Search

Abstract Brown rot and blossom blight caused by fungi of the genus Monilinia are the most important peach diseases. The increased concern with the environment and the health of workers and consumers, as well as the emergence of fungus isolates resistant to the main fungicide molecules favor control strategies such as genetic resistance. The objective of this study was to adjust a phenotyping protocol for evaluation of resistance/susceptibility to blossom blight in peach, as well as to quantify the antioxidant compounds present in the petals of these flowers and their correlation with the disease incidence and severity. The experiment was arranged in a randomized complete block split-split plot design, the plot being four concentrations of Monilinia fructicola conidia; the subplot two phenological flower stage; and the sub-subplot four peach genotypes. The quantification of antioxidant compounds and their correlation with susceptibility to blossom blight was performed in the four genotypes analyzed. Phenotyping was more efficient when concentrations between 400 and 4,000 conidia mL-1 were used, regardless of phenological flower stage. The phenolic compounds, anthocyanins and antioxidant activity are positively correlated among them, and negatively correlated with the blossom blight incidence and severity. In order to estimate the blossom blight susceptibility, it is recommended to use flowers at the pink or bloom stage, inoculum equivalent to 20-200 conidia per flower, and perform the evaluation at 96 hours after inoculation. This study suggests that more intense pink flowers have a higher content of antioxidant compounds and less blossom blight susceptibility.

Abstract Feathering in apple nursery trees is a critical operation used to increase the quality of planting material. Plant growth regulators (PGR) could be used to form feathers in apple nursery trees. The main goal was to study the impact of different PGR and concentrations on feathering promotion in different nursery apple trees. The study had three different trials where the specific aims were to study the impact of: i) different rates of 6-benzyladenine (6-BA); ii) different PGR (6-BA and 6-BA + GA4+7) on feathering promotion, and; iii) 6-BA on feathering promotion and prohexadione calcium (P-Ca) on trunk thickening under greenhouse conditions. Both 6-BA and 6-BA + GA4+7 were effective inducing feathering in the different cultivars tested. 6-BA reduced final young plants grafted height only in one out of three seasons, reducing an average of 15 and 10 cm on ‘Early Red One’ and ‘Fuji’ apple nursery trees, respectively. P-Ca reduced tree growth rate 4-5 weeks after sprayed, but the difference did not persist until the end of the season. Trunk diameter was not affected by the different plant growth regulators and concentrations tested. 6-BA alone or in combination with GA4+7 is an efficient tool to feathering formation in different nursery apple cultivars and conditions.

ABSTRACT The adaptation of temperate fruit crops is a challenge being increased by the global warming. Chilling requirement is a key factor for adaptation. The objective of this study was to estimate the chilling requirement of peach cultivars BRS Bonão, Esmeralda, Granada and Eragil, using the Tabuenca test. Chilling accumulation was computed using four different chilling hour (≤ 7.2 ºC and ≤ 11 ºC) models; and chill units using the Low Chill model and the Taiwan model. The fresh bud weight and bud water contents were also evaluated. The Tabuenca test (based on differences in bud´s dry weight) showed a fairly good efficiency for estimating the end of dormancy in peach. However, under mild winter conditions, it is better to use fresh bud weights. Either one of three chilling accumulation computation models (temperature ≤ 7.2 °C, ≤ 11°C, or Taiwan model) is suitable to classify comparatively different cultivars, but none is accurate enough to conclude on the adaptation of a given cultivar to a specific site. Using hours of temperatures ≤ 11 ºC: ‘BRS Bonão’ needed around 180 hours for dormancy release; ‘Esmeralda’ around 250 hours; ‘Granada’ between 300 and 400 hours, and ‘Eragil’ more than 500 hours.

