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Long-term persistence and, hence, agronomic success as a pasture of the annual species subterranean clover depend primarily on seed yield and seed survival over seasons . In natural populations, plant characteristics influencing seed setting and formation of seed reserves in the soil are expected to be `adjusted' to the prevailing environmental conditions of the sites of origin . Knowledge on plant/environment relationships may provide information on adaptive strategies of persistence, and guidelines for selecting adapted varieties to specific conditions. On pure lines from a number of populations such relationships were assessed for flowering time, seed yield, burr fertility, individual seed weight, initial hardseededness, and rate of hardseededness breakdown over summer . Flowering time decreased on decreasing annual rainfall, i .e ., on shortening the growing season, as adaptive response to the need of producing adequate seed before the onset of the dry season . Individual seed weight decreased on decreasing rainfall, and increasing temperatures . Hard-seed maintenance over summer was higher in populations from hot and dry environments, where the marked effect of temperature on hardseededness breakdown exerts a strong selective pressure . Within-population variation, assessed on flowering time, was particularly wide, with early genotypes occurring even in populations from long-season environments. The adaptive relevance of maintaining high levels of within-population polymorphism to cope with unpredictable climatic fluctuations is discussed. Number of constituent lines as a measure of the population structure, and intra-population variation were both influenced by altitude and rainfall, tending to decrease as the climatic selective pressure becomes severe, under both low-rainfall, hot conditions and high-elevation, cold-prone environments .

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alistic: the host provides the endophyte with shelter, nutrients, and an easy means of propagation; the fungus Tall fescue [Festuca arundinacea Schreb. var. arundinacea Schreb. improves its host survival through enhanced growth and (2n ϭ 6x ϭ 42)] breeding objectives are to exploit the natural variation fertility, better drought tolerance, increased resistance of the associated endophytic fungi and to select specific plant-fungus combinations that optimize the host fitness but do not cause detrimen-to pests and diseases, and a more efficient utilization of tal effects on grazing animals. This study investigated the presence soil nitrogen and phosphorus (Wilkinson and Schardl, of endophytes in 60 tall fescue natural populations from Sardinia, Italy; and short-conidia endophyte variants, the latter producing only about entiation, alkaloid pattern production, and conidia and 25% of the ergovaline produced by the former. A coevolutionary colony morphology, revealed remarkable morphologispecificity between the native Sardinian fescue germplasm and its cal and biochemical variation among isolates. They deassociated endophyte was suggested by the agreement between morscribed two new taxonomic groupings (FaTG ϭ Festuca phology of the host plant (distinct from germplasm originating in temperate environments) and morphological and biochemical charac-arundinacea Taxonomic Grouping) distinct from N. coeteristics of the harbored fungus.

Endophytic fungi may reportedly improve summer persistence in tall fescue (Festuca arundinacea Schreb.). The objective of this study was assessing whether endophytes contributed to better persistence in 2 climatically contrasting Italian locations (Sanluri, Mediterranean climate, 382 mm average rainfall; Lodi, subcontinental climate, 802 mm average rainfall). Twelve populations from Sardinia were evaluated for 4 years in each site with or without nitrogen application. The populations hosted either of 2 endophyte forms (long-conidia, Neotyphodium coenophialum; short-conidia, FaTG-2 group) and belonged to the European race of fescue (hosting N. coenophialum) or the Mediterranean race (hosting FaTG-2). Three European-race commercial varieties (hosting N. coenophialum) were included as controls. The evaluated material was present both in the endophyte-infected and the endophyte-free (after chemical treatment) status. Stand persistence was recorded at the end of each year. The effect of the endophyte presence on persistence was nil in the Mediterranean site and slightly positive in the subcontinental location. Populations of the 2 geographic races had contrasting behaviour in the 2 sites irrespective of their endophyte status. The Mediterranean-race populations persisted well in the Mediterranean environment but not in the subcontinental one, and the reverse occurred for the European-race germplasm (including the controls). The results suggest that Mediterranean conditions may be too extreme for any enhancement of persistence to be solely provided by the endophyte, and highlight the overwhelming importance of the physiological adaptation of the grass germplasm to target environment.