Life cycle of Puccinia

 Life cycle of Puccinia 

Systematic position:-

Class - Basidiomycetes 

Sub - class - Heterobasidiomycetidae 

Order - Uredinales 

Family - Pucciniaceae 

Genus - Puccinia 


The genus include about 1800 Cosmopolitan species which are obligate parasite and are extremely host specific. 

There are two types of species :-

1) Autoecious

 Which complete their life cycle on a single host as Puccinia butlei.

2) Heteroecious

Which complete their life cycle on two hosts as Puccinia graminis.

Puccinia causes rust disease of several economically important plants like wheat, barely, oats, etc.

The life history of Puccinia graminis is divided into five stages which are based on the nature of spores at a particular stage. These are as follows:-

1. Uredospores

 ( Binucleate) On wheat plant

2. Teleutospores 

 ( Binucleate) On wheat plant

3. Basidiospores 

( Uninucleate ) infect barberry plant

4. Pycnidiomycetes 

( Uninucleate ) on barberry plant

5. Aecidiomycetes

( Binucleate) infect wheat plant

Life cycle of Puccinia

1. Uredospores

In plants of India wheat is sown in October or November but the infection become evident only in the month of February or March, when vertically elongated reddish brown or black pustules appear mostly on the stem of leaf.

These pustules in reality uredosori containing uredospores.

Uredosori developed from branched and shifted mycelium which is divided into several multicellular hyphae arrange themselves in clusters.

Life cycle of Puccinia

Life cycle of Puccinia

Each hypha is called as sporophore.

These are situated below the epidermis. The apical cell of sporophore enlarge and divides into an upper export initial and lower basal cell. 

The basal cell forms stalk on elongation while spore cell form uredospores.

Each spore is surrounded by an outer brownish wall exospore and inner delicate endospore.

It consists of two nuclei and cytoplasm also.

On uredosori the epidermis of host bursts and they are liberated in air.

Uredospore after dissemination, germinate in favourable conditions and form germ tube which infect other healthy wheat plants.

Thus the rust disease get spread up through uredospore in the entire field of wheat.

2. Teleutospores

Later in the season, in April in the plains of Northern India, when the wheat grains are maturing the uredia being to produce  a few teleutospores.

As the season advances more and more teleutospores are formed.

A pustules producing teleutospores is called as teleutospores or telium outwardly these appear as elongated black coloured streaks on the stem and leaf of wheat plants 

This stage is called black stage or teleutospores stage or rust.

Like uredospore teleutospores also develop from multicellular hyphae possessing dikaryotic cells.

The teleutospores is bicelled and spindle shaped.

It is covered by exospore and endospore.

The dikaryotic nuclei fuse together in the teleutospores and form a diploid nucleus.

The teleutosporesare shut out by the rupture of epidermis and are carried to long distance by wing.

3. Basidiospores

Teleutospores after liberation fall in soil and in the next spring season these teleutospores germinate into a hyphae branch called epibasidium or promycelium. 

The diploid nucleus migrates into basidium and the fights by reduction division to form 4 haploid in nuclei. 

The four haploid nuclei thus produced in each basidium come to lie at more or less equal distance. 

Septa appear between the nuclei dividing the basidium into four uninuclear haploid cells.

From each cell arises a short basidia, at the apex of which develops a basidiospores, in which passage the haploid nucleus.

The basidiospores are small unicellular, uninuculate haploid and heterothallic in nature as mostly two of them represent positive and other negative strain. 

The basidiospores is 4 or discharged by the water droplet method with a force into the air. 

They are carried by wind to the lives of alternate host which is Barberry (Berberis vulgaris).

4. Pycnidiospores

The basidiospores, which are unable to infect the wheat plant, after being desseminate fall in the leaves of Berberis vulgaris. 

Each basidiospores on germination form a primary hyphae which penetrate into the leaf cells and ultimately forms specific uninucleate monoploid, branched mycelium.

Since the fungus is heterothallic the basidiospores are either of positive or negative strain.

Few days after infection their monokaryotic mycelium result into the formation of pseudoparacymatous mass of tissue, which forms the pycnidia or pycnidial or spermogonia.

Life cycle of Puccinia

A few slender hyphae develop from this pycnidia which are uninucleate and are called as sporophore.

The nucleus of sporophore divides and one daughter nucleus after each division move towards the apex and transforms into a pycnidiospores. 

Pycnidiospores are formed in chains.

Each pycnidiospores is a circular or oval thin walked structure.

By the rupture of epidermis the pycnidiospores are liberated.

The point of rupture is called as ostiole.

A spermogonium or pycnidium is positive or negative according to the mycelium bearing it.

It bears spermatophores and spermatia or pycnidiospores

The spermatia or pycnidial or pycnidiospores are the male sex organ and are extruded through the ostiole in a drop of a thick nectar like fluid.

From the inner side of spermogonial wall arise a large number of hair like, sharp pointed periphysis.

These project out through ostiole

A number of longer, cylindrical and unbranched or slightly branched flexuous hyphae with blunt lips arises just beneath or among the periphysis.

These are the respective hyphae or flexuous, hyphae and represent the female sex organs.

They protrude through the ostiole

All the spermatia and receptive hyphae produced from a spermatogonium bear the same genetic factor positive or negative, according to the genetic make up of the spermogonium

As mentioned already, since multiple infection by positive or negative basidiospores at a random is probable the rule in nature hence positive or negative spermogonia are usually found side by side on a barberry leaf.

Spermatization take place if postive spermatia are transferred to negative receptive hyphae or spermatia of positive receptive hyphae.

In nature this take place by the agency of flies or some other insects which attracted by the scent and sweetness of the spermogonial exudate.

5. Aecidiospores 

The monokaryotic mycelia which form pycnidiospores at the upper surface of lead develops aecidial cups on lower surface.

The primary mycelium collects in patches near the lower epidermis of lead known as protoaecidium

Due to the stimulus of sexulact protoaecidium develops into a cup shape aecium of aecidium.

From the bottom of which arise losely packed parallel chain of aecidiospore or aecidiospores on the side toward the lower epidermis.

During the development of an aecium a badal layer of dikaryotic cells is differentiated in a protoaecium.

As to how this change from uninucleate to binucleate condition is effected, is not very well understood. 

Most probably this is due to spermatization, the spermatia nuclei travelling down the deceptive highfe migrate from cell to cell of the primary mycelium through spectral performation, reach the basal cell of protoaceium.

These dikaryotia cell multiply and form the hymenium of aecidial cup, while the subhymenium is formed of monokaryotic cells.

A few sporophores emerge from dikaryotic hyphae, which form a chain of binucleate or dikaryotic spores called as aecidiospores.

Aecidiospores possess sterile disjunctor cells in between them.

The wall of aecidial cup is made up of sterile cells called peridium.

On maturation of aecium, the spore chains push through the host epidermis and eventually through roof of the peridium; the spores are thus exposed and dispersed by wind.

The aecidiospores are binucleate subglobose the hexagonal, light orange yellow with sex germ pores.

As the aecidiospores can't reinfect the barberry plant, so they are carried by air to plains and infect the wheat plants.

On the wheat plant the germ tube of aecidiospore penetrate through stomach and give rise to dikaryotic mycelium from which uredospore arises.

Thus the life cycle of fungus is completed.

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