Improvement of Native Perennial Forage Plants for Sustainability of Mediterranean Farming Systems

The amount of water available to agriculture in the Mediterranean is declining because of increasing population pressure and greater incidence of drought. Therefore, the efficiency of the use of water for agricultural production must be maximized and, in this context, perennial forage species have a number of advantages in comparison to the predominantly-used annuals. They can utilize water throughout the whole year besides being able to halt rangeland degradation, restore soil fertility and enhance forage production, thereby contributing to greater sustainability of rain-fed agricultural systems in the southern European Union and North Africa. Despite these advantages, the small size of individual national markets has so far worked against the development of a viable forage industry based on perennials. By adopting a multi-national approach and targeting the key breeding objectives of superior drought-resistance and water-use efficiency (WUE), an European Commission-funded project aims to produce commercially cultivars of a number of species of broad regional interest and adaptation

The Potential for Summer-Dormant Perennial Grasses in Mediterranean and Semi-Arid Pastures

In rain-fed Mediterranean and semi-arid areas, herbage production of perennial grasses depends on their ability to grow efficiently during the rainy seasons and to persist over the dry summer. A key survival strategy in these harsh conditions is summer dormancy (Volaire, 2002). Within the species Dactylis glomerata L., two cultivars (cvs.), contrasting in this trait, were compared in order to analyse their suitability in terms of yield and survival in these environments

BRS Paiaguás é mais tolerante à seca que outras braquiárias.

Espécies de Brachiaria (syn. Urochloa) ocupam cerca de 70 milhões de hectares nos biomas Cerrado e Amazônia, mas mudanças no clima podem inviabilizar o uso desse capim em algumas regiões em função de períodos de seca severa. O objetivo do projeto foi estudar os mecanismos de resposta de tipos de Brachiaria ao estresse hídrico e identificar materiais capazes de sobreviver a secas mais severas, reduzindo a vulnerabilidade da pecuária às mudanças climáticas

Measurement of summer dormancy in temperate perennial pasture grasses

The search to improve drought survival in temperate perennial grasses has led to a renewed interest in summer dormancy and how to quantify it. This endogenously controlled trait, found in some temperate perennial grasses, is associated with drought that normally occurs in summer. While cessation of leaf growth and senescence of herbage occurs in all grasses in response to drought, it is under summer irrigation that these same responses are observed only in summer-dormant germplasm and hence the trait can be identified in germplasm. Across the spectrum from completely summer-dormant to non-dormant, there is a range of expression. Our objective here is to highlight differences in characteristics of indices which measure summer dormancy and to identify aspects for incorporation into a superior index for use in measuring this trait. The experimental program comprised three field trials that compared 6 cultivars and a fourth that assessed a larger group of 12 cultivars of the same three species, cocksfoot (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.), and phalaris (Phalaris aquatica L.). Seasonal herbage yield and foliage senescence were measured under three summer watering regimes: complete drought, mid-summer storm, and full irrigation at Mauguio, France. Different indices were calculated to compare against the approach which evaluates senescence under drought. The key outcomes are as follows. (1) The assessment of summer dormancy needs to be viewed as the plant response to a period of non-limiting water supply over summer. It makes little difference whether this is produced by full summer irrigation or a mid-summer simulated storm after a drought. Assessment of this trait under conditions of unbroken drought is discouraged because it can result in false scores. (2) The determination of summer dormancy intensity under full summer irrigation is most appropriate for the intensive study of the dynamics of dormancy expression over the entire summer. A simulated mid-summer storm within a drought gives an instantaneous view of dormancy intensity at a specific observation date and may be well adapted to the requirements of plant breeding. These methods are complementary. (3) Summer dormancy intensity can be assessed either by measuring herbage production or by a visual assessment of the level of herbage senescence. (4) An index of summer dormancy based on comparing irrigated summer herbage yield of any cultivar with that of a high, summer-yielding, non-dormant control cultivar was able to provide a reliable score of dormancy intensity. This index functions across a range of cultivars and species of perennial grasses. Further refinement of the index is needed to identify ‘standard’ high and low summer-dormant populations

Summer dormancy in Dactylis glomerata L.: the influence of season of sowing and a simulated mid-summer storm on two contrasting cultivars

