El pronóstico de cosecha es un gran desafío en la producción de peras. Estimar el tamaño de los frutos a partir de curvas de crecimiento permite predecir tanto la cantidad como la calidad de la fruta para cosecha. Este trabajo tuvo como objetivo ajustar modelos mixtos no lineales multiniveles (MMNL) basados en la curva logística para describir el crecimiento de peras “William´s” en el Alto Valle de Río Negro y Neuquén, Argentina. Los modelos ajustados incorporaron diferentes índices termoacumulativos que contemplan los efectos de la temperatura en la fisiología del crecimiento de los frutos. De esta manera, se logra no solo describir el crecimiento de los frutos, sino también se pueden observar las variaciones ambientales a lo largo de las temporadas de crecimiento. El estudio se realizó en perales “William´s” durante 16 temporadas. Se seleccionaron e identificaron al azar numerosos árboles y frutos. A cada fruto se le midió su diámetro ecuatorial semanalmente con un calibre digital electrónico. Los datos climáticos se obtuvieron de la estación meteorológica del INTA Alto Valle y los índices termoacumulativos se calcularon a partir de los datos de temperaturas. Los mejores modelos fueron seleccionados según los criterios de información. El MMNL multinivel permitió discernir y cuantificar las fuentes de variabilidad estocástica en diferentes niveles, lo que permitió obtener mejores criterios de información en comparación con los modelos que solo consideraron un único nivel de variabilidad entre los efectos aleatorios. La incorporación de índices termoacumulativos mejoró notablemente la performance de los modelos obtenidos.

Long-term vegetation cover can affect soil organic carbon content and carbon flow within the soil food web. Nematode trophic structure and soil properties were evaluated in pear rows (intra) maintained without weeds applying herbicide and in the inter-rows (between rows) covered with: Medicago+grasses (MG), fescue or spontaneous vegetation. Soil samples were taken at 0-20 and 20-40 cm depths from 2012 to 2014. Nematode assemblage was different in each inter-row and row, mainly in the topsoil. The inter-rows were reservoirs of omnivores-predators. The MG inter-row promoted the highest accumulation of organic carbon, total N and exchangeable K in the soil. The enrichment index was related to the quantity of dry matter produced by cover crops with the highest index observed in MG. Nematode biomass showed a positive correlation with intra and inter-rows soil organic carbon. Carbon flow through bacterivores prevailed in intra-rows, while bacterivores or herbivores canalized the inter-rows. Highlights: Each cover crop (Medicago+grasses, spontaneous vegetation and fescue) was associated with a different nematode assemblage, mainly in the topsoil. Omnivores-predators were higher in the inter-row than its associated row. Nematode Biomass showed a positive correlation with the content of SOC in the row and in the inter-row. Soil energy channels revealed higher carbon flow within the soil food web under Medicago+grasses and spontaneous vegetation than under fescue.

A method for early prediction of fruit drop would be a valuable tool to predict initial fruit set and to make thinning decisions. One of the first indicators of fruit abscission is a reduction in the fruit growth rate. In this paper a model for predicting fruit drop was adapted for 'Bartlett' pears from a model that had been previously developed for apples. This model suggests that a fruit will abscise if its growth rate is less than 50% of the growth rate of the fastest growing fruits at a given period of time. A trial was carried out in a 'Bartlett' pear orchard in Rio Negro, Argentina, during two seasons (2009-2010, 2017-2018). Between 360 and 480 fruit clusters were randomly selected and their main fruit were marked for this study. Growth rate of fruits was measured from 22 to 30 days after full bloom until their abscission or harvest. The model was evaluated using the fruit growth rates obtained between the first two measurements. During the trial, about 30-40% of fruits abscised. In both seasons the highest number of abscised fruits was registered during November (more than 85% of total abscised fruits) in concordance with "June drop". Fruits with initial growth rate lower than 40%, showed more than 75% of abscission. Similarly, as it was observed during the "June drop" period, fruits that abscised close to harvest also showed decreased growth rates in the previous weeks. In conclusion, pear fruits similarly to apple fruits, decelerate their growth rate during the weeks before abscission. This physiological phenomenon could be used for the prediction of fruit drop in 'Bartlett' pears.

