Oomycetes : The Algal Fungi | Structure & Characteristics
- Hyphal wall contains cellulose and other glucans in many members.
- The mycelium is coenocytic (multinucleate and aseptate).
- Asexual reproduction involves the formation of spore containing sacS or sporangia. In aquatic forms, the sporangia produce zoospores.
- Zoospores generally have two laterally inserted flagella with heterokont condition, in which one flagellum is smooth (whiplash) while the other is of tinsel type (having fine surface outgrowths called mastigonemes).
- Sexual reproduction is by planogametic fusion or gametangial contact.
- The product of sexual reproduction and site of meiosis is oospore.
|(i) Phytophthora infestans causes late blight of potato and occasionally of tomato as well. Great Irish famine of 1845 1847 was due to late blight of potato.
(ii) Albugo candida (Cystopus candidus) causes white rust of crucifers and is characterised by the appearance of irregular white blisters on the leaves and stems.
(iii) Pythium debaryanum causes damping off disease in seedlings of tomato, chilles, castor, mustard.
(iv) Sclerospora graminicola causes downy mildew in cereals particularly, Pennisetum typhoides (vern. Bajra) green ear disease.
(v) Peronospora parasitica causes downy mildew in a number of plants, such as pea, mustard, spinach, onion etc.
(vi) Saprolegnia causes salmon disease of gills in fishes.