Phylogeny of fungi by Ajay Kumar Patel

1. Presentation on Phylogenetic relationship of Fungi Presented by- Ajay Kumar Patel Ph.D. ( Ag.) 1st year Department of plant pathology

2. Phylogeny • Phylogeny is the study of the evolutionary history and relationships among individuals or groups of organisms. • Refers to the evolution of a group of organisms through time and their hypothetical ancestors. • These relationships are discovered through phylogenetic inference methods that evaluate observed heritable traits, such as DNA sequences or morphology under a model of evolution of their traits.  20220581

3. Theories of Algal Ancestory • Algae Fungi • Loss of chlorophyll • Occurred in the thallus and asexual and sexual processes ( Breteld, 1889; C.E. Bessey, 1985; Harper, 1899) • Their theory visualize that fungi are polyphyletic, “the Phycomycetes’’ are derived either from Chlorophyceae or Xanthophyceae and the Ascomycetes and rusts from Rhodophyceae. • According to (Dennison and Caroll 1966) and Kohlenmeyer (1973, 1975) – that the reproductive features of ascomycetes and red algae are common. • These include the presence of a trichogyne on the female sex organ, gametic union by means of non-motile spermatia and analogies between ascogenous hyphae and gonimoblast filaments. 20220581

4. Phycomycetes Ascomycetes and rusts 20220581

5. Bessey (1942 ,1950) thought that “The Phycomycetes” are derived either from unicellular coccoid members of Xanthophyceae which have zoospores having two anteriorly situated flagella, one of the whiplash type and the other of the tinsel type. • Three different lines of evolution have diverged- Chytridiaceous fungi evolved with a single posterior whiplash type of flagella by loosing Tinsel flagella Hypochytridiaceous lines with simple anterior tinsel type of flagella by loosing the whiplash flagella Both the flagella were retained giving rise to biflagellates 20220581

6. Chytridiaceous fungi zoospore Hypochytridiaceous fungi zoospore Xanthophyceae zoospore Oomycetes Biflagellated fungi zoospore 20220581

7. Cell wall composition • Chytridiaceous and Hyphochytridiomycetous fungi are of chitin while those of bifllagellatae (now Oomycetes) have cellulose. • Studies of wall composition of Rhizidiomyces have shown the presence of cellulose along with chitin in the cell wall (Bartnicki-Garcia, 1970). Objections • Uniflagellate zoospores do not occur in algae • Chitinous walls do not occur in Xanthophyceae so that the physiological nature of wall is undermined 20220581

8. ProtozoansAncestery of Fungi Gobi (1884) Fungi protozoan Some favour a monophyletic while others a polyphyletic system, but all agreed that the derivation of fungi from the algae present more difficulties than does a theory of protozoan origin (Martin, 1968). • Bold et al. (1980), fungi with plants in the cellular structure of their • thalli and their reproduction by spores, mycologists now believe • that most fungi have originated from some protozoan like flagellate. 20220581

9. Origin of lower fungi (Sparrow’s view) • According to Sparrow (1958), "Phycomycetes" are not a homogeneous monophyletic group but rather an artificial category of coenozoic, zoosporic fungi. • Chytridiomycetes, with posterior whiplash uniflagellate zoospores and associated characters; • Hyphochytridiomycetes, with a single anterior tinsel flagellum, with body types paralleling those of Chytridiomycetes and in sexuality i.e. resting-spore formation of like thalli; • Plasmodiophoromycetes, with plasmodial thallus, protozoan-like (not Myxomycetes like) nuclear-division figures, and biflagellate, heterokont zoospores, with both flagella of the whiplash type; and • Phycomycetes (now designated as Oomycetes), the Saprolegniacean-Lagenidiacean - Peronosporaceangallaxy, with diplanetic, biflagellate zoospores with oppositely directed flagella, the forward of the tinsel type, and posterior of the whiplash type, and with well developed oogamous reproduction. 20220581

