Basic of Phytopathology 2

BASIC OF PHYTOPATHOLOGY 2. LECTURE CAUSES AND AGENTS OF PLANT DISEASES AND DISORDERS

I. Abionosis -Non-infectious causes or physiological disorders

• Extreme temperatures • Extreme soil wetness • Excess or lack of light • Oxygen deficiency • Air pollution, exposure to emissions • Nutrient deficiency (macroelements (K,Ca), microelements (B)) • Inappropriate pH • Inappropriate agrotechnic management • The toxicity of pesticides • Toxicity of minerals

CAUSES AND AGENTS OF PLANT DISEASES AND DISORDERS

II. Infections (biotic) disease (and damage)

• Viruses and viroids • Prokaryots (Bacteria and Phytoplasmas) • Fungi • Parasitic higher plants and green algae • Protozoa • Nematodes, mites, insects EXAMPLES OF ABIOTIC DISORDERS EXAMPLES OF ABIOTIC DISORDERS Frost damage of cherries (Prunus) Drought in Spruce (Picea) Ozone damage on Nicotiana tabacum

INFECTIOUS AGENTS OF DISEASES

. Bionosis – infectious diseases . A. NON-CELLULAR ORGANISMS A.1. Viroids A.2. Viruses . B. PROKARYOTIC ORGANISMS B.1. Bacteria B.2. Phytoplasmas . C. EUKARYOTIC ORGANISMS C.1. Fungi C.2. Algae C.3. Higher plants C.4. Protozoa C.5. Nematodes, mites, insects

MORPHOLOGY AND WAYS OF MULTIPLICATION OF SOME OF THE GROUPS OF PLANT PATHOGENS SCHEMATIC DIAGRAM OF THE VARIOUS PLANT PATHOGENS IN HOST CELL A.NON CELLULAR ORGANISMS A.1. Viroids . Uncoated, small, circular, single-stranded RNA, which replicated autonomously when inoculated into a host plant.

. They differ from viruses or bacteriophages by absence of a protein capsid and a small genom.

. The smallest known agents of infectious plant diseases. Discovered to r. 1971, until most of the diseases caused by viroids were considered to be viral diseases.

. It is not known how viroids actually replicate probably all components necessary for their replication provides host.

. Pathogenesis modifies metabolic regulatory networks, the transcription of a number of genes, transcription factors and their ability to activate promoters

A.NON CELLULAR ORGANISMS A.1. Viroids . Most of viroids is localized in the nucleus of the host cell, usually they are transmitted by sap (míza) also by pollen or vegetatively.

. They are resistant to high temperatures.

. Most of viroids causes in the infected plants no symptoms. General symptom of infected plants are dwarf growth, epinastic deformation and creased leaves.

. To date, it was found that around 40 different plant diseases are caused by viroids. Viroids act only disease in plants. They were not found in animals and humans. Taxonomy of viroids Avsunviroid (ASBVd)-replication occurs in chloroplasts Pospiviroid (PSTVd)- replication occurs in nucleus Unassigned viroides SYMPTOMS CAUSED BY VIROIDS

Potato spindle tuber disease

Chrysanthemum stunt disease Examples of diseases caused by viroids POTATO SPINDLE TUBER - Potato spindle tuber viroid (PSTVd)– It causes big losses, attacks all varieties and is spreading rapidly

CITRUS EXOCORTIS CACANG- (Citrus CADANG of exocortis COCONUT PALM viroid) (Coconut cadang- cadang CCCVd) – On Phillipines devastates coconut palms

CHRYSANTHEMUM STUNT (Chrysanthemum stunt viroid – CSVd) A. NON CELLULAR ORGANISMS B. A. 2. Viruses . Obligate parasites reproducing only in host cells (replication is dependent on the host cell). They usually have a very narrow host range.

. They attack all species of living organisms, distinguish plant viruses, animal viruses and bacteriophages (viruses on bacteria). Recently it is described about 2000 species of viruses, half of them infecting the plant.

. Diseases caused secondly disturbance of metabolism in the cells and the use of energy in cells.