El ensamble de nematodos del suelo fue estudiado en una cronosecuencia (S1, S2 y S3) que incluyó a los ciclos productivos 2008-2009, 2009-2010 y 2010-2011 con distinto plan de fertilización nitrogenada: 776, 375 y 80 kg N ha-1, respectivamente, en un suelo salino (5,2 dS m-1) franco limoso, en un huerto comercial de pera. La aplicación de nitrógeno en S1 y S2 fue repartida en siete veces y en S3 tres veces. Se evaluaron características del suelo, abundancia de nematodos, índices ecológicos y el rendimiento de fruta. El contenido de materia orgánica (4,2%) y de nitrato (29,5 mg kg-1) en el suelo y el pH del suelo (7,64) no variaron en la cronosecuencia. Las arcillas esmectitas, minerales dominantes en el suelo, presentan gran capacidad buffer y tienen alta resistencia al cambio del pH cuando se agrega fertilizante nitrogenado al suelo. Los nematodos fitófagos fueron el grupo trófico más abundante (48%) y las familias pertenecientes a los herbívoros del grupo c-p=2 fueron dominantes. Aporcelaimellus representó el 16% de la abundancia total de nematodos. En S1, el aumento en el índice de enriquecimiento (78,6%) fue atribuido a una alta abundancia de bacteriófagos del grupo c-p=1 (Ba1) y fungívoros del grupo c-p=2 (Fu2), donde la dosis de nitrógeno aplicada fue mayor, respecto a S2 y S3. El número de Panagrolaimidae y Rhabditidae aumentó en S1. El contenido de nitrato en el suelo no se correlacionó con la abundancia de Ba1 y Fu2. Ni la densidad de nematodos omnívoros y carnívoros ni los índices de estructura (81,4%), canal (14,2%) y basal (11,1%) fueron alterados por la aplicación de nitrógeno en los ciclos productivos. El valor bajo del índice canal indicó una ruta de descomposición bacteriana de la materia orgánica del suelo. El rendimiento total de frutos fue similar en la cronosecuencia.

In flies and humans, bitter chemicals are known to inhibit sugar detection, but the adaptive role of this inhibition is often overlooked. At best, this inhibition is described as contributing to the rejection of potentially toxic food, but no studies have addressed the relative importance of the direct pathway that involves activating bitter-sensitive cells versus the indirect pathway represented by the inhibition of sugar detection. Using toxins to selectively ablate or inactivate populations of bitter-sensitive cells, we assessed the behavioral responses of flies to sucrose mixed with strychnine (which activates bitter-sensitive cells and inhibits sugar detection) or with l -canavanine (which only activates bitter-sensitive cells). As expected, flies with ablated bitter-sensitive cells failed to detect l -canavanine mixed with sucrose in three different feeding assays (proboscis extension responses, capillary feeding, and two-choice assays). However, such flies were still able to avoid strychnine mixed with sucrose. By means of electrophysiological recordings, we established that bitter molecules differ in their potency to inhibit sucrose detection and that sugar-sensing inhibition affects taste cells on the proboscis and the legs. The optogenetic response of sugar-sensitive cells was not reduced by strychnine, thus suggesting that this inhibition is linked directly to sugar transduction. We postulate that sugar-sensing inhibition represents a mechanism in insects to prevent ingesting harmful substances occurring within mixtures.

In the article “LRP4 Is Critical for Neuromuscular Junction Maintenance” by Arnab Barik, Yisheng Lu, Anupama Sathyamurthy, Andrew Bowman, Chengyong Shen, Lei Li, Wen-cheng Xiong, and Lin Mei, which appeared on pages 13892–13905 of the October 15, 2014 issue, the authors regret that the labels of the two curves were accidentally swapped in Figure 4G. This correction does not affect the interpretations or conclusions of the study. The corrected Figure 4 is shown below.

Sample- and gene- based hierarchical cluster analyses have been widely adopted as tools for exploring gene expression data in high-throughput experiments. Gene expression values (read counts) generated by RNA sequencing technology (RNA-seq) are discrete variables with special statistical properties, such as over-dispersion and right-skewness. Additionally, read counts are subject to technology artifacts as differences in sequencing depth. This possesses a challenge to finding distance measures suitable for hierarchical clustering. Normalization and transformation procedures have been proposed to favor the use of Euclidean and correlation based distances. Additionally, novel model-based dissimilarities that account for RNA-seq data characteristics have also been proposed. Adequacy of dissimilarity measures has been assessed using parametric simulations or exemplar datasets that may limit the scope of the conclusions. Here, we propose the simulation of realistic conditions through creation of plasmode datasets, to assess the adequacy of dissimilarity measures for sample-based hierarchical clustering of RNA-seq data. Consistent results were obtained using plasmode datasets based on RNA-seq experiments conducted under widely different conditions. Dissimilarity measures based on Euclidean distance that only considered data normalization or data standardization were not reliable to represent the expected hierarchical structure. Conversely, using either a Poisson-based dissimilarity or a rank correlation based dissimilarity or an appropriate data transformation, resulted in dendrograms that resemble the expected hierarchical structure. Plasmode datasets can be generated for a wide range of scenarios upon which dissimilarity measures can be evaluated for sample-based hierarchical clustering analysis. We showed different ways of generating such plasmodes and applied them to the problem of selecting a suitable dissimilarity measure. We report several measures that are satisfactory and the choice of a particular measure may rely on the availability on the software pipeline of preference.

