DNA fingerprinting to confirm possible genetic duplicates in cassava germplasm

In large ex situ germplasm collections, such as that maintained at CIAT for cassava, it is common to observe duplicates. The presence of duplicate clones increases the cost of conservation without contributing to representation or the available genetic base for crop improvement. To identify groups of suspected duplicates, identical in their morphology and alfa beta-esterase isozyme patterns, ClAT`s Cassava Program (in collaboration with the Genetic Resources, Biotechnology, and Biometry units) is implementing a model in which DNA fingerprinting is an important component. DNA fingerprinting has been carried out using M13 (Cla1 - Bsm1 fragment) and cassava genomic probes, improving the discriminatory resolution among suspected duplicates. Southern blot hybridization was used to screen 85 clones that formed 35 groups of possible genetic duplicates. The number of clones per group ranged from two to four. Fingerprint analysis indicated that 29 groups (83 percent) showed undistinguished M13 hybridization patterns of the initial population, while the other six groups (17 percent) differed in their M13 and cassava genomic probes hybridization patterns. Given the success of this first test, the technique has been adopted for testing the remaining clones (about 1000) suspected of being possible duplicates. Priority has been given to groups that contain more than six clones, to those country collections represented by a relatively large number of clones, to core collection materials, and to country collections suspected as contributing a high percentage of duplicates