STRUCTURE OF VIRAL PARTICLES

• Virion - virus particles, which is composed of protein and one type of nucleic acid (ss RNA, ds RNA, ss DNA, ds DNA)

• Protein component - capsid not only protects the nucleic acid, but generally increases the infectivity of the virus ELECTRON MICROPHOTOGRAPHS OF DIFFERENT MORPHOLOGICAL TYPES OF VIRUSES A. NON CELLULAR ORGANISMS B. A. 2. Viruses . TRANSFER - viruses get into cells mostly through injuries or transmission of sucking insects, nematodes, by fungal vectors (Polymyxa, Spongospora, Olpidium), seeds, pollen, vegetative propagation. In the plant virus spreads by plasmadesm and then by the vascular bundles.

. SATELIT VIRUSES They represent the highest level of parasitism. These are virus particles, which can not occur separately, but only with a different virus particles - in the tobacco mosaic virus (Tobacco necrosis satelite virus). Their replication is dependent on the synthesis of viral RNA.

. PROTECTION AGAINST VIRUSES - quarantine: control of vectors - insects, using clear seeds, virus inactivation by heat. It is not yet known chemical control. PLANT VIRUS TRANSMISSION PLANT VIRUS TRANSMISSION II. INSECT VECTORS OF PLANT VIRUSES TRANSMISSION OF PLANT VIRUSES BY NEMATODES, MITES AND FUNGI SYMPTOMS OF VIRUSES ON PLANTS LEAVES – chlorotic or VIRAL PLANT – growth retardation, necrotic lesions, mosaic, vein dwarfism, shortened internodes, wilting yellowing, stripes, deformaiton

FLOWERS - the colorfulness of the flowers, streaking Histological symptoms – hyperplasy, hypoplasy, necrosis

Cytological changes – formation of incluses SYMPTOMS OF VIRUSES ON PLANTS SYMPTOMS OF VIRUSES ON PLANTS

CURRENT PLANT VIRUSES TAXONOMY

I: Single-stranded (+)sense DNA (+ ssDNA) single stranded DNA

II: Double-stranded DNA with RNA intermediate (ds DNA (RT) (double stranded DNA, replicates using reverse transcriptase)

III: Single-stranded (+)sense RNA (+ ssRNA) single stranded RNA (replicate using polymerase; RNA with function m-RNA)

IV: Single-stranded (-)sense RNA (-ssRNA) single RNA complementary to m-RNA

V: Single-stranded (+)sense RNA with DNA intermediate in life-cycle (ssRNA (RT)) single stranded RNA (replicates using reverse transcriptase)

VI: Double-stranded RNA (dsRNA) double stranded RNA

REPRESENTATIVE EXAMPLES OF INDIVIDUAL GROUPS OF VIRUSES

I. ssDNA – single stranded DNA - Geminiviridae – Maize streak virus (MSV) On maize (Zea mays)

II. (ds DNA (RT) double stranded DNA, replicates using reverse transcriptase Cauliflower mosaic virus (CaMV) – on cauliflower (Brassica oleracea var. botrytis) III. (+) sense ssRNA viruses (single stranded RNA (replicate using polymerase; RNA with function m-RNA) Bromoviridae, Caliciviridae, Comoviridae, Coronaviridae (Pea enation mosaic virus), Potyviridae (Potato virus Y), Flaviviridae, Leviviridae (Tobacco necrosis virus, Barley yellow dwarf virus), Sequiviridae, Tetraviridae (Tobacco mosaic virus), Tombusviridae

Tobacco mosaic virus (TMV) Pea enation on tobacco (Nicotiana tabacum) mosaic virus Barley yellow dwarf (PEMV) – on pea luteovirus (BYDV) (Pisum sativum) on barley (Hordeum vulgare) IV. (-) sense ssRNA viruses – single RNA complementary to m-RNA Rhabdoviridae (Lettuce necrotic yellows virus), Bunyaviridae, Orthomyxoviridae.

Lettuce necrotic yellows virus (LNYV) - on lettuce (Lactuca sativa)

V. ssRNA (RT) single stranded RNA (replicates using reverse transcriptase) Pseudoviridae

VI. ds-RNA – double stranded RNA - Reoviridae Rice ragged stunt virus (RRSV) on rice (Oryza sativa) B. PROKARYOTIC ORGANISMS

ONLY REPRESENTATIVES OF GROUP BACTERIA CAUSE PLANT DISEASES B. TAXONOMY of BACTERIA

BACTERIA AS PLANT PATHOGENS

GRACILICUTES (GRAM-NEGATIVE BACTERIA) CLASS: PROTEOBACTERIA (families Enterobacteriaceae (Erwinia), Pseudomonadaceae (Pseudomonas, Xanthomonas), Rhizobiaceae (Agrobacterium)

FIRMICUTES (GRAM-POSITIVE BACTERIA) CLASS ACTINOBACTERIA Streptomyces, Clavibacter CLASS FIRMICUTES (Bacillus, Clostridium)

MOLLICUTES (Spiroplasma, Phytoplasma)

BACTERIAL TAXONOMY

• Bacterial /Archaeal species are defined on the basis of phenotypic and genotypic differences.

