Q.3. Give the systematic position and important characters of following:
1. Mucor (Black mould)
2. Agaricus (Snake umbrella) ( 2009)
3. Alternaria (2009, 13)
Ans. 1. Mucor (Black mould)
Systematic Position: -
Kingdom - Mycota
Division - Eumycotina
Sub-division - Zygomycotina
Class - Zygomycetes
Order - Mucorales
Family - Mucoraceae
Genus - Mucor
Characters:-
1. It is a common saprophytic fungus which grow on dead organic material.
2. Fungal mycelium looks like cottony threads.
3. Mycelium is white, profusely branched and interwoven.
4. Mycelium is coenocytic and multinucleate oil drops and glycogen present.
5. Cytoplasm is granular.
6. It produces an enzyme which converts carbohydrate into sugar.
7. Vegetative, asexual and sexual all types of reproduction take place.
2. Agaricus (snake umbrella)
Systematic Position: -
Kingdom - Mycota
Division - Eumycotina
Sub - division - Basidiomycotina
Class - Hymononymycetes
Order - Agaricales
Family - Agaricaceae
Genus - Agaricus
Characters:-
1. A. compestris or snake umbrella or dhingri is common gilled fungus (Mushroom)
2. It grows in soil rich in humus.
3. The plant body is divided into two main parts.
(a) vegetative mycelium or rhizomorph.
(b) Fruitification or sporophore.
4. Mycelium or rhizomorph grows under soil.
5.Hyphae are septate and multinucleate.
6. Oil drops are found in hyphae.
7. Sporophore is aerial part of plant body and it looks like a umbrella in which gills are present in under side.
8. Reproduction takes place by basidiospores.
3. Alternaria
Systematic Position: -
kingdom - Mycota
Division - Eumycotina
Sub-division - Deuteromycotina
Class - Hyphomycetes
Order - Moniliales
Family - Dematiaceae
Genus - Alternaria
Characters:-
1. The fungus Alternaria occurs commonly in potato plants and causes the disease early blight of potato.
2. It appears as yellow spots on the leaves.
3. Mycelium is intercellular or interacellular and no haustoria present.
4. It is an endophytic fungus.
5. Hyphae are profusely branched septate and light brown in colour.
6. Only asexual reproduction takes place.
7. Asexua1 reproduction takes place by conidia. These conidia are attached with conidiophores.
Q.4. Write short note on Basidiospore liberation mechanism. (2002)
Ans. Dispersal of basidiospore takes place by water drop method. As the basidiospore matures, a drop of water or liquid appears at the hillar appendics, surrounded by a limiting membrane. The basidiospore lies just above this drop. Gradually the drop enlarges and attains size about 1/5th of the spore. The basidiospore is suddenly shot away from the sterigma. Within few seconds the four basidiospores are liberated one by one.
Q.5. Only with the help of diagrams describe the life cycle of causal organism of early blight of potato. (2009)
Fig. Lify cycle of Alternaria.
Q.6. Write short note on Heterothallism. (2005, 10)
Related Question -
Q. What is heterothallism ? Write the name of two fungi in which it occurs. Describe in brief. (2006)
Ans. Heterothallism:-
Heterothallism may be defined as the condition in which zygospore formation takes place only when mycelia arising from asexual spores of two genetically different mating types (+) and (-) are allowed to interact. It may also be defined as presence of two different strains in a fungus is called heterothallism.
Example: -
Rizopus , Mucor, Puccinia etc.-
Blakeslee and his co-workers (1904), on the basis of his experiment, suggested that some members of fungi are monoecious and while others are dioecious. In dioecious fungus, male and female gametes are produced on separate fungul hyphae. Hence, such forms are called heterothallic.
In heterothallic species of Mucor mucedo, the zygospores upon germination produced germsporangia which contain spores of only one strain (either + or -). In this case, zygospores could be formed only when mycelia formed from spores of (-) strain formed in germsporangia produced on germination of zygospores are allowed to come in contact with the mycelia produced from the spores of (+) strain. But in the heterothallic species of phycomyces nitens, spores Of (+) and (-) strains are produced in the same green sporangium. Blackeslee thus regarded the (+) and (-) strains of heterothallic species as differing in sex and term heterothallism may therefore be treated as equivalent to dioecism in haploid organisms. All heterothallic species share one common feature of intermycelial contact. Heterothallism may be of two types:
(1) Morphological Heterothallism :-
Morphological heterothallism may be defined as the condition when morphologically different male and female sex organs are produced in two closely associated mycelia.
Example :-
Achlya ambisexualis, A. bisexualis, Dictyuchus monosporus.
(2) Physiological Heterothallism :-
In physiological heterothallism the interacting thalli differ in mating type or incompatibility, irrespective of the presence or absence of the sex.
Heterothallism may be of two types organ or gametes. This means that sexual reproduction takes place by two morphologically similar but physiological different hyphae in physiological heterothallism. Physiological heterothallism may be of two types:
(1) Two Allelomorphs or Twó-Allele Heterothallism:-
When nuclei of both the mating types are different in genetic characters this type of hetrothallism is known as Two Allele heterothallism. In these types compatibility is governed by a pair of alleles represented by A and a located at single same locus of the chromosome. Due to the dominance of A over a, A is represented by (+) and a by (-). This type of heterothallism is found in Ascobolus magnificus, Puccinia graminis, Ustilago kolleri etc.
(2) Multiple Allelomorphs or Multiple Allele Heterothallism:-
In this type of heterothallism more than two alleles determine the sexual compatibility. These may be located at one (bipolar) or two (tetrapolar). loci. Multiple allele heterothallism, is of two types:
(i) Bipolar multiple-allele Heterothallism :-
This type of heterothallism is controlled by multiple alleles at a single locus instead of a pair of alleles. Bipolar multiple allele heterothallism is a characteristic of Basidiomycetes except rust and smuts.
(ii) Tetrapolar multiple allele Ileterothallism :-
This type of heterothallism is characteristic of Basidiomycetes except rusts. In this type of heterothallism which is very similar to bipolar multiple allele heterothallism compatibility is determined by two loci. This type of heterothallism encourages out breeding. Whereas in bipolar multiple allele heterothallism, the outbreeding is 25%, in tetrapolar, it is 100%. According to Garrett (1963) , heterothallism promotes the out breeding and therefore subserves the same end as the sexual process, which it renders more efficient. Heterothallism is not the same as sex, it is refinement superimposed upon it.
Q. 7. What is unique fature of the class Deuteromycetes which makes it different from other classes of fungi.
Ans. The class Deuteromycetes is called “artificial group of fungi.” The members of this class are devoid of perfect stage . (sexual stage). Hence, this group is named as “Fungi Imperfecti.” This class includes about 1350 genera and 11,000 species. It has been generally suggested that the members of this group are actually members of Ascomycetes and Basidiomycetes having conidial stage only. The sexual phases are not known, hence, their life - cycle is incomplete. Because of these reasons class Deuteromycetes is different from other classes of fungi.