Nowadays, despite of being a typically temperate fruit crop, peach is found in subtropical and even tropical altitude zones, due to breeding efforts. Genetic knowledge and phenotypic and environmental parameters directly or indirectly influence the characters of economic importance in peach, and they are of great importance for breeding programs orientation. The aim of this study was to estimate heritability of a color shade character of peach flesh, measured by the Hue angle, chroma and lightness to evaluate its distribution in the populations, testing the possible existence of maternal effect. Results showed that parameters related to color shade of peach flesh have a medium heritability. Parents selection based on phenotype allows a medium genetic improvement for the mentioned character. This heritability is predominantly additive, without maternal effect. The Hue angle is the correct parameter to be used to classify and study yellow-flesh peaches and nectarines in relation to their color shade. However, the multivariate analysis of principal components, using the three parameters Hue angle, chroma and lightness, is an alternative of high accuracy.

Chilling requirement is a characteristic that limits temperate fruit crops cultivation under subtropical climate. Several mathematic models, differing on the relative value of chilling units have been developed, in order to estimate the chilling accumulation on a given site. The present work compared eight of these models using data from hourly temperatures from May to August, from a period of 11 years, collected in Pelotas, RS, Brazil, aiming to characterize the region regarding the chilling accumulation for the cultivation of deciduous fruit trees and it also had as objective to check if a model using average temperatures is suitable enough to be used when hourly temperatures were not available. The eight tested models were: Chilling Hours (≤7.2°C); Chilling Hours (≤11°C); Utah; Low Chill; Dynamic; Mean Temperatures; Positive Utah and Taiwan. The results showed large differences between years, regardless of the used model. However, the Taiwan and Low Chill models seemed more suitable for the estimation of the accumulation of cold in the Pelotas region. The Medium Temperatures model can be used as a valid option since it has a high correlation with the other models and easy data availability.

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The fungus Monilinia fructicola, which causes brown rot in fruits, is one of the main peach pathogens. The emergence of fungicide-resistant fungus isolates, as well as the attempt to reduce sprays, favors adoption of other control strategies. Among them, one of the most important is genetic resistance. This study was carried out aiming to evaluate the susceptibility of 16 peach and 4 nectarine genotypes to brown rot, as well as to evaluate how well the sporulation area and diameter correlate with number of spores in the lesions. Both wounded and non-wounded fruits were inoculated with 10 μL of M. fructicola suspension. Wounded fruits from all genotypes (nectarines and peaches) showed susceptibility to M. fructicola, from 92 to 100% of incidence. The disease incidence was between 18 and 100% when non-wounded fruits were inoculated. High variability was detected for the fungus sporulation, in both wounded and non-wounded fruits, with ranges between 16 to 96% and 0 to 94%, respectively. The fungus sporulation was variable among the genotypes (between 0.1 to 96.0 conidia per mm2) and it is positively correlated with the diameter and area of sporulation. The genotypes Conserva 947, Conserva 1662, Conserva 672, Conserva 1600, and 'Bolinha', are the ones with less susceptible to brown rot.

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The adaptation of a temperate climate fruit cultivar to a certain area depends mainly on its chilling requirement and the chilling accumulation in such places. Several attempts have been made to estimate these two conditions, using different models. The great variation among the models to calculate chilling requirement makes it necessary to determine their efficiency in a given location. Aiming to estimate the chilling requirement of ten peach cultivars, including Bonão, Pepita, Maravilha, Precocinho, Turmalina, Diamante, BR-3, Marfim, Coral, and Cambará do Sul, seven models were tested: Utah, Positive Utah, Low Chill, Taiwan, Chilling Hours (≤7.2°C), Chilling Hours (≤11°C), and Dynamic. The results showed that the estimation of chilling accumulation for all the studied cultivars in all the tested models showed a large variability. None of the tested models was Original Research Article

No abstract

Embryo culture is a technique used to rescue immature embryos which would not germinate under natural conditions. However, one of the biggest problems of this process is the contamination by microorganisms. The objective of this work was to test asepsis methods and the use of PPM TM (Plant Preservative Mixture TM ) in the culture medium for the germination and development of 'Precocinho' peach embryos. After extraction from the fruits, seeds were submitted to treatments with thimerosal, sodium hypochlorite (NaClO), flame sterilization and moxifloxacin hydrochloride, in culture medium with and without addition of PPM TM , totaling nine treatments. The experimental design was completely randomized, with 20 replicates per treatment. Three evaluations were performed: in vitro establishment (at 55 days of cultivation), embryo development (at 65 days of cultivation) and acclimatization (20 days after transplanting in the greenhouse). Six treatments did Original Research ArticleTM is shown as the most efficient treatment, among the tested ones, for the germination and development of 'Precocinho' peach embryos.