The barley chloroplast mutator (cpm) mutant: all roads lead to the Msh1 gene

The barley chloroplast mutator (cpm) is a nuclear gene mutant that induces a wide spectrum of cytoplasmically inherited chlorophyll deficiencies. Plastome instability of cpm seedlings was determined by identification of a particular landscape of polymorphisms that suggests failures in a plastome mismatch repair (MMR) protein. In Arabidopsis, MSH genes encode proteins that are in charge of mismatch repair and have anti-recombination activity. In this work, barley homologs of these genes were identified, and their sequences were analyzed in control and cpm mutant seedlings. A substitution, leading to a premature stop codon and a truncated MSH1 protein, was identified in the Msh1 gene of cpm plants. The relationship between this mutation and the presence of chlorophyll deficiencies was established in progenies from crosses and backcrosses. These results strongly suggest that the mutation identified in the Msh1 gene of the cpm mutant is responsible for the observed plastome instabilities. Interestingly, comparison of mutant phenotypes and molecular changes induced by the barley cpm mutant with those of Arabidopsis MSH1 mutants revealed marked differences.Instituto de GenéticaFil: Lencina, Franco Daniel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; ArgentinaFil: Landau, Alejandra Mabel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; ArgentinaFil: Prina, Alberto Raul. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentin

Efficiency of cytogenetic methods in detecting a chromosome rearrangement induced by ionizing radiation in a cultivated chili pepper line (Capsicum baccatum var. pendulum – Solanaceae)

Purpose: To locate transient chromosome aberrations on a selected pepper cultivar and determine the tracing efficiency of different cytogenetic methods. Materials and methods: Seeds from Capsicum baccatum var. pendulum cultivar ‘Cayenne’ were treated with an acute dose of X-rays (300 Gy) and chromosome aberrations were analysed by different cytogenetic methods [Feulgen, silver staining for nucleolus organizer regions (silver positive nucleolus organizing regions or AgNOR), fluorescent banding, fluorescence in situ hybridization (FISH) and meiotic analysis]. Results: A rearranged chromosome carrying two nucleolus organizing regions (NOR) induced by ionizing radiation was detected in the cultivar, with the occurrence of a small reciprocal exchange between a chromosome of pair no. 1 and another chromosome of pair no. 3, both carrying active NOR in short arms and associated chromomycin A positive/diamidino-phenylindole negative (CMA+/DAPI−) heterochromatin. Meiotic analysis showed a quadrivalent configuration, confirming a reciprocal translocation between two chromosomes. Conclusions: The use of X-rays in Capsicum allowed us to develop and identify a pepper line with structural rearrangements between two NOR-carrying chromosomes. We postulate that all the cytological techniques employed in this research were efficient in the search for chromosome aberrations. Particularly, Feulgen and AgNOR were the most suitable in those cases of transient rearrangements, whereas fluorescent banding and FISH were appropriate for intransitive ones.Instituto de Patología VegetalInstituto de GenéticaFil: Scaldaferro, Marisel Analía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Grabiele, Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Seijo, Jose Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste; ArgentinaFil: Debat, Humberto Julio. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Romero, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Ducasse, Daniel Adrian. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Prina, Alberto Raul. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; ArgentinaFil: Moscone, Eduardo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal; Argentin

Plastome mutations and recombination events in barley chloroplast mutator seedlings

The barley chloroplast mutator (cpm) is an allele of a nuclear gene that when homozygous induces several types of cytoplasmically inherited chlorophyll deficiencies. In this work, a plastome Targeting Induced Local Lesions in Genomes (TILLING) strategy based on mismatch digestion was used on families that carried the cpm genotype through many generations. Extensive scanning of 33 plastome genes and a few intergenic regions was conducted. Numerous polymorphisms were detected on both genic and intergenic regions. The detected polymorphisms can be accounted for by at least 61 independent mutational events. The vast majority of the polymorphisms originated in substitutions and small indels (insertions/deletions) in microsatellites. The rpl23 and the rps16 genes were the most polymorphic. Interestingly, the variation observed in the rpl23 gene consisted of several combinations of 5 different one nucleotide polymorphisms. Besides, 4 large indels that have direct repeats at both ends were also observed, which appear to be originated from recombinational events. The cpm mutation spectrum suggests that the CPM gene product is probably involved in plastome mismatch repair. The numerous subtle molecular changes that were localized in a wide range of plastome sites show the cpm as a valuable source of plastome variability for plant research and/or plant breeding. Moreover, the cpm mutant appears to be an interesting experimental material for investigating the mechanisms responsible for maintaining the stability of plant organelle DNA.Inst. de Genética "Ewald A. Favret"- IGEAFFil: Landau, Alejandra Mabel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética "Ewald A. Favret"; ArgentinaFil: Lencina, Franco. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética "Ewald A. Favret"; ArgentinaFil: Pacheco, Maria Gabriela. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética "Ewald A. Favret"; ArgentinaFil: Prina, Alberto Raul. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética "Ewald A. Favret"; Argentin

The rpl23 gene and pseudogene are hotspots of illegitimate recombination in barley chloroplast mutator seedlings

