Data from: Introgression from modern hybrid varieties into landrace populations of maize (Zea mays ssp. mays L.) in central Italy

Landraces are domesticated local plant varieties that did not experienced
a deliberate and intensive selection during a formal breeding programme.
In Europe, maize landraces are still cultivated, particularly in marginal
areas where traditional farming is often practised. Here, we have studied
the evolution of flint maize landraces from central Italy over 50 years of
on-farm cultivation, when dent hybrid varieties were introduced and their
use was widespread. We have compared an 'old' collection,
obtained during the 1950s, before the introduction of hybrids, and a
recent collection of maize landraces. For comparison, a sample of maize
landraces from north Italy, and of improved germplasm, including hybrids
and inbred lines were also used. A total of 296 genotypes were analysed
using 21 microsatellites. Our results show that the maize landraces
collected in the last 5-10 years have evolved directly from the flint
landrace gene pool cultivated in central Italy before the introduction of
modern hybrids. The population structure, diversity and linkage
disequilibrium analyses indicate a significant amount of introgression
from hybrid varieties into the recent landrace populations. No evidence of
genetic erosion of the maize landraces was seen, suggesting that in-situ
conservation of landraces is an efficient strategy for preserving genetic
diversity. Finally, the level of introgression detected was very variable
among recent landraces, with most of them showing a low level of
introgression; this suggests that co-existence between different types of
agriculture is possible, with the adoption of correct practices that are
aimed at avoiding introgression from undesired genetic sources.