Cytological Observations of the Infection Process by Phomopsis helianthi (Munt.‐Cvet) in Leaves of Sunflower

Abstract

The infection process of Phomopsis helianthi and the specific degradation of infected tissue were studied in detail using light and transmission electron microscopy. In comparison with other vascular pathogens, the infection and degradation process was in some aspects different. The favourite tissue for the pathogen to grow in was the phloem. Parenchymatic cells in and around vascular bundles were extremely sensitive to infection long before hyphae arrived, probably due to a toxin. In the parenchymatic cells the first changes were visible at the chloroplasts where electron‐dense material accumulated in the thylakoid space. The chloroplast stroma changed contrast and later the whole cytoplasm also appeared electron dense. In the vascular bundles, first the phloem was destroyed and then hyphae invaded the adjacent mesophyll, the cambium, and finally the vessel elements. In particular, the compact mesophyll of the midvein was severely affected. Vessel elements were lined with electron‐dense material and some were filled with flocculent material. Severe wall destruction indicated the action of a complete set of cell wall‐degrading enzymes before hyphae entered the tissue; it always started at the innermost wall layer. Wall degradation in vascular tissue and adjacent parenchyma with intercellular spaces was different. Before the degradation of the protoplasts started, the cell walls were completely metabolized and only the secondary walls of the vessels resisted for longer. There were no host–cell reactions visible that could be interpreted as a defence reaction.

Interactions of arbuscular mycorrhizal and endophytic fungi improve seedling survival and growth in post-mining waste

“…Diaporthe spp. have been reported to cause a wide range of plant diseases (Scheper et al 2000; Heller and Gierth 2001). Xylaria species occur on a broad diversity of plant hosts; however, they are frequently isolated from wood tissues (Frohlich et al 2000; Wang et al 2014).…”

Minor loading vein acclimation for three Arabidopsis thaliana ecotypes in response to growth under different temperature and light regimes

“…Insect vectors that tap into loading veins can furthermore introduce various pathogens that utilize the phloem to travel to other portions of the leaf and throughout the plant (Ding et al, 1995, 1998; Gilbertson and Lucas, 1996; Lucas and Wolf, 1999; Cheng et al, 2000; Heller and Gierth, 2001; Zhou et al, 2002; Taliansky et al, 2003; Waigman et al, 2004; Scholthof, 2005; Rasheed et al, 2006; Requena et al, 2006; Saha et al, 2006; Gosálvez-Bernal et al, 2008; Peter et al, 2009; Vuorinen et al, 2011). Perhaps not surprisingly, the minor loading veins are responsive to not only pathogenic attack (Rioux and Quellette, 1991; Kpemoua et al, 1996; Narváez-Vásquez and Ryan, 2004; Narváez-Vásquez et al, 2005) but also to various signaling pathways involving reactive oxygen, antioxidants, and plant hormones (Provencher et al, 2001; Hofius et al, 2004; Maeda et al, 2006; Amiard et al, 2007; Scarpella et al, 2010; Wenzel et al, 2012; Baylis et al, 2013; Demmig-Adams et al, 2013; Zhiponova et al, 2013).…”

Caracterización morfológica y molecular de una colección de aislamientos de Phomopsis longicolla (teleomorfo desconocido: Diaporthales) de la región templada y subtropical de Argentina

“…Sin embargo, la definición de endófitos incluye, además, a aquellas especies patógenas que desarrollan una fase o período de latencia prolongada durante su ciclo de vida (Saikkonen, 2007;Sakadilis, Hardy, & Burgess, 2011). En ese contexto, se han descrito numerosos géneros fúngicos necrotróficos o hemi-biótrofos, entre ellos Phomopsis, con una fase endofítica y/o parasitaria asociadas a la planta y una fase saprofítica asociada a los residuos orgánicos (Heller & Gierth, 2001;Debaeke & Moinard, 2010).…”