Nine important agronomic traits were used to assess the genetic diversity of Tunisian tall fescue and to investigate the extent of genotype X environment (GE) interaction and its implications for breeding programs. These traits were studied for three consecutive years in thirty-five spontaneous populations and three cultivars. Panicle size contributed to seeds production, while the plant height at harvest and dry matter yield were selected for forage performance. Analysis of variance demonstrated that population attitude depended on the year and environmental conditions. Principal component analysis revealed significant similarities among some spontaneous populations and cultivars. The relationship between environmental conditions and agronomic traits revealed the influence of altitude, soil texture and minimum temperature on forage production, seed yield, and the architecture of plants, respectively. In addition, the local adapted ecotypes originating from Bizerte, Sidi Nsir, and Rass Rajel attained greater agronomic potentialities than control cultivars and were of considerable economic interest for the improvement of Tunisian tall fescue. 1. Introduction Festuca L. is one of the largest genus in the Poaceae family with more than 400 species. The Tunisian natural flora is rich in diverse forage and pasture species including tall fescue [1, 2]. Tall fescue (Festuca arundinacea Schreb.), a perennial hexaploid species ( ) [3], has many positive agronomic characteristics and is widely used as a forage, pasture, and turf grass in the temperate and Mediterranean climates [4]. The species has many useful qualities but fails to provide sufficient energy for optimum animal performance, primarily because of modest digestibility (this depends on maturity). Its ability to grow on wet soils, to tolerate both alkalinity and salinity, and to produce heavy turf makes it an excellent grass for marginal sites for either forages or soil conservation purposes. In addition, tall fescue can be used flexibly in various farming systems, as it can be cultivated in monoculture or in association with legumes, in mixture with other grasses, grazed or cut, and made into hay or silage [5]. Excellent fall growth potential of Tunisian hexaploid accessions indicates that they might provide useful germplasm for breeding programs when crossed with European tall fescue [6]. In Tunisia, these phylogenetic resources are currently being lost due to severe genetic erosion associated overgrazing, irregular rainfall, and the loss of rangeland. Therefore, a survey of the genetic diversity in
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