Monitoring of Venturia inaequalis virulences

Collection of standardized and validated data

Data collection
Incidence and severity of scab on the differential hosts will be determined yearly at the end of the primary season and (optional) at the end of the season (harvest).
Severity will be assessed according to the modified scale of Lateur and Populer (1994, Table 3)

Table 3: Evaluation scale for severity (adapted from Lateur and Populer 1994)

Score		Definition of the symptoms		Proportion of affected organs* (%)
0		No observation (missing plant)		-
1		No visible symptom.		0 %
2		One or very few lesions detectable on close scrutiny of the tree.		0 to 1 %
3		Immediately apparent lesions  in general clustered in few parts of the tree		1 to 5 %
4		intermediate		x
5		Numerous lesions widespread over a large part of the tree.		± 25 %
6		intermediate		x
7		Severe infection with half of the leaves** badly infected by multiple lesions		± 50 %
8		intermediate		± 75 %
9		Tree completely affected with (nearly) all the leaves** badly infected by multiple lesions		> 90 %

*	leaves or fruits
**	or fruits

To down load the recommended scoring procedure
To down load the recommended scoring table

Validation of data
Particular attention will be given to the quality of the collected data. When scab is found for the first time on an accession at a specific place, this event has to be documented and verified as following:

Digital picture of a scabbed leaf

Test of the infected plant with the ECPGR SSRs to verify “true to typeness” of the plant (this check can also be outsourced).

Production of single spore cultures of virulent isolates or send the infected leaf to a partner (to be defined) responsible for isolation and conservation of the virulent isolates.