Genetic Diversity in Tef [<Emphasis Type="Italic">Eragrostis tef</Emphasis> (Zucc.) Trotter] Germplasm

One hundred and forty-four heterogeneous tef germplasm accessions collected from 10 major tef growing areas in Ethiopia were evaluated for 18 quantitative traits in a simple lattice design, at Holetta and Ginchi, in 2001 main growing season to study the genetic diversity in tef. The combined analysis of variance revealed the presence of significant variation among germplasm accessions for all traits studied. Cluster analysis revealed the overlapping of the germplasm accessions from different origin and the accessions were grouped into eight distinct clusters of 1–78. Generalized distance square confirmed the presence of significant genetic distance between clusters. In principal component (Prin) analysis, the first four principal components with latent root values above one accounted for about 80.6% of the variability existing among the germplasm accessions. Prin1 constituted about 55% of the variability mainly from almost equal contribution of 10 quantitative traits, indicating that most of the traits are equally important in tef diversity. In this study, the regions and altitudes of origin were not found to have a substantial effect on the genetic diversity in tef germplasm. Diversity within the regions was found to be significant and, hence, an opportunity for exploitation in tef improvement.     

Evaluation of phenotypic variation in a worldwide germplasm collection of safflower (<Emphasis Type="Italic">Carthamus tinctorius</Emphasis> L.) grown under organic farming conditions in Germany

An investigation was conducted to determine the extent of diversity and relationships among a worldwide safflower (Carthamus tinctorius L.) germplasm collection and to find out adapted accessions that can be used in an organic safflower breeding program in Germany. A total of 468 accessions was studied under organic farming conditions at Kleinhohenheim experimental station during the seasons of 2004 and 2005. All the accessions were evaluated for 12 phenotypic traits and three rated diseases. Multivariate analyses have been used to measure the diversity in a subset of 200 accessions and 11 geographical regions. Generally, the study showed that there was a large genetic variation within accessions. A coefficient of variation (CV%) for investigated traits and diseases ranged from 2.9 to 91.0% with the highest CV was recorded for yield/m2, yield/plant and seeds/plant. The most accessions that originated in Europe revealed relatively better performance compared to non-Europeans. High yielding, early maturing, and disease tolerant accessions were identified. However, the low oil content (8.7–22.8%) is the primary concern in this germplasm collection. The degree of heritability varied between 10% for lodging to 86% for plant height. Genotypic coefficient of correlation (r _g) was slightly higher for many traits than the respective phenotypic coefficient. Oil content and seed yield/m2 were highly significantly correlated (r _g = 0.78). The genotypic coefficient of correlation showed that selection for seeds/plant and thousand kernel weight was effective for improvement of seed yield and oil content. The results of the principal component analysis and the clustering pattern of accessions were consistent with the results of analysis of variance. About 78% of the total phenotypic diversity in the germplasm was explained on the basis of four principal components and 88% of the total variation among geographical regions was contributed by the first three principal components. The distribution of the accessions within clusters has no apparent relationship with the geographical origin. However, many of the European accessions have a tendency to stay together.     

Relationships among different geographical groups,agro-morphology,fatty acid composition and RAPD marker diversity in Safflower (<Emphasis Type="Italic">Carthamus tinctorius</Emphasis>)

Patterns of geographical diversity, and the relationship between agro-morphological traits and fatty acid composition were assessed for 193 safflower (Carthamus tinctorius) accessions representing forty countries. Accessions were assigned to eight groups based on geographical proximity. Cluster and Principal Component analyses were performed to assess patterns of diversity among the accessions and to select the most distant accessions from each of eight groups for analysis of randomly amplified polymorphic DNA (RAPD) markers. There was a large amount of diversity for agro-morphological traits, fatty acid composition, and RAPD markers. Most correlations among different traits were rather low. Plant height showed a positive correlation with days to flowering (r = 0.63**). Palmitic acid was positively correlated with stearic acid and oleic acid values, and negatively correlated with linoleic acid (P < 0.01). Oleic acid and linoleic acid showed a strong negative correlation (r = −0.89**). The first three principal components together explained 59% of the variation, however, neither principal component analysis (PCA) nor marker analysis revealed a clear relationship between diversity pattern and geographical origin. Accessions from some geographical regions tended to group together, such as accessions from South Western Asia, Central Western Europe, and the Mediterranean region. The correlation between the morphological matrix and the genetic matrix based on RAPD markers was not significant (r = 0.027). Wide diversity in safflower germplasm indicates a considerable potential for improving this crop for both agronomic and quality traits.     

