Physiological Specialization

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In Plant Pathogens

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PHYSIOLOGICAL SPECIALISATION : 

PHYSIOLOGICAL SPECIALISATION IN PARASITIC FUNGI

The Definition : 

The Definition Race/Biotype - A population of individuals the members of which are similar to other such populations on morphological grounds but differ on physiological or pathological grounds In pathogenic fungi Races are identified on the basis of infections on different species of the host Biotypes are identified on the basis of infections on different varieties of the host

Variability In Plants & Pathogens : 

Variability In Plants & Pathogens Many plants disease fungi are known to be complex & variable Many crop plants in which fungi live are equally complex More than 14000 varieties of wheat are available Similarly, unnumbered var. of apples , beans, corn, roses are present Besides , man & nature are also making new var. by mutation & hybridization

BASIS OF IDENTIFICATION : 

BASIS OF IDENTIFICATION The principles & procedures in classifying & naming fungi are similar to those for higher plants Sp. of higher plants are determined by morphological characters of the vegetative & reproductive structures ,including seeds Similarly sp. of fungi are determined by the char. Of the mycelium , of the spore producing organs, & of the spores themselves

Spores & Mycelium : 

Spores & Mycelium

Stem Rust of Wheat : 

Stem Rust of Wheat

Pustules on Leaves : 

Pustules on Leaves

Varieties of Puccinia graminis : 

Varieties of Puccinia graminis

Races & Biotypes within Varieties : 

Races & Biotypes within Varieties

Differential Varieties : 

Differential Varieties There are slight morphological differences bt.Races within a variety The most important & most recognizable diff. are in the degree of infection Those crop varieties, designated as Differential Varieties, are used differential var. , are used to distinguish races within the var. of P. graminis

Differential var. of Wheat : 

Differential var. of Wheat Little Club ( T. compactum ) Marquis,Reliance, Kota (T. vulgare) Arnantaka ( T. durum) Mindum, Spelmar, Kubanka ( T. durum) Eincorn ( T. monococcum) Vermal, Khapli ( T. dicoccum)

Reaction Classes & Infection Types : 

Reaction Classes & Infection Types When inoculated with diff. races , these differential var. may be Susceptible (S), Resistant (R) or Heterogenous (X) Each of these classes is subdivided into infection types, based on size of pustules & condition of wheat tissue in which pustules are formed

Reaction Classes of Two Races : 

Reaction Classes of Two Races Diff. var. Race 56 Race 59 Little Club S S Marquis S R Reliance S R Kota S R Arnantka R R Mindum R R Spelmar R R Kubanka S M Acme S S Einkorn R S Vermal R R Khapli R R

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Infection Types

Conclusion : 

Conclusion In a general sense physiological race means a biotype or a group of biotypes which can be distinguished with certainty by its physiologic characters including pathogenicity & in some fungi by growth characters on artificial media