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Frank F. White - One of the best experts on this subject based on the ideXlab platform.

  • avoidance of host recognition by alterations in the repetitive and c terminal regions of avrxa7 a type iii effector of xanthomonas oryzae pv oryzae
    Molecular Plant-microbe Interactions, 2005
    Co-Authors: Bing Yang, Akiko Sugio, Frank F. White
    Abstract:

    avrXa7 is a member of the avrBs3/pthA gene family. The gene is a critical type III effector in several strains of Xanthomonas oryzae pv. oryzae (Virulence activity), and in the presence of the Xa7 host gene for resistance, controls the elicitation of resistance in rice (aVirulence activity). The ability of strains containing avrXa7 to adapt to the presence of Xa7 in the host population is dependent, in part, on the genetic plasticity of avrXa7. The potential for the conversion of avrXa7 to a Virulence effector without Xa7-dependent elicitor activity was examined. Internal reorganization of avrXa7 by artificially deleting a portion of the central repetitive region resulted in gene pthXo4, which retained Virulence activity and lost Xa7-dependent aVirulence activity. Similarly, spontaneous rearrangements between repetitive regions of avrXa7 during bacterial culture gave rise to gene pthXo5, which also had Virulence activity without Xa7-dependent aVirulence activity. pthXo5 appeared to be the result of recomb...

  • avoidance of host recognition by alterations in the repetitive and c terminal regions of avrxa7 a type iii effector of xanthomonas oryzae pv oryzae
    Molecular Plant-microbe Interactions, 2005
    Co-Authors: Bing Yang, Akiko Sugio, Frank F. White
    Abstract:

    avrXa7 is a member of the avrBs3/pthA gene family. The gene is a critical type III effector in several strains of Xanthomonas oryzae pv. oryzae (Virulence activity), and in the presence of the Xa7 host gene for resistance, controls the elicitation of resistance in rice (aVirulence activity). The ability of strains containing avrXa7 to adapt to the presence of Xa7 in the host population is dependent, in part, on the genetic plasticity of avrXa7. The potential for the conversion of avrXa7 to a Virulence effector without Xa7-dependent elicitor activity was examined. Internal reorganization of avrXa7 by artificially deleting a portion of the central repetitive region resulted in gene pthXo4, which retained Virulence activity and lost Xa7-dependent aVirulence activity. Similarly, spontaneous rearrangements between repetitive regions of avrXa7 during bacterial culture gave rise to gene pthXo5, which also had Virulence activity without Xa7-dependent aVirulence activity. pthXo5 appeared to be the result of recombination between avrXa7 and a related gene in the genome. Loss of aVirulence activity and retention of Virulence activity also resulted from replacement of a portion of the C-terminal coding region of avrXa7 with the corresponding sequence from avrBs3. The results demonstrated the potential for a critical Virulence effector to lose aVirulence activity while retaining effector function. The results also demonstrated that features of both repetitive and nonrepetitive C-terminal regions of AvrXa7 are involved in aVirulence specificity.

  • diverse members of the avrbs3 ptha family of type iii effectors are major Virulence determinants in bacterial blight disease of rice
    Molecular Plant-microbe Interactions, 2004
    Co-Authors: Bing Yang, Frank F. White
    Abstract:

    AvrXa7 is a member of the avBs3/pthA gene family and the only known type III secretion system effector gene from Xanthomonas oryzae pv. oryzae with a major contribution to bacterial growth and lesion formation in bacterial blight disease of rice. We examined the general requirement for effectors of the AvrBs3/PthA family in bacterial blight of rice by identifying effectors from diverse strains of the pathogen. Inactivation of single effector genes in representative strains from Japan, Korea, and the Philippines resulted in severely limited growth in plants. Five strains harbored one gene of the avrBs3/pthA family, while one strain had two genes with the equivalent Virulence activity of avrXa7. Sequence analysis revealed three genes with unique repeat arrangements in comparison to avrXa7. Comparison of the repetitive regions revealed a potential motif for the group that was also present in the repetitive region of avrBs3. However, the repetitive region of avrBs3 could not support Virulence activity but, in combination with the C-terminal coding region of avrXa7, triggered a Xa7-dependent aVirulence reaction. The results revealed diverse members of the avrBs3/pthA gene family with Virulence activity in X. oryzae pv. oryzae and supported the hypothesis that bacterial blight disease of rice is highly dependent on a single class of type III effectors. The results also indicated that avrXa7 aVirulence specificity is separable from Virulence activity.