• A bacterial strain is a population of organisms that descends from a single organisms or pure culture

• A bacterial species is a collection of strains that share main stable characteristics and differ significantly from other groups of strains

BIOVARS – differ biochemically or physiologically MORPHOVARS – differ morphologically SEROVARS – differ in antigenic properties

B.1. BACTERIA . Prokaryotic organisms, their DNA is not coated by nuclear membrane. Do not contain membrane organelles (mitochondria, nucleus, plastids ..) . They have cell walls (one exception representatives of - Mollicutes). . They have tremendous ability of propagation (usually division, and budding) . They occur mainly in warm and moist areas . Expansion of bacteria - water, insects, animals, humans

. MORPHOLOGY OF BACTERIA - bacteria can be rod-shaped, oval, spiral, fibrous, with flagella or without flagella, they can produce spores or not. Protein capsid. Nucleoid - a circle of DNA; plasmids. .DETERMINATION OF BACTERIA : shape, number and location of flagella, Gram stain, infestation symptoms (wilting, spotting), cultivation - shape, coloration of colonies, biochemical tests, serology, molecular identification methods – RFLP, PCR. MORPHOLOGY OF BACTERIA

Rod-shaped (A), oval (B,C,D), spiral (E), fibrous (G) G Monotricha

Number of flagella: monotrichous (1), polytrichous (more than 1) The arrangement of flagella: monopolar, bipolar, lofotrich, peritrich, amfitrichal, atricha Polytricha

Monopolar Peritrich Lofotrich Amfitrich (bipolar lofotricha) MEANS OF DISSEMINATION OF BACTERIA (AND FUNGI) SYMPTOMS OF BACTERIA Discoloration INFECTION ON PLANTS

Anthracnosis, necrosis

Clavibacter michiganense

wallnut Xanthomonas campestris Bacterial wilting - break down the walls of the xylem

Pseudomonas syringae pv. lachrymans

Erwinia tracheiphilla SYMPTOMS OF BACTERIA INFECTION ON PLANTS II. Bacterial soft rot Bacterial canker

Erwinia carotovora subsp. Carotovora /Pectobacterium/

Formation of tumors

Pseudomonas syringae pv. syringae

Agrobacterium tumefaciens SYMPTOMS OF BACTERIA INFECTION ON PLANTS III.

Bacterial common scab Soil bacteria on the roots of legume plants Capable of fixing of atmospheric nitrogen

Streptomyces scabies

Rhizobium sp. SIMPLE SCHEME FOR THE DIFFERENTIATION OF GROUPS OF PHYTOPATHOGENIC BACTERIA THE MOST IMPROTANT GENERA OF BACTERIAL PLANT PATHOGENS GRAM NEGATIVE (PROTEOBACTERIA) Agrobacterium – is closely related to the genus Rhizobium, it causes tumors by genetically modifying host cells to tumor cells Erwinia/Pectobacterium – mobile, pectolytic enzymes, infects only plants Pseudomonas – causing spotting and cancer, have a wide host range and also live on the surface of epiphytic plants Ralstonia – previously referred to the genus Pseudomonas – but it differs in that it does not produce fluorescent enzymes Xanthomonas – have a high host specificity and cause wilting and leaf blotch Xylella - aerobic, unicellular and producing long chains under certain conditions, requires special media, because normally inhabits the xylem. GRAM POSITIVE (FIRMICUTES) Clavibacter (Corynebacterium) - mostly immobile Streptomyces - form mycelium (chains cells), produce antimicrobial substances against fungi, bacteria, algae, viruses, protozoa and tumor tissues GRAM NEGATIVE BACTERIA (PROTEOBACTERIA)

Agrobacterium

Erwinia /Pectobacterium/ carotovora Erwinia amylovora GRAM NEGATIVE BACTERIA (PROTEOBACTERIA) Pseudomonas

