Scientia Horticulturae 185 (2015) 145–150 Contents lists available at ScienceDirect Scientia Horticulturae journal h om epage: www.elsevier.com/locate/scihorti Chlorophyll role in berry sunburn symptoms studied in different grape (Vitis vinifera L.) cultivars Laura Rustioni ∗ , Clara Milani, Simone Parisi, Osvaldo Failla Università degli Studi di Milano, CIRIVE—Centro Interdipartimentale di ricerca per l’innovazione in Viticoltura ed Enologia, via G. Celoria 2, I-20133 Milano, Italy a r t i c l e i n f o Article history: Received 4 December 2014 Received in revised form 23 January 2015 Accepted 26 January 2015 Keywords: Abiotic stress Grapevine Optical properties Pigments Photo-oxidation Reflectance spectroscopy a b s t r a c t In grape berries, extreme oxidative stress results in skin tissue bleaching and brownish areas appearance. Thus, these damages could negatively affect the fruit quality and the commercial value. The paper focuses on the chlorophyll roles in sunburn symptoms appearance in white skinned grape berries. In the present work, 20 cultivars were studied in three phenological stages. Berries were kept under temperature and light controlled conditions. Chlorophyll content and symptom appearance were quantified by reflectance spectroscopy indexes. The central role of radiation (and, thus, photo-oxidative damages) in berry sunburn injuries was underlined. Cultivars were classified, based on their susceptible or tolerant responses to radiation excess. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Chlorophylls are composed by a porphyrin ring and a lateral hydrocarburic chain with a magnesium atom in the center of the ring. The alternating system of single and double bounds of the chlorophyll ring is the typical structure of those molecules able to strongly absorb in the visible spectra region (Solomon et al., 2008). Two are the main chlorophyll molecules: a and b. They just differ for having a methilic or a carbonilic substituent. This difference shifts the wavelength of the adsorbed and reflected bands: chlorophyll b appears yellow–green, while chlorophyll a looks brilliant green (Solomon et al., 2008). In nature, chlorophyll optical properties allow the conversion of luminous energy in chemical energy through the photosynthetic process, upon which all life ultimately depends. The primary event is a light-driven electron transfer (Allen et al., 1995). The photo- synthetic redox reactions reveal their importance not only in the well-known energetic conversion, but also in their oxidative stress inductive and signaling roles (Allen et al., 1995; Kreslavski et al., 2012; Müller et al., 2001). Stressful conditions shift the balance between oxidant and antioxidant compounds toward the former. This becomes the ∗ Corresponding author. Tel.: +39 02 503 16556. E-mail addresses: laura.rustioni@unimi.it (L. Rustioni), clara milani@hotmail.it (C. Milani), simone.parisi@unimi.it (S. Parisi), osvaldo.failla@unimi.it (O. Failla). reason of the intracellular oxidative stress development (Kreslavski et al., 2012). Oxidative burst could be determined by various rea- sons, however, one of the main reactive oxygen species (ROS) sources in the cell is known to be the photosynthetic process. Unfavorable environmental conditions suppress the Calvin cycle function, resulting in an over-reduction of the electron transport chain components. The consequence is the production of ROS such as superoxide radical (O 2 • ) and hydroxyl radical (OH•), singlet oxygen ( 1 O 2 ) and hydrogen peroxide (H 2 O 2 ) (Kreslavski et al., 2012). In grape berries, extreme oxidative stress results in irreversible damages manifested as photosynthetic pigment bleaching, brownish areas appearance related to melanin-like pig- ments formation and, in severe cases, tissues death (Müller et al., 2001; Rustioni et al., 2014). These symptoms lead to fruit depreci- ation especially concerning table grapes. The radiation quantity reaching berries is subject to enormous changes on a time scale that ranges from seconds to months. Under radiation excess conditions, plants need to minimize photo- oxidative damages regulating the light interception and removing the already absorbed excess light energy. This is the case of non-photochemical protective mechanisms able to quench singlet- excited chlorophylls and to dissipate excess excitation energy as heat (Müller et al., 2001). Due to environmental conditions, and physiological adaptations, radiative stress is often associated to high temperatures. In the last decades, many studies were final- ized to distinguish between the radiative and thermal damages in viticulture (Bergqvist et al., 2001; Ristic et al., 2007; Rustioni http://dx.doi.org/10.1016/j.scienta.2015.01.029 0304-4238/© 2015 Elsevier B.V. All rights reserved.