  • the Virulence factor avrxa7 of xanthomonas oryzae pv oryzae is a type iii secretion pathway dependent nuclear localized double stranded dna binding protein
    Proceedings of the National Academy of Sciences of the United States of America, 2000
    Co-Authors: Bing Yang, Weiguang Zhu, Lowell B. Johnson, Frank F. White
    Abstract:

    AvrXa7 is a member of the avrBs3 aVirulence gene family, which encodes proteins targeted to plant cells by a type III secretion apparatus. AvrXa7, the product of avrXa7, is also a Virulence factor in strain PXO86 of Xanthomonas oryzae pv. oryzae. AVirulence and Virulence specificities are associated with the central repeat domain, which, in avrXa7, consists of 25.5 direct repeat units. Mutations in three C-terminal nuclear localization signal motifs eliminated aVirulence and Virulence activities in rice and severely reduced nuclear localization in a yeast assay system. Both pathogenicity functions and nuclear localization were restored on the addition of the sequence for the nuclear localization signal motif from SV40 T-antigen. The loss of aVirulence activity because of mutations in the acidic transcriptional activation domain was restored by addition of the activation domain from the herpes simplex viral protein VP16. The activation domain was also required for Virulence activity. However, the VP16 domain could not substitute for the endogenous domain in Virulence assays. In gel shift assays, AvrXa7 bound double-stranded DNA with a preference for dA/dT rich sequences. The results indicate that products of the avrBs3-related genes are Virulence factors targeted to host cell nuclei and have the potential to interact with the host DNA and transcriptional machinery as part of their mode of action. The results also suggest that the host defensive recognition mechanisms are targeted to the Virulence factor site of action.

Xianming Chen - One of the best experts on this subject based on the ideXlab platform.

  • inheritance and linkage of Virulence genes in chinese predominant race cyr32 of the wheat stripe rust pathogen puccinia striiformis f sp tritici
    Frontiers in Plant Science, 2018
    Co-Authors: Long Wang, Dan Zheng, Xianming Chen, Hua Zhuang, Lili Huang, Zhensheng Kang, Jie Zhao
    Abstract:

    Puccinia striiformis f. sp. tritici (Pst) is the causal agent of stripe (yellow) rust on wheat. It seriously threatens wheat production worldwide. The obligate biotrophic fungus is highly capable of producing new virulent races that can overcome resistance. Studying the inheritance of Pst Virulence using the classical genetic approach was not possible until the recent discovery of its sexual stage on barberry plants. In the present study, 127 progeny isolates were obtained by selfing a representative Chinese Yellow Rust (CYR) race, CYR32, on Berberis aggregate. The parental isolate and progeny isolates were characterized by testing them on 25 wheat lines with different Yr genes for resistance and 10 simple sequence repeat (SSR) markers. The 127 progeny isolates were classified into 27 Virulence phenotypes, and 65 multi-locus genotypes. All progeny isolates and the parental isolate were avirulent to Yr5, Yr8, Yr10, Yr15, Yr24, Yr26, Yr32 and YrTr1; but virulent to Yr1, Yr2, Yr3, Yr4, Yr25, Yr44 and Yr76. The Virulence phenotypes of the parental isolate to nine Yr genes (Yr6, Yr7, Yr9, Yr17, Yr27, Yr28, Yr43, YrA and YrExp2) and the aVirulence phenotype to YrSP were found to be heterozygous. Based on the segregation of the Virulence/aVirulence phenotypes, we found that the Virulence phenotypes to Yr7, Yr28, Yr43 and YrExp2 were controlled by a dominant gene; those to Yr6, Yr9 and YrA (Yr73, Yr74) by two dominant genes; those to Yr17 and Yr27 by one dominant and one recessive gene; and the aVirulence phenotype to YrSP by two complementary dominant genes. Molecular mapping revealed the linkage of 10 Virulence/aVirulence genes. Comparison of the inheritance modes of the Virulence/aVirulence genes in this study with previous studies indicated complex interactions between Virulence genes in the pathogen and resistance genes in wheat lines. The results are useful for understanding the plant-pathogen interactions and developing wheat cultivars with effective and durable resistance.

