In drought-affected maize production zones with short growing periods, the development and use of early maturing drought-tolerant cultivars can stabilize maize production. We evaluated 10 improved and 25 farmers' early maturing maize varieties under moisture deficit and well-watered conditions for 2 years to identify suitable genetic materials for breeding drought-tolerant cultivars. The varieties exhibited significant differences in grain yield and other traits under both moisture deficit and well-watered conditions. Changes in the rank order of the varieties for grain yield was not significant across the different levels of moisture supply in this study. Grain yield was significantly correlated with days to anthesis, days to silking, plant height, ear height, ear number and anthesis–silking interval (ASI) under the two irrigation treatments and with leaf death scores under moisture deficit, suggesting that the common traits were beneficial in maximizing grain yield under both sufficient water supply and moisture deficit. Grain yield and the traits significantly correlated with it differentiated the early maturing maize varieties into two distinct groups under well-watered condition and moisture deficit. The improved varieties were superior to the farmers' varieties in grain yield and other traits under moisture deficit, possibly due to selection of their progenitors for improved performance in multiple locations. We found some farmers' and improved varieties with similar yield potential and flowering time under well-watered conditions but with marked differences in grain yield and other traits under moisture deficit. Use of such promising landraces that would also be invaluable sources of desirable farmers-preferred end-use quality traits in combination with promising improved varieties as breeding materials could enhance the genetic grain from selection for drought tolerance in early maize.

In this paper, Shannon–Weaver diversity indices were employed to examine the phenotypic diversity in 271 Ethiopian tetraploid wheat accessions in relation to characters, regions of origin and altitude. Moreover, review of genetic diversity studies in Ethiopian tetraploid wheat was made to explore breeding opportunities. The diversity index varied widely across regions. Among the four altitudinal classes, the highest (0.72) and lowest (0.61) mean diversity indices were observed in altitude classes II and IV, respectively. The diversity index (H′) showed that most traits are polymorphic. The partitioning of the total phenotypic diversity into within- and among-region diversity indicated that 71% of the total variation was attributed to the within-region diversity. Principal component analysis was computed to examine the regional and altitudinal patterns of variation. On regional bases, the first four axes, whose eigenvalues are greater than 1, explained about 82% of the observed phenotypic diversity in the 271 tetraploid wheat accessions. On altitudinal bases, however, only the first two principal components explained 89.7% of the total variation. In general, phenotypic diversity showed considerable differences for each trait in different geographical regions and altitudinal classes which could be utilized in wheat improvement programmes. Breeding opportunities and strategies are suggested.

Extensive research has been conducted on the characterization of hundreds of date palm (Phoenix dactylifera L.) cultivars worldwide. However, the population genetics of date palms has never been studied. In this study, we collected 200 individuals from 19 populations of different geographical locations in Sudan. The collection sites were grouped according to the type of dates (date palm fruits) that dominates in the area. Ten microsatellite markers were used to investigate the genetic diversity within and among populations and the correlation between the genetic and geographical distances. The tested microsatellite markers showed a high level of polymorphism. A total of 261 alleles were detected at the ten loci. The overall mean value of fixation indices equalled − 0.163, which shows the presence of excess heterozygosity. However, the χ2 tests conducted for every locus in each population indicated no significant deviation from the Hardy–Weinberg equilibrium. The analyses of molecular variance exhibited that about 95% of the total genetic variation existed within populations, while significant differentiation within the type groups could be detected. Although significant isolation by distance (r2 = 0.552, P < 0.05) was detected by a Mantel test, it seems that the spatial effect has become complicated as a result from the exchange and introduction of different kinds of plant materials by date palm growers and traders, as well as seed dispersal. This complexity was clearly apparent in the weak clustering relationships among most of the tested populations.

The conservation of crop genetic resources is an international priority and requires the continued collection and characterization of farmer varieties. We collected and characterized maize and upland rice populations cropped by farmers in Panama's Azuero region. The objective of our study was to evaluate the crop genetic diversity of farmer varieties of maize and upland rice grown by poor farmers in Panama. We found that: (1) farmers' naming practices only partially corresponded to genetic relationships and were the strongest for rice populations; (2) farmers' classification of populations as ‘modern’ or ‘traditional’ was reflected in phenotypic differences; (3) Panamanian maize populations were molecularly distinct from populations collected elsewhere in Latin America; and (4) heterogeneous rice populations were common and heterogeneity was often due to admixture of recognized farmer varieties. Our results indicate that poor farmers in Panama continue to farm ‘traditional’ varieties that harbour genetic diversity of interest. There has, however, been substantial adoption of ‘modern’ varieties.

