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.     

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.     

Phenotypic diversity in the pigeonpea (<Emphasis Type="Italic">Cajanus cajan</Emphasis>) core collection

The pigeonpea core collection developed at ICRISAT genebank consists of 1,290 accessions from 53 countries. The core collection, which includes selected lines in extra early, early, medium and late maturity groups was evaluated for 18 qualitative and 16 quantitative characters during the 2004 rainy season, to assess the phenotypic diversity and determine the relative importance of different characters in evaluating pigeonpea germplasm accessions. The four maturity groups differed significantly for all characters under study. The medium maturity group showed significantly higher mean number of primary, secondary and tertiary branches, number of racemes, pod bearing length, pods per plant, shelling percent and plot seed yield. Late maturity group showed significantly higher mean for leaf size, plant height, pod length, seeds per pod and 100-seed weight, indicating this group as a good source of vegetable pigeonpea. Significant positive correlations were found between number of secondary branches and pods per plant in extra early group (r = 0.756), late maturity group (r = 0.776) and entire core (r = 0.728) and between number of racemes and pods per plant in all maturity groups and entire core. Principal coordinate and principal component analysis showed that seven qualitative and nine quantitative traits were important in explaining multivariate polymorphism. The Shannon–Weaver diversity index (H′) varied for different maturity groups and traits. Phenotypic diversity, averaged over all the 16 characters, increases from extra early group (0.36 ± 0.04) to late maturity group (0.42 ± 0.04) suggesting that medium and late maturity groups have greater diversity compared to extra early and early maturity groups.     

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.     

Development of Core Subset of Finger Millet Germplasm Using Geographical Origin and Data on 14 Quantitative Traits

Finger millet [Eleusine coracana (L.) Gaertn.] is an important cereal food crop in Africa and South Asia. It is a hardy crop that can be grown in very diverse environments from almost at sea level to about 2400 m.a.s.l. Finger millet has an excellent food value as its seeds contain protein ranging from 7 to 14% and are particularly rich in methionine amino acid, iron, and calcium. Despite all these merits, this crop has been neglected from the main stream of crop improvement research. One of the means to boost its production and productivity is to enhance utilization of finger millet germplasm to breed superior varieties. Keeping this objective in view, a core subset of finger millet germplasm (622 accessions) based on origin and data on 14 quantitative traits was developed from the entire global collection of 5940 accessions held in the genebank at ICRISAT, Patancheru, India. The comparison of means, variances, frequency distribution, Shannon-Weaver diversity index (H′) and phenotypic correlations indicated that the core subset represents the entire collection. These tests indicated that sampling was optimal and the diversity has been captured very well in the core subset. The correlation analysis indicated that panicle exsertion and longest finger length could be given lower priority in the future germplasm evaluation work of finger millet.     

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.     

Analysis of the contribution of Mesoamerican and Andean gene pools to European common bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.) germplasm and strategies to establish a core collection

Common bean (Phaseolus vulgaris L.) was introduced in Europe from both Mesoamerican and Andean centres of origin. In this study, a collection including 544 accessions from all European regions showed that the Andean phaseolin types ‘T’ (45.6%) and ‘C’ (30.7%) prevailed over the Mesoamerican ones ‘S’ (23.7%), and accessions with cuboid seed shape (34.9%), maroon coat darker colour seed (44.3%), uniform seed colour (69.6%) were the most frequent. European accessions with phaseolin ‘S’ showed a significantly larger average seed size compared to those from America in the same phaseolin class while those presenting ‘T’ and ‘C’ phaseolin did not. This suggests that, during crop expansion in Europe, sampling or selection favoured the large-seeded races within the Mesoamerican ‘S’ gene pool or, possibly, introgression from Andean germplasm did occur. A core collection was developed using sampling approaches based on the information available in the genebank databases and on phaseolin patterns. Four sampling strategies were used: simple random sampling, and three random-stratified samplings, by logarithm of frequency of accessions by country, by European region, and by phaseolin pattern, respectively. Two sampling strategies resulted in core collections significantly different for phaseolin electrophoretic patterns from the whole collection. Stratification by phaseolin patterns increased the frequency of ‘S’ types (‘C’ type = 33%, ‘T’ type = 5.7% and ‘S’ type = 31.3%). The core collections were validated using seven seed characters, and no significant difference was observed in all strategies. This first developed European bean core collection will help to assess the contribution of the two American gene pools to the European germplasm and their relative importance for breeding purposes.     

