Search

Grapevine phenology and total soluble solids (TSS) accumulation are important information to plan agricultural operation in the vineyards over the season. The study aims at identifying the main environmental factors and related high spatial auxiliary information that could be used to define within-field zones of phenology and TSS accumulation. An experiment was carried out in the Maule Valley, Chile, considering two representative vineyards with different environmental characteristics: vineyard 1 (cv. Cabernet Sauvignon) which presents differences in elevation and vineyard 2 (cv. Chardonnay) which is considered flat. Within each vineyard, a regular sampling grid was defined to perform measurements: phenology, TSS accumulation, plant water status, vegetative expression, yield, soil physical properties and soil apparent electrical conductivity. Observations were made during four and two years respectively for vineyard 1 and 2. The analysis of the results is based on principal component analysis (PCA) to identify the relationships between variables. Results show that factors affecting the spatial variability of phenology and TSS accumulation are different for each vineyard. For vineyard 1, topography is the main factor that affects the spatial variability both in phenology and TSS accumulation. For vineyard 2, the soil apparent electrical conductivity was the most important factor explaining the spatial variability observed in the phenology, while balance between vegetative expression and fruit load affected the TSS accumulation. These results highlight the possibility to define zones of differentiated management in relation to the phenology and TSS accumulation using auxiliary information easy to acquire or available with high spatial resolution. [ABSTRACT FROM AUTHOR]

The aim of this study is to propose an empirical spatial model to estimate the spatial variability of grapevine phenology at the within-field scale. This spatial model allows the characterization of the spatial variability of a given variable of the fields through a single measurement performed in the field (reference site) and a combination of site-specific coefficients calculated through historical information. This approach was compared to classical approaches requiring extensive sampling and phenology models based on climatic data, which do not consider the spatial variability of the field. The study was conducted on two fields of Vitis vinifera, one of cv Cabernet Sauvignon (CS, 1.56 ha) and the other one of cv Chardonnay (CH, 1.66 ha) located in Maule Valley, Chile. Date of occurrence of grapevine phenology (budburst, flowering and veraison) were observed at the within field level following a regular sampling grid during 4 seasons for cv CS and 2 seasons for cv CH. The best results were obtained with the devised spatial model in almost all cases, with a Root Mean Square Errors (RMSE) lower than 3 days. However, if the variability of phenology is low, the traditional method of sampling could lead to better results. This study is the first step towards a modeling of the spatial variability of grapevine phenology at the within-field scale. To be fully operational in commercial vineyards, the calibration process needs simplification, for example, using low cost, inexpensive ancillary information to zone vineyards according to grapevine phenology. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology to improve grape yield sampling and yield estimation of the current season by using historical yield data. This approach is based on the conjoint use of (i) historical yield data all over the study field and (ii) several yield measurements collected at specific sites within the field during the current season. The proposed methodology (Optimized targeted sampling, OTS) assumes that, in viticulture, within-field yield spatial patterns are temporally stable over time as shown in previous studies (this assumption will also be verified with the data used in this study). The first principal component (PC1) of a principal component analysis (PCA) applied to the historical yield data was used to characterize the temporal behaviour of the within-field yield spatial patterns. Results showed that PC1 was always able to explain a significant percentage of the within-field yield variability across different years meaning that yield temporal stability could be assumed. PC1 scores were then used to choose the best sites to sample (targeted sampling) to estimate the yield of the current season. Yield measurements at these specific sites were used to calibrate a model relating yield values of the current season to PC1 scores. This latter model was finally used to estimate the yield of the current season at all remaining sites. This sampling method was tested on three vine fields (Vitis vinifera L.) in Chile and France with different cultivars (Chardonnay, Cabernet Sauvignon and Syrah). For each of these fields, yield data of several years (between four and seven years) were available at the within-field level. The optimised targeted sampling method (OTS) was applied to the fields under study once the temporal stability of yield patterns was validated. Results were compared to those arising from (i) a uniform random sampling method (URS) and (ii) a stratified random sampling method (SRS). Errors in yield estimates were reduced by more than 6% and 1% on average with respect to the URS and SRS methods, except when yield stable patterns were affected by specific events, i.e. early frost occurring in the season 2014 on the Chardonnay field. The findings demonstrate that the use of localized historical yield data helps to choose reliable sampling sites to improve grape yield estimation. [ABSTRACT FROM AUTHOR]

Knowledge and monitoring of the grapevine phenology during the season are important requirements for characterization of productive regions, climate change studies and planning of various production activities at the vine field scale. This work aims at studying the spatial variability of grapevine phenology at the within field scale. It was conducted on two fields, one of cv Cabernet Sauvignon of 1.56 ha and the other of cv Chardonnay of 1.66 ha, both located in Maule Valley, Chile. Within each vine field, a regular sampling grid was designed, to carry out weekly measurements of phenology and maturation. The main results show that there is a significant spatial variability in the phenological development and maturation at the within field scale for both fields. This variability is spatially organised and temporally stable from the beginning of the season (post-budburst) to harvest and over the years. A cluster analysis allowed us to define two clearly contrasted zones in terms of phenology and maturation in both fields, explained by the microclimate. The magnitude of difference between zones varied from 4 to 9 days depending on phenological stages and from 5 to 43 days for maturation. These differences are similar and comparable to that observed at larger scales or under scenarios of climate change. These results highlight the necessity to better take into account this variability to improve sampling and to base decisions of production activities (spraying, harvest, pruning, etc.) application on more relevant information. Further investigations should determine the environmental factors that determine the observed spatial variability. [ABSTRACT FROM AUTHOR]

The genus Thunnus is composed of eight species, which are separated into two groups, the temperate subgenus Thunnus (bluefin tunas group) and the tropical subgenus Neothunnus (yellowfin tunas group). We obtained the mitochondrial genome for two species from the yellowfin group, Thunnus albacares and Thunnus atlanticus, and compared to those from extant Thunnus species to reconstruct the mtDNA phylogenetic relationship within the genus. Our results coincide with previous studies using mtDNA and nuclear loci in the paraphyly of the bluefin group mainly as a result of the position of Thunnus obesus within the tree. Also, we support the introgression hypothesis of the mtDNA from albacore into Pacific Bluefin tuna. [ABSTRACT FROM AUTHOR]

Coryphaena hippurus is an economically relevant fish species that is highly exploited by commercial and sport fisheries throughout its geographical range. We tested a set of 30 primers derived from next generation sequencing and optimized conditions for amplification of sixteen polymorphic microsatellite loci. These were also tested for cross amplifications in the congeneric species C. equiselis. We registered high genetic variation among loci (mean number of alleles per locus = 9.42, SD = 6.01; mean H = 0.67 SD = 0.24). These loci are expected to be useful for population genetic studies for both species and as reference for stock delineation and conservation plans. [ABSTRACT FROM AUTHOR]