  • Virulence and simple sequence repeat marker segregation in a puccinia striiformis f sp tritici population produced by selfing a chinese isolate on berberis shensiana
    Phytopathology, 2016
    Co-Authors: Yuan Tian, Xianming Chen, Lili Huang, Jie Zhao, Gangming Zhan, Angkana Tungruentragoon, Xia Lu, Zhensheng Kang
    Abstract:

    Puccinia striiformis f. sp. tritici, the causal agent of wheat stripe rust, frequently produces new races overcoming resistance in wheat cultivars. A recently identified race, V26 with Virulence to Yr26 and many other stripe rust resistance genes, has a high potential to cause epidemics in China. In this study, teliospores from a single-urediniospore isolate of V26 (Pinglan 17-7) produced on the wheat line 92R137 (Yr26) were used to produce a sexual population through selfing by infecting Berberis shensiana plants under controlled conditions. One hundred and eighteen progeny isolates and the parental isolate were phenotyped for Virulence/aVirulence on 24 Yr gene lines of wheat. These progeny isolates were all avirulent to Yr5, Yr8, Yr15, and YrTr1 and virulent to Yr1, Yr2, Yr7, Yr9, Yr10, Yr17, Yr24, Yr25, Yr26, YrA, YrExp2, and YrV23, indicating that the parental isolate is homozygous avirulent or homozygous virulent at these loci. The progeny population segregated for aVirulence to Yr6, Yr43, and YrSP a...

  • Virulence variations of puccinia striiformis f sp tritici isolates collected from berberis spp in china
    Plant Disease, 2016
    Co-Authors: Zhiyan Wang, Xianming Chen, Lili Huang, Jie Zhao, Yuelin Peng, Shilei Zhao, Zhensheng Kang
    Abstract:

    The stripe rust pathogen Puccinia striiformis f. sp. tritici frequently causes significant yield losses in China, due to rapid development of new races that overcome resistance in wheat cultivars. Indirect evidence suggests that sexual reproduction occurs in the P. striiformis f. sp. tritici population in China but direct evidence was still lacking. In this study, a large-scale survey of barberry (Berberis spp.) was conducted in Gansu, Shaanxi, Tibet, and Xinjiang provinces in western China. In total, 9,297 single-aecial (SA) samples were used to inoculate a susceptible wheat cultivar to identify samples of P. striiformis f. sp. tritici. Sixteen of the SA samples were identified as P. striiformis f. sp. tritici. When tested on the wheat differentials for identifying P. striiformis f. sp. tritici races, 15 of the 16 SA samples had different Virulence patterns, indicating that they were sexually produced through barberry. From the 16 SA samples, 118 single-uredinium (SU) isolates were obtained, from which 88 Virulence patterns were identified when tested on 17 Yr single-gene lines. The Virulence patterns had relatively narrow Virulence spectra, ranging from 0 to 9, with a mean of four Virulences per SU isolates. Of the 17 Yr genes, no Virulences were detected for Yr5, Yr10, and Yr15; Virulences to YrTr1, Yr24, and Yr27 were extremely low (<3%); those to YrSP, Yr9, Yr28, and Yr2 were low (13.6 to 28.0%); those to Yr7, Yr17, Yr8, and YrExp2 were moderate (33.1 to 48.3%); and those to Yr6, Yr44, and Yr25 were high (52.5 to 72.9%). This study provides direct evidence that natural sexual reproduction occurs in the P. striiformis f. sp. tritici population in China, but the frequency appears to be very low. The sexual reproduction on alternate host plants can generate a great Virulence diversity, which may have contributed to the high variation in the P. striiformis f. sp. tritici population in China.

  • Virulence characterization of puccinia striiformis f sp tritici using a new set of yr single gene line differentials in the united states in 2010
    Plant Disease, 2014
    Co-Authors: Anmin Wan, Xianming Chen
    Abstract:

    Puccinia striiformis f. sp. tritici causes stripe rust (yellow rust) of wheat and is highly variable in Virulence toward wheat with race-specific resistance. During 2010, wheat stripe rust was the most widespread in the recorded history of the United States, resulting in large-scale application of fungicides and substantial yield loss. A new differential set with 18 yellow rust (Yr) single-gene lines was established and used to differentiate races of P. striiformis f. sp. tritici, which were named as race PSTv in distinction from the PST races identified in the past. An octal system was used to describe the Virulence and aVirulence patterns of the PSTv races. From 348 viable P. striiformis f. sp. tritici isolates recovered from a total of 381 wheat and grass stripe rust samples collected in 24 states, 41 races, named PSTv-1 to PSTv-41, were identified using the new set of 18 Yr single-gene differentials, and their equivalent PST race names were determined on the previous set of 20 wheat cultivar differentials. The frequencies and distributions of the races and their Virulences were determined. The five most predominant races were PSTv-37 (34.5%), PSTv-11 (17.5%), PSTv-14 (7.2%), PSTv-36 (5.2%), and PSTv-34 (4.9%). PSTv-37 was distributed throughout the country while PSTv-11 and PSTv-14 were almost restricted to states west of the Rocky Mountains. The races had Virulence to 0 to 13 of the 18 Yr genes. Frequencies of Virulences toward resistance genes Yr6, Yr7, Yr8, Yr9, Yr17, Yr27, Yr43, Yr44, YrTr1, and YrExp2 were high (67.0 to 93.7%); those to Yr1 (32.8%) and YrTye (31.3%) were moderate; and those to Yr10, Yr24, Yr32, and YrSP were low (3.4 to 5.7%). All of the isolates were avirulent to Yr5 and Yr15.

  • Virulence characterization of international collections of the wheat stripe rust pathogen puccinia striiformis f sp tritici
    Plant Disease, 2013
    Co-Authors: Dipak Sharmapoudyal, Xianming Chen, Zhensheng Kang, Gangming Zhan, Alexey Morgounov, Beyhan Akin, Zafer Mert, Syed Jawad Ahmad Shah, M Ashraf, R C Sharma
    Abstract:

    Abstract Wheat stripe rust (yellow rust [Yr]), caused by Puccinia striiformis f. sp. tritici, is an economically important disease of wheat worldwide. Virulence information on P. striiformis f. sp. tritici populations is important to implement effective disease control with resistant cultivars. In total, 235 P. striiformis f. sp. tritici isolates from Algeria, Australia, Canada, Chile, China, Hungary, Kenya, Nepal, Pakistan, Russia, Spain, Turkey, and Uzbekistan were tested on 20 single Yr-gene lines and the 20 wheat genotypes that are used to differentiate P. striiformis f. sp. tritici races in the United States. The 235 isolates were identified as 129 Virulence patterns on the single-gene lines and 169 Virulence patterns on the U.S. differentials. Virulences to YrA, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17, Yr25, YrUkn, Yr28, Yr31, YrExp2, Lemhi (Yr21), Paha (YrPa1, YrPa2, YrPa3), Druchamp (Yr3a, YrD, YrDru), Produra (YrPr1, YrPr2), Stephens (Yr3a, YrS, YrSte), Lee (Yr7, Yr22, Yr23), Fielder (Yr6, Yr20), Tyee (YrT...

Bing Yang - One of the best experts on this subject based on the ideXlab platform.

  • avoidance of host recognition by alterations in the repetitive and c terminal regions of avrxa7 a type iii effector of xanthomonas oryzae pv oryzae
    Molecular Plant-microbe Interactions, 2005
    Co-Authors: Bing Yang, Akiko Sugio, Frank F. White
    Abstract:

    avrXa7 is a member of the avrBs3/pthA gene family. The gene is a critical type III effector in several strains of Xanthomonas oryzae pv. oryzae (Virulence activity), and in the presence of the Xa7 host gene for resistance, controls the elicitation of resistance in rice (aVirulence activity). The ability of strains containing avrXa7 to adapt to the presence of Xa7 in the host population is dependent, in part, on the genetic plasticity of avrXa7. The potential for the conversion of avrXa7 to a Virulence effector without Xa7-dependent elicitor activity was examined. Internal reorganization of avrXa7 by artificially deleting a portion of the central repetitive region resulted in gene pthXo4, which retained Virulence activity and lost Xa7-dependent aVirulence activity. Similarly, spontaneous rearrangements between repetitive regions of avrXa7 during bacterial culture gave rise to gene pthXo5, which also had Virulence activity without Xa7-dependent aVirulence activity. pthXo5 appeared to be the result of recomb...

