Varieties resistant to tomato leaf mould

Identifying and growing varieties with known resistance to tomato leaf mould (Passalora fulva) can counter its spread and maximise your crop yield.

Back to: Tomato leaf mould best practice

Resistant strains

Genetic resistance to P. fulva works on a gene-for-gene basis. Most commercial plant varieties list their claimed resistance, or lack of it, to tomato leaf mould. This is expressed as ‘A–E’, where strains are grouped – please see Table 1.

But novel strains of the pathogen have recently been identified in Japan, China, Korea and Poland where no varietal resistance currently exists.

There is a concern that these strains will spread further west to the Netherlands and the UK.

One nursery reported that every variety grown except Avalantino showed infection with P. fulva to differing degrees. Avalantino does claim resistance to A–E, but several of the other varieties grown also did. This indicates Avalantino contains additional resistance genes not claimed by the breeder that may offer hope for the future.

Table 1. Race groups of tomato leaf mould (A-E) and their ability to overcome five Cf resistance genes

Leaf mould race group	Tomato resistance genes
Leaf mould race group	Cf-1	Cf-2	Cf-3	Cf-4	Cf-5
A	S	S	S	R	R
B	(S)	R	(S)	S	R
C	(S)	S	(S)	S	R
D	R	R	R	R	S
E	R	S	R	S	S

S – susceptible interaction; (S) – race group can sometimes overcome this resistance gene; R – resistant interaction

Best practice

If you know tomato leaf mould infection is likely to occur and you have struggled to control the disease in the past, growing a variety that does not claim any resistance would be unwise. So, where possible, you should grow varieties with known resistance to the disease.

Growers who suffered significant issues with tomato leaf mould in the past experienced no infection when they then used resistant varieties.

Whatever varieties you plan to grow, make sure you put an effective plan in place to minimise risk of tomato leaf mould infection and limit its spread.