In recent years, there has been an increased interest in Europe and in the USA in grafting watermelon onto bottle gourd, Lagenaria siceraria (Mol.) Standl. In this study, genetic diversity and relationships were examined [using 236 sequence-related amplified polymorphism markers] among 56 United States plant introductions (PIs) of L. siceraria and PIs of important cucurbit crops [including Cucurbita maxima Duchesne (winter squash), Cucurbita pepo L. (squash and pumpkin), Citrullus spp. (watermelon), Cucumis melo L. (melon) and Cucumis sativus L. (cucumber)]. The analysis showed that L. siceraria is distinct and has similar genetic distances to the cucurbit species examined herein. The L. siceraria PIs were assembled into two major clusters. One cluster includes groups of PIs collected mostly in South Asia (India) and a few PIs collected in the Mediterranean region and in Northeast Africa. The second cluster includes groups of PIs collected mainly in Southern Africa and in North, Central and South America, and PIs collected in China, Indonesia and Cyprus. All L. siceraria PIs in this study were susceptible to the southern root-knot nematode (RKN) [Meloidogyne incognita (Kofoid and White) Sandground]. However, several PIs, among them a group of closely related PIs collected in Mexico and Florida, were less infected with southern RKNs. All L. siceraria PIs were infested with whiteflies [Bemisia tabaci (Gennadius)], while several PIs were less infested than others and need further evaluation and selection for developing breeding lines that may be less appealing to this pest. Most of the PIs that showed resistance to zucchini yellow mosaic virus and tolerance to powdery mildew were collected in India and belong to the same phylogenetic groups (PGs). Experiments with L. siceraria PIs representing different PGs showed similar grafting compatibility with watermelon. Findings from this study should be useful for the development of superior L. siceraria rootstock lines with enhanced resistance to diseases and insect pests of cucurbit crops.

Gloriosa superba L. is a highly valued indigenous medicinal plant. It is available throughout India with noticeable variations in morphology and colchicine content. In the present study, morphological, phytochemical, cytological and molecular data are employed to screen the polymorphism, if present, in five different populations of G. superba L. Based on gross morphological traits, the plants can be grouped into two clusters: Amtala (AM) and Baruipur (BR) plants belonging to one cluster, and Siliguri (SG), Darjeeling (DJ) and Sikkim (SK) plants belonging to the other. Colchicine content of the tubers ranged from 0.06% in AM plants to 0.37% in BR plants. Cytological analysis revealed that the SK plants showed 44 chromosomes, i.e. tetraploid status, whereas the other four were diploid. Assessment of the karyomorphology of the four diploid populations indicated a close similarity between AM and BR plants, whereas the SG plants exhibited slightly different karyomorphology and lacked sm-type chromosomes. Random Amplified Polymorphic DNA (RAPD) analysis revealed 76% polymorphism among the populations. Cluster analysis using RAPD resulted in three main cluster groups; BR and SG plants clustered together indicating that they are most closely related when compared with other populations.

Wild relatives of pigeonpea (Cajanus cajan L.) possess many useful genes that can be utilized for crop improvement, most importantly genes for resistance to Helicoverpa armigera, the legume pod borer. The present study aimed at quantifying diversity in a collection of Cajanus scarabaeoides, Cajanus sericeus, Cajanus reticulatus and C. cajan species selected from a wide geographic range using two PCR-based marker systems, amplified fragment length polymorphism (AFLP) and simple sequence repeats (SSRs), and the hybridization-based restriction fragment length polymorphism (RFLP). Polymorphism was higher among the wild accessions than among the cultivated genotypes. Wild and cultivated Cajanus accessions belonging to different species clustered into four distinct major groups largely based on the interspecific differences. C. scarabaeoides accessions derived from same geographical origins formed one group reflecting similar genetic makeup of these accessions. Dendrograms generated using AFLP, RFLP and SSR marker data were comparable with minor clustering differences, which suggests that either method, or a combination of both can be applied to expanded genetic studies in Cajanus. Mantel testing confirmed the congruence between the genetic distances of three markers, indicating that the markers segregated independently, giving similar grouping patterns of all accessions having similar genetic origin.