  • avoidance of host recognition by alterations in the repetitive and c terminal regions of avrxa7 a type iii effector of xanthomonas oryzae pv oryzae
    Molecular Plant-microbe Interactions, 2005
    Co-Authors: Bing Yang, Akiko Sugio, Frank F. White
    Abstract:

    avrXa7 is a member of the avrBs3/pthA gene family. The gene is a critical type III effector in several strains of Xanthomonas oryzae pv. oryzae (Virulence activity), and in the presence of the Xa7 host gene for resistance, controls the elicitation of resistance in rice (aVirulence activity). The ability of strains containing avrXa7 to adapt to the presence of Xa7 in the host population is dependent, in part, on the genetic plasticity of avrXa7. The potential for the conversion of avrXa7 to a Virulence effector without Xa7-dependent elicitor activity was examined. Internal reorganization of avrXa7 by artificially deleting a portion of the central repetitive region resulted in gene pthXo4, which retained Virulence activity and lost Xa7-dependent aVirulence activity. Similarly, spontaneous rearrangements between repetitive regions of avrXa7 during bacterial culture gave rise to gene pthXo5, which also had Virulence activity without Xa7-dependent aVirulence activity. pthXo5 appeared to be the result of recombination between avrXa7 and a related gene in the genome. Loss of aVirulence activity and retention of Virulence activity also resulted from replacement of a portion of the C-terminal coding region of avrXa7 with the corresponding sequence from avrBs3. The results demonstrated the potential for a critical Virulence effector to lose aVirulence activity while retaining effector function. The results also demonstrated that features of both repetitive and nonrepetitive C-terminal regions of AvrXa7 are involved in aVirulence specificity.

  • diverse members of the avrbs3 ptha family of type iii effectors are major Virulence determinants in bacterial blight disease of rice
    Molecular Plant-microbe Interactions, 2004
    Co-Authors: Bing Yang, Frank F. White
    Abstract:

    AvrXa7 is a member of the avBs3/pthA gene family and the only known type III secretion system effector gene from Xanthomonas oryzae pv. oryzae with a major contribution to bacterial growth and lesion formation in bacterial blight disease of rice. We examined the general requirement for effectors of the AvrBs3/PthA family in bacterial blight of rice by identifying effectors from diverse strains of the pathogen. Inactivation of single effector genes in representative strains from Japan, Korea, and the Philippines resulted in severely limited growth in plants. Five strains harbored one gene of the avrBs3/pthA family, while one strain had two genes with the equivalent Virulence activity of avrXa7. Sequence analysis revealed three genes with unique repeat arrangements in comparison to avrXa7. Comparison of the repetitive regions revealed a potential motif for the group that was also present in the repetitive region of avrBs3. However, the repetitive region of avrBs3 could not support Virulence activity but, in combination with the C-terminal coding region of avrXa7, triggered a Xa7-dependent aVirulence reaction. The results revealed diverse members of the avrBs3/pthA gene family with Virulence activity in X. oryzae pv. oryzae and supported the hypothesis that bacterial blight disease of rice is highly dependent on a single class of type III effectors. The results also indicated that avrXa7 aVirulence specificity is separable from Virulence activity.

  • the Virulence factor avrxa7 of xanthomonas oryzae pv oryzae is a type iii secretion pathway dependent nuclear localized double stranded dna binding protein
    Proceedings of the National Academy of Sciences of the United States of America, 2000
    Co-Authors: Bing Yang, Weiguang Zhu, Lowell B. Johnson, Frank F. White
    Abstract:

    AvrXa7 is a member of the avrBs3 aVirulence gene family, which encodes proteins targeted to plant cells by a type III secretion apparatus. AvrXa7, the product of avrXa7, is also a Virulence factor in strain PXO86 of Xanthomonas oryzae pv. oryzae. AVirulence and Virulence specificities are associated with the central repeat domain, which, in avrXa7, consists of 25.5 direct repeat units. Mutations in three C-terminal nuclear localization signal motifs eliminated aVirulence and Virulence activities in rice and severely reduced nuclear localization in a yeast assay system. Both pathogenicity functions and nuclear localization were restored on the addition of the sequence for the nuclear localization signal motif from SV40 T-antigen. The loss of aVirulence activity because of mutations in the acidic transcriptional activation domain was restored by addition of the activation domain from the herpes simplex viral protein VP16. The activation domain was also required for Virulence activity. However, the VP16 domain could not substitute for the endogenous domain in Virulence assays. In gel shift assays, AvrXa7 bound double-stranded DNA with a preference for dA/dT rich sequences. The results indicate that products of the avrBs3-related genes are Virulence factors targeted to host cell nuclei and have the potential to interact with the host DNA and transcriptional machinery as part of their mode of action. The results also suggest that the host defensive recognition mechanisms are targeted to the Virulence factor site of action.

