DNA profiling and plant variety registration. III: The statistical assessment of distinctness in wheat using amplified fragment length polymorphisms

The use of AFLP analysis to produce DNA profiles from a set of 55 wheat varieties, commonly grown in the UK over the past 60 years, is described. Using six different primer pairs, 90 polymorphic bands were readily recognised and recorded. These AFLP bands are not significantly clustered and hence can be used with some confidence, even though they are not mapped. Statistical approaches to the analysis of the data were developed such that the discrimination between the varieties achieved by the use of the six primer pairs, both separately and in combination, could be derived and compared to that achieved by a common set of morphological descriptors. Various criteria for the definition of distinctness in terms of the number of band differences required between pairs of varieties were also compared. In general, higher levels of discrimination were achieved by the inclusion of greater numbers of bands in the analysis. The optimal number of polymorphic bands appears to be between nu and 2 nu, where nu is the number of varieties under test. Discrimination levels were adversely affected if the number of bands was below nu/2. Distinctness levels achieved by the use of molecular markers can be calibrated so that they reproduce those seen with morphological characters. The results are discussed in relation to the possible use of DNA profiling methods for distinctness, uniformity and stability testing.