility ranges for rice blast disease, which is caused by the ascomycete Magnaporthe oryzae. We challenged 61 rice varieties from three rice subspecies with 31 strains of M. oryzae collected worldwide from all major known genetic groups. We determined the compatibility range of each plant variety and pathogen genotype and the severity of each plant−pathogen interaction. Compatibility ranges differed between rice subspecies, with the most resistant subspecies selecting for pathogens with broader compatibility ranges and the least resistant subspecies selecting for pathogens with narrower compatibility ranges. These results are consistent with a nested distribution of R genes between rice subspecies.

scholarly journals Exploring the Distribution of Blast Resistance Alleles at the Pi2/9 Locus in Major Rice-Producing Areas of China by a Novel Indel Marker

Plant Disease ◽  
2020 ◽  
Vol 104 (7) ◽  
pp. 1932-1938
Author(s):  
Dagang Tian ◽  
Yan Lin ◽  
Ziqiang Chen ◽  
Zaijie Chen ◽  
Fang Yang ◽  
...  
Keyword(s):  
Blast Resistance ◽  
Resistance Breeding ◽  
Field Trials ◽  
Indel Marker ◽  
Blast Disease ◽  
Cereal Crops ◽  
R Genes ◽  
Rice Varieties ◽  
Environment Friendly ◽  
The World

Rice blast disease caused by the fungus Magnaporthe oryzae damages cereal crops and poses a high risk to rice production around the world. Currently, planting cultivars with resistance (R) genes is still the most environment-friendly approach to control this disease. Effective identification of R genes existing in diverse rice cultivars is important for understanding the distribution of R genes and predicting their contribution to resistance against blast isolates in regional breeding. Here, we developed a new insertion/deletion (InDel) marker, Pigm/2/9InDel, that can differentiate the cloned R genes (Pigm, Pi9, and Pi2/Piz-t) at the Pi2/9 locus. Pigm/2/9InDel combined with the marker Pi2-LRR for Pi2 was applied to determine the distribution of these four R genes among 905 rice varieties, most of which were collected from the major rice-producing regions in China. In brief, nine Pigm-containing varieties from Fujian and Guangdong provinces were identified. All of the 62 Pi2-containing varieties were collected from Guangdong, and 60 varieties containing Piz-t were from seven provinces. However, Pi9 was not found in any of the Chinese varieties. The newly identified varieties carrying the Pi2/9 alleles were further subjected to inoculation tests with regional blast isolates and field trials. Our results indicate that Pigm and Pi2 alleles have been introgressed for blast resistance breeding mainly in the Fujian and Guangdong region, and Pi9 is a valuable blast resistance resource to be introduced into China.

scholarly journals A Rapid Survey of Avirulence Genes in Field Isolates of Magnaporthe oryzae

Plant Disease ◽  
2020 ◽  
Vol 104 (3) ◽  
pp. 717-723
Author(s):  
Zhen Zhang ◽  
Yulin Jia ◽  
Yanli Wang ◽  
Guochang Sun
Keyword(s):  
United States ◽  
Magnaporthe Oryzae ◽  
Blast Resistance ◽  
Blast Disease ◽  
Southern United States ◽  
R Genes ◽  
Field Isolates ◽  
Pcr Products ◽  
Avr Gene ◽  
Avr Genes

