To reduce the level of redundancy in a collection of cultivated lettuce, data from 160 amplified fragment length polymorphism (AFLP) fragments and 10 polymorphic microsatellites were used in combination with passport data and morphological data, the latter obtained from an experimental field trial performed for verification purposes. Based on the observed distribution of the number of marker differences between and within accessions, a minimum of three AFLP differences and two microsatellite differences were regarded as levels warranting distinction between accessions in the redundancy analysis. The strategy followed in the redundancy analysis was mainly based on the confirmation of duplication by each of two independently generated data sources. The molecular data were used for the validation as well as the identification of potential duplicates, revealing a total number of 198 redundancies, corresponding to 12.9% of the total collection. Trueness to type, number of characterization and evaluation data, and collection management considerations, such as available seed quantities and germination percentages, were used as primary, secondary and tertiary criteria to decide which accession from duplication groups to maintain in the collection. Removal of accessions showed negligible effects on total collection diversity, as quantified for AFLPs and microsatellites, characterization and evaluation traits and resistance profiles against downy mildew pathotypes, indicating that the applied strategy was effective.

Cacao (Theobroma cacao L.) was domesticated in Mesoamerica and is native to the South American rainforest. Belizean Criollo is a group of relic landraces that are thought to be similar to those used by the Olmecs and Mayans during early domestication. Knowledge of genetic diversity is essential for efficient conservation and use of these relic landraces. Using 30 microsatellite markers, we characterized genetic diversity in 77 Belize Criollo accessions collected from the Maya Mountains in Belize, and assessed their relationship with 62 cacao accessions including 25 Trinitario accessions. Genetic diversity and heterozygosity were low in Belizean Criollo germplasm. Eleven distinctive genotypes were identified among the Belizean germplasm. Results of ordination and cluster analysis supported their putative ancestral contribution to the Trinitario cacao. However, results of Bayesian assignment and parentage analysis both suggested that the contribution of Criollo cacao to the Imperial College Selections Trinitario is small. Our preferred hypothesis for the genesis of Trinitario cacao is that a limited population of Criollo × Forastero hybrids emanated from the introduced Forastero population of Trinidad. The present study provides new insights into the origin of the Trinitario cacao, which will be useful in the ex situ and in situ conservation of cacao landraces from Mesoamerica.

To understand the effect of different farming systems on the dynamics of diversity of sorghum (Sorghum bicolor (L.) Moench) crop, genetic structure of widely used landraces and modern varieties collected from two contrasting agroecosystems, in eastern Sudan and western Kenya, were analysed with 16 polymorphic microsatellite markers. A total of 1104 accessions, grouped into 46 samples from individual farmers, were genotyped. Cluster analysis of the samples from the two countries displayed contrasting patterns. Most strikingly, differently named landraces from western Kenya formed widely overlapping clusters, indicating weak genetic differentiation, while those from eastern Sudan formed clearly distinguishable groups. Similarly, samples of the modern variety from Sudan displayed high homogeneity, whereas the most common modern variety from western Kenya was very heterogeneous. The high degree of fragmentation of farmlands of western Kenya, coupled with planting of different sorghum varieties in the same fields, increases the likelihood of inter-variety gene flow. This may explain the low genetic differentiation between the differently named landraces and heterogeneity of the modern variety from western Kenya. This study highlights the important role of farmers in shaping the genetic variation of their crops and provides population parameter estimates allowing forecasting of the fate of ‘modern’ germplasm (conventional or genetically modified) when introduced into subsistence farming systems.

This is the first report on increasing yield and nutritional content of snake melon (Cucumis melo L. var. flexuosus) by exploiting intraspecific genetic variation of genetically diverse melons. Inbred snake melon ‘Punjab Long melon 1’ (PLM1) was hybridized with five genetically diverse inbred melons: KP 7 (var. momordica), AM 72 (var. acidulus), ‘Arya 1’ (var. chate), 04-02 (var. tibish) and ‘Punjab Wanga’ (unknown botanical variety). The parents and hybrids were evaluated at three locations for nine traits. Hybrids PLM1 × 04-02 and PLM1 × ‘Punjab Wanga’ exhibited significant (P0.05) heterosis for the number of marketable fruits per plant, and ascorbic acid and carotenoid contents of marketable fruits.

