Diversity of drought-responsive genes in central and peripheral populations of Dactylis glomerata and Trifolium purpureum

Natural populations of plants of arid lands are threatened by drought. Droughts are increasing in frequency and severity in many parts of the world as a result of desertification and global change processes. A greater extension and intensity of droughts may cause loss of genetic diversity and biodiversity. Loss of genetic diversity and biodiversity has strong agronomic and ecological impacts. Therefore, it is necessary to understand the ways that natural populations of plants respond to deal with drought. Knowledge of gene diversity and genetic structure of natural populations of plants in arid regions will identify which populations to maintain to establish sustainable programs of conservation. In this work DDRT-PCR, differential screening of cDNA libraries, random picks of cDNA libraries and northern analysis were used to isolate and characterize drought-responsive genes in populations of Dactylis glomerata (n = 120) and Trifolium purpureum ( n = 120). Drought-responsive genes were used as probes to perform RFLP analysis on DNA from plants of central and peripheral populations of D. glomerata and T. purpureum. RFLP data was used to perform analysis of molecular variance and estimate F-statistics, gene diversity and gene flow. Thirteen drought-responsive genes were isolated from D. glomerata. Nine drought-responsive genes were isolated from T. purpureum. Diversity of drought-responsive genes was high in both D. glomerata and T. purpureum populations, with average values of H = 0.36 and H = 0.269, respectively. Diversity of drought-induced genes and drought-repressed genes was significantly greater in peripheral populations than in central populations of D. glomerata. Diversity of drought-repressed genes was significantly greater in peripheral than in central populations of T. purpureum. In both species the highest variation of gene diversity was among populations. Variation among populations of drought-induced and drought-repressed genes accounted for ∼80% of the total variation in D. glomerata, and for 87% in T. purpureum. A conservation program should include samples of every population and give special attention to peripheral populations as a potential resource for breeding programs for drought tolerance.