Abstract
Polyploidization is a major evolutionary process. Approximately 70–75% species of Triticeae (Poaceae) are polyploids, involving 23 genomes. To investigate intergenomic rearrangements after polyploidization of Triticeae species and to determine the effects of environmental factors on them, nine populations of a typical polyploid Triticeae species, Kengyilia thoroldiana (Keng) J.L.Yang et al. (2n = 6x = 42, StStPPYY), collected from different environments, were studied using genome in situ hybridization (GISH). We found that intergenomic rearrangements occurred between the relatively large P genome and the small genomes, St (8.15%) and Y (22.22%), in polyploid species via various types of translocations compared to their diploid progenitors. However, no translocation was found between the relatively small St and Y chromosomes. Environmental factors may affect rearrangements among the three genomes. Chromosome translocations were significantly more frequent in populations from cold alpine and grassland environments than in populations from valley and lake-basin habitats (P<0.05). The relationship between types of chromosome translocations and altitude was significant (r = 0.809, P<0.01). Intergenomic rearrangements associated with environmental factors and genetic differentiation of a single basic genome should be considered as equally important genetic processes during species' ecotype evolution.
Highlights
Polyploidization is a major evolutionary process that can generate species reproductively isolated from their diploid progenitors
Analysis of rearrangements among St, P and Y genomes A wide range of St, P and Y chromosome translocations were identified using genome in situ hybridization (GISH) (Fig. 1)
The frequency of P and Y; (P/Y) chromosomal translocation (22.22%) was significantly higher than that of P and St; (P/St) (8.15%) translocation, and no translocation was found between the St and Y chromosomes
Summary
Polyploidization is a major evolutionary process that can generate species reproductively isolated from their diploid progenitors. An entirely different trait can result in increased rates of polyploidization and increased evolutionary ‘‘success’’ [1]. 50–70% of angiosperm species have polyploid origins [2,3,4]. Grant [5] proposed that 47% of all flowering plants were of polyploid origin, and that 58% of monocots and 43% of dicots were polyploid. Polyploid species have a greater potential to adapt to a wider range of habitats and demonstrate better survival in unstable climates than their diploid progenitors, suggesting that polyploidy confers enhanced fitness [11,12,13]. Polyploids are more common than diploids at higher latitudes and altitudes [14]
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