Multivariate Analysis of Diversity of Tetraploid Wheat Germplasm from Ethiopia

The variability of 2420 plants of tetraploid (2n = 4x = 28, AABB genome) wheat germplasm representing 121 accessions from Ethiopia were evaluated for 23 agro-morphological traits at Debre Zeit Agricultural Research Center area, Akaki substation, during the 2003 main season using multivariate methods. This enabled to assess the extent and pattern of variation of the germplasm with respect to regions, altitude classes and species and to identify the major traits contributing to the diversity. The first three and two principal components explained about 83 and 80% of the total variance among regions and altitudinal class, respectively. In the first principal component plant height, days to heading, the length and density of the spike, and kernel color were the most important traits contributing to variation that explained about 50% of regional variance. Cluster analysis grouped the accessions into 15 clusters, with 9 accessions remaining ungrouped. Based on the observed patterns of variation, it is concluded that there exists great variation in the germplasm, which provides opportunities to be utilized for genetic improvement.     

Genetic diversity in wild and cultivated black raspberry (Rubus occidentalis L.) evaluated by simple sequence repeat markers

Breeding progress in black raspberry (Rubus occidentalis L.) has been limited by a lack of genetic diversity in elite germplasm. Black raspberry cultivars have been noted for showing very few phenotypic differences and seedlings from crosses between cultivars for a lack of segregation for important traits. Despite these challenges, little molecular work has been done to explore genetic diversity and relationships in wild and cultivated black raspberry germplasm. Microsatellite, or simple sequence repeat (SSR), markers are highly polymorphic codominant markers useful for studying genetic diversity, population genetics, genetic fingerprinting and other applications. We examined genetic diversity in 148 wild and cultivated black raspberry accessions using 21 polymorphic SSR markers. Black raspberry cultivars clustered tightly and showed higher than expected heterozygosity while that of wild accessions was low. Relationships between wild black raspberry accessions were poorly resolved and regional clusters were mostly absent from our analysis. Our results indicated that wild black raspberry germplasm is a relatively untapped resource available for future breeding.     

Morphological and molecular diversity of an underutilized fruit crop - <Emphasis Type="Italic">Cordia myxa</Emphasis> L. germplasm from the arid region of Rajasthan,India

Twenty two germplasm accessions of Cordia myxa were collected from Rajasthan and established at the field gene bank for conservation and evaluation. Morphological characterization of 10 year-old trees for 17 traits indicated wide variations among the accessions tested. Higher number of flowers per cyme was found in accession ACHM11 and higher pulp:stone ratio in AHCM25. Overall, AHCM22 was found to be a superior germplasm line for most of the horticulturally useful traits among the accessions tested as it had higher percent of fruit set, pulp:stone ratio and fruit weight. High significant positive correlation was obtained between leaf, fruit characters and pulp:stone ratio. However, these characters were found to be negatively correlated with number of flowers per cyme. Out of 50 random decamer primers used for random amplification (RAPD), 25 were polymorphic. Average polymorphism resolved by these markers among these accessions was 69.8% with an average polymorphic information content of 0.43. Genetic diversity revealed by Jaccard’s co-efficient was between 0.44 and 0.94, and three major clusters were identified among these accessions by phylogenetic analysis using NTSYSpc-2.02e software. RAPD markers associated with leaf size and pulp:stone ratio were also identified. This study shows the existence of high genetic diversity among these accessions.     

