Quote:
Originally Posted by Fusion_power
Strong statements because they are needed Carolyn. I went through my garden with a notepad this year to see which were and which were not disease tolerant to any extent. Both potato leaf and regular leaf plants were equally affected by septoria and early blight. In other words, there was no association between tolerance and leaf form. There were individual varieties that handled disease better on average and kept producing longer. Eva Purple Ball is a very good example. Note that it is regular leaf. Bloody Butcher is a potato leaf example. In the end, all of them went down to disease. The only exceptions in my garden were the two S. Pimpinellifoliums that I kept seed from last year and the S. Habrochaites that I saved seed from last year. The Pimpinellifoliums eventually go down to septoria, but they keep producing a few fruit and they stay alive by producing new foliage at the growing tips of the vines.
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I agree completely. Whatever the reason some gardeners have anecdotal evidence that one leaf type is more resistant to certain fungal pathogens than others certainty can't be duplicated in every garden. On another thread I said that Sungold had the worst resistance to Septoria than other varieties in my garden. Some agreed and some had the opposite opinion. I expected as much.
Just like other fungi and oomycete out there in the wild there are different strains of Septoria. some more virulent than others. I think that all of us that are confronted with Septoria every year in our gardens probably don't have the same strains present every year.
I think pathogen resistance all comes down to chemistry. All plants produce chemicals that protect it from certain diseases. On top of that beneficial bacteria and fungi that colonize plants add to that resistance by their own chemical means. Whether a pathogen is successful or not at infecting a plant depends on it's ability to defeat enough of those chemical barriers.
For example, one mechanism that tomato plants have is production of alpha-tomatine, a saponin that is very toxic to fungal pathogens, but tomato pathogens like Septoria, Early Blight, Late Blight and Fusarium all have something in common, they defeat this one barrier by producing tomatinase, an enzyme that detoxifies alpha-tomatine. Even non-pathogenic fungi produce it which allows them to colonize tomato plants.