Genetic Resources and Crop Evolution, Feb 22, 2012
ABSTRACT Paspalum notatum is a subtropical grass present throughout America, and one of the main ... more ABSTRACT Paspalum notatum is a subtropical grass present throughout America, and one of the main constituents of the natural grasslands in Uruguay. An apomictic autotetraploid (2n = 4x = 40) is the most frequent cytotype. The occurrence of sexual diploids (2n = 2x = 20) has also been reported as well as the occasional presence of apomictic triploids and pentaploids in Argentina. In this study, ISSR (inter simple sequence repeats) molecular markers were used to analyze the genetic variability of 210 P. notatum individuals from a collection from Uruguay. Cytometric analyses and chromosome counts were used to assess the ploidy level of the individuals. All plants from Uruguay analyzed were tetraploid. Intra- and inter-population variability was found both in genomic DNA content and at the genotypic level. Several multilocus genotypes were shared among individuals within populations and among populations over moderate geographical ranges, at the same time, very dissimilar genotypes were found within the same population. Part of the genetic variance among populations can be explained by a broader scale geographic structure which is partly coincident with the traditionally recognized grassland management regions. In spite of the apparently high degree of genetic admixture within populations, groups of related genotypes seem to follow a broader geographical structure in the area under study. These results suggest that an efficient collection strategy for this apomictically reproducing species should include carefully planned intra- and inter-population sampling. A broader scale regional sampling strategy should also be considered although further studies will be required to define genetic structure at this level.
Ergot disease (Claviceps paspali) and sterility have the potential to reduce seed yield in bahiag... more Ergot disease (Claviceps paspali) and sterility have the potential to reduce seed yield in bahiagrass (Paspalum notatum Flüggé). Our objective was to determine the genotypic and environmental effects on seed yield, and the levels of ergot and sterility. Seventeen genotypes were evaluated in three locations across two years for seed yield, ergot severity, and total seed fractions (percentage of full seeds, ergot sclerotia and empty seeds). The percentage of full seeds and total seed yield were correlated (r = 0.52) but both were negatively correlated with the percentage of ergot sclerotia (r = −0.81 and −0.51). Empty seeds were negatively correlated with full seeds (r = −0.39), but not with ergot sclerotia and total seed yield. The genotype effect was significant for total seed yield and severity of infection with large heritabilities (H2 = 0.92 and 0.86) but had no effect on the percentage of the seed fractions. Location and the interaction with genotype explained most of the variat...
Controlling a pest species raises questions about the harmful effects its eradication could cause... more Controlling a pest species raises questions about the harmful effects its eradication could cause in ecosystems. Currently, in Uruguay are being analyzed strategies to eradicate the New World Screwworm (NWS), Cochliomyia hominivorax (Diptera: Calliphoridae), an obligatory ectoparasite that causes myiasis in warm-blooded vertebrates, including humans. The loss of a species implies a risk of secondary extinctions and cascading effects that depend on the ecological function of the species and the capacity of the rest of the species with which it interacts to compensate for its loss. To assess the ecological impact of the NWS eradication, we analyzed its ecological redundancy, its effect as an indirect regulatory agent for other species, and its participation in critical ecosystem functions. We conclude that the NWS presents high functional redundancy in most ecological interactions. It does not play an essential role as a regulatory agent of other species and does not play an important...
Bacterial wilt caused by the pathogen Ralstonia solanacearum is a devastating disease of potato c... more Bacterial wilt caused by the pathogen Ralstonia solanacearum is a devastating disease of potato crops. Harmonizing immunity to pathogens and crop yield is a balance between productive, economic, and environmental interests. In this work, the agronomic performance of two events of potato cultivar INIA Iporá expressing the Arabidopsis thaliana EFR gene (Iporá EFR 3 and Iporá EFR 12) previously selected for their high resistance to bacterial wilt was evaluated under pathogen-free conditions. During two cultivation cycles, the evaluated phenotypic characteristics were emergence, beginning of flowering, vigor, growth, leaf morphology, yield, number and size of tubers, analyzed under biosecurity standards. The phenotypic characteristics evaluated did not show differences, except in the morphology of the leaf with a more globose appearance and a shortening of the rachis in the transformation events with respect to untransformed Iporá. The Iporá EFR 3 genotype showed a ~40% yield decrease i...
