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Rust is the main disease affecting Coffea arabica, the most economically important coffee species. The objective of this study was to analyze C. arabica cultivars with different levels of rust resistance, including bean size, raw bean appearance, final sensory scores (FSS), and aroma and taste nuances of the coffee cup. The experiment was designed in randomized blocks (RBD) with three replications and 20 treatments (cultivars), totaling 60 experimental plots. The rust-susceptible cultivars IPR 100, Rubi MG 1192, and Topázio MG 1190 were compared with 17 rust-resistant cultivars. Cultivars IPR 103, MGS Aranãs, and Saíra II presented the highest percentages of high sieves, highest scores of raw bean appearance, and low percentages of mocha-type beans. All cultivars had FSS above 82 and were classified as specialty coffees. The cultivars with the highest FSS (Arara and Catiguá MG2) showed a greater diversity of coffee cup aroma and flavor nuances. Rust-resistant Arabica coffee cultivars are promising for the physical quality of beans and have potential for the specialty coffee market. [ABSTRACT FROM AUTHOR]

Bacterial halo blight of coffee (BHB), caused by Pseudomonas syringae pv. garcae, is one of the main coffee diseases and is economically important mainly in regions of higher altitudes and mild temperatures. The use of resistant cultivars in the management of diseases is the most efficient and least costly technology for producers. The Coffee Germplasm Bank of Minas Gerais State has genotypes with great genetic variability, some of which are sources of resistance to several diseases and pests. Thus, the objective of this study was to evaluate the potential of 34 genotypes from the Coffee Germplasm Bank of Minas Gerais State and five cultivars with resistance to BHB. We evaluated the expression of three plant defence genes (phenylalanine ammonia liase‐PAL, peroxidase‐POX, and cinnamyl alcohol dehydrogenase‐CAD) and quantified the content of total soluble phenolic compounds, lignin, caffeine, trigonelline, and chlorogenic acid in coffee leaves showing different levels of resistance to BHB. The cultivar IPR 102 (resistant control to BHB), the Catimor UFV 7158, Caturra Vermelho × CIFC H 79/1 UFV 339‐34, Catiguá MG2, Volutifolia Vermelho, Caturra Vermelho, Híbrido de Timor UFV 432‐02, Caturra Vermelho × CIFC H 288/14 UFV 319‐04, and Caturra Vermelho × CIFC H 79/1 UFV 339‐02 genotypes showed low disease severity. The UFV 7158 genotype showed higher PAL and POX expression levels than Mundo Novo 376/4 cultivar. The IPR 102 cultivar and UFV 7158 genotype showed high chlorogenic acid content and low caffeine and trigonelline contents. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to investigate the effectiveness of potassium phosphites for the control of anthracnose and the mode of action of these products on common bean plants against Colletotrichum lindemuthianum, comparing it with the standard resistance inducer acibenzolar‐S‐methyl. The protection of plants against anthracnose was evaluated in greenhouse after treatment with potassium phosphites (Phosphite A and B, 5.0 ml/L), acibenzolar‐S‐methyl (0.25 g/L), or no treatment (control). Two sprayings of the treatments were performed, respectively, at V4 stage (three trifoliate leaves) and at the R5 stage (flower buds present). The inoculation with C. lindemuthianum was performed 5 days after the first spraying. Phosphite formulations A and B reduced the severity of anthracnose by 68.7% and 55.6%, respectively, and the presence of phosphites in the leaf tissues were detected at concentrations between 1 and 3 m m by 7 days after spraying. These same concentrations of phosphites reduced the mycelial growth of C. lindemuthianum in vitro by 15.0% to 25.7%. In addition, the activities of defence enzymes and the levels of phenolic compounds and lignin were assessed. Phosphite treatments enhanced the activity of various enzymes, including superoxide dismutase, peroxidase, chitinase, and β‐1,3‐glucanase, and increased the lignin and a small increase in the levels of soluble phenolics. This study provides evidence that phosphite treatments control anthracnose by acting directly on C. lindemuthianum and by inducing the production of defence responses. [ABSTRACT FROM AUTHOR]