Genetic diversity and spatial structure in a new distinct <Emphasis Type="Italic">Theobroma cacao</Emphasis> L. population in Bolivia

Cacao (Theobroma cacao L.) is an important economic crop in the Bolivian Amazon. Bolivian farmers both cultivate cacao, and extract fruits from wild stands in the Beni River region and in valleys of the Andes foothills. The germplasm group traditionally used is presently referred to as “Cacao Nacional Boliviano” (CNB). Using DNA fingerprinting technology based on microsatellite markers, we genotyped 164 Bolivian cacao accessions, including both cultivated and wild CNB accessions sampled from the Amazonian regions of La Paz and Beni, and compared their SSR profiles with 78 reference Forastero accessions from Amazonian cacao populations, including germplasm from the Ucayali region of Peru. Results of multivariate ordination and analysis of molecular variance show that CNB cacao has a unique genetic profile that is significantly different from the known cacao germplasm groups in South America. The results also show that cultivated CNB and wild CNB populations in the Beni River share a similar genetic profile, suggesting that the cultivated CNB is of indigenous origin in Bolivia. The level of genetic diversity, measured by allele richness and gene diversity in the Bolivian cacao, is moderately high, but was significantly lower than gene diversity in the other Amazonian cacao populations. Significant spatial genetic structure was detected in the wild CNB population, using analysis of autocorrelation (rc = 0.232; P < 0.001) and Mantel tests (Rxy = 0.276; P < 0.001). This finding is also highly valuable to support in situ conservation and sustainable use of CNB genetic diversity in Bolivia.     

A wide range of genetic diversity in pear (<Emphasis Type="Italic">Pyrus ussuriensis</Emphasis> var. <Emphasis Type="Italic">aromatica</Emphasis>) genetic resources from Iwate,Japan revealed by SSR and chloroplast DNA markers

Iwateyamanashi (Pyrus ussuriensis var. aromatica) is one of the Pyrus species which grows wild in Japan. The number of Iwateyamanashi trees has been decreasing, so conservation and evaluation is urgently needed. Over 500 accessions of Pyrus species collected from Iwate in northern Tohoku region are maintained at Kobe University as an Iwateyamanashi germplasm collection. In order to investigate the genetic diversity, five SSR (simple sequence repeat) markers, developed from Japanese and European pear were examined for 86 Pyrus individuals including 58 accessions from Iwate. These SSR loci could discriminate between all the Iwate accessions except for 10 that bear seedless fruit, as well as determine the genetic diversity in Iwateyamanashi germplasms. High levels of variation were detected in 41 alleles and the mean observed heterozygosity across 5 loci was 0.50 for the Iwate accessions. Seedless accessions sharing identical SSR genotype with the local pear variety “Iwatetanenashi” were supposed to have been propagated vegetatively via grafting. In an UPGMA phenogram, Japanese pear varieties (P. pyrifolia) were clustered into two groups with some Iwate accessions including seedless ones. Another 38 Iwate accessions were not clustered clearly, and there was no clear relationship between these accessions and geographical distribution or morphological characters. Allele frequency revealed that the Iwate accessions were genetically more divergent than the Japanese pear varieties. Most Japanese pears possessed a 219 bp deletion at a spacer region between the accD and psaI genes in the chloroplast DNA (cpDNA), but other Pyrus species and two Iwateyamanashi trees did not. In the Iwate accessions, 79.3% had a deletion type cpDNA and others had a standard type cpDNA without deletion. These results are indicative of the wide range of genetic diversity in the Iwate accessions which include Japanese pear varieties. A combination of SSR and cpDNA analyses revealed high heterogeneity in Iwateyamanashi and coexistence of Iwateyamanashi and hybrid progeny with P. pyrifolia. These could be reasons for the wide range of continuous morphological variation described previously.     

