Jasmonates and abscisic acid influence fruit ripening and plant water use: practical, physiological and morphological aspects

The aim of the present thesis was to better understand the physiological role of the phytohormones jasmonates (JAs) and abscisic acid (ABA) during fruit ripening in prospect of a possible field application of JAs and ABA to improve fruit yield and quality. In particular, the effects of exogenous application of these substances at different fruit developmental stages and under different experimental conditions were evaluated. Some aspects of the water relations upon ABA treatment were also analysed. Three fruit species, peach (Prunus persica L. Batsch), golden (Actinidia chinensis) and green kiwifruit (Actinidia deliciosa), and several of their cvs, were used for the trials. Different experimental models were adopted: fruits in planta, detached fruit, detached branches with fruit, girdled branches and micropropagated plants. The work was structured into four sets of experiments as follows: (i) Pre-harvest methyl jasmonate (MJ) application was performed at S3/S4 transition under field conditions in Redhaven peach; ethylene production, ripening index, fruit quality and shelf-life were assessed showing that MJ-treated fruit were firmer and thus less ripe than controls as confirmed by the Index of Absorbance Difference (IAD), but exhibited a shorter shelf-life due to an increase in ethylene production. Moreover, the time course of the expression of ethylene-, auxin- and other ripening-related genes was determined. Ripening-related ACO1 and ACS1 transcript accumulation was inhibited though transiently by MJ, and gene expression of the ethylene receptor ETR2 and of the ethylene-related transcription factor ERF2 was also altered. The time course of the expression of several auxin-related genes was strongly affected by MJ suggesting an increase in auxin biosynthesis, altered auxin conjugation and release as well as perception and transport; the need for a correct ethylene/auxin balance during ripening was confirmed. (ii) Pre- and post-harvest ABA applications were carried out under field conditions in Flaminia and O’Henry peach and Stark Red Gold nectarine fruit; ethylene production, ripening index, fruit quality and shelf-life were assessed. Results show that pre-harvest ABA applications increase fruit size and skin color intensity. Also post-harvest ABA treatments alter ripening-related parameters; in particular, while ethylene production is impaired in ABA-treated fruit soluble solids concentration (SSC) is enhanced. Following field ABA applications stem water potential was modified since ABA-treated peach trees retain more water. (iii) Pre- and post-harvest ABA and PDJ treatments were carried out in both kiwifruit species under field conditions at different fruit developmental stages and in post-harvest. Ripening index, fruit quality, plant transpiration, photosynthesis and stomatal conductance were assessed. Pre-harvest treatments enhance SSC in the two cvs and flesh color development in golden kiwifruit. Post-harvest applications of either ABA or ABA plus PDJ lead to increased SSC. In addition, ABA reduces gas exchanges in A. deliciosa. (iv) Spray, drench and dipping ABA treatments were performed in micropropagated peach plants and in peach and nectarine detached branches; plant water use and transpiration, biomass production and fruit dehydration were determined. In both plants and branches ABA significantly reduces water use and fruit dehydration. No negative effects on biomass production were detected. The present information, mainly arising from plant growth regulator application in a field environment, where plants have to cope with multiple biotic and abiotic stresses, may implement the perspectives for the use of these substances in the control of fruit ripening.

Detection and molecular characterization of viruses infecting Actinidia spp.

Kiwifruit (genus Actinidia) is an important horticultural crop grown in the temperate regions. The four world’s largest producers are China, Italy, New Zealand and Chile. More than 50 species are recognized in the genus but the principal species in cultivation are A. deliciosa and A. chinensis. In Italy, as well as in many other countries, the kiwifruit crop has been considered to be relatively disease free and then no certification system for this species has been developed to regulate importation of propagation plant material in the European Union. During the last years a number of fungal and bacterial diseases have been recorded such as Botrytis cinerea and Pseudomonas syringae pv. actinidiae. Since 2003, several viruses and virus-like diseases have been identified and more recent studies demonstrated that Actinidia spp can be infected by a wide range of viral agents. In collaboration with the University of Auckland we have been detected thirteen different viral species on kiwifruit plants. During the three years of my PhD I worked on the characterization of Cucumber mosaic virus (CMV) and Pelargonium zonate spot virus (PZSV). The determination of causal agents has been based on host range, symptom expression in the test plant species and morphological properties of the virus particles using transmission electron microscopy (TEM) and using specific oligonucleotide primers in reverse transcription-polymerase chain reaction (RT-PCR). Both viruses induced several symptoms on kiwifruit plants. Moreover with new technologies such as high-throughput sequencing we detected additional viruses, a new member of the family Closteroviridae and a new member of the family Totiviridae. Taking together all results of my studies it is clear that, in order to minimize the risk of serious viral disease in kiwifruit, it is vital to use virus-free propagation material in order to prevent the spread of these viruses.

