mode of entry of bacteria in plant

1. MODE OF ENTRY OF BACTERIAL
PLANT PATHOGENS
COURSE TEACHER
Dr. PARTHASARATHY S
Asst. Professor (Plant Pathology)
STUDENT
Mr. JEYARAJESH K
ID. NO. 2017021094.
COLLEGE OFAGRICULTURALTECHNOLOGY
(Affiliated to Tamil NaduAgricultural University, Coimbatore-3)
Kullapuram (Po),ViaVaigai Dam, Theni-625 562

2. MODE OF ENTRY OF PLANT
PATHOGENS
Unlike fungal pathogens, bacteria are incapable of
mechanically penetrating the cutinized plant tissues,
cuticle, periderm, etc. Since the ability to form
appressoria is lacking in them. The ways of gaining
entry into the plants are by passive/indirect
method(Through openings).

3. Fig.1 Entry of pathogens

4. Some of the mode of entry of
bacteria in plants.
= Entry through stomata.
= Entry through hydathodes.
= Entry through floral parts.
= Entry through Insect Wounds.
= Entry through Wounds.
= Entry through lenticels

5. Entry through stomata
Stomata are the natural openings present in large numbers on the
lower surface of the leaf which open during day time and more or
less closed at night for gaseous exchange. Bacteria use this natural
opening (stomata) as the way of entry into the plants.
E.g:
1. Pseudomonas tabaci causing wild fire of tobacco.
2. Xanthomonas Phaseoli causing bean blight.
3. Xanthomonas Campestris causing black rot of cabbage.
Fig 2: Wildfire of tobacco

6. Fig.3 Entry through stomata

7. Entry through hydathodes
Hydathodes are the pores at the leaf margin, which are continuous
with the xylem. Under particularly humid condition, droplets of xylem
fluid emerge at the surface of the leaf where they can be exposed to
pathogenic bacteria.
E.g: The cells of black rot of cabbage, Xanthomonas campestris,
Fig.4 longitudinal
section of leaf apex and
hydathodes.
Fig.5 Black rot of cabbage

8. Entry through floral parts
Some bacteria use the openings of floral parts especially
nectarthodes (nectar opening)
E.g:
The fire blight bacterium, Erwinia amylovora, enters the
floral parts through the special nectar producing cells present system.
on host flowers, Erwinia amylovora first multiplies on the
stigmatic surface.At high humidity, the bacteria enter the host flower
tissue through the nectarthodes located in the floral cup.

9. Entry through Insect Wounds
The entry through a wound does not require the formation of specialized
structures. some bacteria take the advantage of wounds caused by the insects
attack on plants. By the openings caused by the insects are utilized for the
entry of bacteria.
E. g: Crown gall of fruit trees and wilt of cucumber.
Fig 6:Wilt of cucumber

10. Entry through Wounds
During various cultivation operations and while harvest, transport
and storage, injuries to various plants parts are caused. Many
bacteria present in vicinity enter the host tissue.
E .g: Erwinia spp. causing soft rot of vegetables.
Agrobacterium tumefaciens causing crown gall of fruit trees.

11. Entry through lenticels
Lenticels are the raised pores that allow gas exchange across the bark
of woody plants.
E.g: The potato scab organism, Streptomyces scabies, gains entry into
the tubers through lenticels.
Fig 8: cross sectional view of lenticels
Fig 7.

12. Reference:
 Dr.Alice D, Dr.Jeyalakshmi C, Dr.Krishnamoorthy AS and
Dr.Karthikeyan M, 2017. Fundamentals of plant pathology,
A.C.Publication, Coimbatore
 http://www.apsnet.org/edcenter/intropp/pathogengroups/pages
/bacteria.aspx
 http://www.agriinfo.in/default.aspx

13. THANK YOU