DOWMY MILDEW FUNGI part 01.pptx

Downy mildew fungi are plant pathogens that cause significant damage to a variety of crops, including grapes, cucumbers, lettuce, and onions. These fungi thrive in cool, moist environments and can spread rapidly through a field, causing devastating losses for farmers.

This slide deck provides an overview of downy mildew fungi, including their life cycle, symptoms, and management strategies. The presentation begins with an introduction to the various types of downy mildew fungi, including the species that affect grapes, cucumbers, and other crops.

Next, the slides detail the life cycle of downy mildew fungi, from spore germination to the development of lesions on plant leaves. The presentation also explains how these fungi spread from plant to plant and from field to field, and highlights the conditions that favor their growth and reproduction.

The slide deck then goes on to describe the symptoms of downy mildew infection, including yellowing and wilting of leaves, stunted growth, and the development of characteristic downy white or gray spores on the undersides of leaves.

Finally, the presentation offers practical tips and strategies for managing downy mildew fungi, including cultural control measures such as crop rotation and sanitation practices, as well as chemical control methods such as fungicides.

Overall, this slide deck provides a comprehensive overview of downy mildew fungi and their impact on agricultural crops, as well as practical strategies for preventing and managing these devastating plant pathogens.

1. ANNAMALAI UNIVERSITY FACULTY OF AGRICULTURE DEPARTMENT OF PLANT PATHOLOGY PAT-501 MYCOLOGY GENERAL CHARACTERS AND LIFE CYCLE OF GENUS PERONOSPORA , PSEUDOPERONOSPORA, PLASMOPARA , BREMIA , SCLEROSPORA , PERONOSCLEROSPORA BY R.LOKESH I -M.sc.,Agriculture Plant pathology Annamalai university TOPIC: Part-1

2. DOWNY MILDEW …….. FUNGI ……..

3. DOWNY MILDEW FUNGI 1. Downy mildew of Pearlmillet Sclerospora graminicola (Green Ear disease) 2. Downy mildew of Sorghum Peronosclerospora sorghi (Leaf shredding disease) 3. Downy mildew of Maize Sclerophthora rayssiae (Crazy top disease) 4. Downy mildew of Grapevine Plasmopara viticola 5. Downy mildew of Cucurbits Pseudoperonospora cubensis 6. Downy mildew of Tobacco Peronospora tabacina (Blue mould disease) 7. Downy mildew of Onion Peronospora destructor 8. Downy mildew of Lettuce Bremia lactucae

4. KINGDOM: CHROMISTA/STRAMENOPILES Have uni- or multicellular somatic phase with absorptive type of nutrition. Cell wall rich in cellulose and synthesize amino acid by a, ẞ aminopimelic acid lysine biosynthetic pathway. The asexual spore is biflagellate zoospore with posteriorly oriented whiplash and anteriorly oriented tinsel flagella (heterokont). Zoospores have tubular mitochondrial cristae, perioxisomes and Golgi bodies.

5. PHYLUM: OOMYCOTA / PSEUDOFUNGI / EGG FUNGI (Heterokonts) /zoosporic fungi They are unicellular and holocarpic or eucarpic filamentous species. The filamentous species have profusely branched, hyaline and coenocytic hyphae . Cell wall primarily made up of B-glucans but also contain amino acid, hydroxyproline as well as small amounts of cellulose. Form diploid thallus and meiosis occurs in the developing gametangia Le. the assimilative phase is diploid. Zoospores are biflagellate , having one short posterior whiplash and another long anterior tinsel flagellum. Many oomycetes produce one kind of zoospores (monoplanetic) and some produce (Saprolegnia) diplanet zoospores. Sexual reproduction is oogamous by gametangial contact of club shaped antheridium(male) and globular oogonium(female).

6. Order: Peronosporales (Higher form of Peronosporomycetidae) Members are obligate parasites of higher plants with well branched, coenocytic intercellular mycelium, which enter the host cell through knob like (Albugo) or elongated or branched haustorium. Asexual reproduction takes place by means of sporangiospores produced inside sporangia. Sporangiophores are strikingly different from the vegetative hyphae and bear sporangia singly (Peronosporaceae) or in chains (Albuginaceae). Zoosporangia germination mostly depends upon temperature. They mosty germinate by producing zoospores but in some they germinate directly and produce germ tube. Zoospores are kidney shaped monoplanetic and laterally biflagellate with whiplash and tinsel type flagella.

7. Order: Peronosporales (Higher form of Peronosporomycetidae) Members are obligate parasites of higher plants with well branched, coenocytic intercellular mycelium, which enter the host cell through knob like (Albugo) or elongated or branched haustorium. Asexual reproduction takes place by means of sporangiospores produced inside sporangia. Sporangiophores are strikingly different from the vegetative hyphae and bear sporangia singly (Peronosporaceae) or in chains (Albuginaceae). Zoosporangia germination mostly depends upon temperature. They mosty germinate by producing zoospores but in some they germinate directly and produce germ tube. Zoospores are kidney shaped monoplanetic and laterally biflagellate with whiplash and tinsel type flagella.