A 170 year spring phenology index of plants in eastern China

Extending phenological records into the past is essential for the understanding of past ecological change and evaluating the effects of climate change on ecosystems. A growing body of historical phenological information is now available for Europe, North America, and Asia. In East Asia, long-term phenological series are still relatively scarce. This study extracted plant phenological observations from old diaries in the period 1834–1962. A spring phenology index (SPI) for the modern period (1963–2009) was defined as the mean flowering time of three shrubs (first flowering of Amygdalus davidiana and Cercis chinensis, 50% of full flowering of Paeonia suffruticosa) according to the data availability. Applying calibrated transfer functions from the modern period to the historical data, we reconstructed a continuous SPI time series across eastern China from 1834 to 2009. In the recent 30 years, the SPI is 2.1–6.3 days earlier than during any other consecutive 30 year period before 1970. A moving linear trend analysis shows that the advancing trend of SPI over the past three decades reaches upward of 4.1 d/decade, which exceeds all previously observed trends in the past 30 year period. In addition, the SPI series correlates significantly with spring (February to April) temperatures in the study area, with an increase in spring temperature of 1°C inducing an earlier SPI by 3.1 days. These shifts of SPI provide important information regarding regional vegetation-climate relationships, and they are helpful to assess long term of climate change impacts on biophysical systems and biodiversity.

Determinación de la época más adecuada para la propagación ágamica de gramíneas ornamentales : : Mendoza (Argentina)

La división de matas es una técnica de propagación difundida con gran éxito entre las Gramíneas. Cuando se trata de la producción comercial de este grupo de plantas, es importante conocer la época en que se realiza esta práctica para obtener plantas de la mejor calidad en el menor tiempo posible. Según algunos autores, la estación apropiada para dividir gramíneas está relacionada con el momento de activo crecimiento: primavera tardía para las especies estivales y otoño o primavera temprana para las invernales. En este trabajo se estudió la influencia de la época del año en la división de matas de Miscanthus sinensis "Variegatus", Miscanthus sinensis "Zebrinus", Miscanthus sinensis "Morning Light", Paspalum haumanii, Leymus arenarius, Pennisetum setaceum y Trichloris crinita en diciembre y febrero. Se evaluaron las características ornamentales y la precocidad, con fines comerciales, de las plantas obtenidas en otoño y primavera tardía. Las variables utilizadas fueron altura vegetativa, diámetro de canopia y de corona, número de cañas y porcentaje de sobrevivencia. Desde el punto de vista comercial y productivo, es conveniente realizar la división de matas en otoño para obtener precocidad sólo en M. sinensis "Variegatus" y M. sinensis "Zebrinus". En el caso de M. sinensis "Morning Light", P. setaceum, T. crinita, P. haumanii y Leymus es más adecuada la división de primavera.

Molluscan biostratigraphy of the Miocene and Chatt in the southern Herzogtum Lauenburg (Schleswig-Holstein)

A study was made of the marine molluscan fauna from 12 borings in the Schwarzenbek area. In the fossil rich facies underlying the 'Braunkohlensande', the Neochatt and Vierland faunal sequences could be described and used to define the Oligocene/Miocene boundary. The Neochatt, defined by Pectinidae, seems to be more closely related to the Miocene than previously thought. Nevertheless, a sufficient number of additional molluscan species are present for placing the Neochatt/Vierland boundary. Overlying the Braunkohlensande, the sandy Reinbek fauna as well as Glimmerton faunas of the Reinbek and Langenfelde stages could be described.

Fossil record of Mollusca from Neogene sediments in Schleswig-Holstein, Germany

Über die Verbreitung, Gliederung und Ausbildung des Jungtertiärs im westlichen Schleswig-Holstein war bisher nicht viel bekannt. Am besten bearbeitet sind die glazial gestauchten Schollen von Morsum/Sylt. Eine Aufzählung erbohrter Miozänvorkommen mit nicht immer überzeugender Begründung lieferte H.-L. HECK 1935. S. THIELE (1941) hat die ihm bekannten Vorkommen hauptsächlich nach faziellen und petrographischen Gesichtspunkten bearbeitet. Er erkannte richtig die Stellung der Braunkohlensande. Die angekündigte palaeontologische Bearbeitung ist nicht erschienen. Eine allgemeine Übersicht über die Entwicklung des Jungtertiärs bringen W. WOLFE und H.-L. HECK 1949. W. HINSCH lieferte wertvolle Beiträge zur Molluskenfauna und zur Gliederung des Miozäns (1952, 1955). Über neue Vorkommen von Braunkohlen-Sanden berichtete E. DITTMER(1 956), eine erste Übersicht über neue Vorkommen der Hemmoorer Stufe gab derselbe Verfasser 1957.

Miocene molluscan biostratigraphy in Schleswig-Holstein, north Germany

Vierlandian, Behrendorfian (Lower Hemmoorian), Oxlundian (Upper Hemmoorian), Lower and Upper Reinbekian, Langenfeldian and Gramian stages could be proved by evaluation of marine molluscan faunas. The diachrone base of 'Braunkohlensande' is demonstrated by underlying Vierlandian mica clay in the E, and by Hemmoorian substages more to the W, at last the fluviatile facies is replaced completely by euhaline to brachyhaline sandy to silty sediments. Brachyhaline effects in adjacent environments make possible an approximate dating on fluviatile sedimentation. The widest extension of 'Braunkohlensand' is during upper Oxlundian, whilst slightly brachyhaline Katzheide beds, defined in this paper to be of Lower Reinbekian age, indicate a limit of 'Braunkohlensande' more to the E. Winnert-fauna was found to be a mixture of Oxlundian and Langenfeldian; the overlying lignitic sands belong to the Kaolinsand group. Upper mica clay overlying Miocene Braunkohlensande can be divided into beds of Upper Reinbekian, Langenfeldian and Gramian ages.