Xanthomonas arboricola pv. juglandis (Xaj) - Cost 873

Evaluation of selections of native walnuts
from Asturias for susceptibility to
Xanthomonas arboricola pv. juglandis (Xaj)
in controlled environment
M.M. López 1 , D. Frutos 2 , C. Moragrega 3 , A. Arrieta 4 , D. Cambronero 2 (†),
A. Carrillo 2 , G. López 2 , C. Lacasa 2 , C. Frutos 2
1
Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Valencia.
2
Instituto Murciano de Investigaciones Agrarias y Alimentarias (IMIDA), Región de Murcia.
3
Instituto de Tecnología Agroalimentaria (INTEA), Girona.
4
Consejería de Medio Ambiente y Desarrollo Rural, Asturias.

OBJECTIVE
First evaluation of 25 walnut genotypes
selected in Asturias, (Spain) against
Xanthomonas arboricola pv. juglandis
­Plant inoculation: leaves and stem
­Looking for resistance: high
inoculum concentration

•Two strains of X. arboricola pv. juglandis
from Spain
•Four treatments: bacterial
suspensions at two concentrations
(10 8 and 10 6 cfu/ml) with and
without diatomaceous earth
•Spray inoculation of the
leaves and two wounds
inoculated in the stems
•Negative control with
buffer

MATERIALS AND METHODS
•Amigo selected as susceptible control
•Twenty-five selected genotypes
grafted on February 2007 onto oneyear-old
seedlings of Juglans regia
•Grafted trees growing in greenhouse
•Inoculations performed in early June
2007

•Pots covered with plastic film and conserved
in a controlled room for 30 days
•Temperature 25-26ºC,
RH 90-95%
•Plants were lied down
in lighted shelves
•After 7, 15 and 30 days, evaluation of the
lessions (10 leaves/plant and two wounds)

Scale of severity
Symptoms on leaves
0 No symptoms
1 From one to ten lessions/leaf
or 75% leaf surface affected
Severity per leaf or plant
N
S = ∑ In . 100
n=1
N.I max

Scale of severity in wounds
0 1 2 3 4

Symptoms on
leaves
RESULTS
Average and confidence intervals
(P

Scale leaves
RESULTS
Leaf symptoms: average and
confidence intervals (P

Stem wounds
RESULTS
Wound symptoms: average and
confidence intervals (P

RESULTS
Evolution of symptoms: average and
confidence intervals (P

RESULTS
•No significant differences among treatments
(different bacterial concentrations and with or
without diatomaceous earth). All of them were
significantly different from the controls
•Any selection was resistant to Xaj in the
assayed conditions
•Significant differences were observed among
selections: seven of them were less susceptible
than Amigo in leaves
•Significant differences between Amigo and
four selections in wound inoculation
•Three selections: As1, As17 and As24
showed very low susceptibility

CONCLUSIONS
•Evaluation of susceptibility of leaves and
stems of walnut selections can be performed
in young plants under controlled conditions
•The methodology utilised has demonstrated
the lack of resistance in the evaluated
selections
•However, differences in susceptibility were
observed
•Further inoculations with lower bacterial
concentrations and less favourable conditions
will be performed with some selections
•Fruit susceptibility will be also evaluated

THANKS FOR
YOUR
ATTENTION!!