Zhensheng Kang - One of the best experts on this subject based on the ideXlab platform.

  • inheritance and linkage of Virulence genes in chinese predominant race cyr32 of the wheat stripe rust pathogen puccinia striiformis f sp tritici
    Frontiers in Plant Science, 2018
    Co-Authors: Long Wang, Dan Zheng, Xianming Chen, Hua Zhuang, Lili Huang, Zhensheng Kang, Jie Zhao
    Abstract:

    Puccinia striiformis f. sp. tritici (Pst) is the causal agent of stripe (yellow) rust on wheat. It seriously threatens wheat production worldwide. The obligate biotrophic fungus is highly capable of producing new virulent races that can overcome resistance. Studying the inheritance of Pst Virulence using the classical genetic approach was not possible until the recent discovery of its sexual stage on barberry plants. In the present study, 127 progeny isolates were obtained by selfing a representative Chinese Yellow Rust (CYR) race, CYR32, on Berberis aggregate. The parental isolate and progeny isolates were characterized by testing them on 25 wheat lines with different Yr genes for resistance and 10 simple sequence repeat (SSR) markers. The 127 progeny isolates were classified into 27 Virulence phenotypes, and 65 multi-locus genotypes. All progeny isolates and the parental isolate were avirulent to Yr5, Yr8, Yr10, Yr15, Yr24, Yr26, Yr32 and YrTr1; but virulent to Yr1, Yr2, Yr3, Yr4, Yr25, Yr44 and Yr76. The Virulence phenotypes of the parental isolate to nine Yr genes (Yr6, Yr7, Yr9, Yr17, Yr27, Yr28, Yr43, YrA and YrExp2) and the aVirulence phenotype to YrSP were found to be heterozygous. Based on the segregation of the Virulence/aVirulence phenotypes, we found that the Virulence phenotypes to Yr7, Yr28, Yr43 and YrExp2 were controlled by a dominant gene; those to Yr6, Yr9 and YrA (Yr73, Yr74) by two dominant genes; those to Yr17 and Yr27 by one dominant and one recessive gene; and the aVirulence phenotype to YrSP by two complementary dominant genes. Molecular mapping revealed the linkage of 10 Virulence/aVirulence genes. Comparison of the inheritance modes of the Virulence/aVirulence genes in this study with previous studies indicated complex interactions between Virulence genes in the pathogen and resistance genes in wheat lines. The results are useful for understanding the plant-pathogen interactions and developing wheat cultivars with effective and durable resistance.

  • Virulence and simple sequence repeat marker segregation in a puccinia striiformis f sp tritici population produced by selfing a chinese isolate on berberis shensiana
    Phytopathology, 2016
    Co-Authors: Yuan Tian, Xianming Chen, Lili Huang, Jie Zhao, Gangming Zhan, Angkana Tungruentragoon, Xia Lu, Zhensheng Kang
    Abstract:

    Puccinia striiformis f. sp. tritici, the causal agent of wheat stripe rust, frequently produces new races overcoming resistance in wheat cultivars. A recently identified race, V26 with Virulence to Yr26 and many other stripe rust resistance genes, has a high potential to cause epidemics in China. In this study, teliospores from a single-urediniospore isolate of V26 (Pinglan 17-7) produced on the wheat line 92R137 (Yr26) were used to produce a sexual population through selfing by infecting Berberis shensiana plants under controlled conditions. One hundred and eighteen progeny isolates and the parental isolate were phenotyped for Virulence/aVirulence on 24 Yr gene lines of wheat. These progeny isolates were all avirulent to Yr5, Yr8, Yr15, and YrTr1 and virulent to Yr1, Yr2, Yr7, Yr9, Yr10, Yr17, Yr24, Yr25, Yr26, YrA, YrExp2, and YrV23, indicating that the parental isolate is homozygous avirulent or homozygous virulent at these loci. The progeny population segregated for aVirulence to Yr6, Yr43, and YrSP a...

