Still marveling and learning

Every once in a while I stub my toe on a piece of information that challenges my understanding of how the world works.

The first time that happened was when I read an academic article written by somebody who took a leaf from a Russet Burbank potato, used enzymes to dissolve the bonds holding the cells together and then cultured a brazillian plants, each from an individual cell.

My understanding, which was wrong, was that every plant would be identical or nearly identical. In fact, there was a radical amount of scatter. Some plants were short-and-squatty. Others were tall-and-lanky. Some were horrifically vulnerable to certain diseases. Others showed unexpected resistance.

The backstory is that the original seed that evolved into the Russet Burbank potato was planted in 1873. By the time of the experiment, more than 100 years of mutations had accumulated within the tissues of what we know as "Russet Burbank Potato". It is a chimera. An agglomeration of random mutations (the worst of which had been rogued out by the seed-potato producers), that in aggregate and from a distance seemed like a homogeneous and stable organism.

Consider an University of Alabama or Ohio State University home football game. From 5000 feet elevation, the crowd seems to be a homogeneous, reddish tinted mass. Only by zooming into a much more granular level do you see the random UK or Purdue fan muddying up the sea of scarlet or crimson. The macroscopic and the microscopic samples are very, very different.

The most recent case of stubbing my toe

Most recently, a paper on Fire Blight in apples and pears came across one of my feeds.

Pear cultivars had very high numbers of E. amylovora in the inoculated shoots as well as in non-inoculated shoots and stems (Fig. 7a and b). Fewer bacteria, but still up to 4.5*10^5 units per plant section, were found in the rootstocks.

My prior understanding was that if a susceptible variety was exposed to ANY Fire Blight, it would rage like wild-fire and kill the tree.

Since many of these trees were grafted on very susceptible root-stock, my prior belief was that resistant varieties would "cork off" or somehow encapsulate or compartmentalize the disease, much like humans wall off tuberculosis.

Resistant pear varieties do cork off the contagion but it is a very leaky dam. It appears that symptoms (and the cascading avalanche of pathogenic organism populations) of Fire Blight do not occur until after some threshold of contagion is exceeded, even in the roots of nominally "very susceptible" individuals.

There were rumblings and rumors of such with Covid-19 in humans. Severity of symptoms seemed to vary with the initial intensity of exposure. That makes a lot more sense in humans with active immune systems. A lower initial exposure gives our immune system time to drag templates back to our lymph nodes to use as patterns for antibodies. Our body tools-up antibody production while virus populations grow. A higher initial exposure gives the virus an almost unbeatable head-start.

But plants don't have adaptive immune systems like animals so there must be other mechanisms in-play. This may be over-thinking the problem. Choose scion varieties and root-stocks with some Fire Blight resistance and follow best-practices with regard to fertilizing and pruning. Don't go nuts with planting density. Life is complicated. There are many different strains of Fire Blight with varying degrees of virulence. A pear or apple variety might be immune to one strain of FB and susceptible to another while a different pear or apple variety might be exactly the opposite.