Red-banded stink bug Piezodorus guildinii (P. guildinii) has been described as the most damaging ... more Red-banded stink bug Piezodorus guildinii (P. guildinii) has been described as the most damaging stink bug regarding soybean crops, leading to seed injury, low germination percentages, and foliar retention, at low population densities. In recent years, RNA interference (RNAi), a conserved eukaryote silencing mechanism has been explored to develop species-selective pesticides. In this work, we evaluated RNAi in P. guildinii to develop new pest-control strategies. For this, we assembled and annotated a P. guildinii transcriptome from a pool of all developmental stages. Analysis of this transcriptome led to the identification of 56 genes related to the silencing process encompassing siRNA, miRNA, and piRNA pathways. To evaluate the functionality of RNAi machinery, P. guildinii adults were injected with 28 ng/mg of body weight of double stranded RNA (dsRNA) targeting vATPase A. A mortality of 35 and 51.6% was observed after 7 and 14 days, respectively, and a downregulation of vATPase A ...
<i>Claviceps</i> species affecting <i>Paspalum</i> spp. are a serious pro... more <i>Claviceps</i> species affecting <i>Paspalum</i> spp. are a serious problem, as they infect forage grasses such as <i>Paspalum dilatatum</i> and <i>P. plicatulum</i>, producing the ergot disease. The ascomycete <i>C. paspali</i> is known to be the pathogen responsible for this disease in both grasses. This fungus produces alkaloids, including ergot alkaloids and indole-diterpenes, that have potent neurotropic activities in mammals. A total of 32 isolates from Uruguay were obtained from infected <i>P. dilatatum</i> and <i>P. plicatulum</i>. Isolates were phylogenetically identified using partial sequences of the genes coding for the second largest subunit of RNA polymerase subunit II (<i>RPB2</i>), translation elongation factor 1-α (<i>TEF1</i>), β-tubulin (<i>TUB2</i>), and the nuc rDNA 28S subunit (28S). Isolates were also genotyped by randomly amplified polymorphic DNA (RAPD) and presence of genes within the ergot alkaloid (<i>EAS</i>) and indole-diterpene (<i>IDT</i>) biosynthetic gene clusters. This study represents the first genetic characterization of several isolates of <i>C. paspali</i>. The results from this study provide insight into the genetic and genotypic diversity of <i>Claviceps paspali</i> present in <i>P. dilatatum</i> and suggest that isolates from <i>P. plicatulum</i> could be considered an ecological subspecies or specialized variant of <i>C. paspali</i>. Some of these isolates show hypothetical alkaloid genotypes never reported before.
This review presents infornlation about lethal hereditary diseases described in Uruguay, with emp... more This review presents infornlation about lethal hereditary diseases described in Uruguay, with emphasis on those that have been confirmed pathologically and by molecular diagnostics. Congenital and 1 or hereditary diseases observed by DILAVE for the eastern region of our country arc estimated to be 3% 9% in the period 2009-2011. We discuss the relevance and importance of controlling these diseases considering the current Uruguayan legislation to detect healthy carrier animals and reduce death losses. We conclude that genetic diseases have a considerable importance in commercial production systems being an opportunity for improvement in our herds.
Background The phytopatogen Claviceps paspali is the causal agent of Ergot disease in Paspalum sp... more Background The phytopatogen Claviceps paspali is the causal agent of Ergot disease in Paspalum spp., which includes highly productive forage grasses such as P. dilatatum. This disease impacts dairy and beef production by affecting seed quality and producing mycotoxins that can affect performance in feeding animals. The molecular basis of pathogenicity of C. paspali remains unknown, which makes it more difficult to find solutions for this problem. Secreted proteins are related to fungi virulence and can manipulate plant immunity acting on different subcellular localizations. Therefore, identifying and characterizing secreted proteins in phytopathogenic fungi will provide a better understanding of how they overcome host defense and cause disease. The aim of this work is to analyze the whole genome sequences of three C. paspali isolates to obtain a comparative genome characterization based on possible secreted proteins and pathogenicity factors present in their genome. In planta RNA-se...
Potato is considered a staple food in the world and its production is limited by the presence of ... more Potato is considered a staple food in the world and its production is limited by the presence of bacterial wilt (bw) disease caused by Ralstonia solanacearum. Host resistance is the most sustainable and cost-effective strategy to manage bw, although resistant commercial potato cultivars are not yet available. Our group incorporated the efr receptor of Arabidopsis thaliana (atefr), which recognizes the elongation factor Tu, preserved in bacteria, triggering an immune response. atefr was tested in two genetic backgrounds: a susceptible commercial cultivar (inia Iporá) and a breeding clone with partial resistance introgressed from Solanum commersonii. In this work, the effect of the atefr receptor on bw resistance was evaluated for the first time, using conditions resembling natural field infection. In addition, the colonization patterns of wild-type and transgenic lines were compared by using luminescent and fluorescent R. solanacearum reporter strains. Both approaches showed a delay ...
