VOLKER SNIADY, WOLFGANG ROHDE, E. RITTER, D. BECKER, ANA HERRÁN
Max-Planck-Institute for Plant Breeding Research, Department of Plant Breeding and Yield Physiology, Germany
Centro de Investigacion y Mejora Agraria (NEIKER), Spain
Coconut (Cocos nucifera L.) and oil palm (Elaeis guineensis JACQ.) are the two most important perennial oil crops. Both crops are being studied in an EC-funded INCO-DEV (International Cooperation with Developing Countries) project with the title: "Construction and exploitation of high density DNA marker and physical maps in the perennial tropical oil crops coconut and oil palm: from biotechnology towards marker-assisted breeding" (LINK2PALM). The objectives are (i) to provide the methodological basis and molecular tools for improving the breeding efficiency in both crops, (ii) to develop DNA marker-based breeding strategies in collaboration with the most important countries in coconut and oil palm production and (iii) to directly transfer to developing countries small-scale technological solutions for the genetic improvement of these tropical oil crops. As a basis to achieve these objectives, high-density (HD) molecular linkage reference maps are being developed for standard mapping populations in coconut and oil palm. These individual reference maps serve for (i) their integration into a general reference map for both crops, (ii) QTL analyses and (iii) physical mapping approaches. Usually in a physical map, defined individual DNA fragments of the crop's genome are ordered and anchored on a linkage map in a way that contiguous regions of overlapping sequences are formed. These maps are useful for genome-wide gene discoveries like map-based cloning of interesting genes, and provide an efficient prerequisite tool to enable marker-assisted selection on important traits in future breeding programs. To develop a physical map, genomic libraries of oil palm and coconut have been constructed consisting of more than 120,000 individualized cosmid clones each (2-3 genome equivalents). Out of these libraries, in house developed software and commercial robots were used to assemble 28,800 individualized COS clones into 30 8-dimensional pools which are currently used for associating single COS clones of genomic DNA to linkage-mapped AFLP markers. With such a multi-dimensional pooling system a minimum of PCR reactions is required. In this efficient way it seems to be feasible to speed up the time-consuming process of physical mapping, and, so far, the time expense to create new breeding lines based on targeted genomic information.
Keywords: Cosmid library, linkage maps, molecular marker, oil crops, physical mapping, pools