Heterothallism in fungi

Heterothallism in fungi

·        If fungi require 2 different strains mycelium to form zygospores it is called heterothallic fungi.

Is all fungi are heterothallic

• ·        No, there are basically 2 types of fungi.one heterothallic that needs different nature mycelium to produce zygospore.

• ·        And  another is homothallic that do not need different nature mycelium.

• ·        The mycelium developed from single spore are compatible for each other.

• ·        They can make zygospores on hyphae of a single mycelium.

About heterothallic fungi

·        The 2 different mycelium are morphological similar but physiological and sexual different.

·        The term + and – for two type of strains.

History

• ·        While studying mucorales- Blakeslee found that some species develop zygospores Independtly ,whereas some (like m.mucedo)produce zygospores in the presence of mass of mycelium.

• ·        The 2 mycellium of mucedo arising from different spores are nessery for the production of zygospores  and also different in strains.

• ·        These mycelium were morphological similar but not physiological and sexual.

Further,

    Work on heterothallism and homothallism by raper proved there is

                            “no absolute separation of sex”

4       type of mycellim in achlya bisexualis are found by them-

1-    Pure male

2-     predominetly male(can make oogonia)

3-    Pure female

4-    Predominantly female ( can make antherdia)

5-    But none of them able to make zygospores alone.

·        Each needs one of three .

·        These type of heterothallism called- gynandromictic.

Hormones

·        These are some chemical that govern sexual process that are called hormones.

·        Raper named them A, B, C, D.

·        One of them is sirenin that is isolated from allomyces .

·        Sirenin is responsible to attract male gametes.

Type of heterothallism

1-morphological heterothallism

2- Physiological heterothallism

Morphological heterothallism

·        When one can distinguish the male and female sex organ by its structure or morphology.

 Physiological heterothallism

• ·        Reproduction place by physiological different hyphae.
• ·        Also known as haploid incompatibility.

           They are two types 
               1.     2 allele
                     2.     Multiple allele

2 allele heterothallism

• ·        Nuclei  of both mating types are genetically different.
• ·        Sexual compatibility is controlled by genetic factor. “A” , “a”.
• ·        Both factors are present in different chromatid of chromosomes.
• ·        Due to dominance of “A” over “a” they also represented by “+” and “-“.
• ·        At meoisi they got seprate with chromatid.
• ·        Spores formed with on “+” allele and another spore formed of  “–“ allele.
• ·        Spore with + allele give rise to + mycelium and – to – mycelium.
• ·        Only “+” and “-“ are compatible together.

To be continue…..