Transgenic crops producing Bacillus thuringiensis- (Bt) insecticidal proteins (Bt crops) have pro... more Transgenic crops producing Bacillus thuringiensis- (Bt) insecticidal proteins (Bt crops) have provided useful pest management tools to growers for the past 20 years. Planting Bt crops has reduced the use of synthetic insecticides on cotton, maize and soybean fields in 11 countries throughout Latin America. One of the threats that could jeopardize the sustainability of Bt crops is the development of resistance by targeted pests. Governments of many countries require vigilance in measuring changes in Bt-susceptibility in order to proactively implement corrective measures before Bt-resistance is widespread, thus prolonging the usefulness of Bt crops. A pragmatic approach to obtain information on the effectiveness of Bt-crops is directly asking growers, crop consultants and academics about Bt-resistance problems in agricultural fields, first-hand information that not necessarily relies on susceptibility screens performed in laboratories. This type of information is presented in this report. Problematic pests of cotton and soybeans in five Latin American countries currently are effectively controlled by Bt crops. Growers that plant conventional (non-Bt) cotton or soybeans have to spray synthetic insecticides against multiple pests that otherwise are controlled by these Bt crops. A similar situation has been observed in six Latin American countries where Bt maize is planted. No synthetic insecticide applications are used to control corn pests because they are controlled by Bt maize, with the exception of Spodoptera frugiperda. While this insect in some countries is still effectively controlled by Bt maize, in others resistance has evolved and necessitates supplemental insecticide applications and/or the use of Bt maize cultivars that express multiple Bt proteins. Partial control of S. frugiperda in certain countries is due to its natural tolerance to the Bt bacterium. Of the 31 pests targeted and controlled by Bt crops in Latin America, only S. frugiperda has shown tolerance to certain Bt proteins in growers' fields, the most reliable indication of the status of Bt-susceptibility in most of the American continent.
Genetic Resources and Crop Evolution, Feb 22, 2012
ABSTRACT Paspalum notatum is a subtropical grass present throughout America, and one of the main ... more ABSTRACT Paspalum notatum is a subtropical grass present throughout America, and one of the main constituents of the natural grasslands in Uruguay. An apomictic autotetraploid (2n = 4x = 40) is the most frequent cytotype. The occurrence of sexual diploids (2n = 2x = 20) has also been reported as well as the occasional presence of apomictic triploids and pentaploids in Argentina. In this study, ISSR (inter simple sequence repeats) molecular markers were used to analyze the genetic variability of 210 P. notatum individuals from a collection from Uruguay. Cytometric analyses and chromosome counts were used to assess the ploidy level of the individuals. All plants from Uruguay analyzed were tetraploid. Intra- and inter-population variability was found both in genomic DNA content and at the genotypic level. Several multilocus genotypes were shared among individuals within populations and among populations over moderate geographical ranges, at the same time, very dissimilar genotypes were found within the same population. Part of the genetic variance among populations can be explained by a broader scale geographic structure which is partly coincident with the traditionally recognized grassland management regions. In spite of the apparently high degree of genetic admixture within populations, groups of related genotypes seem to follow a broader geographical structure in the area under study. These results suggest that an efficient collection strategy for this apomictically reproducing species should include carefully planned intra- and inter-population sampling. A broader scale regional sampling strategy should also be considered although further studies will be required to define genetic structure at this level.
Ergot disease (Claviceps paspali) and sterility have the potential to reduce seed yield in bahiag... more Ergot disease (Claviceps paspali) and sterility have the potential to reduce seed yield in bahiagrass (Paspalum notatum Flüggé). Our objective was to determine the genotypic and environmental effects on seed yield, and the levels of ergot and sterility. Seventeen genotypes were evaluated in three locations across two years for seed yield, ergot severity, and total seed fractions (percentage of full seeds, ergot sclerotia and empty seeds). The percentage of full seeds and total seed yield were correlated (r = 0.52) but both were negatively correlated with the percentage of ergot sclerotia (r = −0.81 and −0.51). Empty seeds were negatively correlated with full seeds (r = −0.39), but not with ergot sclerotia and total seed yield. The genotype effect was significant for total seed yield and severity of infection with large heritabilities (H2 = 0.92 and 0.86) but had no effect on the percentage of the seed fractions. Location and the interaction with genotype explained most of the variat...