Magnaporthe oryzae is the causal agent for the devastating disease rice blast. The avirulence (AVR) genes in M. oryzae are required to initiate robust disease resistance mediated by the corresponding resistance (R) genes in rice. Therefore, monitoring pathogen AVR genes is important to predict the stability of R gene-mediated blast resistance. In the present study, we analyzed the DNA sequence dynamics of five AVR genes, namely, AVR-Pita1, AVR-Pik, AVR-Pizt, AVR-Pia, and AVR-Pii, in field isolates of M. oryzae in order to understand the effectiveness of the R genes, Pi-ta, Pi-k, Pi-zt, Pia, and Pii in the Southern U.S. rice growing region. Genomic DNA of 258 blast isolates collected from commercial fields of the Southern UNITED STATES during 1975–2009 were subjected to PCR amplification with AVR gene-specific PCR markers. PCR products were obtained from 232 isolates. The absence of PCR products in the remaining 26 isolates suggests that these isolates do not contain the tested AVR genes. Amplified PCR products were subsequently gel purified and sequenced. Based on the presence or absence of the five AVR genes, 232 field isolates were classified into 10 haplotype groups. The results revealed that 174 isolates of M. oryzae carried AVR-Pita1, 225 isolates carried AVR-Pizt, 44 isolates carried AVR-Pik, 3 isolates carried AVR-Pia, and one isolate carried AVR-Pii. AVR-Pita1 was highly variable, and 40 AVR-Pita1 haplotypes were identified in avirulent isolates. AVR-Pik had four nucleotide sequence site changes resulting in amino acid substitutions, whereas three other AVR genes, AVR-Pizt, AVR-Pia, and AVR-Pii, were relatively stable. Two AVR genes, AVR-Pik and AVR-Pizt, were found to exist in relatively larger proportions of the tested field isolates, which suggested that their corresponding R genes Pi-k and Pi-zt can be deployed in preventing blast disease in the Southern UNITED STATES in addition to Pi-ta. This study demonstrates that continued AVR gene monitoring in the pathogen population is critical for ensuring the effectiveness of deployed blast R genes in commercial rice fields.

scholarly journals Selection of Differential Isolates of Magnaporthe oryzae for Postulation of Blast Resistance Genes

2018 ◽  
Vol 108 (7) ◽  
pp. 878-884 ◽  
Author(s):  
W. W. Fang ◽  
C. C. Liu ◽  
H. W. Zhang ◽  
H. Xu ◽  
S. Zhou ◽  
...  
Keyword(s):  
Resistance Genes ◽  
Magnaporthe Oryzae ◽  
Blast Resistance ◽  
Polymerase Chain Reaction Analysis ◽  
Colony Growth ◽  
Blast Disease ◽  
Avirulence Genes ◽  
Rice Varieties ◽  
Minimum Number ◽  
Blast Resistance Genes

A set of differential isolates of Magnaporthe oryzae is needed for the postulation of blast resistance genes in numerous rice varieties and breeding materials. In this study, the pathotypes of 1,377 M. oryzae isolates from different regions of China were determined by inoculating detached rice leaves of 24 monogenic lines. Among them, 25 isolates were selected as differential isolates based on the following characteristics: they had distinct responses on the monogenic lines, contained the minimum number of avirulence genes, were stable in pathogenicity and conidiation during consecutive culture, were consistent colony growth rate, and, together, could differentiate combinations of the 24 major blast resistance genes. Seedlings of rice cultivars were inoculated with this differential set of isolates to postulate whether they contain 1 or more than 1 of the 24 blast resistance genes. The results were consistent with those from polymerase chain reaction analysis of target resistance genes. Establishment of a standard set of differential isolates will facilitate breeding for blast resistance and improved management of rice blast disease.

scholarly journals Study of pathogenicity and genetic diversity of Magnaporthe oryzae isolated from rice hybrid Wuyou 308 and detection of resistance genes

2020 ◽  
Vol 56 (No. 3) ◽  
pp. 93-101
Author(s):  
Bo Lan ◽  
Ying-Qing Yang ◽  
Qiang Sun ◽  
Hong-Fan Chen ◽  
Jian Chen ◽  
...  
Keyword(s):  
Resistance Genes ◽  
Magnaporthe Oryzae ◽  
Rice Blast ◽  
Blast Resistance ◽  
Rice Variety ◽  
Climatic Conditions ◽  
Blast Disease ◽  
Rice Varieties ◽  
Rice Blast Resistance ◽  
Rice Hybrid

