Phenotypic, molecular and pathogenic characterization of Colletotrichum scovillei infecting Capsicum species in Rio de Janeiro, Brazil.

Anthracnose is a disease caused by Colletotrichum spp., one of the world's most damaging sweet and chili pepper pathogens, especially in tropical and subtropical regions. In the state of Rio de Janeiro, anthracnose is one of the main obstacles for pepper crops. However, to date no research has focused on the identification and characterization of the pathogen, which is fundamental to understand the scope of the disease in the state. Thus, the correct identification of the fungal species and pathogenicity studies can provide important support for disease management and control, apart from identifying possible resistance sources for exploitation in peppers breeding programs. In this study, 11 Colletotrichum isolates were collected from peppers with typical symptoms in the Rio de Janeiro state. These isolates were characterized based on morpho-cultural characteristics and sequencing data from five regions (ITS, ACT, CAL, ß-TUB and GAPDH), and the genetic variability was estimated by AFLP markers. Simultaneously, microscopy images of the colonization by the fungal species on unripe Capsicum annuum fruits were taken. Pathogenicity was tested and resistance sources were sought by means of infection of ripe and unripe fruits of 50 Capsicum baccatum accessions. The resulting data showed that all isolates belong to Colletotrichum scovillei specie. About the pathogenicity of Capsicum baccatum, differentiated, stage-specific responses, with higher resistance of ripe fruits were recorded. In addition, four possible sources of Colletotrichum scovillei resistance were detected among the tested accessions. The combination of these data can contribute to future studies on the interaction of Colletotrichum scovillei-Capsicum spp., a research line that is still unexploited in the main areas of this anthracnose fungus.

Genome relationships and LTR-retrotransposon diversity in three cultivated Capsicum L. (Solanaceae) species.

BACKGROUND: Plant genomes are rich in repetitive sequences, and transposable elements (TEs) are the most accumulated of them. This mobile fraction can be distinguished as Class I (retrotransposons) and Class II (transposons). Retrotransposons that are transposed using an intermediate RNA and that accumulate in a "copy-and-paste" manner were screened in three genomes of peppers (Solanaceae). The present study aimed to understand the genome relationships among Capsicum annuum, C. chinense, and C. baccatum, based on a comparative analysis of the function, diversity and chromosome distribution of TE lineages in the Capsicum karyotypes. Due to the great commercial importance of pepper in natura, as a spice or as an ornamental plant, these genomes have been widely sequenced, and all of the assemblies are available in the SolGenomics group. These sequences were used to compare all repetitive fractions from a cytogenomic point of view. RESULTS: The qualification and quantification of LTR-retrotransposons (LTR-RT) families were contrasted with molecular cytogenetic data, and the results showed a strong genome similarity between C. annuum and C. chinense as compared to C. baccatum. The Gypsy superfamily is more abundant than Copia, especially for Tekay/Del lineage members, including a high representation in C. annuum and C. chinense. On the other hand, C. baccatum accumulates more Athila/Tat sequences. The FISH results showed retrotransposons differentially scattered along chromosomes, except for CRM lineage sequences, which mainly have a proximal accumulation associated with heterochromatin bands. CONCLUSIONS: The results confirm a close genomic relationship between C. annuum and C. chinense in comparison to C. baccatum. Centromeric GC-rich bands may be associated with the accumulation regions of CRM elements, whereas terminal and subterminal AT- and GC-rich bands do not correspond to the accumulation of the retrotransposons in the three Capsicum species tested.

Transcriptional patterns of Coffea arabica L. nitrate reductase, glutamine and asparagine synthetase genes are modulated under nitrogen suppression and coffee leaf rust.

This study evaluated the transcriptional profile of genes related to nitrogen (N) assimilation in coffee plants susceptible and resistant to rust fungi under N sufficiency and N suppression. For this purpose, we inoculated young coffee leaves with Hemileia vastatrix uredospores and collected them at 0, 12, 24 and 48 hours post-inoculation (HPI) to evaluate the relative expressions of genes encoding cytosolic glutamine synthetase (CaGS1 ), plastid glutamine synthetase (CaGS2 ), nitrate reductase (CaNR), and asparagine synthetase (CaAS). The genes exhibited distinct patterns of transcriptional modulation for the different genotypes and N nutritional regimes. The resistant genotype (I59) presented high levels of transcription in response to pathogen inoculation for CaNR and CaGS1 genes, evaluated under N sufficiency in the initial moments of infection (12 HPI). The gene CaGS1 also showed a peak at 48 HPI. The susceptible genotype (CV99) showed increased transcript rates of CaNR at 12 and 24 HPI in response to rust inoculation. The transcriptional patterns observed for CV99, under N suppression, were high levels for CaAS and CaGS2 at all post-inoculation times in response to coffee leaf rust disease. In addition, CaGS1 was up-regulated at 48 HPI for CV99. Cultivar I59 showed high transcript levels at 12 HPI for CaAS and peaks at 24 and 48 HPI for CaGS2 in inoculated samples. Consequently, total chlorophyl concentration was influenced by N suppression and by rust infection. Regarding enzyme activities in vitro for glutamine synthetase and CaNR, there was an increase in infected coffee leaves (I59) and under N sufficiency. Moreover, CV99 was modulated in both N nutritional regimes for GS activity in response to rust. Our results indicate that N transport genes trigger a differential modulation between genotypes through the action of rust disease.