  • Virulence variations of puccinia striiformis f sp tritici isolates collected from berberis spp in china
    Plant Disease, 2016
    Co-Authors: Zhiyan Wang, Xianming Chen, Lili Huang, Jie Zhao, Yuelin Peng, Shilei Zhao, Zhensheng Kang
    Abstract:

    The stripe rust pathogen Puccinia striiformis f. sp. tritici frequently causes significant yield losses in China, due to rapid development of new races that overcome resistance in wheat cultivars. Indirect evidence suggests that sexual reproduction occurs in the P. striiformis f. sp. tritici population in China but direct evidence was still lacking. In this study, a large-scale survey of barberry (Berberis spp.) was conducted in Gansu, Shaanxi, Tibet, and Xinjiang provinces in western China. In total, 9,297 single-aecial (SA) samples were used to inoculate a susceptible wheat cultivar to identify samples of P. striiformis f. sp. tritici. Sixteen of the SA samples were identified as P. striiformis f. sp. tritici. When tested on the wheat differentials for identifying P. striiformis f. sp. tritici races, 15 of the 16 SA samples had different Virulence patterns, indicating that they were sexually produced through barberry. From the 16 SA samples, 118 single-uredinium (SU) isolates were obtained, from which 88 Virulence patterns were identified when tested on 17 Yr single-gene lines. The Virulence patterns had relatively narrow Virulence spectra, ranging from 0 to 9, with a mean of four Virulences per SU isolates. Of the 17 Yr genes, no Virulences were detected for Yr5, Yr10, and Yr15; Virulences to YrTr1, Yr24, and Yr27 were extremely low (<3%); those to YrSP, Yr9, Yr28, and Yr2 were low (13.6 to 28.0%); those to Yr7, Yr17, Yr8, and YrExp2 were moderate (33.1 to 48.3%); and those to Yr6, Yr44, and Yr25 were high (52.5 to 72.9%). This study provides direct evidence that natural sexual reproduction occurs in the P. striiformis f. sp. tritici population in China, but the frequency appears to be very low. The sexual reproduction on alternate host plants can generate a great Virulence diversity, which may have contributed to the high variation in the P. striiformis f. sp. tritici population in China.

  • Virulence characterization of international collections of the wheat stripe rust pathogen puccinia striiformis f sp tritici
    Plant Disease, 2013
    Co-Authors: Dipak Sharmapoudyal, Xianming Chen, Zhensheng Kang, Gangming Zhan, Alexey Morgounov, Beyhan Akin, Zafer Mert, Syed Jawad Ahmad Shah, M Ashraf, R C Sharma
    Abstract:

    Abstract Wheat stripe rust (yellow rust [Yr]), caused by Puccinia striiformis f. sp. tritici, is an economically important disease of wheat worldwide. Virulence information on P. striiformis f. sp. tritici populations is important to implement effective disease control with resistant cultivars. In total, 235 P. striiformis f. sp. tritici isolates from Algeria, Australia, Canada, Chile, China, Hungary, Kenya, Nepal, Pakistan, Russia, Spain, Turkey, and Uzbekistan were tested on 20 single Yr-gene lines and the 20 wheat genotypes that are used to differentiate P. striiformis f. sp. tritici races in the United States. The 235 isolates were identified as 129 Virulence patterns on the single-gene lines and 169 Virulence patterns on the U.S. differentials. Virulences to YrA, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17, Yr25, YrUkn, Yr28, Yr31, YrExp2, Lemhi (Yr21), Paha (YrPa1, YrPa2, YrPa3), Druchamp (Yr3a, YrD, YrDru), Produra (YrPr1, YrPr2), Stephens (Yr3a, YrS, YrSte), Lee (Yr7, Yr22, Yr23), Fielder (Yr6, Yr20), Tyee (YrT...

Annemarie Fejer Justesen - One of the best experts on this subject based on the ideXlab platform.

  • recovery and Virulence phenotyping of the historic stubbs collection of the yellow rust fungus puccinia striiformis from wheat
    Annals of Applied Biology, 2015
    Co-Authors: Tine Thach, Julian Rodriguezalgaba, Annemarie Fejer Justesen, Mogens S Hovmoller
    Abstract:

    A unique collection of spore samples of Puccinia striiformis, often referred to as the ‘Stubbs collection’, has been stored in liquid nitrogen from 18 to 45 years. A subset of samples representing 35 countries and 28 years was investigated to assess recovery rate, race identity and previously undetected Virulence. A new method for recovery using an airbrush sprayer and Novec™ 7100 for inoculating the host plants was highly successful. Ninety-six percent of 231 isolates were recovered. Virulence phenotyping was done using differential sets of wheat genotypes representing specific-resistance genes. A total of 181 samples represented single genotypes (isolates), whereas 40 samples consisted of at least two genotypes. Race identity was confirmed for 102 of 181 single-genotype isolates. The Virulence phenotype was updated for additional 44 isolates based on improved resolution of results because of updated and more informative wheat-differential sets. The remaining 35 isolates showed discrepancies for one or more Virulences when compared with past results. Additional Virulences corresponding to Yr17, Yr25 and Yr27, respectively, which were not assayed originally, were discovered. The value of biological collections for research and plant breeding is discussed along with the challenges of maintaining collections of biotrophic microorganisms.

