Regional distributions of crop diversity are important to take into account for the spatial design of in situ, farmer-participatory interventions in crop genetic management. Regional seed flows are an important factor in shaping geographical distributions of crop diversity. This study contributes to the insight in these seed flows, focusing on maize (Zea mays L.) in Chimaltenango, an area in the western highlands of Guatemala. A social survey of 257 households on different aspects of seed management produced information on cultivar naming, seed sources, reasons and causes of the discontinuation of seed lots, and important explanatory variables associated with different seed sources. A small portion of the reported seed lots originated from regional seed sources. The main motivation of regional seed exchange and the discontinuation of seed lots was to achieve change in plant characteristics of the crop, especially to obtain lower plants and shorter growing cycles. It is argued that farmer selection fails to achieve such change, and in fact leads to an equilibrium with high plants and long growing cycles. Seed exchange functions as an escape to this trend. Other factors of influence on seed exchange are altitude and ethnicity. The study also highlights the issue of geographical directionality in seed exchange patterns.

Guinea yam (Dioscorea rotundata Poir.) is a dioecious vegetatively propagated tuber crop. It is widely cultivated by traditional techniques in West Africa, its area of origin. The genetic diversity of 146 accessions from Benin was analysed using 10 polymorphic simple sequence repeat (SSR) nuclear markers and agromorphological traits. An average of 8.4 alleles per locus was detected. The mean heterozygosity was 0.57 and the mean polymorphism information content (PIC) for polymorphic markers was 0.51. Some cultivars (23%) were found to have an identical genotype for the 10 markers. The structure of the genetic diversity observed in Benin is the result of farmers' crop management practices and their know-how. The cultivar diversity had a geographical component. We also noted major differentiation between early and late cultivars, with higher diversity in the early ones. Cultivars from northern Benin and early cultivars had the greatest allelic richness. SSR markers proved to be powerful tools for fingerprinting each cultivar and analysing their genetic relationships. The results of this study could be useful for defining a strategy for the conservation of genetic diversity in yams.

Quinoa (Chenopodium quinoa Willd.) is a staple food crop for millions of impoverished rural inhabitants of Andean South America where it has been cultivated for millennia. Interest in quinoa, due largely to its superior nutritional characteristics, is fuelling a growing export market and has led to an increased focus on genetic research and the development of quinoa breeding programmes throughout South America. The success of these breeding programmes will rely heavily on the development of core germplasm collections and germplasm conservation. We report the development of a set of fluorescence-tagged microsatellite molecular markers that can be used to characterize genetic diversity within quinoa germplasm and we use this set of 36 microsatellites markers to genetically characterize the diversity of 121 accessions of C. quinoa held in the USDA germplasm bank, 22 accessions from the CIP-FAO international nursery collection and eight accessions representing parents from genetic mapping populations. A total of 420 alleles were detected among the quinoa accessions with an average of 11 alleles detected per microsatellite locus. Genetic heterogeneity was observed in 32% of the quinoa accessions at a given locus and suggests that many of these accessions represent heterogeneous seed lots or landraces. Both unweighted pair-group method with arithmetic averages (UPGMA) and principle components analysis (PCA) analyses partitioned the quinoa accessions into two main clusters. The first major cluster consisted of accessions from the Andean highlands of Peru, Bolivia, Ecuador, Argentina and extreme northeastern Chile. The other main cluster contained accessions from both the lowlands of Chile and a set of USDA accessions with no known passport data, collected by Emigdio Ballón. Using the patterns of genetic diversity detected within the C. quinoa accessions we discuss hypotheses regarding quinoa's centre of diversity, including highland and lowland ecotype clustering patterns, origin of lowland varieties, origin of domestication, and diversity levels in the USDA and CIP-FAO collections.

Legume flavonoids have received considerable attention due to their beneficial effects on human health. Flavonoid content in the seeds of 36 germplasm accessions of guar [Cyamopsis tetragonoloba (L.) Taub.] was quantified by high-performance liquid chromatography (HPLC). On a per 100 g basis, the seed contained, on average, 1.114 mg (0–2.355) daidzein, 0.700 mg (0–1.685) genistein, 0.553 mg (0–1.250) quercetin and 14.460 mg (10.70–19.82) kaempferol. A significant positive correlation was observed between the content of daidzein and genistein; however, significant negative correlations existed between the content of kaempferol and daidzein and of kaempferol and genistein. Compared to soybean seeds, guar seeds contained very low amounts of daidzein and genistein, but a high amount of kaempferol. The information about the levels of flavonoids in guar seeds will be useful to breeding programmes for improving guar seed quality. Furthermore, the high kaempferol content of guar seeds may expand its nutraceutical and pharmaceutical utilization.

Aegilops markgrafii is a useful source of genes encoding both resistance to biotic stress and high seed lysine content. Bread wheat/Ae. markgrafii introgression lines expressing leaf rust resistance were developed from a cross between a leaf rust-resistant Ae.markgrafii accession and the susceptible bread wheat cultivar ‘Alcedo’. The content of introgressed segments present in five sister introgression lines was assessed with the help of chromosome-specific simple sequence repeats (SSRs). One of the lines was used as a parent of a 140 individual F2 mapping population, by crossing with the leaf rust-susceptible bread wheat cv. ‘Borenos’. The population was tested for susceptibility or resistance to leaf rust, and linkage analysis indicated the presence of a quantitative trait locus (QLr.ipk-2A) originating from the Ae. markgrafii parent, mapping to the distal segment of chromosome arm 2AS.

The allelic diversity within oil palm populations (45 native ones from 10 African countries, three breeding populations and one collection of semi-wild material) was determined using 16 microsatellite markers. A total of 209 alleles were detected, with a mean number of 13.1 alleles per locus. The mean effective number of alleles per locus (Ae) was 3.3 ± 1.3. Although the Duncan's multiple range test only separated the group of populations from Madagascar from the rest on the basis of Ae, the presence of unique and rare alleles and high values of Ae suggest that 23 of the African populations should be conserved to secure allelic diversity.

Bacterial blight (BB) of rice is a widespread disease in tropical Asia, contained largely through the deployment of race-specific resistance genes. Although more than 25 BB resistance genes have been identified, none are effective individually against all the pathotypes prevalent in north-western India. The response of a set of 327 accessions of 13 wild Oryza species and cultivated African rice, O. glaberrima, was evaluated to infection with seven pathotypes of Xanthomonas oryzae pv. oryzae over a period of 3–4 years. Of these, 67 were resistant or moderately resistant to all pathotypes. These comprised 13 accessions of O. glaberrima, 5 of O. barthii, 10 of O. rufipogon, 4 of O. longistaminata, 22 of O. nivara, 6 of O. officinalis, 2 of O. rhizomatis and 5 of O. minuta. Inheritance studies, molecular mapping and transfer of some of these genes into O. sativa ssp. indica are in progress.