Apple Production under Protective Netting Systems

Apple crop is more and more cultivated under protective netting systems. Depending on the location and sunlight intensity, apple orchards can benefit from these installations, as they will be protected against extreme weather events. Depending on the technical features of the thread, the nets will be hail-proof, wind-proof, or rain-proof, while having different shading percentages. Modern fruit production faces high pressure also related to biotic stressors; thus, modern protective nets are designed to aid pest management. These protective systems become interesting, as they will induce changes in the orchards’ microenvironment, with consequences on crop physiology. Netting mainly reduces incoming solar radiation and wind speed, altering the heat balance. Leaf gas exchanges and water relations can be positively influenced by netting in apple cultivation areas with extreme solar radiation, high temperatures, and low water availability. These considerations are important, especially if the final yield and quality are not compromised by shading. These protective systems can allow higher sustainability of apple production, lowering resource use, along with crop protection

How and when fungal endophytes can eliminate the plant growth–defence trade-off: mechanistic perspectives

A central paradigm in plant biology is that there is a trade-off between growth and defence against biotic stresses (Herms & Mattson, 1992; Lind et al., 2013; Karasov et al., 2017; Zust & € Agrawal, 2017; Monson et al., 2022). This paradigm is based on recurrent observations that increased production of chemical defences is associated with compromised plant growth, and it provides obvious limits to increasing the productivity of plants that must also resist pests and pathogens (Ballare & Austin, 2019; Ha et al., 2021; Sestari & Campos, 2021).We have recently challenged this paradigm by proposing that fungal endophytes can simultaneously increase plant growth and defence against biotic stresses (Fig. 1) (Bastıas et al., 2021).Fil: Bastías, Daniel A.. Grasslands Research Centre; Nueva ZelandaFil: Gundel, Pedro Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Talca; ChileFil: Johnson, Richard D.. Grasslands Research Centre; Nueva ZelandaFil: Gianoli, Ernesto. Universidad de La Serena; Chil

Native species facing climate changes: Response of calafate berries to low temperature and UV radiation

Calafate (Berberis microphylla G. Forst) is a wild bush plant widely distributed in the south of Argentina and Chile. Their blue colored fruits present particular flavor and health benefits attributed to high polyphenol contents biosynthesized by the plant under stress. Studies about correlation of abiotic conditions with anthocyanin profiles and physicochemical features of calafate beneath wild origin environment are not described yet. Hence, this research aimed to evaluate the physicochem- ical changes, antioxidant activity and anthocyanin content of calafate fruit in relationship to UV solar radiation (W.m−2) and air temperature (◦C) environment condition during three consecutive years (2017, 2018, 2019). Variations in fruit anthocyanins were determined by comparison between high performance liquid chromatography (HPLC-DAD-ESI)/MSn and CIEL*a*b* colors parameters. Correlations were analyzed by principal component analysis (PCA). Radiation was negatively correlated with fruit size and weight. Physicochemical aspects such as pH, soluble solids, color, total anthocyanins, flavanols and other phenolic compounds were positively correlated with temperature changes. The quantities of monomeric anthocyanins were dependent on both low temperature and global radiation (reaching 20.01 mg g−1 FW in calafate fruit). These results constitute a valuable resource to understand the structural and physiological plasticity of calafate in facing climate changes for future domestication research as well as for agri-food industrial application.This work has been supported by FONDECYT grant 1160899 (CONICYT, Chile) and Secretary of Higher Education of Science, Technology and Innovation of Ecuador (SENESCYT, Ecuador)

Preparation of Poly(vinyl Alcohol) Microparticles for Freeze Protection of Sensitive Fruit Crops

