Bolting and Flowering Response of Lactuca georgica, a Wild Lettuce Relative, to Low Temperatures

Abstract

To learn about the phenological adaptation of Lactuca georgica Grossh., a wild relative of domesticated lettuce, we studied seed sampled accessions obtained from individual plants at 19 locations throughout six regions in Armenia, and from two natural populations in Dagestan (Russian Federation) collected as bulk samples. The effects of various vernalization treatments on time to bolting, flowering and seed production time were investigated during four successive years at different growth stages of L. georgica plants. We demonstrate that low temperatures play a major role in stimulating the reproduction process of L. georgica plants. Our results would suggest that for L. georgica: 1) There is an obligatory (or nearly so) vernalization requirement; 2) Plant age, vernalization duration, and genotype of original sample have a role in bolting and flowering regulation; 3) Some plants behaved as typical annuals, responding to vernalization treatment at the seedling stage, but, most did not; 4) Four months of vernalization could be adequate to reach bolting in plants with a developed vegetative rosette, for most—but not all—samples; 5) In order to find the best solution for stimulating the reproductive process of multiple genotypes, it seems that further study should focus on about 4 - 6 months of vernalization at 4˚C applied to plants of about 10 - 22 months old vegetative rosettes, with controlled post-vernalization condition; 6) L. georgica germplasm could be used as a source for delayed bolting in breeding of domesticated lettuce varieties.