Pseudomonas syringae var. syringae

Ralstonia solanacearum GRAM NEGATIVE BACTERIA (PROTEOBACTERIA)

Xanthomonas

Xanthomonas campestris pv. campestris Xylella fastidiosa GRAM – POSITIVE BACTERIA (FIRMICUTES)

Clavibacter michiganensis

Streptomyces scabies THE MOST IMPORTANT GENERA OF PLANT PATHOGENIC BACTERIA B. PROKARYOTIC ORGANISMS B.2. MOLLICUTES

. MOLLICUTES – . They are referred to the group Bacteria . Prokaryotic organisms without a cell wall, only having plasma membrane . About 200 disease is caused by these organisms . There are two types: Spiroplasms - has a distinctive helical morphology Phytoplasms - oblong, or round, but not spiral . Phytoplasms not to be grown on artificial media . In contrast, some Spiroplasma may be grown on artificial media and transferred to healthy plants .Previously, these organisms considered to be identical with mykoplasms (also Mollicutes class, rather that attack animals and humans), however, genetic studies show that they are distant. . PHYTOPLASMS – previously: Mycoplasma-like organisms - spherical or oblong, it is not yet possible to cultivate the media . Present in the vascular tissue, they are transmitted by insects, sensitive to antibiotics -tetracyklins, and at a temperature higher than 37 ° C. EXAMPLES OF DISEASES CAUSED BY PHYTOPLASMAS

Aster yellows

European stone fruit Apple proliferation yellows on apple (Malus domestica)

Grapevine yellows on Peach X disease Pear decline on on pear grapevine (Vitis vinifera) On peach (Prunus persica) (Pyrus communis) . SPIROPLASMAS - has a distinctive helical morphology . Transfer by insects . They may be isolated in pure form from insect vectors and cultured on artificial medium EXAMPLES OF DISEASES CAUSED BY SPIROPLASMAS

Corn stunt disease Caused by: Spiroplasma kunkelli Citrus stubborn disease Caused by: Spiroplasma citri SYMPTOMS CAUSED BY MOLLICUTES EUKARYOTS

Parasitic plants and Algae

Oomycota

Rhizaria Plasmodiophorida Fungi

Insects, mites, nematodes SAR • SAR or Harosa (informally the SAR supergroup) is a clade that includes STRAMENOPILES (heterokonts), ALVEOLATES, and RHIZARIA

• The first letter of each group provides the "SAR" in the name

• Members of the SAR supergroup were once included under the separate supergroups CHROMALVEOLATA and RHIZARIA, until phylogenetic studies confirmed that stramenopiles and alveolates diverged together with Rhizaria. RHIZARIA, group PHYTOMYXEA • They typically develop within plant PLASMODIOPHOROMYCOTA cells, causing the infected tissue to grow into a gall or scab.

• Important diseases caused by phytomyxeans include CLUB ROOT in cabbage and its relatives, and POWDERY SCAB in potatoes. These are caused by species of Plasmodiophora and Spongospora, respectively. Plasmodiophora brassicae, cause CLUB ROT

Spongospora subterranea Beet necrotic yellow vein virus – transfer by fungus Polymyxa betae Cause POWDERY SCAB LIFE CYCLE - PLASMODIOPHORA BRASSICAE STRAMENOPILA • The heterokonts or stramenopiles (formally, Heterokonta or Stramenopiles) are a major line of eukaryotes currently containing more than 25,000 known species.

• Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which are a primary component of plankton.

• Other notable members of the Stramenopiles include the (generally) parasitic oomycetes, including Phytophthora of Irish potato famine infamy and Pythium which causes seed rot and damping off.

• Unicellular or filamentous organisms, cell wall composed mostly of cellulose

• Flagella (if present) having at least one flagellum with rigid mastigonemata. DIVISION : OOMYCOTA • They are filamentous, microscopic, absorptive organisms that reproduce both sexually (oogonium and antheridium – oospore) and asexually (zoospores in sporangium).

• Oomycetes occupy both saprophytic and pathogenic lifestyles SYMPTOMS OF OOMYCOTA INFECTION

OOMYCOTA

Phytophthora infestans Pythium debaryanum Bremia lactucae

Pseudoperonospora cubensis

Plasmopara viticola LIFE CYCLE - PLASMOPARA VITICOLA