Geographic patterns of histone H1 encoding genes allelic variation in Aegilops tauschii Coss. (Poaceae)

An electrophoretic analysis of histone H1 of Aegilops tauschii was carried out using the collection of 303 accessions (156 of ssp. tauschii and 147 of ssp. stangulata) representing all the species range. Three, four and six allelic variants were found for Hst1, Hst2 and Hst3 locus, respectively. The level of histone H1 allelic variability in ssp. strangulata was considerably higher than in ssp. tauschii. Expected heterozygosity (H_E) for the loci Hst1, Hst2 and Hst3 made up 0.066, 0.484 and 0.224 respectively in ssp. strangulata vs. 0.024, 0.051 and 0.214 in ssp. tauschii. Besides the most common haplotype, Hst1 ¹⁰⁰⁰, Hst2 ¹⁰⁰⁰, Hst3 ¹⁰⁰⁰, five other haplotypes with frequencies of occurrence higher than 0.02 were found in ssp. strangulata, and only one such haplotype—in ssp. tauschii. The most part of histone H1 variation in ssp. tauschii was in the western part of the area. In ssp. strangulata, the alleles Hst2 ⁹⁸⁸ and Hst2 ⁹⁷³ were found only in Caucasia, and the allele Hst1 ¹⁰⁴³—only in Precaspian Iran and south-eastern Azerbaijan. Histone H1 variation patterns in Ae. tauschii are very similar to those of non-coding sequences of chloroplast DNA. Therefore, histone H1 allelic variation in this species seems to be mostly neutral. Nevertheless, the evidences were pointed out, revealing that some part of variation at Hst2 locus in ssp. strangulata could be adaptive. It seems that Hst2 ¹⁰²⁶ allele is disadvantageous in western Precaspian Iran, the region with the high annual rainfall, and being eliminated by natural selection.