Abstract Pyrenophora teres f. maculata is the causal agent of barley spot form net blotch (SFNB), a major stubble-borne disease in many barley-growing areas worldwide. In plants, the Nucleotide-Binding Site-Leucine-Rich Repeat (NBS-LRR) gene family functions in immunity against a variety of pathogens and pests. From a pre-established set of NBS-type resistance gene candidates, we have selected three candidate genes, HvNBS10, HvNBS72 and HvNBS85, to analyze their possible involvement in P. teres f. maculata resistance. The studied genes were mapped on chromosomes 5H and 7H. Expression profiles using qRT-PCR, 48 hours after infection by P. teres. f. maculata, revealed that the transcription of all genes acted in the same direction (down-regulation) in both resistant and susceptible cultivars, although they showed a variation in transcript dosage. This result suggests that coordinated transcriptional responses of multiple barley NBS genes would be required to an efficient response against P. teres f. maculata. Moreover, the phylogenetic analysis revealed that the studied barley candidate R genes were characterized by a high homology with the barley Nbs2-Rdg2a gene conferring resistance to the fungus Pyrenophora graminea, suggesting a common origin of P. graminea and P. teres resistance genes in barley, following pathogens evolution. The genes characterized in the present study hold potential in elucidating the molecular pathways and developing novel markers associated with SFNB resistance in barley.

ABSTRACT Computational investigation of a set of publicly available plant microRNAs revealed 19 barley- and other plants-encoded miRNAs and their near-complement reverse sequences (miRNA*) that have potential to bind all B/CYDV open reading frames (ORFs) except ORF0 and ORF6. These miRNAs/miRNAs*, their binding positions and targets are discussed in the context of biological protection of cereals against B/CYDV, based on antiviral silencing.

Proteins containing nucleotide binding sites (NBS) encoded by plant resistance genes play an important role in the response of plants to a wide array of pathogens. In this paper, an in silico search was conducted in order to identify and characterize members of NBS-encoding gene family in the tribe of Triticeae. A final dataset of 199 sequences was obtained by four search methods. Motif analysis confirmed the general structural organization of the NBS domain in cereals, characterized by the presence of the six commonly conserved motifs: P-loop, RNBS-A, Kinase-2, Kinase-3a, RNBS-C and GLPL. We revealed the existence of 11 distinct distribution patterns of these motifs along the NBS domain. Four additional conserved motifs were shown to be significantly present in all 199 sequences. Phylogenetic analyses, based on genetic distance and parsimony, revealed a significant overlap between Triticeae sequences and Coiled coil-Nucleotide binding site-Leucine rich repeat (CNL)-type functional genes from monocotyledons. Furthermore, several Triticeae sequences belonged to clades containing functional homologs from non Triticeae species, which has allowed for these sequences to be functionally assigned. The findings reported, in this study, will provide a strong groundwork for the isolation of candidate R-genes in Triticeae crops and the understanding of their evolution.

El pulgón verde Schizaphis graminum, es una plaga importante del trigo en todo el mundo. La detección de biotipos de esta plaga es esencial para el desarrollo de programas de manejo de plagas. En esta investigación se colectaron, ocho clones del pulgón verde, en el trigo en la región de cultivo de cereales de Béja (norte de Túnez), y se utilizaron para determinar el daño en seis cultivos de trigo de referencia. Todos los clones ensayados comparten un perfil único de biotipo, similar al biotipo C. Además, el ADN de los clones ensayados y de los siete clones de referencia de biotipos C, E, F, G, H, I y K, se analizaron, utilizando 5 RAPD PCR primers. El método UPGMA agrupó las muestras en dos clados: el primero (I) incluye clones del norte de Túnez, que están claramente asociados a los biotipos agrícolas C, E, I y K, mientras que un segundo clado (II) incluyó los biotipos no agrícolas F, G y H. Los resultados sugieren que los genes de resistencia, la Gb2, Gb3, Gb4, Gb5 y Gb6 en el trigo serían los más eficaces si se utilizan en programas de mejoramiento de trigo para la resistencia contra el pulgón verde en Túnez.

The greenbug Schizaphis graminum, is a major pest of wheat worldwide. Biotype screening of this pest is essential to develop pest management programs. In this research, eight greenbug clones, collected on wheat in the cereal-growing region of Béja (north Tunisia), were used to determine their damage on six reference wheat cultivars. All tested clones shared a unique biotypic profile, similar to biotype C. Moreover, DNA from the tested clones and that from seven reference clones of biotypes C, E, F, G, H, I and K, was analyzed, using 5 RAPD-PCR primers. The UPGMA method clustered samples into two distinct clades: a first one (I) included clones from north Tunisia, which were clearly associated to agricultural biotypes C, E, I and K, while a second clade (II) included non agricultural biotypes F, G and H. Results reported in this paper suggest that resistance genes Gb2, Gb3, Gb4, Gb5 and Gb6 in wheat would be the most efficient if used in wheat improvement programs for resistance against greenbug in Tunisia.

The tomato leaf miner Tuta absoluta Meyrick has invaded tomato (Solanum lycopersicum L.) crop in Tunisia since 2008 and is representing today a major threat to the production of this crop. In this study, we used the Randomly Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) technology to assess the genetic variability within and among seven populations of T. absoluta, collected on tomato from different regions in Tunisia. Using five RAPD-PCR primers and 108 individuals, 140 polymorphic fragments were recorded. From 335 different RAPD phenotypes generated, 71 were redundant and 264 unique to a specific population. The genetic structure of T. absoluta was investigated using analysis of molecular variance (AMOVA), genetic distances (Fst) and multidimensional scaling (MDS). We detected a high genetic diversity within and among populations in conjunction with a significant differentiation between populations, suggesting that different founder genotypes would have been responsible of the introduction of T. absoluta in Tunisia. The presence of overlapping phenotypes probably indicates migration events between populations, mainly through infested plant material carried by humans.

