Regional nutrient ranges are commonly used to diagnose plant nutrient status. In contrast, local diagnosis confronts unhealthy to healthy compositional entities in comparable surroundings. Robust local diagnosis requires well-documented data sets processed by machine learning and compositional methods. Our objective was to customize nutrient diagnosis of peach (Prunus persica) trees at local scale. We collected 472 observations from commercial orchards and fertilizer trials across eleven cultivars of Prunus persica and six rootstocks in the state of Rio Grande do Sul (RS), Brazil. The random forest classification model returned an area under curve exceeding 0.80 and classification accuracy of 80% about yield cutoff of 16 Mg ha⁻¹. Centered log ratios (clr) of foliar defective compositions have appropriate geometry to compute Euclidean distances from closest successful compositions in “enchanting islands”. Successful specimens closest to defective specimens as shown by Euclidean distance allowed reaching trustful fruit yields using site-specific corrective measures. Comparing tissue composition of low-yielding orchards to that of the closest successful neighbors in two major Brazilian peach-producing regions, regional diagnosis differed from local diagnosis, indicating that regional standards may fail to fit local conditions. Local diagnosis requires well-documented Humboldtian data sets that can be acquired through ethical collaboration between researchers and stakeholders.

Understanding the growing process and fruit size differences among peach cultivars is extremely important in the technological domain of the crop and can provide information to improve the proper crop management (thinning and harvesting seasons) and the crop breeding of fruits with a larger caliber. However, this information is still incipient in subtropical regions and requires further research, especially in Brazil. The aim of this study was to determine the influence of temperature on the growing of four peach cultivars (Tropical, Aurora-2, Ouro Mel-4, and Biuti) under subtropical conditions of field cultivation. Fruit development was determined every two weeks throughout the cycle with 30 fruits from previously identified branches from six different plants of each cultivar. Regarding the thermal accumulation in growing degree-days (GDD), the cultivar ‘Tropical’ showed the lowest agronomic fruit properties (size and mass) and required a lower GDD accumulation during the development stages of the fruits, whereas the cultivar ‘Biuti’ showed higher thermal requirements and higher agronomic properties. The number of cells had greater influence on the final fruit size than the cell area.

Nursery trees of stone fruits (Prunus spp.) are traditionally produced by union of two distinct genotypes - the rootstock and the scion - which, by grafting, form a composite plant that will be maintained throughout of all plant life. In Brazil, the rootstocks are predominantly seed propagated and therefore usually results in heterogeneous trees for vigor and edaphic adaptation. However, with advances in rootstock breeding programs that released cultivars and certification in several countries (notably in Europe), the system will come gradually evolving for vegetative propagation (cuttings and tissue culture) and use of seeds of selected rootstocks with specific characteristics and potted nursery trees production. For scion cultivar propagation, the budding system (with its many variations) has predominantly been adopted in major producing countries. This review had as objective to comment main propagation methods adopted for rootstocks and scion in peach, nectarine and plum, and recent technical progress obtained as well as the needs of improvement for nursery tree production.

The objective of this research was to evaluate the technical feasibility of SPAD index in the diagnosis of N status in ‘Esmeralda’ peach. The field trial, with five N rates applied to the soil (0, 40, 80, 120 and 160 kg ha-1 of N as urea form) was conducted in a randomized block design with four replications. During the years 2014, 2015, 2016 and 2017, SPAD readings were carried out with a Minolta SPAD-502 chlorophyll meter, in the leaf middle part, in 40 leaves per plot. The leaf N content determination was performed in CHN-S Elemental Analyzer. SPAD index and leaf N content increased in a linear way in response to increasing N rates applied in soil. There was a positive linear correlation between SPAD index and N concentration in leaves (0.652; 0.756; 0.762 and 0.767, p<0.05). SPAD index can be used for nutritional N diagnosis purpose in peach when readings are taken between the 13th and 15th weeks after full bloom. In the range between 39 and 49, the SPAD index indicates the leaf N content is included in “normal” class (33 – 45 g kg-1) of agronomic interpretation for the States of Rio Grande do Sul and Santa Catarina, Brazil.

Teores de nutrientes foliares indicam o estado nutricional da planta, auxiliam na recomendação de adubação e, em plantas frutíferas enxertadas, podem indicar combinações de copa/porta-enxerto incompatíveis. O objetivo do presente trabalho foi avaliar os teores de nutrientes foliares na cv. Maciel de pessegueiro, enxertada em cinco porta-enxertos (‘Aldrighi’, ‘Capdeboscq’, ‘Flordaguard’, ‘Nemaguard’ e ‘Okinawa’). Dois pomares experimentais, localizados no município de Pelotas-RS, foram avaliados no 2° e no 3° anos após o plantio, respectivamente, nos anos de 2012 e 2013. Conclui-se que os porta-enxertos ‘Aldrighi’, ‘Capdeboscq’, ‘Flordaguard’, ‘Nemaguard’ e ‘Okinawa’ não influenciaram nos teores foliares de P e de Mn da cv. Maciel, em ambos os pomares e anos de avaliação; o porta-enxerto ‘Nemaguard’ reduz os teores foliares de Mg da cv. Maciel, sem alterar a classe de interpretação agronômica; embora os teores foliares de N, Fe, Zn e B tenham sido abaixo do normal ou insuficientes, em praticamente todas as amostras de ambos os pomares e anos de avaliação, os porta-enxertos testados não influenciaram nestas interpretações.

This study aimed to measure the leaf chlorophyll index (SPAD 502 Plus) in three peach cultivars grafted on different clonal rootstocks, totaling 68 scion/rootstock combinations, between five and nine months after planting in the field to determine possible graft incompatibility symptoms in Prunus spp. Three field trials with peach scion cultivars ‘BRS-Kampai’, ‘Jade’, and ‘Maciel’ grafted on 18, 25, and 25 clonal rootstocks, respectively, were established in July and August 2014. Own-rooted scion trees (without rootstock) were used as controls in each trial and all rootstocks were propagated from herbaceous cuttings. The experimental design was a randomized block with four replications and each plot consisting of a single plant. Three SPAD measurements were taken between January and April 2015. SPAD index values for rootstocks ‘Mirabolano 29C’ (P. cerasifera) and ‘Marianna 2624’ (P. cerasifera x P. munsoniana) were significantly lower in the three scion cultivars, culminating with tree death from graft incompatibility. Rootstocks ‘Mirabolano 29C’ and ‘Marianna 2624’ showed translocated graft incompatibility with scion cultivars BRS-Kampai, Jade, and Maciel and tree death was preceded by a reduction in SPAD index values five months after field planting. No reduction in SPAD index values was observed in the other scion/rootstock combinations nine months after planting, but these combinations should be monitored for a longer period to confirm their graft compatibility.