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- Author or Editor: Stephen Kresovich x
Indiscriminate growth can lead to germplasm collections that are too large to maintain, too large to use, or both. Curators' budgets do not often increase with collection size, so conservation and utilization activities are hindered. Maintenance of genetic integrity in large collections is practically impossible. Evaluation is restricted to easily-observed traits, potentially limiting utilization. One strategy to improve management of large collections is the core collection concept, proposed by O.H. Frankel in 1984 and subsequently expounded by A.H.D. Brown. It establishes one subset of accessions, the core, selected to represent “with a minimum of repetitiveness, the genetic diversity of a crop species and its relatives”. The other subset, the reserve, includes all accessions not in the core. Both subsets are conserved according to the highest standards feasible, but the core receives priority for characterization and evaluation to facilitate use and provide subsequent directed access to the entire collection. Use and abuse of the core concept will be discussed, including: definition of terms, genetic and statistical assumptions, and practical implementation.
Genetic variation and relationships in genetic resources collections can be assessed using molecular genetic markers. We examined the applicability of the RAPD assay for quick, cost-effective, and reliable use in improving collection management. Fourteen accessions of Brassica oleracea spp. capitata `Golden Acre' (cabbage) were screened using nine decamer oligonucleotide primers. We obtained 110 reproducible fragments, of which 80 were polymorphic, ranging in size from 370-1730 bp. Individual accessions were readily distinguished. A cluster analysis of genetic distances generated by bootstrapping reflected all known genetic relationships, except one. Bulking strategies were also investigated. RAPD markers can be applied to gene bank management to measure variation, identify accessions, and establish genetic similarity at the intra-specific level addressing the needs of both curators and users.
Fifty-two germplasm accessions of Chinese vegetable Brassicas were analyzed using 112 random amplified polymorphic DNA (RAPD) markers. The array of material examined spanned a wide range of morphological, geographic, and genetic diversity, and included 30 accessions of Brassica rapa (Chinese cabbage, pakchoi, turnip, broccoletto), 18 accessions of B. juncea (leaf, stem, and root mustards), and 4 accessions of B. oleracea ssp.alboglabra (Chinese kale). The RAPD markers unambiguously identified all 52 accessions. Net and Li genetic similarities were computed and used in UPGMA cluster analyses. Accessions and subspecies clustered into groups corresponding to the three species, but some accessions of some subspecies were most closely related to accessions belonging to another subspecies. Using genetic similarities, it was found that Chinese cabbage is more. likely to have been produced by hybridization of turnip and pakchoi, than as a selection from either turnip or pakchoi alone. RAPD markers provide a fast, efficient technique for diversity assessment that complements methods currently in use in genetic resources collections.
Fifty-two germplasm accessions of Chinese vegetable brassicas were analyzed using 112 random amplified polymorphic DNA (RAPD) markers. The array of material examined spanned a wide range of morphological, geographic, and genetic diversity, and included 30 accessions of Brassica rapa L. (Chinese cabbage, pakchoi, turnip, and broccoletto), 18 accessions of B. juncea (L.) Czern. (leaf, stem, and root mustards), and four accessions of B. oleracea L. ssp. alboglabra (Chinese kale). The RAPD markers unambiguously identified all 52 accessions. Nei-Li similarities were computed and used in unweighed pair group method using arithmetic means (UPGMA) cluster analyses. Accessions and subspecies were clustered into groups corresponding to the three species, but some accessions of some subspecies were most closely related to accessions belonging to other subspecies. Values for Nei-Li similarities suggest that Chinese cabbage is more likely to have been produced by hybridization of turnip and pakchoi than as a selection from either turnip or pakchoi alone. RAPD markers are a fast, efficient method for diversity assessment in Chinese vegetable brassicas that complements techniques currently in use in genetic resources collections.