El minador de hojas de tomate Tuta absoluta Meyrick ha invadido el cultivo del tomate (Solanum lycopersicum L.) en Túnez desde 2008 y actualmente representa una importante amenaza para su producción. En este estudio usamos la tecnología de ADN polimórfico amplificado al azar-reacción de cadena polimerasa (RAPD-PCR) para evaluar la variabilidad genética dentro y entre siete poblaciones de T. absoluta, colectadas desde tomate en diferentes regiones de Túnez. Usando cinco primers RAPD-PCR y 108 individuos, se registraron 140 fragmentos polimórficos. Se generaron 335 fenotipos RAPD diferentes, entre los cuales 71 fueron redundantes y 264 únicos para una población específica. La estructura genética de T. absoluta se investigó usando análisis de varianza molecular (AMOVA), distancias genéticas (Fst) y escalamiento multidimensional (MDS). Detectamos una alta diversidad genética dentro y entre poblaciones en conjunto con una diferenciación significativa entre poblaciones, sugiriendo que los genotipos fundadores podrían haber sido responsables de la introducción de T. absoluta en Túnez. La presencia de fenotipos superpuestos probablemente indica eventos de migración entre poblaciones, principalmente a través de material vegetal infestado transportado por humanos.

Hessian fly, Mayetiola destructor (Say), is a destructive pest of wheat worldwide and an endemic pest in Tunisia. Two natural populations of this insect from the North of Tunisia were evaluated, in the field, for their virulence, based on response developed by bread wheat (Triticum aestivum L.) cultivars carrying H3, H5, H6, H7H8, H11, H13 and H16 resistance genes. H11, H13 and H16 showed a high effectiveness against both populations; therefore, their implication in Hessian fly breeding programs would be of interest. The level of infestation, as well as the yield loss, was assessed, based on the percentage of infested plants and variation in growth parameters due to infestation. The percentage of infested plants, over a 2-yr period in Mateur, averaged 18.82% for durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn.) and 32.50% for bread wheat. For the improved durum wheat cv. Karim used as reference, the plant height, number of internodes, number of productive tillers per plant, and 100-seed weight were negatively affected by infestation, while the number of tillers per plant was positively affected. Aiming to update information about the annual number of the fly generations occurring on wheat, we surveyed infestation in Jédéida. At least three Hessian fly generations were detected on bread wheat and durum wheat. Continued regular surveying of Hessian fly populations in terms of virulence, impact on yield and annual generations is required for optimal deployment of resistance genes and integrated management of Hessian fly across all wheat production areas.

La mosca de Hess, Mayetiola destructor (Say), es una plaga mundial destructiva del trigo y endémica en Túnez. Se evaluaron dos poblaciones naturales de este insecto desde el Norte de Túnez, en el campo, por su virulencia, basado en la respuesta desarrollada por cultivares de trigo panadero (Triticum aestivum L.) portando los genes de resistencia H3, H5, H6, H7H8, H11, H13 y H16. H11, H13 and H16 mostraron una alta efectividad contra ambas poblaciones; por lo tanto, su implicancia en programas de producción de mosca de Hess podría ser de interés. Se evaluaron el nivel de infestación y la pérdida de rendimiento, basado en el porcentaje de plantas infestadas y variación en parámetros de crecimiento debidos a infestación. El porcentaje de plantas infestadas, en un período de 2 años en Mateur, promedió 18,82% para trigo candeal (Triticum turgidum L. subsp. durum (Desf.) Husn.) y 32,50% para trigo panadero. Para el trigo candeal mejorado cv. Karim usado como referencia, altura de planta, número de entrenudos, número de cañas productivas por planta, y peso de 100 semillas fueron negativamente afectados por infestación, mientras el número de cañas por planta fue positivamente afectado. Con el fin de actualizar la información sobre el número anual de las generaciones de mosca en trigo, investigamos infestación en Jédeida. Al menos tres generaciones de mosca de Hess se detectaron en trigo panadero y candeal. Se requieren ensayos regulares de virulencia, impacto en rendimiento, y generaciones anuales de poblaciones de mosca de Hess para un óptimo despliegue de genes de resistencia y manejo integrado de la mosca por todas las áreas productoras de trigo.

Se registra información acerca de la estructura del cariotipo de M. Hordei, una mosca que infesta la cebada en el sur de Túnez. El número de cromosomas fue (2n=8) en células somáticas femeninas y (2n-2=6) en células somáticas masculinas, lo cuál es similar al cariotipo de M. destructor. Se describen y comparen las cromosomas mitóticos y politénicos de M. hordei con los de M. destructor. Los datos cariológicos se discuten en términos de los mecanismos genéticos que explican la divergencia entre M. hordei y M. destructor.

We report information about the structure of the karyotype of M. hordei, a fly that infests barley in the south of Tunisia. The number of chromosomes was found to be (2n = 8) in somatic female cells and (2n – 2 = 6) in somatic male cells, which is similar to the karyotype of M.destructor. Mitotic and polytene chromosomes of M. hordei are described and compared with those of M. destructor. The karyological data are discussed in terms of genetic mechanisms underlying divergence of M. hordei and M. destructor.