ABSTRACT Blossom blight and brown rot caused by Monilinia fructicola is the most important peach disease in Brazil. Genetic resistance is a control strategy that is gaining importance in breeding programs worldwide. This study aimed to identify genotypes with higher levels of blossom blight resistance to estimate the heritability of this character; study the frequency distribution in populations; and test the possibility of maternal effect. Blossom blight susceptibility was tested in reciprocal hybridizations seedlings, as well as their parents. The detached flower technique was used in a randomized complete block design, considering each genotype as a treatment. Flower inoculation was made by spraying a M. fructicola suspension and evaluations were carried out after 72 and 120 hours using a scale of five severity levels. The studied populations presented low phenotypic variability regarding the flower resistance/susceptibility to M. fructicola, being most of them susceptible or very susceptible. Among the tested genotypes, the cultivars Maciel and Cerrito showed less blossom blight susceptibility, transmitting this character to their progenies. Heritability estimates of the blossom blight resistance were medium to low. The low heritability and its distribution in the progenies suggest that the character has additive inheritance, without detecting deviations associated with maternal effects.

Despite the fact that brown rot is the most economically important disease in stone fruits, the relationship between mechanical stress and infection has never been explored. Thus, to explore this connection, we carried out four experiments linking nectarine wounding and M. laxa infection. First, we evaluated a possible systemic reaction of the fruit to wounding that could impact the M. laxa infection. Afterward, we study the impact of the fruit in the environment on M. laxa colonies grown in vitro. Subsequently, we tested the disease susceptibility of fruits inoculated with M. laxa placed in the same environment as wounded fruits. Finally, in the fourth experiment, the effect of wounding on the subsequent fruit infections was evaluated at three fruit stages. As a result, we observed that there was no evidence of a fruit systemic reaction to wounding and M. laxa infection. In the study related to the impact of the fruit in the environment of M. laxa, the findings suggest that M. laxa “perceived” the fruit’s presence, resulting in accelerated in vitro growth. Moreover, the presence of wounded fruits in the box increased the susceptibility to brown rot. Inoculated fruits showed a delayed and reduced infection 7 h after being wounded, during the second stage of fruit development (15–19 weeks after full bloom). Moreover, a red reaction associated with inoculation was detected immediately after the fruits were wounded. Nine phenolic compounds exclusively related to the red areas were extracted, while six other compounds were present in higher proportions. These compounds may be actively involved in plant–pathogen interactions and the activation of metabolic pathways involved in nectarine susceptibility/resistance to M. laxa.

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.

ABSTRACT: Diversification of rootstock varieties, with consequent reduction in phytosanitary risks, has great importance to the sustainability of citrus cultivation in the south of Brazil. This study evaluated the performance of 42 rootstocks in the nursery phase to generate ‘Valencia Late’ sweet orange seedlings. Therefore, nucellar seedlings from the rootstocks under study were analyzed in relation to plant height, stem diameter, mortality rate and percentage of bud set after grafting. The experimental design was completely randomized with four replications of 20 sample units. Not adapted genotypes had high mortality rates, and the ones of both hybrids LCR x CTSW - 009 and LVK x LCR - 038 were 100% and 90%, respectively. Other 13 genotypes had mortality rates above 30%, and ‘Sunki’ mandarin was the female genitor of ten of them. ‘Swingle’ citrumelo was the rootstock with the highest development (plant height and stem diameter), associated with low mortality rate. In relation to the other rootstocks, the best results were the fast grafting diameter, associated with low mortality rate obtained by hybrids HTR - 053, LRF x (LCR x TR) - 005, CLEO x TRBN - 245, CLEO x TRSW - 287, and citrandarins ‘Indio’, ‘Riverside’ and ‘San Diego’, as well as Trifoliate orange and ‘Rangpur’ lime. In addition to Trifoliate orange, which is widely used in Rio Grande do Sul, these rootstocks have great potential in citriculture in the south of Brazil.