[Abstract] Poly(vinyl alcohol) (PVA) displays ice recrystallization inhibition (IRI) properties as many antifreeze proteins found in cold tolerant organisms. The molecular architecture and composition (molecular weight and distribution of pendant OH and acetate groups) have been studied to improve the antifreezing properties of PVA, suggesting that the molecular architecture of PVA plays an important role in IRI activity. The present work deals with the preparation of PVA microparticles using an alkaline treatment. The effect of PVA molecular weight on the morphology and antifreezeing properties of PVA microparticles was investigated. The antifreezeing property of PVA microparticles on the susceptibility of flower bud tissues to freeze damage was also evaluated. The alkaline treatment of an aqueous PVA solution produced stable polymer chain aggregates with spherical shapes. The average size of the PVA microparticles increased significantly with the increasing molecular weight of the PVA macromolecule precursor. The PVA microparticles inhibited the growth of ice crystals and blocked ice growth at concentrations as low as 0.01 % w/v. The effect of impeding ice crystal growth by preventing the joining of adjacent ice crystals is attributed to the larger size of the PVA particles adsorbed on the ice surface compared to the aggregated PVA macromolecules in saline solution. The thermal hysteresis activity of PVA macromolecules and microparticles was not detected by differential scanning calorimetry analysis. The PVA microparticles reduced the incidence of freeze injuries in flower bud tissues by 55% and their application, considering the low toxicity of PVA, has a high potential for freeze protection in fruit crops.Chile. Comisión Nacional de Investigación Científica y Tecnológica; ID16I10425Chile. Comisión Nacional de Investigación Científica y Tecnológica; ID16I20425Chile. Gobierno Regional del Biobío; R17A10003Chile. Agencia Nacional de Investigación y Desarrollo; ACE210016Chile. Agencia Nacional de Investigación y Desarrollo; ACE210012Chile. Comisión Nacional de Investigación Científica y Tecnológica; AFB170007This research was funded by projects CONICYT + FONDEF/tercer concurso IDeA en Dos Etapas del Fondo al Desarrollo Científico Y Tecnológico, FONDEF/CONICYT 2016 [grant numbers ID16I10425 and ID16I20425], CIPA, ANID Regional, GORE BIO BIO [grant number: R17A10003], ANID [grant numbers: ACE210016 and ACE210012] and CONICYT PIA/APOYO CCTE [grant number: AFB170007

LIGHT QUALITY MANAGEMENT IN FRUIT ORCHARDS: PHYSIOLOGICAL AND TECHNOLOGICAL ASPECTS

Light quality (sunlight spectrum) management promises to provide a new technological alternative to sustainable production in horticultural crops. However, little information exists about physiological and technological aspects on light quality management in fruit crops. Sunlight composition changes widely in orchard canopies, inducing different plant responses in fruit trees mediated by phytochrome (PHY) and cryptochrome (CRY) activity. High proportion of far-red (FR) in relation to red (R) light increases shoot elongation, while blue (B) light induces shoot dwarfing. Red and ultraviolet (UV) light increases fruit skin anthocyanin synthesis, while FR light shows a negative effect. Red and B light can also alter leaf morpho-physiological traits in fruit trees, such palisade thickness, stomatal aperture, and chlorophyll content. Besides improvement of photosynthetically active radiation (PAR) availability, the use of reflective films improves UV and R light proportion, with positive effects on PHY mediated-responses (fruit color, fruit weight, shoot growth), as reported in apple ( Malus domestica Borkh.), peach ( Prunus persica [L.] Batsch), and sweet cherry ( Prunus avium [L.] L.). Colored nets widely alter spectral light composition with effects on plant growth, yield, and quality in apple, kiwifruit ( Actinidia deliciosa [A. Chev.] C.F. Liang & A.R. Ferguson), peach, and blueberry ( Vaccinium corymbosum L.) orchards. Mechanisms of colored nets seem to be associated to photosynthetic and morphogenetic process regulated by PAR availability, R/B light proportion, and CRY activity. Alteration of light quality affects significantly fruit tree plant responses and could be a useful tool for sustainable (e.g. lower use of chemicals and labor-practices) management of yield and quality in modern orchards

Red and Blue Netting Alters Leaf Morphological and Physiological Characteristics in Apple Trees

There is little information about the role of red and blue light on leaf morphology and physiology in fruit trees, and more studies have been developed in herbaceous plants grown under controlled light conditions. The objective of this research was to evaluate the effect of red and blue screens on morpho-anatomy and gas exchange in apple leaves grown under ambient sunlight conditions. Apple trees cv. Fuji were covered by 40% red and blue nets, leaving trees with 20% white net as control. Light relations (photosynthetic photon flux density, PPFD; red to far-red light ratio, R/FR and blue to red light ratio, B/R), morpho-anatomical features of the leaf (palisade to spongy mesophyll ratio, P/S, and stomata density, SD) and leaf gas exchange (net photosynthesis rate, An; stomatal conductance, gs; transpiration rate, E; and intrinsic water use efficiency, IWUE) were evaluated. Red and blue nets reduced 27% PPFD, reducing by 20% SD and 25% P/S compared to control, but without negative effects on An and gs. Blue net increased gs 21%, leading to the highest E and lowest IWUE by increment of B/R light proportion. These findings demonstrate the potential use of red and blue nets for differential modulation of apple leaf gas exchange through sunlight management under field conditions

