Albugo Or Cystopus
Albugo or Cystopus
Note: Albuginaceae is a monotypic family. It includes only single genera Albugo.
It is an obligate, inter cellular parasite.
It cannot be grown on culture medium. It causes "White-rust disease in the plants of family cruciferae or brassicaceae. It shows specificity towards the host.
Etiology : - Study of causes of disease in body is called etiology.
Characteristics of White-rust diesase :
(1) The main reason of hypertrophy is the formation of sex organs in the intercellular spaces of host.
(2) In the presence of less temperature and high moisture white rust disease spreads vigorously.
The study of spread of disease is called Epidemiology.
Mycelium is branched, aseptate, coenocytic. (Septa are only formed in mycelium during reproduction).
The hyphal wall is made up of cellulose.
Reserve food material is present in the form of glycogen and oil globules.
Hyphal network is found in the intercellular spaces of the host.
Structure of Hypha
In the apical region of haustorium dense cytoplasm, found but nuclei are absent.
The shape of haustorium have taxonomic importance.
It's mycelium is stained by cotton blue and mounted by lactophenol.
(1) Asexual reproduction
(2) Sexual reproduction
Dispersal & Germination
Conidia are dispersed by air.
Two different types of germination takes place in favourable conditions.
(i) Direct germination :
(ii) Indirect Germination :
Free zoospores swim in water for few minute and finally they reaches on the surface of host, then after withdraw their flagella and round off and secretes a wall around itself.
Deflagellated zoospores with wall germinates through the germ tube. This germ tube enter into the host tissue through stomata or through the teared epidermis and form mycelium.
Structure Of Zoospores
Zoospores of Albugo are uninucleated, reniform or bean-shaped and biflagellated.
Flagella are located on the lateral side of zoospore which are unequal in length.
Out of them small the hairy flagellum is called Tinsel or Pantonematic or Flimmergersal.
(i) Monoplanetic Generation : - Only primary zoospores are formed.
(ii) Polyplanetic Generation : - In which many generation of zoospores are formed, like primary, secondary and tertiary zoospores are formed. (during high availability of water)
(i) Antheridium : -
(ii) Oogonium :
(b) Central cytoplasm : -
Antheridium and oogonium develops very close in the mycelium.
A small protuberance develops from oogonium towards the antheridium. The wall of the antheridium and oogonium become thin at the region of their contact.
This outgrowth stimulate the antheridium for fertilization. The inner wall of stimulated antheridium produces fertilization tube which enters into the oogonium and grows until reaches the oosphere.
The terminal end of fertilization tube burst and introduces a single nucleus along with some cytoplasm.
Male nucleus fuses with the female nucleus and results in the formation of diploid nucleus. Now it is known as zygote.
Prior to fertilization a mass of protoplast is found in ooplasm. It is called coenocentrum. Which is formed by granular cytoplasm.
After the fertilization, zygote secretes a thick tri-layered wall around itself and now it is called oospore (2N).
On returns of favourable conditions the 32 nuclei of oospore undergoes repeated divisions to form 100 or more nuclei.
100 or more zoospores are formed from these nuclei. The zoospores are released/liberated with vesicle by the rupturing of outer thick wall of oospore (formed by inner wall of oospore).
These zoospores are coming in contact with a suitable host (seedling plants) settle down on the host and infect them.
The initial stage of the disease during the growth period is called primary infection and it takes place through the soil born oospores.
According to Stevens all the structures of Albugo are diploid except gamete.
According to Sansome and Sansome meiosis division takes place at the time of gamete formation i.e. gametic meiosis found in Albugo. In Albugo meiosis not takes place in oospore.
Control Of White Rust Disease
1. By crop rotation : - Primary infection can be checked through the growing of crops one after another crops. This is the best method to control the white – rust.
2. By removal of infected plants from the field. Through this it can be eradicated.
3. By application of fungicides – Such as – Bordeaux mixture. It is composed of
CuSO4 + Lime water
(1 : 1)
Diplontic type (according to modern mycologists)/ Haplontic (According to old mycologists)