Graminaceous plants including staple cereals secrete certain phytosiderophores (PS) in calcareous soils with lower iron and zinc availability to enhance their uptake and translocation to the leaves and grains. A few Triticum aestivum cultivars and accessions of six Aegilops species were investigated for release of PS in vitro under iron- and zinc-sufficient and -deficient conditions, and for root and shoot iron and zinc concentrations. All the Aegilops species had three to four times higher release of PS than the wheat cultivars under both nutrient-sufficient and -deficient conditions. The maximum rate of increase of PS was observed on days 11 and 14 under iron- and zinc-deficient conditions, respectively, which levelled off rapidly among the wheat cultivars and continued to be high among Aegilops species till the end of the experiment. The absolute amount of iron and zinc expressed on dry weight basis after 18 d under iron- and zinc-deficient conditions showed nearly three times higher concentration in both roots and shoots of Aegilops species than that of the wheat cultivars. A significantly high correlation between concentrations of iron (r = 0.94) and zinc (r = 0.91) in roots and the PS released was found. The higher grain iron and zinc contents in the Aegilops species reported earlier may be attributed to their diverse and efficient mechanism(s) for PS-mediated micronutrient uptake and translocation system, which could be exploited for biofortification of wheat.

Genetic diversity and phylogenetic relationships among 141 cowpea (Vigna unguiculata L. Walp.) accessions collected throughout the nine geographical regions of Ghana were evaluated using simple sequence repeat (SSR) molecular markers. Twenty-five primer combinations pre-selected by their ability to polymerase chain reaction amplify SSRs from a set of test cowpea germplasm were evaluated. Of these, 20 primer combinations gave reproducible polymorphisms among 97.2% of the cowpea accessions tested, with the remaining accessions being found to be genetically identical. The informative primer combinations revealed a total of 74 alleles at 20 loci with an average of 3.8 alleles detected per locus. Variation in heterozygosity among cowpea SSRs ranged from 0.01 to 0.84 with an average occurrence of 0.19. The polymorphism information content varied from 0.07 to 0.66 with an average of 0.38. The Ghanaian cowpea accessions clustered into five main branches, each of which was loosely associated with the geographical regions from which samples were obtained. Accession GH2288 was found to be the most divergent cowpea accession compared with all others including the outgroup IT84S-2049, a breeding line from Nigeria. Our results provide a framework for future studies aimed at the conservation and management of cultivated cowpea germplasm in Ghana, and a good starting point for the selection of parental lines for genetic improvement programmes.

Genetic structure of five populations of a locally common rice (Oryza sativa L.) landrace Jaulia from parts of Uttarakhand state of India was studied using sequence tagged microsatellite site (STMS) markers. Of these, four populations were on-farm managed, assembled from different niche environments, and one population was conserved ex situ and represented static conservation. The 16 STMS primer pairs fully differentiated the inter- and intrapopulation diversity. A total of 72 alleles were recorded with a mean of 4.5 alleles per locus. Population wise, the total number of alleles ranged from 21 to 41, with maximum number of alleles for population IC 548358 and minimum number of alleles for population IC 100051 representing static conservation. A greater number of alleles specific to populations under farmer management could be recorded. Changes in yield parameters also seemed to be affected under farmer management besides other environmental adaptations for qualitative morphological characters. The marker diversity using STMS primer pairs indicates the genetic differentiation among populations resulting from joint effects of several evolutionary forces operating within the historical and biological context of the crop landrace. The variations in adaptations, on the other hand, indicate the degree to which populations are adapted to their environments and their potential for continued performance or as donors of characters in plant breeding. Both biotic and abiotic aspects of the environment are involved.