To understand the cause of loss of rice blast resistance, we studied the pathogenicity of Magnaporthe oryzae strains isolated from rice hybrid Wuyou 308 and evaluated its resistance genes. A total of 62 M. oryzae strains were isolated and tested in 7 Chinese rice varieties with varying degrees of resistance to rice blast and 30 blast-resistant monogenic lines. Fourteen physiological races of M. oryzae were identified: 8.55% belonging to the ZA group, 86.67% to the ZB group, and 5.00% to the ZC group. ZB15 was the most abundant race (45.00%). Five resistance genes, Pi-3(1), Pi-z5, Pi-k, Pi-kp(C), and Pi-k(C), conferred good resistance to the 62 strains, with resistance frequencies of 95.56, 91.11, 88.89, 82.22, and 82.22%, respectively. In contrast, Pi-a(2) had a resistance frequency of 0%. The hybrid combination Wuyou 308 was found to carry Pi-ta and Pi-b genes. Because Pi-ta and Pi-b both showed low resistance frequencies to M. oryzae isolated from Jiangxi, the hybrid rice variety Wuyou 308 could be infected by most of the 62 M. oryzae strains. The emergence and spread of rice blast disease in Wuyou 308 may thus be difficult to avoid when climatic conditions are favourable.

scholarly journals Determination of Resistance Spectra of the Pi-ta and Pi-k Genes to U.S. Races of Magnaporthe oryzae Causing Rice Blast in a Recombinant Inbred Line Population

Plant Disease ◽  
2009 ◽  
Vol 93 (6) ◽  
pp. 639-644 ◽  
Author(s):  
Yulin Jia ◽  
Fleet N. Lee ◽  
Anna McClung
Keyword(s):  
Inbred Line ◽  
Recombinant Inbred Line ◽  
Magnaporthe Oryzae ◽  
Recombinant Inbred ◽  
Blast Disease ◽  
R Gene ◽  
R Genes ◽  
Marker Assisted Breeding ◽  
Simple Sequence

Molecular tagged resistance (R) genes are useful for developing improved cultivar resistance using marker-assisted breeding. In the present study, R genes to common races of Magnaporthe oryzae, the causal agent of blast disease of rice (Oryza sativa), were mapped using an F10 recombinant inbred line (RIL) population derived from a cross of tropical japonica cv. Katy with breeding line RU9101001. Katy was resistant to 10 common U.S. races: IA-45, IB-1, IB-45, IB-49, IB-54, IC-17, ID-1, IE-1, IG-1, and IH-1 of M. oryzae. RU9101001 was resistant to races IA-45, IB-45, IB-54, IG-1, and IH-1. Katy and RU9101001 were susceptible to race IE-1k. Twenty-three polymorphic simple sequence repeat (SSR) markers were used to map R genes. Segregation ratios of 1:1 (resistant/susceptible) to races IB-1, IB-49, IC-17, ID-1, and IE-1 indicated the presence of a single dominant R gene in Katy. Ratios of 3:1 (resistant/susceptible) to races IA-45, IB-45, IG-1, and IH-1 indicated that a single R gene was present in Katy and a different R gene was present in RU9101001. Resistance to the abovementioned races was correlated with the presences of the Pi-ta gene and 11 Katy SSR alleles, suggesting that Pi-ta confers resistance to IA-45, IB-1, IB-45, IB-49, IC-17, IG-1, ID-1, IE-1, and IH-1. Katy, RU9101001, and all RILs were resistant to race IB-54, which was consistent with the presence of Pi-ks in Katy and Pi-kh in RU9101001. Resistance to IA-45, IB-45, IG-1, and IH-1 correlated with the presence of Pi-kh, suggesting that Pi-kh confers resistance to IA-45, IB-45, IG-1, and IH-1. These data suggest that Pi-ta and Pi-kh are effective R genes with overlapped resistance to the 10 common races of M. oryzae.

scholarly journals Assessment of the Virulence Spectrum and Its Association with Genetic Diversity in Magnaporthe oryzae Populations from Sub-Saharan Africa

2017 ◽  
Vol 107 (7) ◽  
pp. 852-863 ◽  
Author(s):  
S. K. Mutiga ◽  
F. Rotich ◽  
V. Devi Ganeshan ◽  
D. T. Mwongera ◽  
E. M. Mgonja ◽  
...  
Keyword(s):  
Magnaporthe Oryzae ◽  
Genetic Relatedness ◽  
Vegetative Compatibility ◽  
Sub Saharan Africa ◽  
Blast Disease ◽  
Rice Cultivars ◽  
R Genes ◽  
African Rice ◽  
Sub Saharan ◽  
Virulence Spectrum