Brown rot, caused by Monilinia spp., is the main stone fruit disease. Major efforts to detect sources of resistance are being applied by several breeding programs worldwide. The main objective of this study was to seek sources of brown rot resistance, as well as to study the segregation, estimate the heritability, verify the possible existence of the maternal effect, and estimate the genetic advances. For this purpose, 20 parents and 303 seedlings, representing 16 breeding families, and ‘Bolinha’ (control) have been phenotyped for fruit reaction to brown rot using wounded and non-wounded inoculation procedures in 2015–2016, 2016–2017, and 2017–2018 growing seasons. Wounded fruits were very susceptible to brown rot incidence, however, the incidence and severity of non-wounded fruits showed high variability among the evaluated genotypes. Conserva 947 and Conserva 1600 and their progeny, had lower disease incidence and severity than most of the evaluated genotypes. Genetic gain estimation was −5.2 to −30.2% (wounded fruits) and between −15.0 to −25.0% (non-wounded fruits) for brown rot resistance. Selected genotypes were equal to or better than ‘Bolinha’ in relation to brown rot resistance, with several of them far superior in fruit quality than ‘Bolinha’, demonstrating the progress of the Embrapa Peach Breeding Program.

El duraznero es un cultivo de gran importancia económica y social dentro de los países del Cono Sur de Sudamérica. La evolución de este frutal se ha visto condicionada tanto por las particularidades edafoclimáticas, como por las culturales y las económicas de cada país. Sintetizar en un solo documento la situación actual y los distintos aspectos que caracterizan al cultivo de durazneros en Uruguay, Brasil y Argentina fue el objetivo en este trabajo. La incorporación de tecnología en todos los sentidos ha permitido una mejora en los rendimientos, por lo que la producción se ha mantenido a pesar de la reducción del área de plantación. Últimamente se ha dado un proceso de crecimiento en escala y concentración de la producción, aunque las características del cultivo lo siguen haciendo muy apto para el pequeño productor. Grandes esfuerzos de investigación canalizados a través de universidades e institutos especializados han permitido generar información local y regional de alto valor e impacto. La importancia del material genético para el éxito del sistema productivo es clave y la estrategia de generar cultivares con adaptación local ha sido tomada por la región, siendo creciente la disponibilidad de nuevos cultivares generados por los programas de mejoramiento locales. El enfoque de producción integrada ha tomado gran impulso y son cada vez más las alternativas productivas que se desarrollan buscando prescindir de los agroquímicos, principalmente en lo que respecta al control de plagas y enfermedades. La densidad de plantación se ha ido incrementando y los sistemas de conducción y poda están evolucionando hacia formas más simples y pasibles de ser mecanizadas. Numerosos son los desafíos que hay por delante, pero a su vez es grande la convicción, entre los equipos de investigación, de poder seguir aportando para una mayor y mejor disponibilidad de frutos de Prunus en las mesas de los consumidores.

Abstract The aim of this study was to evaluate the effect of different aminoethoxyvinilglycine (AVG), thidiazuron (TDZ) and prohexadione calcium (P-Ca) rates sprayed at different timings on fruit set, yield, and fruit quality of ‘Rocha’ pear trees in different climatic conditions of Southern Brazil. The study was performed in two commercial orchards located in São Joaquim, SC (2015/2016) and Antônio Prado, RS (2016/2017). Plant material consisted of ‘Rocha’ pear trees grafted onto Pyrus calleryana and quince rootstock ‘BA29’ in São Joaquim and Antônio Prado, respectively. Treatments consisted of AVG, TDZ and P-Ca sprayed at different rates and timings. Trunk cross-sectional area increase, fruit set, thinned fruit, fruit per tree, yield, average fruit weight, projected yield, yield efficiency, fruit length, fruit diameter, L/D ratio, seed number, flesh firmness, and soluble solids content were assessed. Fruit set and yield were consistently increased by AVG in all experiments. Fruit set was not affected by P-Ca and was significantly decreased by TDZ. However, yield was positively affected by P-Ca 100 mg L–1 sprayed at full bloom + 7 days after full bloom and TDZ 10 mg L–1 at full bloom. Fruit size was consistently increased by TDZ.