In the Upper Rio Negro Valley, northern Patagonia (Argentina), there is a large variability of soils and the success of a fruit plantation depends mostly on soil characteristics. The main objective of this work was to determine the relationships between yield and fruit internal maturity at harvest of pear trees (Pyrus communis L.) grown in soils with different properties. The soil around each of 30 trees was morphologically characterized by measuring physical, physic-chemical, and chemical variables. At harvest time, total and commercial yields were measured, and maturity was determined by measuring flesh firmness, soluble solids, and titratable acidity. According to edaphic variables, soils were classified into five groups. Yields presented significant differences among such groups and growing seasons. The distribution of commercial sizes was similar in soils with fine texture, and high K content (897 and 663 mg kg(-1)) and cation-exchange capacity. Smaller fruits predominated in soil groups with high salinity (6.1 dS m(-1) in surface and 10.8 dS m(-1) in subsurface horizons) and shallow depth. The soil group with the highest salinity presented fruits with 11% more titratable acidity compared to all other groups. The soil group with the smallest depth presented fruits with high levels of flesh firmness (11.18 kg cm(-2)) and soluble solids (14.8%). The selected set of edaphic variables allowed us to differentiate groups of soils and analyze its influence in pear tree yield, commercial sizes, and fruit internal maturity.

Fire blight (Erwinia amylovora) causes blossom and shoot blight ultimately forming cankers on woody tissues. The magnitude of late season symptom development has not been reported on apple in natural infections. Quantitative and qualitative changes of fire blight symptoms were monitored from July 2007 to April 2008 on cultivars Idared and Golden Delicious in northern Serbia with Idared displaying the highest number of symptoms. In July, shoot blight dominated with 67-88% necrotic shoot tips and completely necrotic shoots. Early blight led to formation of 7-18% cankers of determinate type. Between mid-July and end of September, the number of cankers increased from 65 to 80% on both cultivars. New cankers were of indeterminate type, suitable for pathogen overwintering. Cankers originated from extensive late season pathogen stem invasion from previously diseased shoots. Necrosis size on both cultivars increased significantly between July and September. Increases in canker number and necrosis size indicate a high level of renewed pathogen activity late in the season and its 'preparation' for overwintering. Poor winter pruning in one orchard resulted in considerable number of symptom units which constituted potential infection sources. The high magnitude of late season symptom changes, detected under severe natural infections, shows that the pathogen is vigorously active within previously formed symptoms and that pathogenesis continues clandestinely. The results underline the importance of the often neglected part of late season fire blight development for pathogen survival and enforce the requirement for eradication of cankers as primary sources of inoculum for the next season.

BACKGROUND Pesticide use in orchards creates drift-driven pesticide losses which contaminate the environment. Trunk injection of pesticides as a target-precise delivery system could greatly reduce pesticide losses. However, pesticide efficiency after trunk injection is associated with the underinvestigated spatial and temporal distribution of the pesticide within the tree crown. This study quantified the spatial and temporal distribution of trunk-injected imidacloprid within apple crowns after trunk injection using one, two, four or eight injection ports per tree. RESULTS The spatial uniformity of imidacloprid distribution in apple crowns significantly increased with more injection ports. Four ports allowed uniform spatial distribution of imidacloprid in the crown. Uniform and non-uniform spatial distributions were established early and lasted throughout the experiment. The temporal distribution of imidacloprid was significantly non-uniform. Upper and lower crown positions did not significantly differ in compound concentration. Crown concentration patterns indicated that imidacloprid transport in the trunk occurred through radial diffusion and vertical uptake with a spiral pattern. CONCLUSION By showing where and when a trunk-injected compound is distributed in the apple tree canopy, this study addresses a key knowledge gap in terms of explaining the efficiency of the compound in the crown. These findings allow the improvement of target-precise pesticide delivery for more sustainable tree-based agriculture.

