Genetic erosion in crops: concept, research results and challenges

TLDR

Genetic erosion refers to the loss of crop genetic diversity caused by agricultural modernization, manifesting as a bottleneck that first replaces landraces with modern cultivars and then further reduces diversity through breeding practices, affecting crop, variety, and allele levels. This paper reviews differing perspectives on the concept of genetic erosion in crops. The authors survey recent literature on methods for measuring genetic erosion in crops. The most useful definition of genetic erosion is a reduction in allelic evenness and richness, which should be considered alongside variety-level events; the literature suggests that modernization reduces diversity by replacing landraces with modern cultivars, after which diversity stabilizes.

Abstract

The loss of variation in crops due to the modernization of agriculture has been described as genetic erosion. The current paper discusses the different views that exist on the concept of genetic erosion in crops. Genetic erosion of cultivated diversity is reflected in a modernization bottleneck in the diversity levels that occurred during the history of the crop. Two stages in this bottleneck are recognized: the initial replacement of landraces by modern cultivars; and further trends in diversity as a consequence of modern breeding practices. Genetic erosion may occur at three levels of integration: crop, variety and allele. The different approaches in the recent literature to measure genetic erosion in crops are reviewed. Genetic erosion as reflected in a reduction of allelic evenness and richness appears to be the most useful definition, but has to be viewed in conjunction with events at variety level. According to the reviewed literature, the most likely scenario of diversity trends during modernization is the following: a reduction in diversity due to the replacement of landraces by modern cultivars, but no further reduction after this replacement has been completed.