“Peste negra” is a disease, caused by tospoviruses, that affects tomato crops in Argentina. Knowledge of the diversity, frequency, and distribution of different tospoviruses is essential for developing a rational control program based on genetic resistance sources. A study of the geographical distribution of tospoviruses affecting tomato crops in Argentina is presented in this paper. The areas surveyed were between the Tropic of Capricorn and 40°S and between longitude 58°W and 70°W. Tospovirus species were identified through double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), using polyclonal antisera against Tomato spotted wilt virus (TSWV), Groundnut ringspot virus (GRSV), and Tomato chlorotic spot virus (TCSV). From tomato samples that reacted positively with any of the used antisera, 63% were GRSV, 28.2% were TCSV, and 8.8% were TSWV. A differential geographical distribution of tospoviruses was determined. Every plant that tested positive for GRSV was from central and northwest Argentina, while every plant TCSV-positive was from the northeast. TSWV was found only in the Río Negro Valley region in the south of the country. The wide dispersion of GRSV may be related to the spread of Frankliniella shultzei, which transmits this virus more efficiently than other vectors.

No abstract

Chlorotic dwarf (CD), the most important disease in the sweet potato-producing regions of Argentina, is caused by the synergistic combination of two aphid-transmitted potyviruses with a whitefly-transmitted crinivirus. Sweet potato feathery mottle virus, sweet potato mild speckling virus, and a crinivirus (serologically related to sweet potato chlorotic stunt virus) were associated with CD. The synergistic combination of these three viruses reproduced the disease.

Buffel grass (Cenchrus ciliaris L.) is an important apomictic grass used as forage for ruminant livestock. Biotechnological methods provide opportunities for producing new germplasm. Mature embryos of fourteen buffel grass apomictic cultivars (2n = 4x = 36) were used to induce embryogenic callus formation using a basal medium supplemented with 3% sucrose and with the testing of five concentrations of 2,4‐dichlorophenoxyacetic acid (2,4‐D) and four concentrations of 6‐benzylaminopurine (BAP). The effects of cultivar and culture medium on callus induction and plant regeneration were evaluated. Significant differences were observed among the fourteen cultivars and the five concentrations of 2,4‐D (P < 0·01). Values for embryogenic callus production varied from 0 to 86·7. Most cultivars showed the highest level of embryogenic callus production on the medium with the concentration of 3 mg L−1 2,4‐D. The addition of different BAP concentrations in combination with 2,4‐D in the medium inhibited embryogenic callus growth and did not permit plant regeneration. The data clearly demonstrated that the genotype and concentrations of 2,4‐D had significant effects both on the frequency of embryonic callus formation from mature embryos and on the subsequent efficiency of plant regeneration of apomictic cultivars of buffel grass. Cultivars Biloela and Nunbank showed the greatest efficiency in in vitro culture response.

Buffel grass (Cenchrus ciliaris L.) is an apomictic species that is widely adapted to arid and semi-arid, tropical and warm climates. Six apomictic cultivars used as male parents, one sexual line used as the female parents and 15 putative F1 genotypes were studied using the amplified fragment length polymorphism (AFLP) technique for their evaluation and recognition. The NTSYS programme and Jaccard's Index were used to establish the genetic similarity; and a phenogram was constructed. A total of 152 bands was recorded. Three primer combinations were sufficient to identify the genotypes. The maximum proportion of polymorphisms was 0AE835, and 0AE510 of the polymorphisms consisted in individual bands that strictly diagnosed unique genotypes. Texas 4464 and Americana cultivars were the most different from the sexual line, indicating that they might be the best genotypes for future crossing. Two hybrids were identified among F1 material to demonstrate the usefulness of the AFLP technique in characterizing genotypes and recognizing hybrids in Buffel grass for breeding purposes.

A cDNA library was constructed from viral genomic RNA purified from sweet potato plants affected by "Sweet Potato Chlorotic Dwarf disease" in an attempt to clarify the etiology of this viral complex in Argentina. By sequence analysis, some of the obtained clones were found to belong to sweet potato feathery mottle potyvirus (SPFMV), to a closterovirus and to a new potyvirus. A cDNA clone of 1,103 bp representing the coat protein cistron and 3' non-coding region of the newly identified potyvirus was further characterized. The sequence contained an ORF of 855 nucleotides with a coding capacity of 285 amino acids, followed by a 3' untranslated tail of 248 nucleotides. The core and C-terminal regions have sequences well conserved among potyviruses. Furthermore, amino acid sequence comparisons of the capsid protein with those of other described potyviruses showed 63% homology with SPFMV, 68 to 70% with two different isolates of sweet potato latent potyvirus (SPLV), 57% with sweet potato G potyvirus (SPGV) and 73% with potato virus Y (PVY). These data allowed us to propose the inclusion of this virus as a new member of the family Potyviridae, genus Potyvirus with the designation sweet potato mild speckling potyvirus (SPMSV).

