II Germplasm and Genetic Diversity
Genetic Resources of Triticum
Abstract The political framework and the development of molecular biology and electronic data management caused a general paradigm shift in plant genetic resources (PGR), exemplified here for wheat. (1) In situ versus ex situ maintenance of PGR. Ex situ maintenance lost predominance. Wild wheats are effectively maintained in the wild; landraces do well on farm. New methods did not lead to the expected progress. (2) Inclusion of neglected and underutilized crop species. Some species are probably extinct in traditional cultivation areas, whereas landraces were recently found for others. Wild relatives have gained importance in wheat breeding: besides wild Triticum species, also Aegilops, Secale, Hordeum and other genera are used. ×Triticosecale reached world importance; ×Tritordeum will follow soon.
(3) Methods of analysing diversity within and between taxa. New technology yields new insights in the structure and evolution of populations. (4) Genetic erosion is a problem, also inside genebanks. (5) Landraces show complex morphological diversity. Infraspecific classification systems are useful for their characterization and handling, but less recognised by breeders. (6) Methods of evaluation. Molecular markers identify genetic differences on a fairly simple level without reference to ecological adaptation. (7) Genebanks should expand classical evaluation programmes. Pre-breeding will gain importance. (8) Storage and reproduction in genebanks is done effectively and cost-efficiently under long-term conditions, but strategic concepts for reproduction are needed. Traditional methods are often neglected, and modern possibilities over-emphasized. Maintenance of landraces in genebanks and on farm poses challenges. PGR work is conservative. Landraces can be studied by traditional methods; molecular methods can resolve specific questions.
Keywords Crop wild relatives • Diversity • Ex situ • Evaluation • In situ • Landraces • Neglected crops • Paradigm shift • Wheat
The importance of wheat as a world crop is reflected by the large amount of wheat accessions in the world's genebanks. The FAO (2010) estimated that wheat has the largest number of accessions (856,000), followed by rice (774,000) and barley (467,000). An earlier count (Knüpffer 2009) yielded 732,000 wheat accessions. Large collections have been brought together, especially during the period of the Plant Genetic Resources Movement, described by Pistorius (1997) for ca. 1960–1990. A prominent figure in this Movement has been Erna Bennett (Hanelt et al. 2012) who organised the First Technical Conference on Plant Genetic Resources (Bennett 1967), along with Sir Otto Frankel, Jack Harlan, and Jack Hawkes.
In the beginning of the 1990s, a general paradigm shift (Hammer 2003) was observed in the discipline of plant genetic resources (PGR). The “Convention on Biological Diversity” (CBD 1992) substituted and partly replaced an earlier (1983) instrument, the “International Undertaking on Plant Genetic Resources for Food and Agriculture” of the FAO. A harmonization process between both agreements resulted in the “International Treaty on Plant Genetic Resources” (FAO 2001), still in a state of needing improvements (Moore and Tymowski 2005). Different constituents of plant biodiversity were named differently and, accordingly, treated differently.
Apart from this political framework, a second challenge for PGR arose from the rapid development of molecular biology and of electronic data documentation, management and exchange.
The political and scientific processes together led to a general paradigm shift in PGR, which is here exemplified for wheat.