To characterize five different morphological forms of Russian olive grown in Ladakh, analysis of morphometric data of different variants was performed. Statistically significant differences among these variants were found for all the fruit and seed characters studied. Results of the study indicate presence of infra-specific differentiation within the species. Morphometric data for these variants conform to the system of nomenclature prevalent in the region for these variants. The ringmo (‘long fruited’ variety) type had the longest fruits, while bee (‘small fruited’ variety) had the smallest fruits.

Pigeonpea (Cajanus cajan (L.) Millsp.) seed harvested while it is immature is a nutritious vegetable and forms a substitute for green pea [Pisum sativum (L.)]. Using the characterization data of more than 12,000 accessions conserved at ICRISAT genebank, Patancheru, India, 105 accessions were selected for important traits of vegetable pigeonpea (mature pod length>6 cm, seeds per pod>5 and 100-seed weight>15 g) and evaluated for these traits during 2007–08. From the initial evaluation, 51 accessions were identified as vegetable type and further evaluated for traits of vegetable pigeonpea during 2008–09 to identify most promising accessions. ICP 13831 produced longest immature pods (10.3 cm), ICP 13828 had maximum number of seeds per pod (5.9) and ICP 12746 produced larger seeds (44.8 g/100 seeds). Highest percentage of total soluble sugars (9.7%) was recorded in immature seeds of ICP 13413. ICP 15143 followed by ICP 15186 recorded more dry pods per plant and seed yield per plant. Performance of ICP 12184, ICP 13413, ICP 14085 and ICP 15169 was better than that of the best control for pod length, seeds per pod, soluble sugars and protein content. Cluster analysis based on scores of first five principal components resulted in three clusters that differed significantly for days to 50% flowering, days to 75% maturity, shelling percentage and soluble sugars. Important traits of vegetable pigeonpea such as immature pod length, seeds per pod, seed soluble sugars and protein content had shown strong positive correlation. Caribbean and Eastern Africa were found as the best source regions for vegetable pigeonpea. Evaluation of selected accessions at potential locations in different countries was suggested to identify vegetable pigeonpeas suitable for different regions and for use in crop improvement programs.

Genetic variation in Lactuca serriola, the closest wild relative of cultivated lettuce, was studied across Europe from the Czech Republic to the United Kingdom, using three molecular marker systems, simple sequence repeat (SSR, microsatellites), AFLP and nucleotide-binding site (NBS) profiling. The ‘functional’ marker system NBS profiling, targeting disease resistance genes of the NBS/LRR family, did not show marked differences in genetic diversity parameters to the other systems. The autogamy of the species resulted in low observed heterozygosity and high population differentiation. Intra-population variation ranged from complete homogeneity to nearly complete heterogeneity. The highest genetic diversity was found in central Europe. The SSR results were compared to SSR variation screened earlier in the lettuce collection of the Centre for Genetic Resources, the Netherlands (CGN). In the UK, practically only a single SSR genotype was found. This genotype together with a few other common SSR genotypes comprised a large part of the plants sampled on the continent. Among the ten most frequent SSR genotypes observed, eight were already present in the CGN collection. Overall, the CGN collection appears to already have a fair representation of genetic variation from NW Europe. The results are discussed in relation to sampling strategies for improving genebank collections of crop wild relatives.

Taxonomy plays an essential role in genebank documentation. It is often the first level at which users search material, and it determines the protocols used in the management of collections. Especially, when plant genetic resources information is pooled in systems such as EURISCO, the European catalogue of ex situ plant genetic resources, problems regarding technical handling of taxonomic nomenclature, such as lack of standardization and low quality of data, become apparent. These problems were studied by analysing the content of EURISCO and mapping the taxon names in EURISCO on those used in the United States Department of Agriculture genebank system GRIN-Tax. Thus, the number of spelling errors and the level of standardization could be quantified and improved. An analysis of the content of EURISCO was made, showing a highly unbalanced distribution over crops: 50% of the accessions belong to ten genera only. Mapping EURISCO on the crops listed in Annex 1 of the International Treaty on Plant Genetic Resources for Food and Agriculture showed that 67% of the accessions in EURISCO belong to crops in that list.