Diversity among landraces of Indian snapmelon (<Emphasis Type="Italic">Cucumis melo</Emphasis> var. <Emphasis Type="Italic">momordica</Emphasis>)

Diversity among 36 snapmelon landraces, collected from 2 agro-ecological regions of India (9 agro-climatic sub-regions), was assayed using RAPD primers, morphological traits of plant habit and fruit, 2 yield-associated traits, pest and disease resistance and biochemical composition (TSS, ascorbic acid, titrable acidity). Typical differences among accessions were observed in plant and fruit characteristics and snapmelon germplasm with high titrable acidity and possessing resistance to downy mildew, Cucumber mosaic virus, Zucchini yellow mosaic virus, Papaya ringspot virus, Aphis gossypii and Meloidogyne incognita was noticed in the collection. RAPD based grouping analysis revealed that Indian snapmelon was rich in genetic variation and region and sub-region approach should be followed across India for acquisition of additional melon landraces. Accessions of var. agrestis and var. momordica clustered together and there was a separate cluster of the accessions of var. reticulatus. Comparative analysis of the genetic variability among Indian snapmelons and an array of previously characterized reference accessions of melon from Spain, Israel, Korea, Japan, Maldives, Iraq, Pakistan and India using SSRs showed that Indian snapmelon germplasm contained a high degree of unique genetic variability which was needed to be preserved to broaden the genetic base of melon germplasm available with the scientific community. N. P. S. Dhillon and Ranjana contributed equally to this work and are considered the first authors.     

Patterns of Phenotypic Variation in a Germplasm Collection of Carthamus tinctorius L. from the Middle East

Phenotypic diversity was assessed for quantitative and qualitative traits in a salt-tolerant subset of the international safflower (Carthamus tinctorius L.) germplasm collection originating from 11 countries in three regions (Central Asia, Southwest Asia and Africa) of the Middle East. Phenotypically, the germplasm, among and within regions, was highly variable, especially for rosette- and yield-related traits. Frequency of desirable variants of seven agronomically important traits ranged from 14% for long rosette period to 50% for no or few spines. Level of population differentiation was high for number of capitula per plant (30%), whereas most traits partitioned their diversity (82–87%) within populations. Region-specific nonrandom associations among sets of qualitative traits and the existence of broad morphological and phenotypic diversity in this germplasm were supported by the large number of log-linear models needed to describe qualitative trait associations, the high number of principal components needed to account for total variability, and the low discriminatory power of phenotypic traits among germplasm from regions and countries in the Middle East. These results suggest that adaptation of the species to the wide spatial and temporal variation in the Middle East resulted in a multitude of ecotypes and in enormous amount of local variation. A multivariate selection criterion for high biological and seed yield, long rosette period and no or few spines identified five accessions from Southwest Asia that can be introduced into subsistence farming systems as a multipurpose crop under saline agriculture.     

Sampling a Core Collection of Island Cotton (Gossypium barbadense L.) Based on the Genotypic Values of Fiber Traits

A genetic model, including effects of environments, genotypes, and genotype by environment interaction, was employed to analyze five fiber traits of Island cotton (Gossypium barbadense L.). Genotypic values of 304 accessions were predicted by the adjusted unbiased prediction (AUP). Genetic similarities between different accessions were measured by Mahalanobis distances based on genotypic values. Appropriate sampling strategies, linkage rules in stepwise clustering, and sampling proportion were evaluated. To form a core collection of Island cotton, 60 accessions were sampled by the deviation sampling strategy combined with single linkage rule of hierarchical clustering. The genetic variation and structure captured by the core collection were examined in means, variances, ranges and coefficients of variation, correlation coefficients of quantitative traits, and the accessions distribution plotted by first two principal components between two collections. It was showed that the initial collection was well represented by the core collection for exploiting the Island cotton germplasm. These authors contributed equally to this work.