In Argentina there is a large market for aromatic plants, a trade that reaches its maximum importance in the mountain areas of Córdoba in the centre-west of the country. Of the native species, Minthostachys mollis (Kunth.) Griseb., or the peperina, is the most sought-after, and studies have begun to look for ways to sustainably cultivate crops of this species. The aim of the present work was to determine the response of different peperina populations to cropping (the partial harvest of growing plants). Eight populations from different original locations were grown in the mountains of the Córdoba province under different cropping regimens (i.e., different cropping times and number of cropping events). Plant production and persistence were recorded for each regimen. Large variations were observed in dry matter content and the quantities of essential oil produced; the genotype x environment interaction was found to have a significant effect («environment» refers to that produced by the cropping regimen). The differences between populations in terms of yield and in response to management must be known if clones are to be selected for crop improvement. The sustainable use of high yield populations subject to the best cropping regimen could increase the profits associated with cultivation of this species.Key words: aromatic herbs, crop performance, dry matter, essential oils. ResumenComportamiento productivo de poblaciones de peperina, Minthostachys mollis (Kunth.) Griseb., en el año de implantación, según distintos momentos de cosecha En Córdoba, Argentina, se encuentra muy difundida la explotación y comercialización de aromáticas, siendo las zonas serranas que corresponden al área centro-oeste del país donde adquiere mayor relevancia. De las especies nativas, la peperina, Minthostachys mollis (Kunth.) Griseb., se encuentra entre las que han sufrido mayor extracción. Se han comenzado estudios buscando un cultivo sustentable de esta especie, siendo entonces muy importante la caracterización y evaluación para el manejo y mejora. El objetivo de este trabajo fue determinar la respuesta a cortes productivos efectuados en el cultivo de distintas poblaciones nativas de peperina. El ensayo se ubicó en las serranías de la provincia de Córdoba, donde se evaluaron ocho poblaciones de dos procedencias distintas. Los tratamientos planteados se definieron combinando tres niveles del factor «número de cortes» y tres épocas del año en las que fueron efectuados los cortes. Se evaluó la producción y la persistencia de las plantas en respuesta a los tratamientos. Se encontró gran variación en rendimiento tanto de materia seca como de aceites esenciales entre las poblaciones evaluadas y una fuerte interacción genotipo por ambiente, considerando como ambiente aquel generado por las distintas modalidades de corte. Las diferencias entre poblaciones, encontradas a nivel de producción y como respuesta al manejo, son fundamentales para comenzar con la selección de clones en vista a una optimización de la producción bajo cultivo. El us...

RESUMENMal de Río Cuarto virus en trigo provoca una enfermedad resultante de la acción combinada con su principal vector, Delphacodes kuscheli. La severa sintomatología inducida por virus e insecto condujo a determinar la posible existencia de alteraciones fisiológicas en inducida por virus e insecto condujo a determinar la posible existencia de alteraciones fisiológicas en el cultivar de trigo ProINTA Federal, infectado artificialmente con dos aislamientos geográficamente distantes del MRCV y sometido a picadura de insectos no virulíferos, respectivamente, en tres estadios fenológicos. ProINTA Federal fue picado por insectos no virulíferos e inoculado en la primera hoja emergiendo del coleóptilo, en la cuarta y quinta hojas desplegadas, respectivamente. La condición sanitaria de los diferentes tratamientos fue constatada mediante ELISA. Las plantas tratadas manifestaron alteraciones fisiológicas con similares variaciones entre estadios fenológicos. Azúcares solubles totales, almidón y proteínas solubles incrementaron significativamente su contenido en plantas infectadas por MRCV. En plantas PS y con MRCV, el contenido de clorofilas disminuyó marcadamente y lo inverso sucedió con el malondialdehído, lo que indicaría daño oxidativo por estrés en las mismas. No existieron diferencias entre estadios fenológicos y las variaciones de los indicadores de alteraciones fisiológicas considerados, excepto para el incremento de almidón, significativamente superior en plantas inoculadas en la primera hoja emergiendo del coleóptilo. Palabras clave: infección viral, toxicidad por insectos, azúcares solubles, almidón, proteínas, clorofilas, malondialdehído, estadios fenológicos. ABSTRACT Physiological alterations associated to the Mal de Rio Cuarto virus (MRCV) infection and to vector (Delphacodes kuscheli Fennah) phytotoxicity in wheatMal de Río Cuarto virus produces a wheat disease, resulting from the combined action of this pathogen and its main vector, resulting from the combined action of this pathogen and its main vector, from the combined action of this pathogen and its main vector, of this pathogen and its main vector, this pathogen and its main vector, Delphacodes kuscheli. Knowing that viruses and insects cause a severe symptomatology in different genotypes, the objective of this nowing that viruses and insects cause a severe symptomatology in different genotypes, the objective of this severe symptomatology in different genotypes, the objective of this in different genotypes, the objective of this genotypes, the objective of this the objective of this the objective of this of this work was to determine the possible physiological alterations in three phenological stages of wheat (cv ProINTA Federal) inoculated by was to determine the possible physiological alterations in three phenological stages of wheat (cv ProINTA Federal) inoculated by possible physiological alterations in three phenological stages of wheat (cv ProINTA Federal) inoculated by le physiological alterations in three phenological stages of wheat (cv Pro...