Susceptibility Evaluation to Fire Blight and Genome-Wide Associations within a Collection of Asturian Apple Accessions.

Fire blight, caused by Erwinia amylovora, is one of the most devastating apple diseases. The selection of cultivars of low susceptibility and the study of the genetic mechanisms of the disease play important roles in fire blight management. The susceptibility level to fire blight was evaluated in 102 accessions originating from Asturias, a cider-producing region located in the north of Spain with a wide apple germplasm. Evaluations took place under quarantine conditions using artificial inoculations of grafted plants. The results revealed wide variation in susceptibility responses and low-susceptible cultivars were identified. In addition, 91 cultivars were genotyped using the Affymetrix Axiom® Apple 480 K SNP array to conduct genome-wide association studies (GWAS). A statistically significant signal was detected on chromosome 10 using the multi-locus mixed model (MLMM). Two genes were identified as major putative candidate genes: a TIR-NBS-LRR class disease protein and a protein containing a development and cell death (DCD) domain. The outcomes of this study provide a promising source of information, particularly in the context of cider apples, and set a starting point for future genetic and breeding approaches.

Characterization of Spanish ciders by means of chemical and olfactometric profiles and chemometrics.

A comparative study of the aroma (volatile composition and olfactometric profiles) of Asturian and Basque still ciders in two maturation stages was conducted. Among the major volatile compounds, amyl alcohols, ethyl lactate and ethyl acetate were quantitatively relevant in all of the ciders studied. The minor fraction mainly consisted of fatty acids, volatile phenols and alcohols. Three PLS-discriminant models with low prediction errors were constructed. When the volatile composition was used, ciders could be differentiated by their maturation stage, 4-ethylcatechol being strongly associated to matured ciders. The olfactometric profiles allowed the classification of ciders according to both their origin and maturation stage. Odorants such as p-cresol and a sweet-character unknown component were correlated to origin of ciders, whereas 1-octen-3-one and one unknown spicy-vegetal odorant were highly correlated to the maturation stage.

Impact of different techniques involving contact with lees on the volatile composition of cider.

The effect of different treatments involving contact with natural lees on the aromatic profile of cider has been evaluated. Comparing with the untreated ciders, the contact with lees brought about a significant increase of the concentrations of most of the volatile compounds analysed, in particular fatty acids, alcohols, ethyl esters and 3-ethoxy-1-propanol. The opposite was observed among fusel acetate esters and 4-vinylguaiacol. The addition of ß-glucanase enhanced the increase of ethyl octanoate, but produced a decrease in the contents of decanoic acid and all of the major volatiles excepting acetaldehyde, ethyl acetate and acetoine, whereas the application of oxygen influenced the rise of the level of 3-ethoxy-1-propanol only. The olfactometric profiles also revealed significant effects of the treatment with lees for ethyl propionate, diacetyl, cis-3-hexenol, acetic acid, benzyl alcohol, and m-cresol, while the addition of oxygen significantly influenced the perception of ethyl hexanoate, 1-octen-3-one, 3-methyl-2-butenol, t-3-hexenol and c-3-hexenol.