SUMMARYThe known zones of contact between dipioid and tetraploid DactyUs are reviewed, and two welldocumented examples of intermixed and morphologically similar diploids and tetraploids are considered in detail. The relict subspecies mairei is accompanied, in its particular habitat, by a tetraploid counterpart. The evidence suggests this to be an example of autotetraploidy, the dipioid and tetraploid components of which have been preserved by isolation in a specialized relict habitat.In Dactylis interploid sympatry appears to have arisen in two ways-by changes in the original habitat, whereby morphologically dissimilar and spatially isolated diploids and tetraploids become intermixed, or by the formation of autotetraploids which co-exist in the 'dipioid' habitat and may subsequently be modified by hybridization with other diploids or tetraploids with which they come in contact.No triploid or tetraploid hybrids were discovered in the seedling progeny of dipioid Kerrata plants, hut the numbers screened are considered insufficient. Direct formation of tetraploid hybrids as a consequence of the functioning of unreduced gametes by dipioid parents can be a more effective 'genetic bridge' than the backcrossing of triploid hybrids. Further study of mixed diploid-tetraploid stands is therefore required to determine the frequency and effectiveness of this phenomenon in natural populations.

No abstract

Wild yellow lupin (Lupinus luteus L.) is one of the three species of the genus Lupinus that grows naturally in Galicia (northwestern Spain). In this dairy region imported lupin is widely used as a cheap plant‐derived protein for livestock feed. Our objectives were to investigate variation in yellow lupin accessions from northwestern Spain, determine the relationships among them, and identify useful accessions for production and breeding. Fifty wild accessions and one Portuguese landrace were evaluated for 21 characteristics under winter Mediterranean conditions in northwestern Spain in 2001 and 2002. Accessions showed significant differences for 14 of 21 traits. Accession × environment interaction was significant for seed width and plant height. Based on multivariate analyses, 90% of the accessions grouped together indicating that genetic variation for most studied characters is limited in this germplasm. In general, accessions were late in flowering and maturity, with high levels of vegetative development, small and impermeable seeds, and dehiscent pods. However three accessions (LUP‐0077, LUP‐0080, and LUP‐0125) with high seed yield, water permeability, and relatively large pods and seeds may have potential for seed production and improvement of agronomic characteristics. In addition, LUP‐0196 produced high green mass and could be used for forage production in high rainfall cool‐temperate environments with long growing season conditions.

Twenty-one natural populations (thirteen tetraploids and eight diploids) of Dactylis glomerata ssp. izcoi (an Iberian endemic) were evaluated in the field for three consecutive years, using two clones per genotype, to separate genetic and environmental factors. Many traits showed significant differences between ploidy levels, but all of them overlapped. Therefore, it is justified to include both cytotypes in a subspecies in which tetraploids could be autopolyploids. In general, however, diploids had shorter stomatal guard cells, lower seed production and were later heading than tetraploids. Within tetraploids, most traits differed significantly between and within populations. There was less inter-and intrapopulation variation in the diploids. The range of plant dimensions exceeded that of former descriptions of the subspecies, bringing it closer to ssp. glomerata. Inland populations were not qualitatively different from one coastal population. Diploid populations showed less risk of hypomagnesemia than tetraploids.