Controlling a pest species raises questions about the harmful effects its eradication could cause... more Controlling a pest species raises questions about the harmful effects its eradication could cause in ecosystems. Currently, in Uruguay are being analyzed strategies to eradicate the New World Screwworm (NWS), Cochliomyia hominivorax (Diptera: Calliphoridae), an obligatory ectoparasite that causes myiasis in warm-blooded vertebrates, including humans. The loss of a species implies a risk of secondary extinctions and cascading effects that depend on the ecological function of the species and the capacity of the rest of the species with which it interacts to compensate for its loss. To assess the ecological impact of the NWS eradication, we analyzed its ecological redundancy, its effect as an indirect regulatory agent for other species, and its participation in critical ecosystem functions. We conclude that the NWS presents high functional redundancy in most ecological interactions. It does not play an essential role as a regulatory agent of other species and does not play an important...
Bacterial wilt caused by the pathogen Ralstonia solanacearum is a devastating disease of potato c... more Bacterial wilt caused by the pathogen Ralstonia solanacearum is a devastating disease of potato crops. Harmonizing immunity to pathogens and crop yield is a balance between productive, economic, and environmental interests. In this work, the agronomic performance of two events of potato cultivar INIA Iporá expressing the Arabidopsis thaliana EFR gene (Iporá EFR 3 and Iporá EFR 12) previously selected for their high resistance to bacterial wilt was evaluated under pathogen-free conditions. During two cultivation cycles, the evaluated phenotypic characteristics were emergence, beginning of flowering, vigor, growth, leaf morphology, yield, number and size of tubers, analyzed under biosecurity standards. The phenotypic characteristics evaluated did not show differences, except in the morphology of the leaf with a more globose appearance and a shortening of the rachis in the transformation events with respect to untransformed Iporá. The Iporá EFR 3 genotype showed a ~40% yield decrease i...
Red-banded stink bug Piezodorus guildinii (P. guildinii) has been described as the most damaging ... more Red-banded stink bug Piezodorus guildinii (P. guildinii) has been described as the most damaging stink bug regarding soybean crops, leading to seed injury, low germination percentages, and foliar retention, at low population densities. In recent years, RNA interference (RNAi), a conserved eukaryote silencing mechanism has been explored to develop species-selective pesticides. In this work, we evaluated RNAi in P. guildinii to develop new pest-control strategies. For this, we assembled and annotated a P. guildinii transcriptome from a pool of all developmental stages. Analysis of this transcriptome led to the identification of 56 genes related to the silencing process encompassing siRNA, miRNA, and piRNA pathways. To evaluate the functionality of RNAi machinery, P. guildinii adults were injected with 28 ng/mg of body weight of double stranded RNA (dsRNA) targeting vATPase A. A mortality of 35 and 51.6% was observed after 7 and 14 days, respectively, and a downregulation of vATPase A ...
<i>Claviceps</i> species affecting <i>Paspalum</i> spp. are a serious pro... more <i>Claviceps</i> species affecting <i>Paspalum</i> spp. are a serious problem, as they infect forage grasses such as <i>Paspalum dilatatum</i> and <i>P. plicatulum</i>, producing the ergot disease. The ascomycete <i>C. paspali</i> is known to be the pathogen responsible for this disease in both grasses. This fungus produces alkaloids, including ergot alkaloids and indole-diterpenes, that have potent neurotropic activities in mammals. A total of 32 isolates from Uruguay were obtained from infected <i>P. dilatatum</i> and <i>P. plicatulum</i>. Isolates were phylogenetically identified using partial sequences of the genes coding for the second largest subunit of RNA polymerase subunit II (<i>RPB2</i>), translation elongation factor 1-α (<i>TEF1</i>), β-tubulin (<i>TUB2</i>), and the nuc rDNA 28S subunit (28S). Isolates were also genotyped by randomly amplified polymorphic DNA (RAPD) and presence of genes within the ergot alkaloid (<i>EAS</i>) and indole-diterpene (<i>IDT</i>) biosynthetic gene clusters. This study represents the first genetic characterization of several isolates of <i>C. paspali</i>. The results from this study provide insight into the genetic and genotypic diversity of <i>Claviceps paspali</i> present in <i>P. dilatatum</i> and suggest that isolates from <i>P. plicatulum</i> could be considered an ecological subspecies or specialized variant of <i>C. paspali</i>. Some of these isolates show hypothetical alkaloid genotypes never reported before.
