INTERGENIC RIBOSOMAL SPACER VARIABILITY IN HEXAPLOID OAT CULTIVARS AND LANDRACES

The variability of the ribosomal DNA intergenic spacer (IGS) was analy sed in 58 cultivars from a worldwide collection and 14 Spanish landrac es of hexaploid oats. IGS sequences were amplified by the polymerase c hain reaction using primers complementary to conserved sequences of th e ribosomal genes. Twelve IGS length variants ranging from 4090 to 321 0 bp were observed; some are frequent and distributed worldwide wherea s others seem to be restricted to Spanish landraces. Variability in le ngth variant patterns among cultivars and landraces was extensive: a t otal of 28 different patterns was observed, which included two to six length variants. No variation was detected within cultivars except in six Spanish landraces. Length variants and patterns were unevenly dist ributed between bred cultivars, in which the longest were frequent, an d landraces, in which some of the shortest were observed. No different iation was found between spring and winter sown material. The possible relationship between IGS length variants and breeding and environment al adaptive responses, other than those related to the spring or winte r habit, are discussed.