A collection of 122 isolates of Magnaporthe oryzae, from nine sub-Saharan African countries, was assessed for virulence diversity and genetic relatedness. The virulence spectrum was assessed by pathotype analysis with a panel of 43 rice genotypes consisting of differential lines carrying 24 blast resistance genes (R-genes), contemporary African rice cultivars, and susceptible checks. The virulence spectrum among isolates ranged from 5 to 80%. Five isolates were avirulent to the entire rice panel, while two isolates were virulent to ∼75% of the panel. Overall, cultivar 75-1-127, the Pi9 R-gene donor, was resistant to all isolates (100%), followed by four African rice cultivars (AR105, NERICA 15, 96%; NERICA 4, 91%; and F6-36, 90%). Genetic relatedness of isolates was assessed by single nucleotide polymorphisms derived from genotyping-by-sequencing and by vegetative compatibility tests. Phylogenetic analysis of SNPs of a subset of isolates (n = 78) revealed seven distinct clades that differed in virulence. Principal component analysis showed isolates from East Africa were genetically distinct from those from West Africa. Vegetative compatibility tests of a subset of isolates (n = 65) showed no common groups among countries. This study shows that blast disease could be controlled by pyramiding of Pi9 together with other promising R-genes into rice cultivars that are adapted to East and West African regions.

scholarly journals Novel haplotypes and networks of AVR-Pik alleles in Magnaporthe oryzae

2018 ◽  
Author(s):  
Jin-bin Li ◽  
Qun Wang ◽  
Chengyun Li ◽  
Yunqing Bi ◽  
Xue Fu ◽  
...  
Keyword(s):  
Magnaporthe Oryzae ◽  
Yunnan Province ◽  
Sequence Variation ◽  
Specific Resistance ◽  
Blast Disease ◽  
Base Substitution ◽  
R Genes ◽  
Dna Sequence Variation ◽  
Pcr Products ◽  
Avr Genes

Rice blast disease is one of the most destructive fungal diseases of rice world-wide. The avirulence (AVR) genes of Magnaporthe oryzae are recognized by the cognate resistance (R) genes of rice, and trigger race specific resistance. Here, we studied the possible evolutionary pathways in the evolution of AVR-Pik alleles by analyzing the DNA sequence variation and assayed for their avirulence function to the cognate Pik alleles resistance genes under field conditions in China. Results of PCR products showed that 278 isolates of M. oryzae carry AVR-Pik alleles among genomic DNA of 366 isolates of M. oryzae collected from Yunnan Province, China. Among of them, 66.7-90.3% of M. oryzae carry AVR-Pik alleles from six regions of Yunnan. Moreover, 10 AVR-Pik haplotypes encoding five novel AVR-Pik variants were identified among 201 isolates. The AVR-Pik alleles stepwise evolved to virulence from avirulent forms via base substitution. These findings demonstrate that AVR-Pik alleles are under positive selection and mutations are responsible for defeating race-specific resistance Pik alleles in nature.

scholarly journals Large-Scale Genome Scanning within Exonic Regions Revealed the Contributions of Selective Sweep Prone Genes to Host Divergence and Adaptation in Magnaporthe oryzae Species Complex

2021 ◽  
Vol 9 (3) ◽  
pp. 562
Author(s):  
Guohua Duan ◽  
Jiandong Bao ◽  
Xiaomin Chen ◽  
Jiahui Xie ◽  
Yuchan Liu ◽  
...  
Keyword(s):  
Magnaporthe Oryzae ◽  
Selection Pressure ◽  
Large Scale ◽  
Plant Pathogens ◽  
Composite Likelihood ◽  
Blast Disease ◽  
Cultivated Plants ◽  
Extended Haplotype ◽  
Blast Fungus ◽  
The Impact

