QTL analysis reveals the genetic architecture of domestication traits in Crisphead lettuce

Abstract

The genetic architecture of crop domestication is generally characterized by three trends: relatively few genomic regions with major QTL effects are involved, QTL are often clustered, and alleles derived from the crop do not always contribute to the crop phenotype. We have investigated the genetic architecture of lettuce using a recombinant inbred line population from a cross between a crop Lactuca sativa ('Salinas') and its wild relative L. serriola. Few genomic regions with major QTL, plus various intermediate QTL, largely control the transition from wild to cultivated Crisphead lettuce. Allelic effects of all major QTL were in the expected direction, but there were intermediate QTL where the crop contributed to the wild phenotype and vice versa. We found two main regions with clusters of QTL, one on linkage group 3, where the crop allele induced lower seed output, another on linkage group 7, where the crop allele caused a delay in flowering time. Potentially, knowledge of genetic changes due to the domestication could be relevant for the chance that a transgene inserted in a crop genome will spread to wild relatives due to hitchhiking effects. If a transgene would be inserted in one of these regions, background selection on the crop alleles may lead to a reduced fitness of hybrids with the transgene. QTL research on the effects of domestication genes can thus indicate regions in the crop genome that are less likely to introgress, although these still need to be verified under field conditions.

Abiotic stress QTL in lettuce crop–wild hybrids: comparing greenhouse and field experiments

“…Furthermore, this region is known to be correlated with QTL for leaf shape and seed output traits (Hartman et al. ). We suggest that the combination of the growth response and this earlier found leaf shape QTL indicates that the transition from narrow wild‐type leaves to broad cultivated type leaves has coincided with a reduction in support tissues and an increase in water contents of the leaves of the crop (de Vries ).…”

“…These regions coincide with QTL clusters identified in earlier experiments for morphological and general fitness‐related traits (Hartman et al. , ; Uwimana et al. ,b).…”

“…Such a mosaic of QTL under general “field” conditions was detected for growth‐related traits in lettuce (Hartman et al. , ,b). Here, we will investigate the response to single stress conditions individually.…”

“…These results are opposite to the mosaic of small‐ to medium‐effect QTL found in field studies, referred to above, in the same species (Hartman et al. , ,b).…”

“…In previous work, we used this RIL population to study neutral morphological traits in the greenhouse, such as leaf morphology, bolting and flowering time, and seed morphology (Hartman et al. ). Moreover, we studied demographic and reproductive traits under natural field environments (Hartman et al.…”