Potential of VIS/NIR spectroscopy to detect and predict bitter pit in ‘Golden Smoothee’ apples

Aim of study: A portable VIS/NIR spectrometer and chemometric techniques were combined to identify bitter pit (BP) in Golden apples. Area of study: Worldwide Material and methods: Three different classification algorithms – linear discriminant analysis (LDA), quadratic discriminant analysis (QDA) and support-vector machine (SVM) –were used in two experiments. In experiment #1, VIS/NIR measurements were carried out at postharvest on apples previously classified according to 3 classes (class 1: non-BP; class 2: slight symptoms; class 3: severe symptoms). In experiment #2, VIS/NIR measurements were carried out on healthy apples collected before harvest to determinate the capacity of the classification algorithms for detecting BP prior to the appearance of symptoms. Main results: In the experiement #1, VIS/NIR spectroscopy showed great potential in pitted apples detection with visibly symptoms (accuracies of 75–81%). The linear classifier LDA performed better than the multivariate non-linear QDA and SVM classifiers in discriminating between healthy and bitter pitted apples. In the experiment #2, the accuracy to predict bitter pit prior to the appearance of visible symptoms decreased to 44–57%. Research highlights: The identification of apples with bitter pit through VIS/NIR spectroscopy may be due to chlorophyll degradation and/or changes in intercellular water in fruit tissue

Evaluation of chemical fruit thinning efficiency using Brevis® (Metamitron) on apple trees (‘Gala’) under Spanish conditions

Thinning is an important technique in apple growing which is used to reduce the number of fruits per plant and achieve commercial fruit size and quality. The objective of this work was to evaluate the efficacy of one and two applications of the chemical thinner Brevis® in Gala apple applied at different fruit sizes and at different intervals between the first and second spray. The trials were conducted over two seasons from 2015 to 2016 in apple orchards of the IRTA experimental agricultural stations of Mas Badia and Lleida (Spain). One or two applications with Brevis® were applied at different fruit sizes (king fruit diameter ranging between 7.5 and 13.5 mm) and at a rate of 1.65 kg/ha for all treatments. Under the trial conditions, a Brevis® thinning effect was observed in all trials with a reduction in crop load, fruit set and number of fruits per tree which varied according to the number of applications. In addition, average fruit weight, color and diameter increased significantly with treatments in which Brevis® reduced the number of fruits per tree. The degree of abscission of Brevis® was highly dependent on night temperature and, for this reason, there was a high degree of variability between trials in terms of efficacy. Our results show that the number of days between applications was not as important a factor for Brevis® efficacy as the difference in night temperature in the days immediately after its application.This study was supported financially by project INIA (Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (Spain)) (RTA2012-00116-00-00) in collaboration with ADAMA-Spain

Effect of different application rates of metamitron as fruitlet chemical thinner on thinning efficacy and fluorescence inhibition in Gala and Fuji apple

Crop thinning is an important and difficult agricultural practice. Knowing the effect of the application dose of a product is a crucial element of any thinning program. The aims of this study were to investigate the effect of different metamitron doses on Gala and Fuji apples applied at fruit king diameters of between 8 and 10 mm and to determine fluorescence inhibition at the different application rates. Trials were conducted over two seasons from 2015 to 2016 in apple orchards in Lleida (Spain). Photosynthesis inhibition caused by metamitron was also analysed and measured, using chlorophyll fluorescence and biexponential pharmacokinetic models. Under the trial conditions, the application of metamitron reduced final fruit set, number of fruits per tree and crop load depending on the application rate. A dose effect was observed in all yield parameters. Moreover, when metamitron showed high efficacy, there was an improvement in fruit weight, coloration and diameter. The estimated parameters A, α and B using a biexponential equation were related with final fruit set, however the period of inhibition has to be finished before prediction can be made of metamitron efficacy in the year. The fluorescence analysis showed a dose effect, with metamitron dose increasing inhibition. Additionally, the same result was also observed in the area under curve analysis, with metamitron dose reducing the area and inhibition increasing. In all yield parameters, the fluorescence and area under curve analyses showed differences between cultivars, with the inhibition caused by metamitron higher in Gala than in Fuji. Moreover, differences between years were observed. 2015 was warmer than 2016, and the higher temperatures increased the thinning efficacy of metamitron.This study was supported financially by project INIA (RTA2012-00116-00-00) in collaboration with ADAMA-Spain

Desarrollo de métodos de predicción de la incidencia de 'bitter pit' en plantaciones de manzanas ‘Golden Smoothee’ (Malus domestica, L. Borkh.)

