Pruning is crucial to balance productivity and fruit quality in blueberry orchards. Slight, conventional and severe pruning treatments were applied on 4-and 5-year old bluberry plants cultivar 'Brigitta' to evaluate their effect on yield, leaf area, gas exchange and fruit load as driver of fruit quality traits. Yield and berries per plant decreased with increasing pruning severity, whereas canopy leaf area increased. The resulting fruit load ranged from 0.2 to 1.4 fruit per cm 2 leaf area. Fruit weight, dry matter, glucose and fructose were negatively related to fruit load, with fruit fresh weight decreasing to greater extent than sugars. Berry weight was restricted by source limitation during the initial cell division and initial cell enlargement fruit growth phases as indicated by decreased relative growth rate. Light-saturated photosynthetic rate diminished with increasing pruning severity indicating a sink limitation of photosynthesis. The strong association between photosynthesis and stomatal conductance shows a high corregulation in the response of carbon and water exchange to sink demand. Our results underline agronomic and physiological factors determining blueberry yield and fruit quality and can be useful for agro-technical management.

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Abstract. Monitoring of fruit growth is a measurement widely used in physiology and agronomy 27studies. This is normally done from detached fruits, which can lead to erroneous results when fruits 28 grow asynchronously in clusters as occurs in blueberry plants (Vaccinium spp.). The aim of this 29 communication is to develop a simple allometric model for estimating blueberry weight from 30 diameter measurements. In three growth seasons, weight and diameter of a total of 416 fruits were 31 measured from four field-grown blueberry cultivars. The obtained data set was then randomly 32 divided resulting in 200 data for calibrating model and 216 for validating. Prior to calibration 33 procedure, the use of cultivar-specific models or a common model for four cultivars was evaluated 34by Analysis of Covariance between logarithm transformed diameter and cultivar/season variables. 35From analysis, no interactive effect was observed, so a common allometric model was constructed, 36 giving a power functional relationship between berry diameter and weight. The allometric model 37 was validated with the independent data, giving errors ranging from 4.7% to 6.9%. Residuals 38 showed a random dispersion pattern. Our results showed that a common model was adequate for 39 providing a reliable means of estimating blueberry fruit weight of different cultivars. 40 41

The crop Vitis vinifera (L.) is of great economic importance as Chile is one of the main wine-producing countries, reaching a vineyard area of 145,000 ha. This vine crop is usually very sensitive to local condition changes and agronomic practices; therefore, strategies to counteract the expected future decrease in water level for agricultural irrigation, temperature increase, extreme water stress (abiotic stress), as well as increase in pathogenic diseases (biotic stress) related to climate change will be of vital importance for this crop. Studies carried out in recent years have suggested that arbuscular mycorrhizal fungi (AMF) can provide key ecosystem services to host plants, such as water uptake implementation and enhanced absorption of nutrients such as P and N, which are key factors for improving the nutritional status of the vine. AMF use in viticulture will contribute also to sustainable agronomic management and bioprotection against pathogens. Here we will present (1) the current status of grapevines in Chile, (2) the main problems in grapevines related to water stress and associated with climate change, (3) the importance of AMF to face water stress and pathogens, and (4) the application of AMF as a biotechnological and sustainable tool in vineyards.

The source-sink relationship is one of major determinants of plant performance. The influence of reproductive sink demand on light-saturated photosynthesis (P (max)), dark respiration (R (D)), stomatal conductance (g (s)), intrinsic water-use efficiency (WUEi), contents of soluble sugar (SSC), nitrogen, carbon, and photosynthetic pigments was examined in blueberry (Vaccinium corymbosum L. cv. 'Brigitta') during the final stage of rapid fruit growth. Measurements were performed three times per day on developed, sun-exposed leaves of girdled shoots with 0.1, 1, and 10 fruit per leaf (0.1F:L, 1F:L, and 10F:L, respectively) and nongirdled shoots bearing one fruit per leaf (NG). Girdling and lower fruit amount induced lower P (max), g (s), N, and total chlorophyll (Chl) and higher WUEi, SSC, R (D), Chl a/b ratio and carotenoids-to-chlorophylls ratio (Car/Chl) for the 1F:L and 0.1F:L treatments. The impact of girdling was counterbalanced by 10F:L, with NG and 10F:L having similar values. Variables other than P (max), R (D), g (s), WUEi, and SSC were unaffected throughout the course of the day. P (max) and g (s) decreased during the course of the day, but g (s) decreased more than P (max) in the afternoon, while WUEi was increasing in almost all treatments. SSC increased from the morning until afternoon, whereas R (D) peaked at noon regardless of the treatment. Generally, P (max) was closely and negatively correlated to SSC, indicating that sugar-sensing mechanisms played an important role in regulation of blueberry leaf photosynthesis. With respect to treatments, P (max) and N content were positively related, while R (D) was not associated to substrate availability. The enhanced Car/Chl ratio showed a higher photoprotection under the lower sink demand. Changes in the source-sink relationship in 'Brigitta' blueberry led to a rearrangement of physiological and structural leaf traits which allowed adjusting the daily balance between carbon assimilation and absorbed light energy.CONICYT (Chile) FONDEF D06I1100 Universidad de La Frontera (Temuco, Chile) FRO0601 FONDECYT 113050

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