Spatial and temporal genetic structure of wild emmer wheat in Jordan. II. High-molecular-weight glutenins and allozymes

A study was designed to sample and characterize 12 populations of wild emme r wheat in Jordan at the high-molecular-weight (HMW) glutenin and allozyme levels. Data were collected and individual plants were sampled from 207 per manent sampling points in three central, three peripheral, and six marginal populations during all or part of a five-year study period. Patterns of va riation, based on four HMW-glutenin and 36 allozyme loci, were used in char acterizing these populations. Polymorphisms, based on HMW-glutenins and all ozymes, decreased with increasing aridity of the collection site. A large p ortion of the HMW-glutenin(61.1%) and allozyme (62.7%) variant alleles were localized. Gene differentiation estimates, based on HMW-glutenins and allo zymes among (60.8 and 65.8%, respectively) and within (39.2 and 34.2%, resp ectively) populations, were high and comparatively similar; however less va riation was partitioned among the Jordanian populations when compared to po pulations in the more mesic parts of the Fertile Crescent. Environmental he terogeneity may have been involved in generating significant spatial struct uring in these populations at the HMW-glutenin and allozyme levels. A gradu al increase in allozymic monomorphism with aridity suggests that polymorphi sm is more likely to be found in, heterogeneous environments. Changes in po pulation size and total loss of small populations are warning signs that th ese populations may be vulnerable. Results of the present study are expecte d to complement the existing body of knowledge on the species and enhance t he understanding of its genetic differentiation and evolution across large parts of the Fertile Crescent. The preservation of the endangered, and yet valuable, genetic diversity present in Jordanian wild emmer wheat populatio ns, as an integral part of a holistic regional approach to biodiversity con servation, is urgent.