Tomato blight

Barry South writes:

Pink 6 and Blue 13 10, Principe Borghese 0

Is it a football score line or a code for invasion plans? If it was a football score it would be more like rugby than soccer and if it’s a code it would be a challenge for Alan Turing and the Bletchley Park team. In fact it represents my attempt last year to grow tomatoes and I now know how Napoleon must have felt after Waterloo.

Pink 6 and Blue 13 are the strains of potato blight that massacred last year’s tomato crop. A warm and dry early summer encouraged my tomato plants into good growth and then the rains came. My beautifully lush and green plants turned into a black mush in two weeks!

Nothing made it to red but with gardening you definitely have to accentuate the positive so green tomato chutney was the solution! I would much prefer to make it at the end of the season just before the first frosts cut down the remaining plants.

My plan for this year, to eliminate the negative, is to grow blight resistant tomatoes with ph2 and ph3 genes that confer resistance to both early and late blight. Early blight has not been a problem but late blight, particularly in a season like last year where the conditions were near ideal, now seems to be a bigger problem for tomatoes than potatoes.

Blight tolerant varieties have been around for a few years but recently plant breeding has produced varieties that are claimed to be resistant. We can make that claim with more knowledge of the genetic background to tolerance and resistance. Modern techniques for gene sequencing and manipulation have allowed the identification of specific gene sequences that tell us about the mechanism of disease and resistance.

Crimson crush

In this case, however, blight resistance came about through the more traditional route of field observation of a chance mutation. A PhD student from Bangor University, James Stroud, noticed the green plant amongst the brown and the plant breeder Simon Crawford was able to produce the variety Crimson Crush.

This year I will be trying out Crimson crush, magic mountain and lizzano as a trailing tomato. The cost of seed is quite high at something like £3.50 for 10 F1 seeds so you really need that propagator to ensure good germination.

It feels a bit sad to be abandoning the varieties like Moneymaker and Alicante that I grew with my father in our greenhouse at home, but sometimes there is a good reason beyond marketing and harvesting why heritage varieties fall from favour. In the biological “arms race” pests and diseases simply catch up and overtake them and we respond by looking for disease resistance.

Looking at the seed catalogues we can get very enthusiastic over all colours and sizes of tomato from purple to yellow and from beefsteak to cherry but if they aren’t at least tolerant to blight then you may be in for bitter disappointment.