the genome of the allotetraploid species Coffea arabica L. was sequenced to assemble independently the two component subgenomes (putatively deriving from C. canephora and C. eugenioides) and to perform a genome-wide analysis of the genetic diversity in cultivated coffee germplasm and in wild populations growing in the center of origin of the species. We assembled a total length of 1.536 Gbp, 444 Mb and 527 Mb of which were assigned to the canephora and eugenioides subgenomes, respectively, and predicted 46,562 gene models, 21,254 and 22,888 of which were assigned to the canephora and to the eugeniodes subgenome, respectively. Through a genome-wide SNP genotyping of 736 C. arabica accessions, we analyzed the genetic diversity in the species and its relationship with geographic distribution and historical records. We observed a weak population structure due to lowfrequency derived alleles and highly negative values of Taijma's D, suggesting a recent and severe bottleneck, most likely resulting from a single event of polyploidization, not only for the cultivated germplasm but also for the entire species. This conclusion is strongly supported by forward simulations of mutation accumulation. However, PCA revealed a cline of genetic diversity reflecting a west-toeast geographical distribution from the center of origin in East Africa to the Arabian Peninsula. The extremely low levels of variation observed in the species, as a consequence of the polyploidization event, make the exploitation of diversity within the species for breeding purposes less interesting than in most crop species and stress the need for introgression of new variability from the diploid progenitors.

Cultivated emmer wheat, Triticum dicoccon Schrank, a tetraploid species with hulled grain, has been largely cultivated during seven millennia in the Middle-East, Central and West Asia, and Europe. It has been largely replaced by hulless species and is now a minor crop, with the exception of some countries like India, Ethiopia and Yemen, where its grain is used for preparing traditional foods. Nutritional qualities and specific taste and flavor of emmer wheat products have led to a recent development of the cultivation in some European countries. Emmer wheat also possesses valuable traits of resistance to pests and diseases and tolerance to abiotic stresses and is increasingly used as a reservoir of useful genes in wheat breeding. In the present article, a review concerning taxonomy, diversity and history of cultivation of emmer wheat is reported. Grain characteristics and valuable agronomic traits are described. Some successful examples of emmer wheat utilization for the development of durum or bread wheat cultivars are examined, and the perspectives in using emmer wheat as health food and for the development of new breeding germplasm are discussed.

The effect of foliar application of kinetin on the growth and some physiological processes of pea plants growing in soil supplemented with 25 or 50µM Cd were studied. Cadmium treatment inhibited the growth rate, chlorophyll (Chl) content, net photosynthesis (P N ), content of soluble sugars and free amino acids of either shoots or roots. The application of kinetin (kin) enhanced the growth rate, Chl content, P N , soluble sugars and free amino acids content of shoots and roots; dark respiration rate (R D ), contents of soluble protein and proline were increased by cadmium treatment. The addition of kinetin to Cd-stressed plant reduced R D , soluble protein and proline content. Considerable variations in the content of Na + , K + , Ca 2+ and Mg 2+ were induced by Cd-treatments. Foliar application of kinetin exhibited a favorable effect on the accumulation of some ions and antagonized or ameliorated the inhibitory effect of Cd stress on some others.

This study has been conducted to evaluate the usefulness of carbon isotope discrimination (A) in mature kernels as a criterion for the improvement of water-use efficiency and yield under drought in durum wheat. For this purpose, Triticum durum 'Om Rabi 5' was crossed with T. polonicum pseudochrysospermum 9 (Tp9) which has been found to be more drought tolerant and to have a lower carbon isotope discrimination value of the grain. The Fj population showed a wide segregation for carbon isotope discrimination. Further, divergent selections (selection of plants most diflferent in carbon isotope discrimination) were made among individual Fj plants, and for carbon isotope discrimination in F^ progenies under field conditions. Selected F^ and F^ progenies were evaluated under field conditions for morphological and agronomical traits. Broad-sense heritability {h]), response to selection and realized heritability (/i^) were high. The narrow-sense heritability {h\ = 0.37 + 0.047) indicated that additive and dominance effects were involved in the genetic control of carbon isotope discrimination. Negative correlations were noted between carbon isotope discrimination and grain yield and between carbon isotope discrimination and biomass yield within years and generations. An explanation of this result is attempted by analysing the relationships between carbon isotope discrimination and several phenological and morphological traits influencing the water-use efficiency. The divergent groups selected for low and high carbon isotope discrimination exhibited significant diflFerences for days to heading, plant height, shape of the spike and number of spikelets per spike. Correlations were also found between carbon isotope discrimination and plant height, harvest index, shape of the spike, spike length, and number of spikes per plant. The potential use of carbon isotope discrimination as a criterion for the improvement of water-use efficiency in durum wheat is discussed by considering the genetics of this trait (variability, heritability, response to selection) and also the associations with phenological and morphological traits.Key words: Triticum durum -T. polonicum -carbon isotope discrimination -divergent selection -heritability -wateruse efficiency Improvement of drought resistance is a major objective for all breeders in semi-arid areas (Monneveux 1991). This is particularly true in the case of durum wheat because of its importance as a food crop. While physiological mechanisms of adaptation to water stress have been extensively described in cereals (Acevedo 1987), the genetics of the morphophysiological traits involved in tolerance are less well known and complex interactions between those traits need to be further investigated (Blum 1993). The major physiological attributes that support net carbon gain under drought can be approached by the relationship proposed by Passioura (1983): YE= Tx WUExHI,where YE is economic yield, T is transpiration, and WUE is crop water-use efficiency, which is defined, at the whole-plant level, as...

Nineteen accessions belonging to six tetraploid wheat species were evaluated and compared for carbon isotope discrimination and grain yield during two successive cropping seasons (1995 and 1996) under Mediterranean rainfed conditions. The two seasons differed markedly in precipitation regime. A wide variation for the measured traits was observed among the 19 accessions for carbon isotope discrimination and grain yield in both years. Significant differences were also noted between species accessions for Δ and grain yield. In both years, Triticum timopheevi (AG genome) showed lower Δ values than the other tetraploid species (all carrying the AB genome). Positive correlations were observed between Δ and grain yield in both years. The use of carbon isotope discrimination as an indirect selection criterion for yield under stress and the potential benefits of some alien tetraploid species in improving drought tolerance in durum wheat are discussed.