Arbuscular mycorrhizal fungi (AMF) as bioprotector agents against wilt induced by Verticillium spp. in pepper.

Verticillium dahliae Kleb. is a vascular pathogen that alters water status and growth of pepper plants and causes drastic reductions in yield. Its control is difficult because it can survive in field soil for several years. The application of arbuscular mycorrhizal fungi (AMF) as bioprotector agents against V. dahliae is an alternative to the use of chemicals which, in addition, is more respectful with the environment. The establishment of the mutualistic association of plant roots and AMF involves a continuous cellular and molecular dialogue between both symbionts that includes the preactivation of plant defense responses that may enhance the resistance or tolerance of mycorrhizal plants to soil-borne pathogens. Some AMF can improve the resistance of Capsicum annuum L. against V. dahliae. This is especially relevant for pepper cultivars (i.e. cv. Piquillo) that exhibit high susceptibility to this pathogen. Compared with non-mycorrhizal plants, mycorrhizal pepper can exhibit more balanced antioxidant metabolism in leaves along the first month after pathogen inoculation, which may contribute to delay both the development of disease symptoms and the decrease of photosynthesis in Verticillium-inoculated plants with the subsequent benefit for yield. In stems, mycorrhizal pepper show earlier and higher deposition of lignin in xylem vessels than nonmycorrhizal plants, even in absence of the pathogen. Moreover, AMF can induce new isoforms of acidic chitinases and superoxide dismutase in roots. Mycorrhizal-specific induction of these enzymatic activities together with enhanced peroxidase and phenylalanine ammonia-lyase in roots may also be involved in the bioprotection of Verticillium-induced wilt in pepper by AM

Growth, yield and physiology of Verticillium-inoculated pepper plants treated with ATAD and composted sewage sludge

A greenhouse experiment was conducted to investigate the impact of sanitized sewage sludges, ATAD (aerobic thermophilic autothermic digestion) and composted, on Verticillium-induced wilt in pepper plants (Capsicum annuum L. cv. Piquillo). Two doses of ATAD (15 and 30% v/v) and three of composted sludge (15, 30 and 45% v/v) were applied to a peat-based potting mix. Unamended substrate was included as control. Half of the plants were inoculated with V. dahliae, whereas the other half remained non-inoculated. Result showed that ATAD and composted sludge increased growth and yield of non-inoculated plants. V. dahliae reduced net photosynthesis (P n), mainly as a consequence of stomatal closure, 5 weeks after pathogen inoculation. The actual photosystem II efficiency was also reduced and consequently the electron transport rate (ETR). No photoinhibitory damage was observed at this time in diseased plants. At the end of the experiment, diseased plants showed lower plant biomass and fruit yield. ATAD sludge had little effect on the disease. Compost slightly alleviated Verticillium-induced wilt when applied at lower doses (15% v/v), which resulted in increased P n and ETR, and higher plant biomass and fruit yield. By contrast, higher doses of compost (45% v/v) enhanced the effect of the pathogen, which was related to the high substrate salinity in this treatment

Response of mycorrhizal grapevine to Armillaria mellea inoculation: disease development and polyamines.

A study was conducted with the vine rootstock Richter 110 (Vitis berlandieri Planch. x Vitis rupestris L.) in order to assess whether the colonisation by the arbuscular mycorrhizal fungus (AMF) Glomus intraradices (BEG 72) can delay the disease development in plants inoculated with the root-rot fungus Armillaria mellea (Vahl:Fr) Kummer, and to elucidate if the levels of polyamines (PAs) are modified in response to G. intraradices, A. mellea or by the dual infection. Four treatments were considered: control and G. intraradices-inoculated plants infected or not with A. mellea. Plant growth, mycorrhizal colonisation and disease development were monitored throughout the experiment. High performance liquid chromatography (HPLC) in combination with fluorescence spectrophotometry was used to separate and quantify free root and leaf polyamines. The slower development of pathogenic symptoms and the higher plant biomass of mycorrhizal plants inoculated with A. mellea indicate an increase of tolerance due to the AMF inoculation. The variations in free PA levels detected at the beginning of the pathogenic infection suggest that PAs may have a potential role in the signalling mechanisms of the tolerance of mycorrhizal plants against A. mellea

Characterization of the adaptive response of grapevine (cv. Tempranillo) to UV-B radiation under water deficit conditions

This work aims to characterize the physiological response of grapevine (Vitis vinifera L.) cv. Tempranillo to UV-B radiation under water deficit conditions. Grapevine fruit-bearing cuttings were exposed to three levels of supplemental biologically effective UV-B radiation (0, 5.98 and 9.66 kJ m−2 day−1) and two water regimes (well watered and water deficit), in a factorial design, from fruit-set to maturity under glasshouse-controlled conditions. UV-B induced a transient decrease in net photosynthesis (Anet), actual and maximum potential efficiency of photosystem II, particularly on well watered plants. Methanol extractable UV-B absorbing compounds (MEUVAC) concentration and superoxide dismutase activity increased with UV-B. Water deficit effected decrease in Anet and stomatal conductance, and did not change non-photochemical quenching and the de-epoxidation state of xanthophylls, dark respiration and photorespiration being alternative ways to dissipate the excess of energy. Little interactive effects between UV-B and drought were detected on photosynthesis performance, where the impact of UV-B was overshadowed by the effects of water deficit. Grape berry ripening was strongly delayed when UV-B and water deficit were applied in combination. In summary, deficit irrigation did not modify the adaptive response of grapevine to UV-B, through the accumulation of MEUVAC. However, combined treatments caused additive effects on berry ripening