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Bacteria halo blight (BHB), a coffee plant disease caused by Pseudomonas syringae pv. garcae , has been gaining importance in producing mountain regions and mild temperatures areas as well as in coffee nurseries. Most Coffea arabica cultivars are susceptible to this disease. In contrast, a great source of genetic diversity and resistance to BHB are found in C. arabica Ethiopian accessions. Aiming to identify quantitative trait nucleotides (QTNs) associated with resistance to BHB and the influence of these genomic regions during the domestication of C. arabica , we conducted an analysis of population structure and a Genome-Wide Association Study (GWAS). For this, we used genotyping by sequencing (GBS) and phenotyping for resistance to BHB of a panel with 120 C . arabica Ethiopian accessions from a historical FAO collection, 11 C . arabica cultivars, and the BA-10 genotype. Population structure analysis based on single-nucleotide polymorphisms (SNPs) markers showed that the 132 accessions are divided into 3 clusters: most wild Ethiopian accessions, domesticated Ethiopian accessions, and cultivars. GWAS, using the single-locus model MLM and the multi-locus models mrMLM, FASTmrMLM, FASTmrEMMA, and ISIS EM-BLASSO, identified 11 QTNs associated with resistance to BHB. Among these QTNs, the four with the highest values of association for resistance to BHB are linked to g000 (Chr_0_434_435) and g010741 genes, which are predicted to encode a serine/threonine-kinase protein and a nucleotide binding site leucine-rich repeat (NBS-LRR), respectively. These genes displayed a similar transcriptional downregulation profile in a C. arabica susceptible cultivar and in a C. arabica cultivar with quantitative resistance, when infected with P. syringae pv. garcae . However, peaks of upregulation were observed in a C. arabica cultivar with qualitative resistance, for both genes. Our results provide SNPs that have potential for application in Marker Assisted Selection (MAS) and expand our understanding about the complex genetic control of the resistance to BHB in C. arabica . In addition, the findings contribute to increasing understanding of the C. arabica domestication history., Competing Interests: GCS was employed by company Tropical Melhoramento & Genética (TMG). The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Ariyoshi, Sant’ana, Felicio, Sera, Nogueira, Rodrigues, Ferreira, da Silva, Resende, Destéfano, Domingues and Pereira.)

The largest family of disease resistance genes in plants are nucleotide-binding site leucine-rich repeat genes (NLRs). The products of these genes are responsible for recognizing avirulence proteins (Avr) of phytopathogens and triggering specific defense responses. Identifying NLRs in plant genomes with standard gene annotation software is challenging due to their multidomain nature, sequence diversity, and clustered genomic distribution. We present the results of a genome-wide scan and comparative analysis of NLR loci in three coffee species ( Coffea canephora , Coffea eugenioides and their interspecific hybrid Coffea arabica ). A total of 1311 non-redundant NLR loci were identified in C. arabica , 927 in C. canephora , and 1079 in C. eugenioides , of which 809, 562, and 695 are complete loci, respectively. The NLR-Annotator tool used in this study showed extremely high sensitivities and specificities (over 99%) and increased the detection of putative NLRs in the reference coffee genomes. The NLRs loci in coffee are distributed among all chromosomes and are organized mostly in clusters. The C. arabica genome presented a smaller number of NLR loci when compared to the sum of the parental genomes ( C. canephora , and C. eugenioides ). There are orthologous NLRs (orthogroups) shared between coffee, tomato, potato, and reference NLRs and those that are shared only among coffee species, which provides clues about the functionality and evolutionary history of these orthogroups. Phylogenetic analysis demonstrated orthologous NLRs shared between C. arabica and the parental genomes and those that were possibly lost. The NLR family members in coffee are subdivided into two main groups: TIR-NLR (TNL) and non-TNL. The non-TNLs seem to represent a repertoire of resistance genes that are important in coffee. These results will support functional studies and contribute to a more precise use of these genes for breeding disease-resistant coffee cultivars., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Santos, Resende, Alves, Huguet-Tapia, Resende and Brawner.)