This review presents infornlation about lethal hereditary diseases described in Uruguay, with emp... more This review presents infornlation about lethal hereditary diseases described in Uruguay, with emphasis on those that have been confirmed pathologically and by molecular diagnostics. Congenital and 1 or hereditary diseases observed by DILAVE for the eastern region of our country arc estimated to be 3% 9% in the period 2009-2011. We discuss the relevance and importance of controlling these diseases considering the current Uruguayan legislation to detect healthy carrier animals and reduce death losses. We conclude that genetic diseases have a considerable importance in commercial production systems being an opportunity for improvement in our herds.
Background The phytopatogen Claviceps paspali is the causal agent of Ergot disease in Paspalum sp... more Background The phytopatogen Claviceps paspali is the causal agent of Ergot disease in Paspalum spp., which includes highly productive forage grasses such as P. dilatatum. This disease impacts dairy and beef production by affecting seed quality and producing mycotoxins that can affect performance in feeding animals. The molecular basis of pathogenicity of C. paspali remains unknown, which makes it more difficult to find solutions for this problem. Secreted proteins are related to fungi virulence and can manipulate plant immunity acting on different subcellular localizations. Therefore, identifying and characterizing secreted proteins in phytopathogenic fungi will provide a better understanding of how they overcome host defense and cause disease. The aim of this work is to analyze the whole genome sequences of three C. paspali isolates to obtain a comparative genome characterization based on possible secreted proteins and pathogenicity factors present in their genome. In planta RNA-se...
Potato is considered a staple food in the world and its production is limited by the presence of ... more Potato is considered a staple food in the world and its production is limited by the presence of bacterial wilt (bw) disease caused by Ralstonia solanacearum. Host resistance is the most sustainable and cost-effective strategy to manage bw, although resistant commercial potato cultivars are not yet available. Our group incorporated the efr receptor of Arabidopsis thaliana (atefr), which recognizes the elongation factor Tu, preserved in bacteria, triggering an immune response. atefr was tested in two genetic backgrounds: a susceptible commercial cultivar (inia Iporá) and a breeding clone with partial resistance introgressed from Solanum commersonii. In this work, the effect of the atefr receptor on bw resistance was evaluated for the first time, using conditions resembling natural field infection. In addition, the colonization patterns of wild-type and transgenic lines were compared by using luminescent and fluorescent R. solanacearum reporter strains. Both approaches showed a delay ...
Transgenic crops producing Bacillus thuringiensis- (Bt) insecticidal proteins (Bt crops) have pro... more Transgenic crops producing Bacillus thuringiensis- (Bt) insecticidal proteins (Bt crops) have provided useful pest management tools to growers for the past 20 years. Planting Bt crops has reduced the use of synthetic insecticides on cotton, maize and soybean fields in 11 countries throughout Latin America. One of the threats that could jeopardize the sustainability of Bt crops is the development of resistance by targeted pests. Governments of many countries require vigilance in measuring changes in Bt-susceptibility in order to proactively implement corrective measures before Bt-resistance is widespread, thus prolonging the usefulness of Bt crops. A pragmatic approach to obtain information on the effectiveness of Bt-crops is directly asking growers, crop consultants and academics about Bt-resistance problems in agricultural fields, first-hand information that not necessarily relies on susceptibility screens performed in laboratories. This type of information is presented in this report. Problematic pests of cotton and soybeans in five Latin American countries currently are effectively controlled by Bt crops. Growers that plant conventional (non-Bt) cotton or soybeans have to spray synthetic insecticides against multiple pests that otherwise are controlled by these Bt crops. A similar situation has been observed in six Latin American countries where Bt maize is planted. No synthetic insecticide applications are used to control corn pests because they are controlled by Bt maize, with the exception of Spodoptera frugiperda. While this insect in some countries is still effectively controlled by Bt maize, in others resistance has evolved and necessitates supplemental insecticide applications and/or the use of Bt maize cultivars that express multiple Bt proteins. Partial control of S. frugiperda in certain countries is due to its natural tolerance to the Bt bacterium. Of the 31 pests targeted and controlled by Bt crops in Latin America, only S. frugiperda has shown tolerance to certain Bt proteins in growers' fields, the most reliable indication of the status of Bt-susceptibility in most of the American continent.
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Papers by Marco Dalla Rizza