Patterns of phenotypic diversity for phenologic and qualitative traits in Ethiopian tetraploid wheat germplasm

A total of 4,840 entries of tetraploid wheat germplasm collections representing 121 accessions from Ethiopia were evaluated for phenologic and qualitative trait diversity. The objectives were to assess the diversity patterns of the germplasm with respect to regions, species and altitudinal class. High values of Shannon–Weaver Diversity Index (H′) were recorded for most traits in each region, altitudinal classes, and species. Monomorphism was also high at accession levels. Both H′ and Nei’s gene diversity value for the entire data set (total gene diversity H _T = 0.572; the within accessions gene diversity H _S = 0.112; and gene diversity among accessions D _ST = 0.460) showed the variation for the trait is mainly among accessions/populations rather than within accessions/population. The least mean H′ value over all the traits used for the study was obtained from released varieties (among the origin groups) and Triticum dicoccon (among species). Triticum durum exhibit the highest H′ for a number of traits. Accessions collected from altitudinal class III (2401–2800 m a.s.l.) and class II (2001–2400 m a.s.l.) showed the highest H′ values for a valuable number of traits. Thus classifications using various phenology and qualitative traits enable to identify adaptation of a genotype and would improve the evaluation of genotype for potential adaptation.     

Development of Core Collection in Pigeonpea [<Emphasis Type="Italic">Cajanus cajan</Emphasis> (L.) Millspaugh] using Geographic and Qualitative Morphological Descriptors

Pigeonpea is an important pulse crop grown by smallholder farmers in the semi-arid tropics. Most of the pigeonpea cultivars grown to date are selections from the landraces, with a narrow genetic base. With the expansion of the crop to newer areas, problems of local importance are to be addressed. Hence, an economically feasible and faster germplasm evaluation mechanism, such as a core collection, is required. This article describes the development of core collection from 12,153 pigeonpea accessions collected from 56 countries and maintained at ICRISAT, Patancheru, India. The germplasm accessions from 56 countries were placed under 14 clusters based primarily on geographic origin. Data on 14 qualitative morphological traits were used for cluster formation by Ward’s method. From each cluster ≈10% accessions were randomly selected to constitute a core collection comprising 1290 accessions. Mean comparisons using Newman–Keuls test, variances’ comparisons by Levene’s test, and comparison of frequency distribution by χ²-test indicated that the core collection was similar to that of the entire collection for various traits and the genetic variability available in the entire collection is preserved in the core collection. The Shannon–Weaver diversity index for different traits was also similar for both entire and core collection. All the important phenotypic associations between different traits available in the entire collection were preserved in the core collection. The core collection constituted in the present study facilitates identification of useful traits economically and expeditiously for use in pigeonpea improvement.     

Extent and Pattern of Genetic Diversity for Morpho-agronomic Traits in Ethiopian Highland Pulse Landraces II. Faba Bean (<Emphasis Type="Italic">Vicia faba</Emphasis> L.)

A field experiment was conducted in 2001 at Holetta and Kulumsa, Ethiopia, to study genetic diversity in Ethiopian faba bean (Vicia faba L.) landraces. One hundred sixty random germplasm accessions were grown in an alpha lattice design with two replications. Data on 12 traits were collected and analyzed. Significant differences were observed among the accessions for most of the traits (except number of pods/podding nodes) at each location even though differences pooled over location were mostly non-significant. Cluster analysis distinguished seven diversity classes of different sizes. Accessions from the northern half of the country (North and South Wello, North Gonder and North Shewa) were closely related while those from the southern part of the country (Arsi) were highly diverse. Cumulative effects of a number of characters dictated differentiation of the accessions into clusters. Some overlapping were encountered between accessions from the northern and those from the southern parts of the country. The study revealed that accessions from different regions might have similar genetic background and those from the same origin might also have different genetic background. Therefore, geographic diversity should not necessarily be used as an index of genetic diversity and parental selection should be based on a systematic study of genetic diversity in a specific population. Genetic distances between most of the clusters were significant that crosses between parents selected out of them are expected to generate desirable progenies. Future germplasm collection, conservation and utilization strategies should put more focus not only on inter-regional diversity in the country as a whole but also on intra-regional diversity in Arsi.     

