Flowering Time Diversification and Dispersal in Central Eurasian Wild Wheat Aegilops tauschii Coss.: Genealogical and Ecological Framework

Abstract

Timing of flowering is a reproductive trait that has significant impact on fitness in plants. In contrast to recent advances in understanding the molecular basis of floral transition, few empirical studies have addressed questions concerning population processes of flowering time diversification within species. We analyzed chloroplast DNA genealogical structure of flowering time variation in central Eurasian wild wheat Aegilops tauschii Coss. using 200 accessions that represent the entire species range. Flowering time measured as days from germination to flowering varied from 144.0 to 190.0 days (average 161.3 days) among accessions in a common garden/greenhouse experiment. Subsequent genealogical and statistical analyses showed that (1) there exist significant longitudinal and latitudinal clines in flowering time at the species level, (2) the early-flowering phenotype evolved in two intraspecific lineages, (3) in Asia, winter temperature was an environmental factor that affected the longitudinal clinal pattern of flowering time variation, and (4) in Transcaucasus-Middle East, some latitudinal factors affected the geographic pattern of flowering time variation. On the basis of palaeoclimatic, biogeographic, and genetic evidence, the northern part of current species' range [which was within the temperate desert vegetation (TDV) zone at the Last Glacial Maximum] is hypothesized to have harbored species refugia. Postglacial southward dispersal from the TDV zone seems to have been driven by lineages that evolved short-flowering-time phenotypes through different genetic mechanisms in Transcaucasus-Middle East and Asia.

Differential effects of Aegilops tauschii genotypes on maturing-time in synthetic hexaploid wheats

“…Previously, our group reported that extensive floweringtime variation was present among Ae. tauschii accessions (Matsuoka et al 2008). Early-flowering Ae.…”

Natural variation of morphological traits in wild wheat progenitor Aegilops tauschii Coss.

“…The early-flowering accessions spread mainly in eastern habitats such as Afghanistan and Pakistan, implying that the early-flowering phenotype contributed to eastward dispersal and adaptation to these habitats in Ae. tauschii (Matsuoka et al 2008).…”

Allelic variation of row type gene Vrs1 in barley and implication of the functional divergence

“…Although no appropriate cline, such as the geographic clinal pattern of flowering time found in the natural population of wild wheat Aegilops tauschii Cross. (Matsuoka et al 2008), was detected in wild barley population at this moment, some of the VRS1 isoforms which involve SAPs within well-conserved motifs are limited in their geographical distribution (Table 3). It is, therefore, possible that the function(s) of HvHox1 in wild barley may include adaptation to specific ecological conditions.…”