Puccinia
Puccinia:-
Classification:-
Kingdom - Myceteae
Division - Amastigomycota
Sub-division - Basidiomycotina
Class - Basidiomycetes
Sub-class - Teliomycetidae
Order - Uredinales
Family - Pucciniaceae
Genus - Puccinia
Common Names:- Rust fungi
Order - Uredinales:-
> All the members of this order are called Rust fungi.
> All fungi of this genus are obligate parasites.
> On the basis of the number of hosts, they are of two types:-
i. Monogenetic:- When the parasite completes its life cycle on only one host.
ii. Digenetic:- When the parasite completes its life cycle on two hosts.
> Depending on the type of mycelium, the host is of two types:-
i. Primary Host:- The host on which the secondary mycelium of the parasite is found.
ii. Secondary Host:- The host on which the primary mycelium of the parasite is found.
> Ideally, 5 types of spores are found in different members of this order: -
i. Uredospores
ii. Teleutospores:- They are always present.
iii. Basidiospores
iv. Pycnidiospores
v. Aecidiospores
> Based on the presence or absence of spore stage, 5 types of life cycles are found in the members of this order -
i. Opsis type:- When uredospores are absent.
ii. Brachy type:- When aecidiospores are absent.
iii. Microcyclic type:- When both uredospores and aecidiospores are absent.
iv. Hemicyclic type:- When only uredospores and teleutospores are present.
v. Macrocyclic type:- When all five types of spores are present.
> There are 3 types of teleutospores -
i. Unicellular:- Eg.- Uromyces
ii. Bicellular:- Eg.- Puccinia
iii. Multicellular:- Eg.- Phragmidium
Important Species:-
a. Digenetic:-
i. P. graminis tritici:- Its primary host is wheat (Triticum aestivum) and secondary host is barberry (Berberis vulgaris). It causes Black rust (Stem rust) disease in wheat.
ii. P. recondita (P. triticina):- Its primary host is wheat (Triticum aestivum) and secondary host is Thalictrum flavum. It causes Brown rust (Leaf rust) disease in wheat.
iii. P. striiformis (P. glumerum):- Its primary host is wheat (Triticum aestivum). Its secondary host is unknown. It causes yellow rust (stripe rust) disease in wheat.
b. Monogenetic:-
i. P. asparagi
ii. P. butleri
iii. P. menthae
Habit and Habitat:-
- Puccinia is named after Italian anatomist T. Puccini.
- It is a facultative parasitic fungus.
- It cause rust disease on cereal crops like wheat, barley, oats, sorghum, maize etc.
- Rust disease is known by the names Ratwa, Rauli, Ghairir, Tombora, Gerua etc. in different regions of India.
Thallus structure:-
- Septate and unicellular hyphae.
- Cells are monokaryotic in primary mycelium and dikaryotic in secondary mycelium.
- Branched intercellular mycelium.
Reproduction or Life cycle:- There are 5 types of spore stages found in Puccinia-
i. Uredospores:- They are dikaryotic and are found on wheat.
ii. Teleutospores:- They are dikaryotic and are found on wheat.
iii. Basidiospores:- They are monokaryotic and are found in soil.
iv. Pycnidiospores:- They are monokaryotic and are found on barberry.
v. Aecidiospores:- They are dikaryotic and are found on barberry.
i. Uredospores:-
ii. Teleutospores:-
iii. Basidiospores:-
iv. Pycnidiospores:- These are also called spermatia.
Spermatization:- The mature spermatia are released from the ostiole along with the drop of nectar. Nectar attracts insects due to which spermatia stick to the legs and mouthparts of insects. When these insects come in contact with the receptive fungal hyphae of opposite strain, spermatia stick to it. Due to the desolution of the contact wall, both the nuclei enter the receptive fungal hyphae.
v. Aecidiospores:-
Note:- The formation of secondary mycelium by germination of aesidiospore takes place only on mountains because there, wheat and barberry plants are located close to each other. There are no barberry plants in the plains, so aesidiospores are not formed here.
Annual Recurrence of wheat rust in India:-
> Temperate climate is found in European countries in which wheat and barberry shrubs grow side by side. Due to which primary host and secondary host are available to Puccina in close proximity.
> In India, wheat and barberry shrubs are found side by side on the mountains, but in the plains there is only wheat, not barberry shrubs. Despite this, black rust infection occurs in the plains of India.
> So the question arises that despite the secondary host being so far away, how does black rust actually infect the wheat crop growing in the plains of India?
> The credit for the answer of this question goes to Dr. K. C. Mehta of Agra. He studied this disease continuously for 20 years (1923-43) and presented the following facts -
i. Wheat is sown twice a year in the hills – the first time in April – May and the second time in September – October. The secondary host wheat is available for most of the year. Wheat is not sown only for 3 months in a year, during this time these uredospores survive on self-growing wheat plants and other weeds in the mountains. Weeds that act as reserve hosts for the pathogen are called volunteers. Thus uredospores of black rust are found throughout the year on the mountains.
ii. Wheat is sown in the plains in November-December and uredospores are completely absent in this time. But at the same time, a large amount of uredospores is found on the mountains about 7000 meters height.
iii. In November-December, these uredospores infect the wheat crop and move downwards and by the month of January-February, these uredospores reach the foothills of the mountains. Here they do not get destroyed because the temperature is low at this time.
iv. In January-February, along with the north to south winds, these uredospores start moving to the plains and infect the wheat crop.
> Thus, in the plains of India, the infection of black rust is caused by uredospores and not by acidiospores.