Carbon balance, partitioning and photosynthetic acclimation in fruit-bearing grapevine (Vitis vinifera L. cv. Tempranillo) grown under simulated climate change (elevated CO2, elevated temperature and moderate drought) scenarios in temperature gradient

Although plant performance under elevated CO2 has been extensively studied in the past little is known about photosynthetic performance changing simultaneously CO2, water availability and temperature conditions. Moreover, despite of its relevancy in crop responsiveness to elevated CO2 conditions, plant level C balance is a topic that, comparatively, has received little attention. In order to test responsiveness of grapevine photosynthetic apparatus to predicted climate change conditions, grapevine (Vitis vinifera L. cv. Tempranillo) fruit-bearing cuttings were exposed to different CO2 (elevated, 700 ppm vs. ambient, ca. 400 ppm), temperature (ambient vs. elevated, ambient +4 °C) and irrigation levels (partial vs. full irrigation). Carbon balance was followed monitoring net photosynthesis (AN, C gain), respiration (RD) and photorespiration (RL) (C losses). Modification of environment 13C isotopic composition (δ13C) under elevated CO2 (from −10.30 to −24.93‰) enabled the further characterization of C partitioning into roots, cuttings, shoots, petioles, leaves, rachides and berries. Irrespective of irrigation level and temperature, exposure to elevated CO2 induced photosynthetic acclimation of plants. C/N imbalance reflected the inability of plants grown at 700 ppm CO2 to develop strong C sinks. Partitioning of labeled C to storage organs (main stem and roots) did not avoid accumulation of labeled photoassimilates in leaves, affecting negatively Rubisco carboxylation activity. The study also revealed that, after 20 days of treatment, no oxidative damage to chlorophylls or carotenoids was observed, suggesting a protective role of CO2 either at current or elevated temperatures against the adverse effect of water stress

Evolución de la marchitez vascular inducida por Verticillium dahliae en plantas micorrizadas de pimiento

Comunicación presentada en el VI Simposium Hispano-Luso de Relaciones Hídricas en Plantas, Pamplona, 200

Etude de l'effet des stress oxydants et des régulateurs de croissance sur la production d'alcaloides indoliques dans des suspensions cellulaires de pervenche tropicale (catharanthus roseus [L] G. Don)

We investigated the mechanisms involved in the regulation of monoterpene indole alkaloid (MIA) production by plant growth regulators in suspension cells (line C20D) of the Madagascar periwinkle (Catharanthus roseus). In these cells, MIA production was induced by the suppression of 2,4-D from the culture medium and enhanced by cytokinin treatment. The importance of the cell redox state was pointed out by studying: (i) the major enzymatic activities of the defence antioxidant systems in cells grown under various hormonal conditions; (ii) the effects of oxidants and antioxidants on MIA production. A search for putative molecular markers of MIA production led to the characterisation of two cDNAs encoding geranyl diphosphate synthase and a CrPS protein belonging to [a]b hydroxylase superfamily, respectively. Studying the expression pattern (Northern blots) of CrPS gene in suspension cells, and the localisation of CrPS mRNA (in situ hybridisation) in developing leaves highly suggested a role of CrPS in the signal transduction pathway leading to MIA production.Nous avons étudié les mécanismes impliqués dans la régulation de la production des alcaloides indoliques monoterpéniques (MIA) par des substances de croissance dans des suspensions cellulaires (lignée C20D) de Pervenche de Madagascar (Catharanthus roseus). Dans ces cellules, la production de MIA est augmentée par la suppression du 2,4-D du milieu et stimulée par un traitement avec une cytokinine. L'importance de l'état rédox a été soulignée par l'étude : (i) des activités enzymatiques principales des systèmes de défense antioxydants dans des cellules sous diverses conditions hormonales; (ii) des effets des oxydants et antioxydants sur la production de MIA. Une recherche de possibles marqueurs moléculaires de la production des MIA a conduit à caractériser deux ADNc codant respectivement une géranyl diphosphate synthase et une protéine CrPS appartenant à la super-famille des [a]b hydroxylases. Des études portant sur le patron d'expression (par Northern blot) du gène CrPS dans des cellules in vitro et sur la localisation des ARNm CrPS (par hybridation in situ) dans des feuilles en développement suggèrent une implication de la protéine CrPS dans la signalisation conduisant à l'induction de la production de MIA.TOURS-BU Sciences Pharmacie (372612104) / SudocSudocFranceF

Defence-related enzymes in pepper roots during interactions with arbuscular mycorrhizal fungi and/or Verticillium dahliae

Comunicación presentada en el 5th International Conference on Mycorrhiza, 23-27, July 2006, Granad

Efectividad de tres especies de Glomus como agentes de biocontrol de la "seca" del pimiento inducida por Verticillium

Resumen de la comunicación presentada en el XII Congreso de la Sociedad Española de Fitopatología, 26 de septiembre al 1 de octubre de 2004, Lloret de Mar (Girona)Fundación Universitaria de Navarra y Gobierno Vasco (AE-2000