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11. Origin of Zygomycota • Bessey (1950) and Hesseltine (1952)- Zygomycetes have evolved from Saprolegniales (genera- Aplanes) , which produces nonmotile asexual spores. • Objections raised against these concepts – • In fungus of Saprolegniaceae , chitinous walls are not found where as Mucorales have chitinous walls. • Gametangia of Saprolagniaceae are quite different organizationally and functionally dissimilar. • Isogametangic condition is found in Mucorales whereas gamentangia of different sizes have been found in Dicranophora and Zygorhynchus. 20220581

12. According to Gaeumann and Dodge (1928), Jaczewski (1929, 1930), Gaeumann (1952,1964) • Mucorales (Zygomycetes) derived Chytridiomycetes. • His view was strengthened by late Prof. S.B. Saxena (discovered Saksenaeavasinformis, which shows the following characters – • A flask shape sporangium • Opening of this sporangium is covered with mucilaginous plug. Resembles with Nowakowskiella(chytridiomycetes) 20220581

13. He opposed the earlier theory- • On the basis of cell wall contents- fungus of Saprolagniaceae have the cellulosic wall, whereas Mucorales have chitinous wall. • Asexual reproduction- sporangia produced by Mucorales have the collumella whereas Saprolagniales do not posses such structures. • Sexual reproduction- heterogametangia are found in Saprolegniales , whereas isogametangic condition in Mucorales have been observed. • Fertilization tubes are formed in Saprolegniaceae whereas cytoplasmic fusion in Zygomycetes occurs by dissolving cells of gametangia. 20220581

14. Origin of Ascomycetes • Atkinson, 1915; Gaeumann, 1964 ; Klein and Cronquist 1967; depicted that The higher mycelia fungi Zygomycetes and Hemiascomycetes were evolved from water molds . 20220581

15. Count.. • Sedimentation pattern of the tryptophan biosynthesis enzymes is distinctive in both Zygomycetes and Hemiascomycetes. • The cell wall characteristic of the two groups are also different unlike those in the Chytridiomycetes, Euascomycetes and Basidiomycetes • Bartnicki-Garcia (1970), Most probably ancestral Chytridiomycetes gave rise to the primitive Ascomycetes from which the present day Euascomycetes have been evolved. • On the basis of comparative study of the structure of ascus, Cain (1972) suggested that the main ascus types might have originated separately from algae, and this is supported by (Eriksson (1981). • According to Hawksworthet al. (1983), although the ascus of Peltigerales has been considered to be primitive but it did’nt show the evidence that higher fungi were autotrophic lichen-like associations. 20220581

16. Herterobasidiomycetes Homobasidiomycetes ↑ Euascomycetes ↑ Hemiascomycetes ↑ Zygomycetes ↑ Oomycetes HypochitridiomycetesChytridiomycetes • ↑ …………………………………………………………………………………… HeterosiphonalesFlagellatae Evolutionary scheme of fungi on morphological characters (From Gaumann,1964) 20220581

17. Origin of Basidiomycetes • Basidiomycetes had arisen from Ascomycetes and that the basidium is a modified ascus which produces the spores exogenously. • Linder’s view (1940) regards the phragmobasidium asprimitive and the holobasidium a derived structure from it • Gaeumann’s view (1912, 1964) regards the holobasidium as primitive and the phragmobasidium as the derived structure and evolution of higher fungi from water molds as follows: • Chytridiomycetes → Zygomycetes → Hemiascomycetes→ • Euascomycetes → Homobasidiomycetes→ Heterobasidiomycetes 20220581

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19. Recent concept on origin and phylogeny of fungi fig. - Estimated time of divergence of fungal phyla based on molecular evidence comparisons of 18S RNA gene sequences of over 30 species of fungi. (Based on M.L. Berbe and J.W. Taylor (2000), The Mycota, Springer-Verlag Berlin). • On the basis 18S – ribosomal DNA gene sequences of 30 species of fungi and on earliest appearance of key structures in fossil record • Cambrian era (500 million years ago) – 1st terrestrial fungi from chytrid like ancestor 20220581

20. Phylogenetic tree based on the nucleotide sequence of 18s DNA kingdom Fungi is more closely related to Animalia than to Plantae 20220581

21. References • Aneja K. R., Mehrotra R. S. • 2nd Edition “An Introduction to Mycology” • New Age International Publisher • (Page No. 593-602) 20220581

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