So, in 2017, I grew a Carolina Cross #183 watermelon plant (probably a cross of one, though, since it was from seeds I saved in 2016). Anyway, it started getting a nice-sized fruit, but it got BER. I saved the seeds, and wanted to find out if seeds from BER fruits were more or less likely to get BER themselves. I grew some of those seeds, this year, and the only fruit has BER. So, this isn't conclusive, but it doesn't look like it builds resistance, so far (none of my other watermelons this year have BER).
BER stands for blossom end rot.
Location: SW Idaho, USA
USDA hardiness zone: 6
Elevation: 2,260 feet Profile post