Genetic Diversity in A Core Subset of Wild Barley Germplasm

Yong-Bi Fu,Carolee Horbach

doi:10.3390/d4020239

Abstract

Wild barley [Hordeum vulgare ssp. spontaneum (C. Koch) Thell.] is a part of the primary gene pool with valuable sources of beneficial genes for barley improvement. This study attempted to develop a core subset of 269 accessions representing 16 countries from the Plant Gene Resources of Canada (PGRC) collection of 3,782 accessions, and to characterize them using barley simple sequence repeat (SSR) markers. Twenty-five informative primer pairs were applied to screen all samples and 359 alleles were detected over seven barley chromosomes. Analyses of the SSR data showed the effectiveness of the stratified sampling applied in capturing country-wise SSR variation. The frequencies of polymorphic alleles ranged from 0.004 to 0.708 and averaged 0.072. More than 24% or 7% SSR variation resided among accessions of 16 countries or two regions, respectively. Accessions from Israel and Jordan were genetically most diverse, while accessions from Lebanon and Greece were most differentiated. Four and five optimal clusters of accessions were obtained using STRUCTURE and BAPS programs and partitioned 16.3% and 20.3% SSR variations, respectively. The five optimal clusters varied in size from 15 to 104 and two clusters had only country-specific accessions. A genetic separation was detected between the accessions east and west of the Zagros Mountains only at the country, not the individual, level. These SSR patterns enhance our understanding of the wild barley gene pool, and are significant for conserving wild barley germplasm and exploring new sources of useful genes for barley improvement.

Highlights

Recent decades have seen an increasing research effort to conserve and explore germplasm of crop wild relatives [1,2]
These simple sequence repeat (SSR) patterns enhance our understanding of the wild barley gene pool, and are significant for conserving wild barley germplasm and exploring new sources of useful genes for barley improvement
Wild barley is fully inter-fertile with cultivated barley (Hordeum vulgare ssp. vulgare L.), is considered as the progenitor of cultivated barley, and forms part of the primary gene pool for barley improvement [13,14]

Summary

Introduction

Recent decades have seen an increasing research effort to conserve and explore germplasm of crop wild relatives [1,2]. Crop wild relatives are weedy plants closely related to crops, including their progenitors, harbour beneficial traits such as pest or disease resistance and high yield [3], and represent the best genetic hope for improving genetically impoverished cultivars for human food production [4,5]. Successful introgression of exotic disease- and pest-resistance genes from wild into cultivated plants of many crops has been well documented (e.g., see [6,7]). Its natural occurrence presumably is from the eastern Aegean islands and (possibly) Egypt over Middle East through Iran and eastward to Afghanistan, western Pakistan, and Tajikistan [11] This plant grows in a wide range of habitats such as meadows or mesic steppes to semiarid and arid regions and man-made habitats like abandoned fields and roadsides [12]. It has been known to harbor fruitful sources of beneficial genes for barley breeding such as those genes associated with disease resistance to powdery mildew [15], abiotic stress tolerance [16,17], important agricultural traits [18,19]

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