L.G. Santesteban

Are precision agriculture tools and methods relevant at the whole-vineyard scale?

Precision viticulture (PV) has been mainly applied at the field level, for which the ability of high resolution data to match within-field variability has been already shown. However, the interest of PV for grape growers would be greater if its principles could also apply at a larger scale, as most growers still focus their management on a multi-field scale, not considering each field as an isolated unit. The aim of this study was to analyse whether it is possible and relevant to use PV tools to define meaningful management zones at the whole-vineyard scale. The study was carried out on a 90-ha vineyard made of 27 contiguous fields. The spatial variability of vine vigour, estimated with the Normalized Difference Vegetation Index (NDVI), was analysed at within-field and whole-vineyard scales. The spatial variability of the vigour was significant and spatially organized whatever the considered scale. Besides, vineyard spatial variability was characterised using information on environmental factors (soil apparent conductivity and elevation) and vine response (yield, vigour and grape composition). At both scales, NDVI and measured environmental factors were used to establish a three-level classification, whose agronomic significance was tested comparing the vine response observed for each class. The analysis of high resolution information allowed the definition of classes with agronomic and oenological implications, although there was not a straightforward correspondence between the classes defined and quality. Analysing the variability at the whole-vineyard scale highlighted a trend of spatial variation associated to elevation that was hardly visible at the within-field level.

Vegetative Growth, Reproductive Development and Vineyard Balance

In the last decades, viticultural research has made important progress due to the implementation of many technical advances to this field. In addition to “classical” viticultural research, it is now possible to analyze vine behaviour with many different approaches, such as plant physiology, genomics, proteomics, precision viticulture and so on. These changes extend our understanding of viticulture, but they may also lead to a certain heterogeneity in the methodology used to estimate the basic characteristics of the vineyards (e.g.: vegetative and reproductive growth). Even worse, measurements of those parameters are sometimes neglected. In order to optimize the relevance and inter-disciplinarity of our work, and its applicability to the vineyard, we should tend toward protocol standardization, the most suitable measurements and ways of expressing results should be determined for each circumstance. This chapter attempts to shed some light on some methodological aspects related to the measurement of vine vegetative and reproductive growth and vineyard balance. We have tried to be comprehensive, but not exhaustive, since some topics are also the subject of other chapters in this book whereas others are beyond its scope.

Evaluating the Influence of the Microsatellite Marker Set on the Genetic Structure Inferred in Pyrus communis L.

Fingerprinting information can be used to elucidate in a robust manner the genetic structure of germplasm collections, allowing a more rational and fine assessment of genetic resources. Bayesian model-based approaches are nowadays majorly preferred to infer genetic structure, but it is still largely unresolved how marker sets should be built in order to obtain a robust inference. The objective was to evaluate, in Pyrus germplasm collections, the influence of the SSR marker set size on the genetic structure inferred, also evaluating the influence of the criterion used to select those markers. Inferences were performed considering an increasing number of SSR markers that ranged from just two up to 25, incorporated one at a time into the analysis. The influence of the number of SSR markers used was evaluated comparing the number of populations and the strength of the signal detected, and also the similarity of the genotype assignments to populations between analyses. In order to test if those results were influenced by the criterion used to select the SSRs, several choosing scenarios based on the discrimination power or the fixation index values of the SSRs were tested. Our results indicate that population structure could be inferred accurately once a certain SSR number threshold was reached, which depended on the underlying structure within the genotypes, but the method used to select the markers included on each set appeared not to be very relevant. The minimum number of SSRs required to provide robust structure inferences and adequate measurements of the differentiation, even when low differentiation levels exist within populations, was proved similar to that of the complete list of recommended markers for fingerprinting. When a SSR set size similar to the minimum marker sets recommended for fingerprinting it is used, only major divisions or moderate (F ST>0.05) differentiation of the germplasm are detected.

Analysis of the genetic diversity and structure of the Spanish apple genetic resources suggests the existence of an Iberian genepool

87 Pags.- 3 Tabls.- 5 Figs.- 1 Suppl. Fig.- 5 Suppl. Tabls. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1744-7348

Terahertz time domain spectroscopy allows contactless monitoring of grapevine water status

Agriculture is the sector with the greatest water consumption, since food production is frequently based on crop irrigation. Proper irrigation management requires reliable information on plant water status, but all the plant-based methods to determine it suffer from several inconveniences, mainly caused by the necessity of destructive sampling or of alteration of the plant organ due to contact installation. The aim of this work is to test if terahertz (THz) time domain reflectance measurements made on the grapevine trunk allows contactless monitoring of plant status. The experiments were performed on a potted 14-years-old plant, using a general purpose THz emitter receiver head. Trunk THz time-domain reflection signal proved to be very sensitive to changes in plant water availability, as its pattern follows the trend of soil water content and trunk growth variations. Therefore, it could be used to contactless monitor plant water status. Apart from that, THz reflection signal was observed to respond to light conditions which, according to a specifically designed girdling experiment, was caused by changes in the phloem. This latter results opens a promising field of research for contactless monitoring of phloem activity.

GMI Magnetoelastic Sensor for Measuring Trunk Diameter Variations in Plants

Sensors based on giant magnetoimpedance effect are widely used in different technological applications. In this paper, a magnetoelastic sensor based on the changes of the high-frequency electrical impedance (

Evaluation of spectral-based and canopy-based vegetation indices from UAV and Sentinel 2 images to assess spatial variability and ground vine parameters

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Agronomic significance of the zones defined within vineyards early in the season using NDVI and fruit load information

) of a soft magnetic sample under applied mechanical stress has been optimized to measure the cyclical diameter variations in plants (grapevines in particular) in order to characterize their water status. Micrometric trunk shrinkage and growth take place during daylight and night, respectively, due to the changes in transpiration process and in within-plant water balance in a daily basis. The characterization of these variations (usually performed through linear variable differential transducers) represents a powerful tool in the agronomic sector regarding irrigation plant schedule.

Influence of the freezing method on the changes that occur in grape samples after frozen storage

New remote sensing technologies have provided unprecedented results in vineyard monitoring. The aim of this work was to evaluate different sources of images and processing methodologies to describe spatial variability of spectral-based and canopy-based vegetation indices within a vineyard, and their relationship with productive and qualitative vine parameters. Comparison between image-derived indices from Sentinel 2 NDVI, unfiltered and filtered UAV NDVI and with agronomic features have been performed. UAV images allow calculating new non-spectral indices based on canopy architecture that provide additional and useful information to the growers with regards to within-vineyard management zone delineation.

Allometric relationships for estimating vegetative and reproductive biomass in grapevine (Vitis vinifera L.)

Wine quality is known to be highly dependent on grape quality and, therefore, wineries aiming to produce premium wines are concerned with obtaining top quality grapes. However, since grape quality is not uniform within a vineyard sometimes it is necessary to evaluate which zones within a single vineyard are producing the best grapes in order to segregate them at harvest. The aim of this work was to compare the performance of two methods to delineate zones within vineyards: (1) expert knowledge (ExpZ); and (2) fuzzy k-means analysis (FuzZ) using NDVI and fruit load as information sources, procedures that were applied to 4 adjacent vineyards located in Villamanta, (Madrid, Spain). Both methodologies were suitable to delineate parts of a vineyard with differences in grape composition, although FuzZ provided a more significant zoning than ExpZ from an oenological point of view.