Plant viruses pose a threat to the acquisition, maintenance and distribution of lupin germplasm (genus Lupinus, family Fabaceae). The availability of sufficient quantities of healthy and virus-free seeds from maintained lupin collections is mandatory for conducting lupin research. The objective of this research was to determine which lupin species were potentially infected with potyviruses (presumably seed-borne) upon germination in the greenhouse. The procedure for screening lupin seedlings in the greenhouse for potyviruses incorporated enzyme-linked immunosorbent assay followed by elimination or segregation of infected seedlings from the population before transplantation into the field plots for regeneration and accession characterization. None of the accessions in this evaluation had been tested previously for virus. From 2002 to 2005, 15 perennial (30 accessions) and 6 annual lupin species (213 accessions) were evaluated on site at the Western Regional Plant Introduction Station in Pullman, WA, USA. While none of the greenhouse perennial seedlings tested positive for potyvirus, seedlings in three annual species (Lupinus albus, Lupinus angustifolius and Lupinus luteus) were infected by potyviruses, presumably by seed transmission. Future testing may focus on the annual species, thus saving limited germplasm maintenance resources.

To date, there are only a few sequenced-tagged site (STS) markers associated with genes controlling fruit quality in watermelon. A normalized cDNA library for watermelon fruit (Citrullus lanatus var. lanatus) was constructed. Sequence analysis of the cDNA clones resulted in the development of 4700 non-redundant ESTs (EST unigenes) expressed in watermelon fruit (http://www.ncbi.nlm.nih.gov, http://www.icugi.org). One hundred of these EST unigenes [including 40 EST unigenes that contain simple sequence repeat (SSR) motives (EST-SSRs) and 60 customary EST unigenes (not containing SSR motives)] were used for designing primer pairs for PCR experiments. The EST primer pairs were tested in PCR experiments with genomic DNA of 25 watermelon heirloom cultivars and 13 United States Plant Introductions (US PIs) of Citrullus sp., including four C. lanatus var. lanatus, five C. lanatus var. citroides PIs and four Citrullus colocynthis PIs. The 40 EST-SSR and 60 EST primer pairs produced 108 and 142 EST-PCR markers, respectively, among the Citrullus PIs and watermelon cultivars. A large number of the EST-PCR markers were polymorphic between the Citrullus PIs and the watermelon cultivars, but significantly less polymorphic among the cultivars. Of the 108 EST-PCR markers associated with EST-SSRs, 103 exist in the Citrullus PIs and 64 in the cultivars. Of these 64 markers, 45 (70.3%) were polymorphic among the cultivars. Of the 142 EST-PCR markers associated with customary ESTs, 134 exist in the Citrullus PIs and 108 in the cultivars. Of these 108 markers, 86 (79.6%) were polymorphic among cultivars. The results in this study indicate that polymorphism exists in coding regions of genes expressed in fruits of watermelon cultivars. In total, 131 polymorphic EST-PCR markers (45 associated with EST-SSRs and 86 associated with customary ESTs) related to watermelon fruit genes were generated using the above data. These markers should be useful for DNA fingerprinting of cultivars and breeding lines, for assessing genetic relationships and for genetic mapping of watermelon.

Nineteen kenaf genotypes from Cuba, Taiwan, the USA, El Salvador, Guatemala, Russia, Spain and Indonesia, and three wild types collected in South Africa were analysed for genetic diversity using AFLP analysis. All could be uniquely distinguished from one another, but only a low level of genetic diversity was present. The most distinct accession, Guatemala 4, was 85% similar to all other accessions. The accessions clustered more or less according to known pedigree and/or origin. Two of the three wild types (Hibiscus cannabinus c and H. cannabinus a) clustered separately from the commercial and Russian accessions. One of the wild types, H. cannabinus b clustered with some of the commercial accessions. Commercial accessions in the first subgroup all originated from central and North America, and surrounding islands (Cuba and El Salvador). The Russian accessions are all grouped together. The second subgroup was the only group that contained accessions from different geographical origins.

A collection of 18 landraces of common bean (Phaseolus vulgaris L.) from northern Portugal was evaluated for both phaseolin pattern and a set of qualitative and quantitative traits. The phaseolin Contender and Tendergreen types were the most commonly occurring, with Boyaca and Huevo de Huanchaco present, but rare. The colour of the flower standard and wing, and seed shape, colour and size were all highly variable. On the basis of morphological traits, the landraces and testers clustered into two main groups. No relationship was found between phaseolin profile and any of the quantitative traits measured. Based on phaseolin patterns, the origin of Portuguese common bean populations was probably the Andean region of South America.