Irrigation Management Based on Theoretical Requirements Reduces Water Consumption in Apple (Malus domestica Borkh.) Orchards without Effects on Fruit Yield and Components

This research examines the effects of two irrigation strategies on water use efficiency and fruit yield components of ‘Royal Gala’ and ‘Brookfield Gala’ apple orchards in south-central Chile. The study was carried out during the 2008–2009 and 2009–2010 growing seasons at two sites. A randomized block experimental design was established with two water application treatments: theoretical volume required by the plant (T1) and farm protocol (T2). Soil water content, plant water potential and yield components were evaluated. The soil water content in T2 was near field capacity while T1 was between the permanent wilting point and field capacity for both seasons and varieties. With T1, the seasonal volume applied was 21 to 28% less compared to T2, with season savings of 1600 m3 ha−1. No effect on plant water potential was observed. In ‘Royal Gala’ the lower volume applied in T1 did not lead to significant differences in fruit diameter, weight, or yield in either season as compared to T2. In ‘Brookfield Gala’, yield during the 2008–2009 season increased significantly, by 22.9% in treatment T1, and in the 2009–2010 season, significant reductions (p < 0.05) in fruit diameter (5.3%) and weight (12.9%) were observed in T2. Productivity per volume of applied water in T1 was 32% to 56% greater than that obtained with T2. The results show the effectiveness of the irrigation strategy considering the theoretical volume of water required by the plant

EXPLORING THE POTENTIAL USE OF PHOTO-SELECTIVE NETS FOR FRUIT GROWTH REGULATION IN APPLE

The effect of shading (i.e. reduction of sunlight availability) on fruit growth physiology has been widely studied in apple ( Malus domestica Borkh.), but little knowledge exist about fruit growth responses to changes in the light spectrum. The aim of the present research was to study the effect of use of colored nets with differential sunlight transmission in the blue (B, 400-500 nm), red (R, 600-700 nm) and far-red (FR, 700-800 nm) spectra on apple fruit growth and physiological associated responses. Three year old 'Fuji' apple trees were covered with 40% photo-selective blue and red shade nets, 40% neutral grey shade net, and 20% neutral white net as control. Red and blue net reduced in the same proportion (27%) the photosynthetically active radiation with respect to control. However, blue net increased by 30% and reduced by 10% the B:R and R:FR the light relations, respectively. Maximal fruit growth rate under blue and grey nets was 15-20% greater than control. Fruit weight under blue net was 17% greater than control, but no significant differences in fruit weight were found among red net and control. Leaf photosynthesis and total leaf area under blue net were 28% and 30% higher than control, respectively; with ensuing positive effect on tree net C assimilation rate and total dry matter production. Results suggest that shifting the B, R, and FR light composition with photo-selective nets could be a useful tool to manipulate the photosynthetic and morphogenetic process regulating the carbohydrate availability for apple fruit growth

Response of Maize (<i>Zea mays</i> L.) to Drought under Salinity and Boron Stress in the Atacama Desert

The Lluta valley in northern Chile is a hyper-arid region with annual precipitation lower than 1.1 mm, and high levels of boron (B) from alluvial deposits are present together with other salts that originated from the Cretaceous. Under these abiotic conditions, the ‘lluteño’ maize (Zea mays L.) is of interest because it has adapted to the Lluta valley with high salinity levels and B excess in the soil and irrigation water. Water and salt stress coincide in heavily irrigated hyper-arid agricultural areas, yet they are usually studied in isolation. We investigated in field conditions the combined effects of drought (22 days with no irrigation) under salinity (ECe: 5.5 mS cm−1; Na+: 17.8 meq L−1) and B (21.1 meq L−1) stress on physiology, growth, yield, and hourly water relations. The results allow to hypothesize that the measurement of the pre-dawn water potential represents the balance between the water potential of the soil and the root. Besides, under drought a significant effect of irrigation and time interaction was observed presenting a high differential between the leaf and stem water potential in both phenological stages. Furthermore, a decrease in net assimilation was observed, and it could be explained in part by non-stomatal factors such as the high radiation and temperature observed at the end of the season. Despite the drought, the cobs did not present a significantly lower quality compared to the cobs of plants without stress