El bitter pit és la fisiopatia més important en molts cultivars de pomes. No obstant, no existeix una estratègia completament efectiva per al seu control, per aquest motiu, un mètode de predicció que identifiqui anys i plantacions amb un alt potencial de desenvolupar la fisiopatia permetrà evitar pèrdues econòmiques, especialment durant la conservació i confecció. L’objectiu principal de la present tesi doctoral va ser la posada a punt d’un sistema de predicció de la incidència del bitter pit en plantacions de poma ‘Golden Smoothee’. Per això, es van investigar diferents mètodes basats en tres tecnologies diferents: i) l’anàlisi mineralògic de fruits en diferent època (en estadis primerencs i a recol·lecció), ii) la inducció de símptomes (infiltració de Mg, banys amb etefón, embossat de fruits i mètode passiu) i iii ) l’espectroscopía VIS/NIR. Els diferents mètodes es van avaluar en diferents períodes de creixement del fruit. Paral·lelament, es va avaluar i quantificar l’eficàcia de diferents estratègies per mitigar l’aparició de bitter pit basades en aplicacions de CaCl2 a pre i postcollita (aplicacions radiculares, foliars i banys en poscosecha). L’anàlisi primerenc de Ca en fruit a 60 dies després de la floració (DDPF) va mostrar una precisió en la predicció similar o millor que l’anàlisi a recol·lecció. Es va definir un valor de referència de 60 DDPF de 11 mg de Ca 100 g-1 de pes fresc, per sobre del qual es minimitza la incidència de bitter pit. La majoria de mètodes basats en induir símptomes, a excepció de l’embossat, van mostrar eficàcia a partir dels 40 dies abans de la recol·lecció (DAR), amb una correlació amb el bitter pit de postcollita del 70-80%. La espectroscopía VIS/NIR va mostrar resultats poc satisfactoris per a la predicció del bitter pit, però va ser capaç de discriminar fruits afectats quan els símptomes eren visibles a postcollita. Finalment, es va disenyar un model de predicció per al bitter pit basat en l’anàlisi de Ca en fruit a 60 DDPF i el mètode passiu a partir de 40 DAR. Respecte la mitigació del bitter pit, els resultats obtinguts en els anys amb alta incidència van mostrar una reducció del 20% a un 12%, 8% o 3% mitjançant aplicacions foliars, banys de postcollita o la combinació d’ambdues, respectivament, per tant, les aplicacions foliars de CaCl2 així com els banys postcollita serien pràctiques a recomanar en els casos d’alt risc de bitter pit.El bitter pit es la fisiopaía más importante en muchos cultivares de manzana. Sin embargo, no existe una estrategia de control completamente efectiva, por lo que un método de predicción que identifique años y plantaciones con alto potencial de desarrollar la fisiopatía permitirá evitar pérdidas económicas, especialmente durante la conservación y confección. El objetivo principal de la presente tesis doctoral fue la puesta a punto de un sistema de predicción de la incidencia de bitter pit en plantaciones de manzanas ‘Golden Smoothee’. Para ello, se investigaron diferentes métodos de predicción basados en tres tecnologías distintas: i) el análisis mineralógico de fruto (en estadios tempranos y en recolección), ii) la inducción de síntomas (infiltración de Mg, baños con etefón, embolsado de frutos y método pasivo) y iii) la espectroscopía VIS/NIR. Los distintos métodos se evaluaron en diferentes períodos de crecimiento del fruto. Paralelamente, se evaluó y cuantificó la eficacia de distintas estrategias para la mitigación del bitter pit basadas en aportaciones de CaCl2 en pre y poscosecha (aplicaciones radiculares, foliares y baños en poscosecha). El análisis temprano de Ca en fruto a 60 días después de plena floración (DDPF) mostró una precisión de predicción similar o mejor que el análisis de Ca en recolección. Se definió un umbral de referencia a 60 DDPF de 11 mg Ca 100 g-1 de peso fresco, por encima del cual se minimizó el riesgo de aparición del bitter pit. La mayoría de métodos basados en inducir síntomas, a excepción del embolsado de frutos, mostraron eficacia a partir de los 40 días antes de recolección (DAR), con una correlación con el bitter pit de poscosecha del 70-80%. La espectroscopía VIS/NIR mostró resultados poco satisfactorios para la predicción del bitter pit, sin embargo, sí fue capaz de discriminar frutos afectados cuando los síntomas eran visibles en poscosecha. Finalmente, se diseñó un modelo de predicción del bitter pit basado en el análisis de Ca en fruto a 60 DDPF y el método pasivo a partir de 40 DAR. Respecto la mitigación del bitter pit, los resultados obtenidos en años con alta incidencia mostraron una reducción de un 20% a un 12%, 8% o 3% mediante aplicaciones foliares, baños en poscosecha o la combinación de ambas, respectivamente, por lo que tanto las aplicaciones foliares de CaCl2 como los baños poscosecha serían prácticas a recomendar en el caso de riesgo de bitter pit.Bitter pit is the most important physiological disorder in many apple cultivars. However, there is no a completely effective control strategy, therefore, a prediction method that identifies years and orchards with high potential to develop bitter pit will allow reducing economic losses, especially during storage and fruit packing. The main objective of this PhD thesis was the development of a system to predict the incidence of bitter pit for ‘Golden Smoothee’ apple orchards. For this, different methods to predict bitter pit based on three different technologies were investigated: i) mineral analysis (at early stages and at harvest period, ii) induction of symptoms (Mg infiltration, dips with etephon solution, bagging of fruit and passive method) and iii) VIS/NIR spectrophotometry. The different methods were tested in different fruit growth stages. At the same time, the efficacy of different strategies based on CaCl2 applications at pre- and postharvest (fertigation, foliar and postharvest dips) to mitigate bitter pit incidence, were evaluated and quantified. The accuracy of mineral analysis at early development fruit after 60 days after full bloom (DAFB) was better or equal than Ca analysis at harvest. A reference threshold at 60 DAFB of 11 mg Ca 100 g-1 fresh weight was defined. Values equal or higher indicated a low risk of bitter pit. Most methods based on inducing symptoms, with the exception of bagging fruit, showed efficacy from 40 days before harvest (DBH), with a correlation with bitter pit at postharvest of 70-80%. VIS/NIR spectrophotometry showed unsatisfactory results for bitter pit prediction, however, it was able to discriminate affected apples when the symptoms were visible at postharvest. Finally, a bitter pit prediction model based on the analysis of Ca in fruitlet at 60 DAFB and the passive method from 40 DBH was designed. Regarding bitter pit mitigation, the results obtained in seasons with a high incidence showed a reduction from 20% to 12%, 8% or 3% using Ca sprays, postharvest dips or the combination of both, respectively. Therefore, Ca sprays and postharvest dips in CaCl2 solutions are recommended practices when there is a diagnostic of high risk of bitter pit