The genus Limnanthes (Limnanthaceae), also known as meadowfoam, has attracted attention for industrial use due to the unique characteristics of its seed oil. Samples from wild populations showed variability in agronomically important traits involved in seed oil yield, warranting the establishment and continued development of a germplasm collection. The level of genetic diversity within the United States Department of Agriculture, Agriculture Research Service, National Plant Germplasm System (USDA-ARS-NPGS) Limnanthes collection was evaluated using 15 simple sequence repeat (SSR) markers across 62 accessions representing 7 species. Parsimony analysis separated the accessions into two main groups consistent with the traditional taxonomic sections Inflexae and Reflexae, but there was little resolution within groups. These two groups were confirmed using neighbour-joining analysis and principal coordinate analysis. SSR marker variation suggests that the Limnanthes germplasm collection is genetically diverse and the accessions within the species likely contain novel alleles, and therefore the collection contributes to the conservation of the wild Limnanthes gene pool.

Thirty-eight melon accessions, which are of primary breeding importance in the Ukraine, were analysed for diversity. These collections represent a major non-US and non-western Europe source of melon germplasm that have not yet been subjected to molecular characterization. Molecular diversity was estimated based on a robust set of 465 polymorphisms gathered by amplified fragment length polymorphisms and simple sequence repeats (SSR). In this paper, we report 12 newly developed polymorphic SSR primer pairs, and their use for molecular characterization in the Ukrainian melon collections. Based on these polymorphisms, we estimated similarity indices that ranged from 0.70 to 1.00 among various accessions. The phylogenetic tree based on the similarity indices and a three-dimensional plot of the first three vectors of the principal component analysis corresponded fairly well with the existing three classical morphotypes namely aestivalis, europeus and hiemalis, under the convarEuropeus, which is also known as adana. The polymorphisms generated in the current study, which are specific to the grouping of fruit types and days to maturity will be very useful for further genetic studies and marker-assisted selections.

Helianthus annuus and H. petiolaris (Asteraceae) are wild sunflowers native to North America but have become naturalized in central Argentina covering an area of about 5 million hectares. Wild H. annuus has been recognized as invader species in several countries, but no research has been done to study the ecological determinants of their distribution. In a survey covering seven provinces between 31°58′–38°S and 60°33′–69°W, we described the ecology of the main wild populations. Wild Helianthus populations were located in three of the 18 ecological regions of Argentina, on five Mollisol and seven Entisol soil groups. The associated plant communities were comprised 60 species belonging to 16 families, all being frequent components of the native flora. Disease symptoms were seldom observed in wild populations, with Alternariahelianthi being the most commonly observed pathogen. Population size varied from less than 100 to more than 100,000 plants, covering from 100 to more than 60,000 m2 with densities most frequently up to 3 plants/m2, but reaching 80 plants/m2 at certain sites. Intermediate plant phenotypes between wild species and cultivated sunflower were found in one-third of the populations providing evidence of intense gene flow. Hybrid swarms were found at three localities with population sizes between 100 and 10,000 individuals.

The Germplasm Enhancement of Maize (GEM) Project is a cooperative effort between the USDA-ARS, private industry and public researchers to broaden and enhance the germplasm base of maize. In this program, selected accessions from the Latin American Maize Project, and seven tropical hybrids donated by DeKalb to the GEM Project, were crossed to elite proprietary inbred lines contributed by commercial plant breeding programs. In most cases, the resulting hybrids were crossed to a second commercial inbred line and the resulting 25% exotic hybrids were used as breeding populations for further development. To identify GEM germplasm with value to protein quality breeding programs, we developed a process for evaluating the content of the essential amino acids methionine, lysine and tryptophan in the grain of GEM germplasm that balances the need for multiple-year evaluations with the constantly changing entry list of this germplasm screening program. This process involves annual field trials with common checks. Weak entries are dropped from the trial each year to make room for new entries, while strong entries are retained. Methionine exhibited the most significant variation, followed by lysine and then tryptophan. A number of GEM lines had methionine or lysine levels that were significantly better than Corn Belt checks and some were competitive with high-amino acid checks.