Genetic variation among populations of wild safflower, <Emphasis Type="Italic">Carthamus oxyacanthus</Emphasis> analyzed by agro-morphological traits and ISSR markers

Wild species of safflower, Carthamus oxyacanthus Bieb., is highly crossable with cultivated species, C. tinctorius L. and could be directly exploited in broadening safflower gene pool and improving the crop for biotic and abiotic stress environments. In this study, genetic diversity among accessions of C. oxyacanthus and their relationships with cultivated safflower were evaluated using agro-morphological traits and polymorphic inter-simple sequence repeats (ISSR) markers. Significant variation was observed among accessions particularly for seeds per capitulum, seed yield per plant, harvest index and capitula per plant. Cluster analysis based on agro-morphological traits classified the wild accessions in two groups according to their geographical regions, and separated them from the cultivated genotypes. ISSR marker also revealed a high genetic variation among the accessions, and cluster analysis based on this marker divided genotypes into four groups, with cultivated ones in a separate clade. Genetic variation observed among the wild safflower germplasm at the DNA level was higher than the agro-morphological traits, indicating that ISSR is an effective marker system for detecting diversity among safflower genotypes and their genetic relationships. Accessions of C. oxyacanthus with high genetic relationship to cultivated species could be used for interspecific hybridization in breeding programs of safflower.     

Wild melon diversity in India (Punjab State)

We present here the first comprehensive genetic characterization of wild melon accessions from northern India. The genetic diversity among 43 wild melon accessions collected from the six agro-ecological regions of the Punjab State of India was assessed by measuring variation at 16 Simple Sequence Repeat (SSR) loci, morphological traits of plant habit and fruit morphological traits, two yield-associated traits, root nematode resistance and biochemical composition (ascorbic acid, carotenoids, titrable acidity). Variation among accessions was observed in plant habit and fruit traits and wild melon germplasm with high acidity and elevated carotenoid content and possessing resistance to Meloidogyne incognita was identified in the collection. A high level of genetic variability in wild melon germplasm was suggested by SSR analysis. Comparative analysis using SSRs of the genetic variability between wild melons from the north and other melons from the south and east regions of India and also reference accessions of cultivated melon from Spain, Japan, Korea, Maldives, Iraq and Israel, showed regional differentiation among Indian melon accessions and that Indian germplasm was not closely related to melon accessions from other parts of the world. A highly drought tolerant accession belonging to var. agrestis Naud. was also identified.     

Variation in melon (<Emphasis Type="Italic">Cucumis melo</Emphasis>) landraces adapted to the humid tropics of southern India

We present here the first comprehensive genetic characterization of melon landraces from the humid tropics of southern India. The genetic diversity among 50 melon landraces collected from 3 agro-ecological regions of southern India (6 agro-ecological sub-regions) was assessed by variation at 17 SSR loci, morphological traits of plant habit and fruit, 2 yield-associated traits, pest and disease resistance, biochemical composition (ascorbic acid, carotenoids, titrable acidity) and mineral content (P, K, Fe, Zn). Differences among accessions were observed in plant and fruit traits. Melon germplasm with high titrable acidity, higher than average amounts of mineral content and resistance to Cucumber mosaic virus, Zucchini yellow mosaic virus, powdery mildew (races 1, 2, 3, 5), Fusarium wilt (races 1, 2), Aphis gossypii and leafminer was recorded in the collection. A high level of genetic variability in melon germplasm was suggested by the SSR analysis. Comparative analysis using SSRs of the genetic variability between Indian melons from north, south, and east regions and reference accessions of melon from Spain, France, Japan, Korea, Iraq, Zambia showed regional differentiation between Indian melon accessions and that Indian germplasm was weakly related to the melon accessions from other parts of the world, suggesting that an important portion of the genetic variability found within this melon collection has not been used yet for the development of new cultivars. Additional collections of acidulus melon germplasm should be made in southern India and adequate management of this important genetic resource is clearly a necessity.     

