An evaluation of germination efficiency in a range of genotypes of Thymus species differing in susceptibility to drought

Abstract

The aim of this study was to compare the germination of a range of Thymus genotypes subjected to different levels of drought stress, in order to identify differences in germination response to water stress, important to inform plant breeders aiming to produce more drought tolerant crops. Germination is the first, and arguably the most important and vulnerable stage in the life cycle of plants. Thymus spp seeds from a range of genotypes were germinated under four external osmotic potentials (0, -2, -4 and -6 Bar) imposed using appropriate concentrations of PEG6000. Following 10 days of exposure to drought, fresh weight, dry weight, radicle and plumule length, water content, percentage germination and germination time were recorded. There was considerable variation between the genotypes in their response to drought. Under mild stress (-2 bar) T. serpyllum and T. vulgaris (Iran) were more tolerant than other varieties. However, under moderate stress (-4 bar), T. serpyllum (Spain) was the most tolerant. Under -6 bar (severe stress), T. vulgaris (Spain), T. zygis (Spain) and T. kotchyanous (Iran) were scored as tolerant.