How combining beneficial traits can have negative consequences

How combining beneficial traits can have negative consequences


so our work in tomato over the last
several years stumbled upon an interesting case of where domestication and
breeding has led to negative interactions between beneficial
mutations and what we found is that there was a mutation that arose in the
gene thousands of years ago that benefitted one particular trait for the
production of tomato and this became widespread in the tomato breeding germ
plasm as it’s called to the point where it was represented in more than 90
percent of all the breeding material that currently exists then about 70
years ago a new mutation arose that had a benefit for a separate trait and when
breeders attempted to work with this new mutation that they discovered they found
that by crossing it into the other varieties they had a dramatic negative
interaction on productivity specifically what happened is that the plant started
to over produce flowers by making too many branches on the flowering shoots
known as inflorescences and normally this would be considered a beneficial
trait more flowers more fruits coming from more branches but in fact this
leads to an imbalance in the production of vegetative aspects of growth and
reproductive aspects of growth and this imbalance shifted towards more
reproductive aspects of growth flower production is so extreme that the plant
can’t handle setting all of those flowers into fruits and leading to
higher yield so in fact by breeding with the new
beneficial mutation in the background of the old beneficial mutation you actually
had a reduction in yield so when we decided to understand this negative
interaction this epistasis between these two beneficial mutations that together
gave a negative effect on the plant we’re able to dissect the genetic
interaction identify the specific genes and mutations that were responsible and
essentially neutralize that negative interaction even more than that once we
identified the genes and identify the specific mutations once we neutralize
those negative interactions we understand the genetic architecture of
how these genes were working together to control flower production
and we were able to then exploit the system by mixing and matching the genes
in precise ways through natural crosses and this natural crossing and mixing of
these mutations or combining of these mutations in different ways than
breeders had done previously allowed us to create very weakly branched
inflorescences in other words you’re not causing as much of an imbalance on
the plant between vegetative and reproductive growth this weak branching
then translates to a nice bump in flower production and this bump and flower
production then translates to higher yield

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