Disease cycle of Alternaria in apple
Dalphy HarteveldPhD student (1st year)
Tree Pathology Centre
Tree Pathology Centre (A
gri-science QLD
& U
Q)
Principal supervisor:A/Prof. André Drenth (UQ&DEEDI)
Associate supervisor:Dr. Olufemi Akinsanmi (UQ)
Alternaria leaf blotch and fruit spot symptoms
Alternaria fruit spot symptoms
Premature defoliation in Royal Gala trees by Alternaria leaf blotch
Tree Pathology Centre (A
gri-science QLD
& U
Q)
Alternaria leaf blotch symptoms
Alternaria leaf blotch and fruit spot
Pathogen: Alternaria spp.
First report leaf blotch Stanthorpe 1990’s
Fruit losses (15–25 %) of high value apple varieties ‘Royal Gala’, Pink Lady™, ‘Fuji’ and ‘Red Delicious’.
Tree Pathology Centre (A
gri-science QLD
& U
Q)
Alternaria leaf blotch
Alternaria fruit spot
Problem
Erratic control of the diseases.
Identity of the Alternaria species involved is still uncertain.
No information on disease cycle.
Lack of understanding of the identity of the pathogen and its epidemiology in Australia hinders effective disease management
Tree Pathology Centre (A
gri-science QLD
& U
Q)
Elucidate the etiology and diversity of Alternaria leaf blotch and fruit spot of apples in Australia
Research Aims
Overwintering
Seasonal dynamics inoculum
2. Disease cycle
Sources of inoculum
1. Pathogen
Diversity
Distribution
Identity
3. Infection process
leaf
fruit
Tree Pathology Centre (A
gri-science QLD
& U
Q)
Climatic requirements
The pathogen
1. What is the identity/ diversity of the Alternaria species involved in causing the diseases?
2. What is the geographical distribution of the species?
3. Do the same species infect both leaf and fruit?
Tree Pathology Centre (A
gri-science QLD
& U
Q)
The pathogen
Most reported: Alternaria mali (Alternaria alternata f.sp. mali, Alternaria alternata apple pathotype)
In Australia anecdotal reports: Species not A. mali, but species of the A. alternata-complex.
Species within complex: A. alternata, A. infectoria, A. arborescens and A. tenuissima
Tools for identification: DNA Sequencing Morphology: species specific sporulation patterns
Tree Pathology Centre (A
gri-science QLD
& U
Q)
Identity and diversity of Alternaria species
Tree Pathology Centre (A
gri-science QLD
& U
Q)
DNA Sequencing genes:
- EndoPG (endopolygalacturonase)(Peever et al. (2004))
- Alt a1 (Hong et al. (2005))
Alternaria species could be differentiatedinto 2 groups
A. tenuissima/ A. alternata
A. arborescens
Disease cycle
1. What are the sources of inoculum in the orchard?
2.When during the season are symptoms expressed in the orchard?
3. What climatic conditions may influence inoculum production and infection?
Tree Pathology Centre (A
gri-science QLD
& U
Q)
Source of inoculum
Scherm H, Savelle AT, Boozer RT, Foshee WG (2008) Plant Disease 92(1), 47-50
Three orchards at Applethorpe, Queensland.
Monthly sample collection of 3 trees per orchard from July 2010- March 2011
Numbers of Alternaria spp conidia determined using a method from
Scherm et al. (2008)
Tree Pathology Centre (A
gri-science QLD
& U
Q)
Source of inoculum
Autumn
Summer
Spring
Winter
161
91
25
No leaves yet
Canopy leaf
102
161
103
41
Twigs
No buds
No buds
No buds
0
Buds
1053
Residueremoved
1969
6841
Leaf residueSeason
Sources of inoculum and average quantities of Alternaria spp. conidia per cm²
Tree Pathology Centre (A
gri-science QLD
& U
Q)
Disease incidence35.0
Alternaria fruit spot : end of January 2011- harvest February 2011
Alternaria leaf blotch disease incidence
A
Tree Pathology Centre (A
gri-science QLD
& U
Q) 0.0
5.0
10.0
15.0
20.0
25.0
30.0
Nov-10 Dec-10 Jan-11 Feb-11
% D
isea
se In
cide
nce
C
Fruit set Harvest
Climate
Climate data obtained from Bureau of Meteorology (Applethorpe station)
Tree Pathology Centre (A
gri-science QLD
& U
Q) 0
5
10
15
20
25
30
Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 Dec-10 Jan-11 Feb-11
Tem
pera
ture
(ºC
) /%
Dis
ease
inci
denc
e
0
5
10
15
20
25
30
35
40
45
50
Day
s
Rain days
Mean temperature
Alternaria leaf blotch disease incidence
Tree Pathology Centre (A
gri-science QLD
& U
Q)
Fungus overwinters in leaf residue and twigs
Multiple Alternaria species involved
Symptom development
Leaf blotch: Nov–Feb
Fruit spot: end Jan-Feb
Temperature ± 20ºC + high rainfall
Disease cycle of
Alternaria in apple
Dispersal?
Infection?
AcknowledgementsTree Pathology Centre (A
gri-science QLD
& U
Q)