Genetic diversity of drought-responsive genes in populations of the desert forage Dactylis glomerata Ricardo Trejo-Calzada a , Mary A. O’Connell b, * a Universidad Auto ´noma Chapingo, Durango, Me ´xico b Department of Agronomy and Horticulture, New Mexico State University, MSC 3Q, P.O. Box 30003, Las Cruces, NM 88003, USA Received 16 September 2004; received in revised form 18 January 2005; accepted 20 January 2005 Available online 2 February 2005 Abstract Restriction fragment length polymorphisms were used to estimate genetic diversity in six populations of Dactlylis glomerata collected in two different geographical locations in Israel. The objective of this study was to test the hypothesis that drought-responsive genes would have a higher genetic diversity in populations adapted to arid environments. Drought-responsive and non-responsive genes were isolated as cDNAs from leaves of D. glomerata. These cDNAs were used as probes on genomic Southern blots. Populations of D. glomerata collected in the southern arid region of Israel had greater genetic diversity for drought-responsive genes (0.388, repressed; 0.340, induced) than populations of plants collected in the northern Mediterranean region of Israel (0.308, repressed; 0.314, induced). The populations collected in the Mediterranean region had greater genetic diversity for the genes that were non-responsive to drought (0.185 versus 0.086). The gene flow between populations was relatively high, 2.47 for induced, 1.96 for repressed and 3.5 for non-responsive genes. These results suggest that plant conservation analyses should also consider stress responsive genes in estimates of genetic diversity, to select populations for conservation. # 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Central and peripheral populations; Orchard grass; Desertification; RFLP 1. Introduction Dactylis glomerata (orchard grass) is a perennial, cross- pollinated species native to Mediterranean areas of Europe. This species comprises a natural polyploidy complex distributed throughout Eurasia. The complex is composed of three ploidy levels that include 15 diploid (2n =2x = 14), three widespread tetraploid (2n =4x = 28), a few localized tetraploid and one hexaploid (2n =6x = 42) subspecies. This complex has been introduced to most other temperate regions of the world because of its high agronomic value [15]. It can now be found widely distributed around the world in different habitats. Some forms of this species are cultivated, while other wild forms are used for livestock feeding in Mediterranean and semi-arid lands. Drought or reduced water availability is the main factor limiting crop production [1]. Droughts are now more frequent and severe in large regions of the world because of desertification processes [2,3]. Global desertification con- stitutes a significant risk for the persistence of native populations of plants [4]. Some plant species have morphological, physiological and/or biochemical mechan- isms that allow the organisms to grow and reproduce in drought-prone areas. Understanding the genetic bases for the persistence of certain populations in the face of environ- mental change or stress has agronomic as well ecological implications [5,6]. Genes involved in the responses of plants to short-term and season-long water deficit have been studied in great detail in many agronomic plants but in much less detail in native plants. Genes induced during drought stress are involved in the movement of water across membranes, turnover of proteins, detoxification, synthesis of osmolytes, www.elsevier.com/locate/plantsci Plant Science 168 (2005) 1327–1335 * Corresponding author. Tel.: +1 505 646 5172; fax: +505 646 4681. E-mail address: moconnel@nmsu.edu (M.A. O’Connell). 0168-9452/$ – see front matter # 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.plantsci.2005.01.010