A series of trials to increase understanding of the summer dormancy trait in Dactylis glomerata was conducted. Autumn-sown reproductive and younger, spring-sown plants of 2 drought-resistant cultivars, contrasting for summer dormancy, were established and then tested in summer 2002 under long drought, drought + midsummer storm, or full irrigation. The autumn-sown reproductive plants of cv. Kasbah were summer dormant under all moisture regimes and exhibited the characteristic traits including growth cessation, rapid herbage senescence, and dehydration of surviving organs (-6.7MPa). Cultivar Kasbah used 8% less soil water over the summer and also began to rehydrate its leaf bases from conserved soil water before the drought broke. The non-dormant cv. Medly grew for 10 days longer under drought and whenever moisture was applied; Medly also responded to the storm with a decline in dehydrin expression in leaf bases, whereas no decline occurred in Kasbah, presumably because it remained dormant and therefore much drier. The irrigated, younger, spring-sown swards of cv. Kasbah had restrained growth and produced only about 25% of the herbage of cv. Medly. Drought reduced activity and growth of young plants of both cultivars, but whereas Medly regrew in response to the storm, cv. Kasbah did not, indicating that dormancy, although only partially expressed after spring sowing, was reinforced by summer drought. A longer drought in 2003 caused a 22% loss of the basal cover in cv. Medly, whereas Kasbah fully maintained its sward and therefore produced a higher post-drought autumn yield. This work confirms summer dormancy as a powerful trait for improving persistence over long, dry summers

Production of cultivars and native populations of Trifolium subterraneum L. in the south of France (Corsica)

International audienceOn the northern Mediterranean island of Corsica, 28 populations of subterranean clover were tested during 3 years: 18 French native ecotypes, and 5 Australian and 5 Spanish cultivars. A principal component analysis showed that dry matter yields, seasonal growth rhythms, and maturity date were the most important factors in the observed variability. By cluster analysis, 6 groups of subterranean clover were defined from these factors. Seasonal and total yields were linked to annual rainfall, but with a specific coefficient for each group. For 100 mm of rainfall, we obtained a range of production from 0.4 t DM/ha for the least productive group to 1.1 t DM/ha for the highest yielding group. The Australian cultivar, Clare, and 9 native Corsican ecotypes were the most productive genotypes (up to 10 t DM/ha.year in a wet year, with 2 t DM/ha during the winter period). These highest yielding ecotypes could be exploited to breed new mid-to-late-maturing cultivars better adapted to northern Mediterranean environments. In the short term, Clare may be used on large scale, for establishment of improved pastures in this region

Summer dormancy in Phalaris aquatica L., the influence of season of sowing and summer moisture regime on two contrasting cultivars

A series of trials to increase understanding of the summer dormancy trait in Phalaris aquatica was conducted. Autumn-sown and younger, spring-sown plants of two cultivars (cvv), known to contrast in expression of summer dormancy, were established and then tested over the following summer under three moisture regimes: long drought; drought+mid-summer storm; or full irrigation. The autumn-sown plants of cv. Atlas PG expressed substantial but incomplete summer dormancy under all moisture regimes and exhibited the characteristic responses including significant growth reduction and herbage senescence. The summer-dormant cv. Atlas PG used 31mm less soil water over the summer and also began to rehydrate its leaf bases from conserved soil water before the drought broke. The non-dormant cv. Australian grew whenever moisture was applied and also responded to the mid-summer storm with a decline in dehydrin expression in leaf bases, whereas no decline occurred in Atlas PG, presumably because it remained dormant. The irrigated, younger, spring-sown swards of cv. Atlas PG had restrained growth and produced only about 37% of the herbage of cv. Australian. Drought reduced activity and growth of young plants of both cultivars but while Australian regrew in response to the storm, cv. Atlas PG, grew much less (59% of Australian) indicating that dormancy, although only partially expressed after spring sowing, was reinforced by summer drought. Australian used more soil water over summer than Atlas PG, and it is suggested that this is why cv Australian is limited to the higher rainfall zones of south-eastern Australia, particularly where soil water holding capacity is limited

Measuring dehydration tolerance in pasture grasses to improve drought survival

Cool-season grasses, both annual and perennial, typically employ the strategies of dehydration avoidance and dehydration tolerance to help them to survive extended periods of low soil moisture. Summer dormancy is an extra trait employed by perennial grasses particularly adapted to regions experiencing extended hot, dry summers. Of the three strategies, it appears that least is known about dehydration tolerance. Using and extending a methodology developed for cocksfoot (Dactylis glomerata L.), this study compared a range of cultivars of cocksfoot, tall fescue and phalaris differing in expression of summer dormancy. Both inter- and intra-specific variation in dehydration tolerance was observed, with cocksfoot expressing the trait strongly, whereas it was least evident in phalaris. The trait was more strongly evident in cultivars originating in drier environments, and the ability to express dehydration tolerance appeared to be independent of summer dormancy. It has been confirmed that dehydration tolerance is a powerful drought-survival trait, one that warrants increasing attention in plant breeding programs for drying environments