Genetic diversity and relationships among 112 mango (Mangifera indica) plants native to 16 states of Mexico and four controls [three mango cultivars (Ataulfo, Manila and Tommy Atkins) and one accession of Mangifera odorata] were evaluated based on amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) molecular markers. Mango germplasm shows broad dispersion through Mexico and genetically similar germplasm from different agroecological regions has previously been found by our group. Both AFLP and SSR analyses indicated high genetic similarity among mango populations that were clustered in two major groups: mangos from Gulf of Mexico coastline and mangos from Pacific Ocean coastline and locations far away from the sea. The highest genetic diversity was found within plants from each state, and significant genetic differentiation (FST = 0.1921, AFLPs and 0.1911, SSRs) was also observed among mango populations based on geographical origin and genetic status (cultivars versus landraces). Heterozygosity values ranged from low (0.38) to moderate (0.68), and no heterozygote deficits were found. The highest genetic variability was found in mango populations from Tabasco, Michoacán and Oaxaca. Data suggested that mangoes are subjected to natural or induced pollination, so segregation as well as genetic recombination plays major roles on genetic diversification of Mexican mangos. AFLP analysis was more robust than SSR for determining the genetic relationships among mango landraces from Mexico.

Season-long monitoring of on-farm rice (Oryza sativa, L.) plots in Nepal explored farmers' decision-making process on the deployment of varieties to agroecosystems, application of production inputs to varieties, agronomic practices and relationship between economic return and area planted per variety. Farmers deploy varieties [landraces (LRs) and modern varieties (MVs)] to agroecosystems based on their understanding of characteristics of varieties and agroecosystems, and the interaction between them. In marginal growing conditions, LRs can compete with MVs. Within an agroecosystem, economic return and area planted to varieties have positive relationship, but this is not so between agroecosystems. LRs are very diverse on agronomic and economic traits; therefore, they cannot be rejected a priori as inferior materials without proper evaluation. LRs have to be evaluated for useful traits and utilized in breeding programmes to generate farmer-preferred materials for marginal environments and for their conservation on-farm.

Characterization and genotype identification are essential for rational conservation, management and genetic diversity evaluation. In this work, simple sequence repeat (SSR) markers were used to identify 57 accessions of sweet potato kept at the ‘in vitro’ Gene Bank of INTA, Argentina. This collection includes primitive materials from primary zones of dispersion, commercial varieties, breeding clones and foreign materials from different parts of the world (Africa, Asia and USA). Average similarity between the materials evaluated was 0.367. Grouping analysis revealed six clusters and a strong association with skin colour of storage roots. The set of selected SSR markers allowed us to verify identity, detect duplicates and estimate the genetic similarity of the materials analysed. This characterization complements morphological data and provides tools to estimate the variation of diversity between local and foreign germplasm groups.

The fatty acid composition of peanut seed oil from a range of samples included in the core of the core or the ‘mini core’ of the US peanut germplasm collection was determined using gas chromatography. Oil contents of the seeds ranged from 31.4 to 47.9%. Very long-chain fatty acids are defined as those having more than 22 carbons in chain length. Although it has been reported in peanuts seed previously, the presence of hexacosanoic acid (C26:0) was quantified in a large variety of samples here for the first time along with docosanoic (C22:0) and tetracosanoic acids (C24:0) to demonstrate the potential of peanut seed as a source of very long-chain fatty acids that have been associated with widely varying effects such as the metabolism of the dietary fatty acids and physical properties of the oils themselves. Use of representative samples from the peanut germplasm collection allowed for comparison of very long-chain fatty acid content among seeds of different origins, and showed, although values overlapped, the seeds did cluster according to area of origin.

Rice varietal diversity was assessed in Guinea on the basis of surveys of 1679 farms located in 79 villages of the four natural regions of the country. The descriptors used were the number of known varieties, the number of cultivated varieties and Shannon's diversity and evenness index. On the basis of their use rates, varieties were classified as major or minor types at the village scale and as regionally and/or nationally eminent varieties at these scales. Varietal diversity was high, especially in forest Guinea and lower Guinea. Diversity pattern was typical of the subsistence farming system. The high share of local variety reflected the predominance of low management and low input cropping systems. The presence of improved varieties confirms farmers' openness to innovation and to the government policy of promoting improved varieties. Regional diversity reflected the agro-ecological diversity and specificities of each region, the history and the extent of rice-growing systems, and the importance of rice in the local diet. Recent dissemination of NERICA varieties has not caused any reduction of pre-existing varieties. The short-duration NERICA are mainly used as a complement to the long-duration traditional varieties and thus enhance varietal diversity. Risks of diversity erosion seem limited in the current setting of farming system and diversity structure. However, at the village level, the diversity pattern is fragile as the proportion of farmers who used each variety of the village is low and heterogeneous. A continuous monitoring of the dynamics of rice varietal diversity in Guinea is needed.