@duylinh
@Leo80221
*edit added links*
Really it comes down to how much similarites the Isekai world have with our own.....
Some Isekai have totally new fruits and grains that is described by the main character as mixs of diffrent fruits and/or veggies because he himself lack the means to describe them otherwise.
Also slective breeding the best crops and animals to genetically modify them have been a thing for thousands of years, and while nowhere near as effective as today it have been effective in a lot of things and don't really need much technology to do properly.
Some examples of crops can be found to have been selectively bread as far back as 8000 BC so its not that strange to find crops with similar fetures as we have.
Potatoes, carrots and corn being prime examples of old stuff being selectively breed.
And a lot of the problems can be fixed with magic and is usually the excuse for Isekai worlds being less advanced in the first place.
That said sellective breeding have not allways turned out well.
A good example of breeding gone wrong is the giant mess that is the bulldog.
They used to be able to kill bulls (
altho usually with something preventing the bull from just running way, look up bull baiting if you want to learn more )
Now they are a sloppy mess of skin and bone problems that can´t even give birth without killing themselves unless given surgical help to do so.
Overall it adds to the imersion if there are familiar things in the fantasy world to relate too.
But yeah, most of the time its just because people are lazy and don't want to reinvent the wheel with new crops and stuff.
As for meat, dried/salted/smoked meat can be preserved for a long time and is super old and super basic level of tech.
Fresh stuff on the other hand have allways been hard to come by unless its grown in the area or you are super rich like the nobles usually are.
I actually know a few Isekai manga´s that do adress this tho.....
here is a example of one. ( this one deals with fresh fish being rare in a land locked city )