Previously, through a TILLING (Targeting Induced Local Lesions in Genomes) approach applied on barley chloroplast mutator (cpm) seedlings a high frequency of polymorphisms in the rpl23 gene was detected. All the polymorphisms corresponded to five differences already known to exist in nature between the rpl23 gene located in the inverted repeats (IRs) and the rpl23 pseudogene located in the large single copy region (LSC). In this investigation, polymorphisms in the rpl23 gene were verified and besides, a similar situation was found for the pseudogene in cpm seedlings. On the other hand, no polymorphisms were found in any of those loci in 40 wild type barley seedlings. Those facts and the independent occurrence of polymorphisms in the gene and pseudogene in individual seedlings suggest that the detected polymorphisms initially arose from gene conversion between gene and pseudogene. Moreover, an additional recombination process involving small recombinant segments seems to occur between the two gene copies as a consequence of their location in the IRs. These and previous results support the hypothesis that tInstituto de GenéticaFil: Lencina, Franco. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética "Ewald A. Favret"; ArgentinaFil: Landau, Alejandra Mabel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética "Ewald A. Favret"; ArgentinaFil: Petterson, Maria Elizabeth. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética "Ewald A. Favret"; ArgentinaFil: Pacheco, Maria Gabriela. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética "Ewald A. Favret"; ArgentinaFil: Kobayashi, K. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada. Departamento de Fisiología, Biología Molecular y Celular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Prina, Alberto Raul. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética "Ewald A. Favret"; Argentin

Isolation and characterization of a new imidazolinone tolerant mutant in cotton

Cotton cultivars resistant to different herbicides have generated important advances in crop management. There is a wide range of cotton resistance to herbicides, however, commercial imidazolinone (IMI)-tolerant cultivars are not available. In this research, a new mutation that confers tolerance to IMI in cotton was isolated in the M2 generation after seed mutagenic treatments with sodium azide water solutions. The mode of inheritance of the trait was evaluated in the F2 generation by the application of imazethapyr. The inheritance corresponds to a semi-dominant type, with a 1:2:1 distribution off tolerant: intermediate tolerance: not tolerant, in agreement with that observed in most IMI tolerant crops. The IMI-tolerant line behavior was evaluated in the field nursery after the application of the herbicide in the form of foliar and pre-emergence sprays. The tolerance level was high in pre-emergence applications and intermediate in foliar applications in comparison to the non-tolerant genotype, which showed a decrease in fiber yield and quality with both methods of application. After sequencing the AHAS gene, a point mutation corresponding to Ala205Val in the AHAS enzyme was found, which suggests it could be responsible for the increased IMI tolerance observed in cotton line SP 4172-32. Based on results from field assays it can be concluded that this mutant is a promising experimental line that can be used in obtaining IMI tolerant commercial cotton cultivars.EEA Sáenz PeñaFil: Tcach, Mauricio Alfredo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Sáenz Peña; ArgentinaFil: Landau, Alejandra Mabel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; ArgentinaFil: Montenegro, Alex. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Sáenz Peña; ArgentinaFil: Diaz, Daniel Gustavo. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; ArgentinaFil: Acuña, C.A. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste; ArgentinaFil: Acuña, C.A. Universidad Nacional del Nordeste. Instituto de Botánica del Nordeste; ArgentinaFil: Prina, Alberto Raul. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentin

Mutation Breeding for Sustainable Food Production in Latin America and the Caribbean Under Climate Change

The region of Latin America and the Caribbean is characterized by the great diversity of crops and environmental conditions where the crops coexist under the effects of different abiotic and biotic stresses, which impact unfavorably the food and nutrition security. This vulnerability increases by the effect of climate change due to increase in minimal and maximal temperatures, changes in rainfall pattern that increased the intensity of drought, and rise of sea level affecting coastal areas by intrusion of salty water. To alleviate these constraints, several programs of genetic improvement have been developed with the support of the International Atomic Energy Agency (IAEA) directed to obtain new high-yielding varieties under different stressful conditions. From these projects, several mutants have been obtained which are used directly in the production areas because of their good productive potential or as parental in breeding programs. These advances have been achieved in crops such as rice (Oryza sativa L.), tomato (Solanum lycopersicum L.), common bean (Phaseolus vulgaris L.), soybean (Glycine max Merrill), quinoa (C. quinoa Willd), and Hibiscus sabdariffa L. Rice is the crop in which the largest number of mutants have been obtained, and more Latin American countries are involved in rice improvement. In this chapter, we have presented an overview of the progress in mutation breeding in the Latin American and the Caribbean region with successful examples.Instituto de GenéticaFil: González Cepero, María Caridad. National Institute of Agricultural Science (INCA); CubaFil: Gómez Pando, Luz. Agrarian National University La Molina; PerúFil: De Andrade, Alexander. Estação Experimental de Itajaí. Empresa de Pesquisa Agropecuária e Extensão Rural de Santa Catarina (Epagri); BrasilFil: Arguello Delgado, Juan Felix. National University of Costa Rica; Costa RicaFil: Nakayama Nakashima, Héctor. Asuncion National University. Multidisciplinary Center of Technological Investigations; ParaguayFil: Landau, Alejandra Mabel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; ArgentinaFil: Prina, Alberto Raul. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; ArgentinaFil: Rodríguez García, Mayra. Genetic and Engineering and Biotechnology Center (CIGB); CubaFil: Suchini Farfan, Aura. Science and Agricultural Technology Institute (ICTA); MéxicoFil: de la Cruz Torres, Eulogio. National Institute of Nuclear Investigations (ININ); Méxic