A nematode community was used as a bioindicator of changes in agroecosystems caused by fertilization. The effect of applying nitrogen (N) fertilizer on a soil nematode community structure was studied in a soil which had not been fertilized for six years in the Rio Negro Valley, Argentina. Treatments were: i) 100 kg N ha-1 (N100); ii) 200 kg N ha-1 (N200); in each case 50% of the dosage was applied at the time of petal fall and 50% at fruit harvest in 2004/2005, 2005/2006, 2006/2007 growing seasons; and iii) control with no fertilizer (N0). Soil samples were collected in the 0 to 30 cm soil layer in October, November, April and July in each growing season. The number of bacterivores increased in N200 compared to N0. Cephalobidae were present in greater numbers in N200 than in N100 and N0. Predator abundance was lower under N200, after the first N application in each growing season. The ratio of fungivores to bacterivores (F/B) was 0.21, 0.3 and 0.41 in N200, N100 and N0, respectively. N200 resulted in a community with a lower maturity index (MI) than N0. Structure index (SI) was lower in N200 than N100 and N0. The enrichment index (EI) was less sensitive at detecting fertilizer effects. In November and April, soil nitrate concentrations were higher in N200 than in N100 and N0. Soil nitrate concentration was positively correlated with EI and negatively with MI, SI and F/B. N200 affected the trophic structure of the nematode community consistent with a less stable soil system.

The objective of the study was to evaluate the seasonal patterns of physical-chemical properties, biological and enzymatic activities in soil surface horizons implanted with pear (Pyrus communis) trees cv. Williams. The study was conducted during three growing seasons, in three commercial orchards with ten experimental sites in each location. Soil samples were collected in spring and autumn. Soil texture, pH, electrical conductivity (EC), exchanging sodium percentage (PSI) total organic carbon, potassium exchange, biomass carbon (C-BM), respiration (RE), dehydrogenase (DH-ase), mineralization index (MI) and ratio of fungivores to bacterivores nematodes (F/B) were determined. Multiple factorial analyses were used to group the sites according to spring or autumn measurements. CE and PSI decreased 25% in autumn in saline soils. The levels of C-BM and RE varied between 113 and 179 mg C 100 g(-1) ss and between 5.5 and 8.7 mg CO2 g(-1) ss in spring, while in autumn they varied between 57 and 110 mg C 100 g(-1) ss and 2.8 and 5.3 mg CO2 g(-1) ss, respectively. Dhase levels were lower in shallow soils and higher in saline soils (1.7 mu g TPF g(-1) h(-1)). MI showed loss of COT in spring due to high mineralization in all soil groups. F/B was lower in saline soils (0.24) than in shallow soils (0.80) and deep and nonsaline soils (0.66), indicating that bacteria mediated decomposition. In the last two groups of soils, fungivores had more contribution to the decomposition processes. Value of F/B did not change between seasons in each soil group.

The aims of this study were to assess in vivo fertility and in vitro sperm characteristics of different sires and to identify sperm variables important for the prediction of conception rate. Multiparous Nelore cows (n = 191) from a commercial farm underwent the same timed artificial insemination (timed-AI) protocol. Three batches of frozen semen from three Angus bulls were used (n = 9). A routine semen thawing protocol was performed in the laboratory to mimic field conditions. The following in vitro sperm analyses were performed: Computer Assisted Semen Analysis (CASA), Thermal Resistance Test (TRT), Hyposmotic Swelling Test (HOST), assessment of plasma and acrosomal membrane integrity, assessment of sperm plasma membrane stability and of lipid peroxidation by flow cytometry and assessment of sperm morphometry and chromatin structure by Toluidine Blue staining. For statistical analyses, Partial Least Squares (PLS) regression was used to explore the importance of various sperm variables in the prediction of conception rate. The following in vitro sperm variables were determined to be important predictors of conception rate: total motility (TM), progressive motility (PM), TM after 2 h of thermal incubation (TM_2 h), PM after 2 h of thermal incubation (PM_2 h), Beat Cross Frequency after 2 h of thermal incubation (BCF_2 h), percentage of rapidly moving cells after 2 h of thermal incubation (RAP_2 h), intact plasma membrane evaluated by HOST, intact plasma and acrosomal membranes evaluated by flow cytometry, intact plasma membrane suffering lipid peroxidation, major defects, total defects, morphometric width/length ratio, Fourier_0 and Fourier_2 and Chromatin Heterogeneity. We concluded that PLS regression is a suitable statistical method to identify in vitro sperm characteristics that have an important relationship with in vivo bull fertility.