Chemical characterization and antimicrobial activity of essential oils from Croton grewioides Baill. accessions on the phytopathogen Xanthomonas campestris pv. campestris.

Croton grewioides Baill. is an aromatic species with proven bioactive properties. Considering the potential of the species, the aim of this study was to chemically characterize and evaluate the in vitro antibacterial activity of the essential oils of C. grewioides on Xanthomonas campestris pv. campestris. The essential oils of the accessions of C. grewioides were extracted by the hydrodistillation method and analyzed by gas chromatography - mass spectrometry. For determination of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the essential oils and of the compound eugenol, the microdilution method was used at concentrations that ranged from 125 to 4000 µg.mL-1. Streptomycin sulfate was used as a positive control (12.5 to 100 µg.mL-1). Growth kinetics and the membrane permeability trial were evaluated for the concentrations 2×, 1×, 1/2×, 1/4×, and 1/8× MIC of the essential oil CGR-108. The major compounds identified in the essential oils were eugenol, methyl eugenol, and methyl chavicol. The essential oil of the accession CGR-108 had a lower MIC (> 500 and < 1000 µg.mL-1) and MBC equal to <2000 µg.mL-1. For eugenol, MIC was obtained with contractions >250 and < 500 µg.mL-1 and MBC with >500 µg.mL-1 and < 1000 µg.mL-1. A loss of cell viability of the bacteria was observed after 30 min of exposure to the essential oil of the accession CGR-108 at the concentrations of 2× and 1× MIC, which was proven by the fluorescence intensity with propidium iodide. The essential oils of Croton grewioides Baill. and the compound eugenol show antibacterial potential on Xanthomonas campestris pv. campestris.

Designing the best breeding strategy for Coffea canephora: Genetic evaluation of pure and hybrid individuals aiming to select for productivity and disease resistance traits.

Breeding programs of the species Coffea canephora rely heavily on the significant genetic variability between and within its two varietal groups (conilon and robusta). The use of hybrid families and individuals has been less common. The objectives of this study were to evaluate parents and families from the populations of conilon, robusta, and its hybrids and to define the best breeding and selection strategies for productivity and disease resistance traits. As such, 71 conilon clones, 56 robusta clones, and 20 hybrid families were evaluated over several years for the following traits: vegetative vigor, incidence of rust and cercosporiosis, fruit ripening time, fruit size, plant height, canopy diameter, and yield per plant. Components of variance and genetic parameters were estimated via residual maximum likelihood (REML) and genotypic values were predicted via best linear unbiased prediction (BLUP). Genetic variability among parents (clones) and hybrid families was detected for most of the evaluated traits. The Mulamba-Rank index suggests potential gains up to 17% for the genotypic aggregate of traits in the hybrid population. An intrapopulation recurrent selection within the hybrid population would be the best breeding strategy because the genetic variability, narrow and broad senses heritabilities and selective accuracies for important traits were maximized in the crossed population. Besides, such strategy is simple, low cost and quicker than the concurrent reciprocal recurrent selection in the two parental populations, and this maximizes the genetic gain for unit of time.