8. Sexual reproduction is oogamous. Oospore wall is hyaline or brownish and smooth (Peronosporaceae) or ornamented (Albuginaceae). Oospore germinates either by a germ tube (Peronosporaceae) or by theproduction of large number of zoospores (Albuginaceae).

9. Family: Peronosporaceae (Downy mildew fungi ) Members of this family cause "downy mildews" disease in dicots, which etymologically means "hairy fungi" as the sporangiophores look like hairs on the lower surface . Produce sporangia singly or in chains at the tip of branched sporangiophore. Sporangia germinate directly i.e conidial type of germination. The membersof the Peronosporaceae are differentiated chiefly by the branching of their sporangiophores. The sporangia are wind dispersed and germinate in water films on plant surface to release zoospores. The sporangia of the genus Peronospora germinate directly into the germ tube.Fundamentals of Phytopathology. Produce smooth walled oospores. The Peronosporaceae currently includes downy mildews, Halo phytophthora. Phytophthora and Phytopythium

10. DOWNY MILDEW FUNGI It is the most highly specialized family of the order Peronosporales. Members of this family are causing "downy mildews" disease in dicots, which etymologically means "hairy fungi", as the sporangiophores look like hairs on the lower surface. The members of the Peronosporaceae are differentiated chiefly by the branching of their sporangiophores.

11. DOWNY MILDEW GENERA Bremia Peronospora Plasmopara Pseudoperonospora PerenoSclerospora Sclerospora

12. BRANCHING OF SPORANGIOPHORES

13. General Characters of Peronospora Peronospora  was first described in 1837 by August Carl Joseph Corda , a Czech mycologist and physician, in his first of six volumes of his  Icones fungorum hucusque cognitorum . Peronospora  is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamental plants. Peronospora  has far more species than any other genus of the downy mildews. However, many species have been moved from this genus to be reclassified to other or new genera. Among these was the most famous  Peronospora  species, formerly known as  Peronospora parasitica , and now known as  Hyaloperonospora parasitica .  Now, the  Peronospora  species of most importance is likely the   Peronospora tabacina . Peronospora tabacina  causes blue mold on tobacco plants and can severely reduce yields of this economically important crop to the point where it has been classified as a bioweapon .

14. General Characters of Peronospora Peronospora  was first described in 1837 by August Carl Joseph Corda , a Czech mycologist and physician, in his first of six volumes of his  Icones fungorum hucusque cognitorum . Peronospora  is a genus of oomycetes that are obligate plant pathogens of many eudicots. Most species in this group produce a downy mildew disease, which can cause severe damage to many different cultivated crops, as well as wild and ornamental plants. Peronospora  has far more species than any other genus of the downy mildews. However, many species have been moved from this genus to be reclassified to other or new genera. Among these was the most famous  Peronospora  species, formerly known as  Peronospora parasitica , and now known as  Hyaloperonospora parasitica .  Now, the  Peronospora  species of most importance is likely the   Peronospora tabacina . Peronospora tabacina  causes blue mold on tobacco plants and can severely reduce yields of this economically important crop to the point where it has been classified as a bioweapon . BLUE MOLD ON TOBACCO Peronospora parasitica

15. Disease cycle of Peronospora tabacina

16. GENERAL CHARACTERS OF PSEUDOPERONOSPORA Pseudoperonospora cubensis  is a species of  water mould  known for causing  downy mildew  on  cucurbits  such as cantaloupe, cucumber, pumpkin, squash and watermelon. Berkeley and Curtis first reported the disease in Cuba in 1868.  The pathogen causes angular  chlorotic  lesions on the foliage. The disease is sometimes called wildfire because of how rapidly it progresses, as if the crop were burned by fire. Pseudoperonospora cubensis  is an  obligate parasite  or  biotroph , meaning that it requires live host tissue in order to survive and reproduce.

17. Scientific classification Kingdom: Chromista Phylum: Oomycota Order: Peronosporales Family: Peronosporaceae Genus: Pseudoperonospora Species: P. cubensis Binomial name Pseudoperonospora cubensis (Berk. & M.A. Curtis) Rostovzev DOWNY MILDEW  ON  CUCURBITS

18. SYMPTOMS ON Cucumber, squash and pumpkin Symptoms on cucumber and squash are angular lesions that are limited by the leaf veins. During periods of leaf wetness from dew, irrigation or rainfall, incipient lesions can become conspicuously water-soaked (Figure 1). This is the earliest symptom produced by the disease, but will disappear as moisture dissipates. Early lesions are light green in appearance (Figures 2 and 3) and become chlorotic and finally necrotic as host plant cells die (Figure 4). FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4

19. Severe infection results in leaves that are completely dead and curled up. This symptom has been described as “wildfire” as the leaves appear to be burned (Figure 5).

20. REFERENCES https://plantlet.org/oomycetes-order-peronosporales/ https://en.wikipedia.org/wiki/Pseudoperonospora_cubensis https://www.apsnet.org/edcenter/disandpath/oomycete/pdlessons/Pages/Cucurbits.aspx An Introduction to Fungi- H.C.Dube