The document discusses phytoalexins, which are low molecular weight antimicrobial compounds derived from plants that serve as part of the defense system against pathogens. Various types of phytoalexins, such as ipomoeamarone and gossypol, are produced in response to pathogen exposure and their quantity is influenced by several factors including host age and temperature. Phytoalexins are characterized by their broad-spectrum antifungal properties and typically do not persist in host tissues.

1. PAT 301- DISEASES OF FIELD CROPS AND
THEIR MANAGEMENT (2+1)
Phytoalexin

2. PHYTOALEXINS
DEFENCE SYSTEM
PRE -EXISTING POST EXISTING
STRUCTURAL BIOCHEMICAL
PHYTOALEXINS

4. Phytoalexin:
 It is derived from Greek word phyto meaning plant
and alexin means warding off compound.
 Muller and Borger(1958) .
 He was initiated hypersensitive response against soft-
fruit pathogen Monilinia fructicola in bean.
 Low molecular weight,
 Anti-microbial compounds

5.  Fabaceae and Solanaceae families.
 Fungistatic action rather than fungicidal activity.
 It is chemically diverse , but large number of
Phytoalexin products are produced by shikimatic acid
pathway.

7. Salient features:
 Phytoalexin are produced when host cell come contact
with parasite.
 Broad based anti fungal compounds
 Quantity may be influenced by age of host, inoculum
concentration, temperature etc.
 Not translocated & rarely persistent.
 Non specific in its toxicity

8. Types of Phytoalexin:
Ipomoeamarone:
Sweet potato - black rot fungus Ceratocystis fimbriata.

9. Isocoumarin:
Carrot fruit rot -Ceratocystis fimbriata.

10. Gossypol:
Black spot of rose-Diplocarpon rosa

11. Glyceollin:
Soybean -Phytophthora megasperma

12. Pisatin:
Detached Pea -Monilia fructicola.

13. Camalexin:
Arabidopsis thaliana-Pseudomonas syringae

14. Capsidiol:
Pepper fruit rot:

16. Others:
Phaseollin:
Beans - S.fructigena.
Medicarpin:
Alfalfa (Medicago sativa)

17. REFERENCE:
Plant pathology (George N Agrios)

18. thanK you.