  • sexual structures and recombination of the wheat rust fungus puccinia striiformis on berberis vulgaris
    Fungal Genetics and Biology, 2014
    Co-Authors: Julian Rodriguezalgaba, Mogens S Hovmoller, Stephanie Walter, Chris K Sorensen, Annemarie Fejer Justesen
    Abstract:

    An isolate of the basidiomycete Puccinia striiformis, which causes yellow (stripe) rust on wheat, was selfed on the newly discovered alternate host, Berberis vulgaris. This allowed a study of the segregation of molecular markers and Virulence in the progeny isolates, and of the development of fungal sexual structures and spore forms. Pycnia and aecia were obtained after inoculation of B. vulgaris with basidiospores resulting from germinating teliospores from infected wheat leaves. Subsequent inoculation of wheat with aeciospores from bulked aecia resulted in 16 progeny isolates of the S1 generation. Genotyping with 42 simple sequence repeat (SSR) markers confirmed a parental origin of progeny isolates. Of the 42 analyzed loci, 15 were heterozygous in the parental isolate and 14 revealed segregation in the progenies. This resulted in 11 new multilocus genotypes (MLGs), which confirmed segregation following sexual reproduction. Additionally, parental and progeny isolates were phenotyped using a genetic stock of wheat genotypes representing 21 resistance genes. All S1 progeny isolates had Virulence for 14 out of 15 loci where the parental isolate was virulent. This was consistent with the hypothesis that Virulence in plant pathogens is often recessive to aVirulence, i.e., only expressed in a homozygous state. Furthermore, no segregation was observed for five out of six loci, for which the parental isolate had an avirulent phenotype. The results for one of the two segregating Virulence/aVirulence loci suggested that the parental isolate was heterozygous with Avr alleles resulting in different but clearly avirulent phenotypes. The other locus indicated that additional genes modifying the phenotypic expression of aVirulence were involved.

  • rates of evolution of aVirulence phenotypes and dna markers in a northwest european population of puccinia striiformis f sp tritici
    Molecular Ecology, 2007
    Co-Authors: Mogens S Hovmoller, Annemarie Fejer Justesen
    Abstract:

    The effects of evolutionary processes in fungal pathogen populations may occur more rapidly and display larger effects in agricultural systems than in wild ecosystems because of human involvement by plant breeding and crop management. In this study, we analysed the rate of evolution in three lineages of a northwest European population of a biotrophic and asexual reproduced fungal pathogen, Puccinia striiformis f. sp. tritici, causing yellow rust on wheat. Pathogen samples were collected between 1975 and 2002 in the UK and Denmark, and assayed for 14 individual aVirulence/Virulence alleles and up to 234 amplified fragment length polymorphism (AFLP) primer pairs producing approximately 17 000 AFLP fragments. The large number of fragments and a targeted sampling of isolates allowed a reconstruction of phylogenies in great detail, i.e. no homoplasy and a representation of sequential, evolutionary steps by pathogen samples. A recent, phenotypic loss of aVirulence was observed at least once for loci corresponding to P. striiformis f. sp. tritici resistance Yr2, Yr3, Yr4, Yr7, Yr9, and Yr15, whereas Avr6 and Avr17 were lost independently in all three lineages, corresponding to 16 events of loss of aVirulence (emergence of Virulence). The opposite process, restoration of aVirulence, was observed for Yr9 and Yr32. An interpretation of phenotypic changes within lineages as independent mutation events resulted in mutation frequencies from 1.4 × 10−6 to 4.1 × 10−6 per AFLP fragment (locus) per generation, whereas the effective rate by which a mutation from aVirulence to Virulence was established in the pathogen population, when subject to selection by host resistance genes, was approximately three orders of magnitude faster.