Magnaporthe oryzae, one of the most notorious plant pathogens in the agronomic ecosystem, causes a destructive rice blast disease around the world. The blast fungus infects wide arrays of cultivated and non-cultivated plants within the Poaceae. Studies have shown that host speciation exerts selection pressure that drives the evolution and divergence of the M. oryzae population. Population genetic relationship deducted by genome-wide single nucleotide polymorphisms showed that M. oryzae differentiation is highly consistent with the host speciation process. In particular, the rice-infecting population of M. oryzae is distinct from populations from other hosts. However, how genome regions prone to host-mediated selection pressures associated with speciation in M. oryzae, especially at a large-scale population level, has not been extensively characterized. Here, we detected strong evidence of sweep selection throughout the genomes of rice and non-rice pathotypes of M. oryzae population using integrated haplotype score (iHS), cross population extended haplotype homozygosity (XPEHH), and cross population composite likelihood ratio (XPCLR) tests. Functional annotation analyses of the genes associated with host-mediated selection pressure showed that 14 pathogenicity-related genes are under positive selection pressure. Additionally, we showed that 17 candidate effector proteins are under positive and divergent selection among the blast fungus population through sweep selection analysis. Specifically, we find that a divergent selective gene, MGG_13871, is experiencing host-directed mutation in two amino acid residues in rice and non-rice infecting populations. These results provide a crucial insight into the impact of selective sweeping on the differentiation of M. oryzae populations and the dynamic influences of genomic regions in promoting host adaptation and speciation among M. oryzae species.

scholarly journals The impact of maternal genetic merit and country of origin on ewe reproductive performance, lambing performance and ewe survival

2021 ◽  
Author(s):  
N Fetherstone ◽  
N McHugh ◽  
T M Boland ◽  
F M McGovern
Keyword(s):  
New Zealand ◽  
Birth Weight ◽  
Litter Size ◽  
Country Of Origin ◽  
Reproductive Traits ◽  
Gestation Length ◽  
Genetic Merit ◽  
Genetic Groups ◽  
One Year ◽  
The Impact

Abstract The objective of this study was to investigate the impact of the ewe’s maternal genetic merit and country of origin (New Zealand or Ireland) on ewe reproductive, lambing and productivity traits. The study was performed over a four year period (2016 to 2019) and consisted of three genetic groups: high maternal genetic merit New Zealand (NZ), high maternal genetic merit Irish (High Irish) and low maternal genetic merit Irish (Low Irish) ewes. Each group contained 30 Suffolk and 30 Texel ewes, selected based on the respective national maternal genetic indexes; i.e. either the New Zealand Maternal Worth (New Zealand group) or the €uro-star Replacement index (Irish groups). The impact of maternal genetic merit on reproductive traits such as litter size; lambing traits such as gestation length, birth weight, lambing difficulty, mothering ability, and productivity traits such as the number of lambs born and weaned were analyzed using linear mixed models. For binary traits, the impact of maternal genetic merit on reproductive traits such as conception to first AI service; lambing traits such as dystocia, perinatal lamb mortality and productivity traits such as ewe survival were analyzed using logistic regression. New Zealand ewes outperformed Low Irish ewes for conception to first AI (P<0.05) and litter size (P=0.05). Irish ewes were more likely to suffer from dystocia (6.84 (High Irish) and 8.25 (Low Irish) times) compared to NZ ewes (P<0.001); birth weight and perinatal mortality did not differ between groups (P>0.05). Lambs born from NZ ewes were 4.67 (95% CI: 1.89 to 11.55; P<0.001) and 6.54 (95% CI: 2.56 to 16.71; P<0.001) times more likely to stand up and suckle unassisted relative to lambs born from High or Low Irish ewes, respectively. New Zealand and High Irish ewes had a greater number of lambs born and weaned throughout the duration of the study compared to their Low Irish counterparts (P<0.001). New Zealand ewes tended to be more likely to survive from one year to the next compared to Low Irish ewes (P=0.07). Irish ewes of high maternal genetic merit outperformed their Low counterparts in total number of lambs born and weaned per ewe, but performance did not differ across other traits investigated. This highlights the importance of continuous development of the Irish maternal sheep index to ensure favourable improvements in reproductive, lambing and productivity traits at farm level. Overall, results demonstrate the suitability of NZ genetics in an Irish production system.

Sign in / Sign up

Export Citation Format

Share Document