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The world collection of pearl millet at ICRISAT genebank includes 19,696 landraces. Passport and characterization data of 2,929 accessions belonging to 89 named landraces originating in 15 countries of Africa was used to study the adoption pattern and genetic potential. Out of 89 named landraces under study, 71 were grown in one country, 11 in two countries, six in three countries and one in four countries. Latitude and prevailing climate at collection sites were found as the important determinants of cultivation pattern of landraces. A hierarchical cluster analysis using 12 agronomic traits resulted in five clusters. Cluster 1 for late flowering, short height in rainy season, high tillering and thin panicles; cluster 2 for early flowering; cluster 3 for stout panicles in both the seasons and larger seeds and cluster 5 for longer panicles in both seasons, were found as promising sources. IP 8957, IP 8958, IP 8964 of Iniadi landrace for short height, downy mildew and rust resistance and high seed iron and zinc contents; IP 17521 of Gnali (106.9 ppm) and IP 11523 of Idiyouwe (106.5 ppm) for high seed iron content; IP 17518 of Gnali (79.1 ppm) and IP 11535 of Iniadi (78.4 ppm) for high seed zinc content were the important sources. All accessions of Raa for high seed protein content (>15%) and those of Enele for drought tolerance, were found to be promising sources. Further evaluation of promising sources identified in this study is needed for enhanced utilization of germplasm in pearl millet improvement.
The genebank at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, India holds a collection of 542 accessions from the Caribbean and Central American (CCA) regions, of which 424 were evaluated for eight qualitative and 17 quantitative traits at ICRISAT farm. A hierarchical cluster analysis was performed using the scores of the first nine principal components that resulted in four clusters. The accessions of these four clusters exhibited the following good characteristics: cluster 1 had high pod-bearing length and high seed protein content; those of cluster 2 had high degree of branching, large number of pods per plant and high seed yield per plant; those of cluster 3 had long pods; and those of cluster 4 had larger seeds. In the whole collection of accessions, diversity was found to be maximum (H′ = 0.630+0.026) for plant height and minimum for tertiary branches per plant (H′ = 0.259+0.026). The highest correlation coefficient was observed between racemes per plant and pods per plant (r= 0.914) followed by between pods per plant and seed yield per plant (r= 0.744), and between shelling percentage and the harvest index (r= 0.703). In view of the poor representation of the world collection of pigeonpea (13,771 accessions) from the CCA regions, launching of collection missions in these countries has been suggested to fill gaps and increase the variability. Multi-location evaluation of the collections for agronomic traits at potential locations in the CCA regions and systematic evaluation for nutritional traits and resistance to biotic and abiotic stress could result in the identification of useful genotypes, particularly vegetable types, for use in breeding programmes to develop high-yielding cultivars as well as to release as varieties in these regions.
The International Crops Research Institute for the Semi-Arid Tropics conserves 335 accessions of Pennisetum glaucum subsp. monodii originated in 13 countries. In the present study, the collection was evaluated and assessed for diversity and geographical gaps. A wide variation was observed in the collection for total tillers per plant (16 to 609), productive tillers per plant (12 to 368), leaf length (21.3 to 58.8 cm) and leaf width (8.1 to 33.1 mm), indicating high fodder yield potential of the collection. The accessions of cluster 3 flowered late, grew tall with thick stems and long and broad leaves, and differed significantly from those of cluster 1 and cluster 2. The accessions of cluster 2 were found to be promising for tillering. The highly significant positive correlation (r= 0.944) between total and productive tillers per plant suggests that the selection for total tillers will result in selection for productive tillers. A total of 354 districts located in 86 provinces of eight countries in the primary centre of origin for pearl millet were identified as geographical gaps. The probability map generated using FloraMap in the present study matched quite closely to the origin of pearl millet, supporting the prediction of P.glaucum subsp. monodii occurrence in the primary centre of diversity for pearl millet. The high fodder yield potential of P.glaucum subsp. monodii germplasm and low intensity of collection in countries under study suggest the need for launching germplasm collection missions, exclusively for pearl millet wild relatives to fill taxonomic and geographical gaps in the collection.
The genebank at ICRISAT, Patancheru, India conserves a total of 19,063 pearl millet landraces from latitudes ranging from 33.00° in the Southern Hemisphere (SH) to 34.37° in the Northern Hemisphere (NH). In the present study, the NH was found to be the major region for growing pearl millet landraces (80.5%). More landraces were found at lower latitudes ( < 20°) in both hemispheres than at higher latitudes. The latitude range of 10°–15° in the NH and 15°–20° in the SH were found to be important source regions for the prevalence of pearl millet, with 39.6% and 13.1% in the world collection of landraces, respectively. Landraces from lower-latitude regions on either side of the equator varied widely for all traits. Landraces from the 5°–10°N latitude region flowered late and grew tall in the rainy and post-rainy seasons and produced more tillers. Landraces from the 10°–15°N latitude region produced few tillers and had long and thick panicles with larger seeds. Long-bristled bird-resistant landraces were considerable at latitudes of 10°–15°S and 20°–25°S. The minimum temperature at the collection sites was found to be one of the important factors for determining the patterns of the prevalence of pearl millet across the latitudes. Late-maturing, tall and high-tillering landraces from lower-latitude regions were better sources for fodder production. Early-maturing landraces producing long and thick panicles with large seeds from mid-latitude regions (15°–20°) in both hemispheres were useful for developing high-yielding cultivars. Using the latitudinal patterns of diversity in pearl millet landraces, missions may be launched to explore high-diversity, under-collected and threatened areas for the collection of materials of interest at latitudes of 15°–20°.
