Genetic variation among and within Quercus suber L. populations in survival, growth, vigor and plant architecture traits

Cork oak is an important forest tree species in the Western Mediterranean region due to the high economic value of its renewable cork and its ecological and social services. However, studies regarding the genetic variation within cork oak populations are scarce, and this gap of knowledge is contributing to the delay of the set-up of a breeding and conservation strategy for the species. In this study, the genetic variation in fitness (survival, height, and stem diameter) and plant architecture traits (apical dominance, stem straightness, stem inclination degree, branchiness), and tree vigor was evaluated among and within cork oak populations in two progeny field trials established in Portugal. Measurements were carried out in each trial in two different periods: ages 9 and 14 years at Monte da Fava trial and 8 and 14 years at Herdade da Caniceira trial. A significant genetic variation among and within cork oak populations was detected for survival, growth, and form traits (stem straightness and inclination). Growth traits presented high values of heritability estimates at the family mean level (≥0.75), and genetic gains were obtained when families with superior growth were selected. Additionally, results highlighted that early selection of families with superior performance could be performed, and it is possible to achieve improvement in both growth and form traits simultaneously, with implications on the profitability and sustainability of cork oak standsinfo:eu-repo/semantics/publishedVersio

Polyphenoloxidase activity and browning in fresh-cut "Rocha" pear as affected by pH, phenolic substrates and antibrowning additives

tThe effect of pH, phenolic substrates, and food additives on polyphenoloxidase (PPO) activity and ontissue browning was studied in fresh-cut ‘Rocha’ pear. Substrates 4-methylcatechol, caffeic acid, (+)-catechin hydrate, catechol, chlorogenic acid, dopamine hydrochloride, and pyrogallol, were preparedin citric acid-phosphate buffer at pHs ranging from 3.0 to 8.0. pH optima for PPO activity dependedon the phenolic substrate. Activity was optimal at pH 5.0 for catechol and 4-methylcatechol; pH 6.0 forchlorogenic acid; pH 7.0 for dopamine, caffeic acid, and catechin; and pH 8.0 for pyrogallol. Discrepancieswere observed between the pH dependency of PPO activity and browning, as assessed by objective colormeasurement. Significant correlations were obtained between enzyme activity and metric-hue difference( H*) over the pH range 3.0–8.0 for four of the eight phenolics. Chlorogenic acid, the main PPO substratein ‘Rocha’ pear, induced high tissue browning but very low PPO activity at pH 3.0–4.0. Chemical inhibitionof PPO was tested using catechol as substrate, and buffer solutions containing 250 mM Ca2+in four salts(ascorbate, chloride, lactate and propionate), 57 mM ascorbic acid, 61 mM N-acetyl-l-cysteine and 3 mM4-hexylresorcinol. PPO inhibition by additives was affected by the pH of the buffer, and was more effectivewith ascorbic acid, N-acetyl-l-cysteine and calcium ascorbate. It was concluded that inferences on tissuebrowning based on PPO activity can be misleading. Measurement of tissue color is proposed as a reliablemeans to assess the antibrowning effectiveness of additives and the pH of additives for cut pear shouldbe corrected to reduce the browning potentialinfo:eu-repo/semantics/publishedVersio