Morphological and reproductive characterization of guar (<Emphasis Type="Italic">Cyamopsis tetragonoloba</Emphasis>) genetic resources regenerated in Georgia,USA

Guar, Cyamopsis tetragonoloba is used worldwide for food stabilization, fiber source, food, and industry. The United States Department of Agriculture, Agricultural Research Service, Plant Genetic Resources Conservation Unit (USDA, ARS, PGRCU) conserves 1,298 accessions originating from India, Pakistan, and breeding lines from the USA. My objectives were to determine: (1) if these guar accessions can successfully be regenerated in Georgia, USA, (2) which traits contribute the most variation, and (3) to provide estimates for genetic relatedness among these accessions. Guar accessions were directly seeded to the field in Griffin, GA between early May and mid June 2006–2008. At 50% maturity, 73 accessions were characterized for morphological, phenological, and reproductive traits during the regeneration cycles. High quality plants regenerated from most of the accessions and produced 80 to more than 9,300 seeds per accession. Guar can be successfully grown and regenerated in Griffin, GA. Coefficients of variation and principal component analysis revealed variability among accessions for these traits evaluated. Cluster analysis separated guar accessions into three groups (clusters) based on low, intermediate or high seed numbers. Guar accessions clustered in groups 2 and 3 appear to be more genetically related than those in group 1.     

Extent and Pattern of Genetic Diversity for Morpho-agronomic Traits in Ethiopian Highland Pulse Landraces: I. Field Pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

An experiment was conducted in 2001 at Holetta and Kulumsa, Ethiopia, to study the extent and pattern of genetic diversity in Ethiopian field pea (Pisum sativum L.) landraces. One hundred forty-eight germplasm accessions were grown in an alpha lattice design with 2 replications. Data on 12 traits were collected and analyzed. Differences among the accessions were significant for most of the traits (except number of seeds/ pod) at each location even though differences pooled over location were mostly non-significant. The accessions were grouped into five clusters of different sizes. Accessions from the southern part of the country (Arsi) distributed overall clusters while those from the northern half (North and South Wello, North Gonder and North Shewa) fell into clusters C₁ to C₃. Cumulative effects of a number of characters dictated differentiation of the accessions into clusters. There was no definite relationship between geographic diversity and genetic diversity as overlapping was encountered in clustering pattern among accessions from different parts of the country. Accessions from different regions might have similar genetic background and those from the same origin might also have different genetic background. Therefore, geographic diversity should not necessarily be used as an index of genetic diversity and parental selection should be based on a systematic study of genetic diversity in a specific population. Genetic distances among most of the clusters were significant that crosses between parents selected out of them are expected to generate desirable genetic recombination. Selection should also consider the special advantages of each cluster and each accession within a cluster. Future germplasm collection, conservation and breeding efforts should focus not only on inter-regional diversity but also on intra-regional diversity.     

Characterization of <Emphasis Type="Italic">Prosopis cineraria</Emphasis> (L.) Druce germplasm with suitable horticultural traits from the hot arid region of Rajasthan,India

Sixteen germplasm accessions of Prosopis cineraria with suitable horticultural traits were identified from north-western Rajasthan, India, propagated clonally by budding on seedling rootstock and maintained in the field gene bank. Morphological characterization of seven-year-old trees of these accessions by 21 traits indicated a lot of variation among the accessions tested. Higher number of flowers per raceme was found in accession CIAH/K2, higher width of ripened pod in CIAH/K5, higher number of seeds per pod in CIAH/K12 and a higher weight of seed per pod in CIAH/K6. Overall, CIAH/K16 was found to be a superior genotype for most of the useful traits. High significant positive correlation was obtained with traits useful for horticultural values. Out of 62 random decamer primers for random amplification (RAPD) reaction, and four minisatellite core sequence for direct amplification of minisatellite DNA (DAMD) screened with these accessions, 12 RAPD and 2 DAMD primers were found polymorphic. Average polymorphism resolved by these markers among the accessions was 93.2%. Genetic diversity revealed by Jaccard’s co-efficient was between 0.11 and 0.77, and four major clusters were identified among these accessions by phylogenetic analysis using NTSYSpc-2.02e software. This study shows the existence of high genetic diversity within these accessions.