Crop wild relatives are important components of agro-ecosystems as potential gene contributors for crop improvement programmes. Cajanus scarabaeoides (L.) Thou., a pigeonpea wild relative is crossable with cultivated pigeonpea and possesses several beneficial traits. Hundred accessions conserved at the ICRISAT genebank were characterized for 13 quantitative and ten qualitative traits to assess the diversity in the collection. Highly significant genotypic variance for leaflet length, days to 5% maturity, seeds per pod, 100-seed weight, seed protein content and trichome density and length was observed. All C. scarabaeoides accessions used in the present study are the best sources for extra early ( < 80 d to 50% flowering) and early maturity (80–100 d to 50% flowering). Eight accessions (ICP 15692, ICP 15696, ICP 15698, ICP 15699, ICP 15712, ICP 15719, ICP 15732 and ICP 15758) and the control ICP 15695 have produced more than 92% healthy pods per plant and higher number of seed per pod (4–6 seeds). Accessions in cluster 2, 3 and 4 with low mean values for days to 50% flowering were found as the best sources for early flowering and maturity. Accessions in cluster 2 and 3 for seeds per pod and cluster 2 for healthy pods per plant were found as promising sources for use in crop improvement. Mean diversity over all clusters was highest (H= 0.57 ± 0.01) for seeds per pod and lowest for days to 50% flowering (0.48 ± 0.02). Significant negative correlation between pods per raceme and healthy pods per plant ( − 0.213) indicated high pod damage in racemes having more pods. Trichome length had highly significant negative association with healthy pods per plant ( − 0.293). The probability map generated using FloraMap, a GIS tool, revealed the occurrence of C. scarabaeoides quite close to the origin and dispersal of pigeonpea. The probability (>75%) map identified a total of 118 provinces covering 790 districts in Bangladesh, Cambodia, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Papua New Guinea, Philippines, Thailand and Vietnam as geographical gaps in the collection. Complete passport data including location coordinates should be collected while collecting the germplasm to analyze the spatial aspects of species distribution.
Chickpea is the third most important grain legume grown in the arid and semi-arid regions of the world. In spite of vast germplasm accessions available in different genebanks, there has been very limited use of these accessions in genetic enhancement of chickpea. However, in recent years, specialized germplasm subsets such as global composite collection, core collection, mini core collection and reference set have been developed. In parallel, significant genomic resources such as molecular markers including simple sequence repeats (SSRs), single nucleotide polymorphisms (SNPs), diversity arrays technology (DArT) and transcript sequences, e.g. expressed sequence tags, short transcript reads, have been developed. By using SSR, SNP and DArT markers, integrated genetic maps have been developed. It is anticipated that the use of genomic resources and specialized germplasm subsets such as mini core collection and reference set will facilitate identification of trait-specific germplasm, trait mapping and allele mining for resistance to biotic and abiotic stresses and for agronomic traits. Advent of the next generation sequencing technologies coupled with advances in bioinformatics offers the possibility of undertaking large-scale sequencing of germplasm accessions so that modern breeding approaches such as genomic selection and breeding by design can be realized in near future for chickpea improvement.
Pigeonpea (Cajanus cajan (L.) Millsp. is one of the most important legume crops as major source for proteins, minerals and vitamins, in addition to its multiple uses as food, feed, fuel, soil enricher, or soil binder, and in fencing, roofing and basket making. ICRISAT's genebank conserves 13,632 accessions of pigeonpea. The extensive use of few parents in crop improvement is contrary to the purpose of collecting a large number of germplasm accessions and has resulted in a narrow base of cultivars. ICRISAT, in collaboration with the Generation Challenge Program, has developed a composite collection of pigeonpea consisting of 1000 accessions representing the diversity of the entire germplasm collection. This included 146 accessions of mini core collection and other materials. Genotyping of the composite collection using 20 microsatellite or simple sequence repeat (SSR) markers separated wild and cultivated types in two broad groups. A reference set comprising 300 most diverse accessions has been selected based on SSR genotyping data. Phenotyping of the composite collection for 16 quantitative and 16 qualitative traits resulted in the identification of promising diverse accessions for the four important agronomic traits: early flowering (96 accessions), high number of pods (28), high 100-seed weight (88) and high seed yield/plant (49). These accessions hold potential for their utilization in pigeonpea breeding programmes to develop improved cultivars with a broad genetic base. Pigeonpea germplasm has provided sources of resistance to abiotic and biotic stresses and cytoplasmic-male sterility for utilization in breeding programmes.
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.
We analysed the patterns of variation for 14 qualitative and 12 quantitative traits in 11,402 pigeonpea germplasm accessions from 54 countries, which were grouped into 11 regions. Semi-spreading growth habit, green stem colour, indeterminate flowering pattern and yellow flower colour were predominant among qualitative traits. Primary seed colour had maximum variability and orange colour followed by cream were the two most frequent seed colours in the collection. Variances for all the traits were heterogeneous among regions. The germplasm accessions from Oceania were conspicuous by short growth duration, short height, fewer branches, pods with fewer seeds, smaller seed size and lower seed yields. The accessions from Africa were of longer duration, taller, with multi-seeded pods and larger seeds. The germplasm diversity indicated by Shannon–Weaver diversity index (H′) pooled over all traits, was highest for Africa (0.464±0.039) and lowest for Oceania (0.337±0.037). The cluster analysis based on three principal component scores using 12 quantitative traits revealed formation of three clusters: cluster 1 includes accessions from Oceania; cluster 2 from India and adjacent countries; and cluster 3 from Indonesia, Thailand, the Philippines, Europe, Africa, America and the Caribbean countries. Pigeonpea-rich countries such as Myanmar, Uganda, and others like Bahamas, Burundi, Comoros, Haiti and Panama are not adequately represented in the collection, and need priority attention for germplasm exploration.
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