OCCURRENCE AND INHERITANCE OF MICROSATELLITES IN PINUS-RADIATA

Microsatellites are an important class of DNA marker because of their abundance and length hypervariability. As part of a project mapping th e Pinus radiata genome, we have characterized some of the microsatelli tes in this species. Southern blots were screened with oligonucleotide probes [(CA)(10), (GA)(10), (GAA)(9), (CAA)(8), (CAC)(5), (GACA)(4)] to assess their abundance. CA and GA were the most abundant microsatel lites, while GAA was least abundant. A genomic library in lambda ZAP, coveting 9 X 10(4) kb, was screened with a combined poly(CA) + poly(GA ) probe and yielded 120 positives, approximately one CA or GA microsat ellite every 750 kb of the P. radiata genome. It was found that 25% of the positives were embedded within highly repetitive DNA. Four of the five subclones sequenced contained compound microsatellites, with TA predominating as the additional repeat. Segregation analysis of PCR pr oducts for two microsatellites, PR4.6 and PR9.3, in 96 progeny of a co ntrolled outcross verified simple Mendelian inheritance. Both loci are highly polymorphic with Polymorphism Information Content values of 0. 63 and 0.70 for PR4.6 and PR9.3, respectively. These results indicate that microsatellites are abundant in a conifer genome and can be valua ble markers for pine mapping, fingerprinting, and population genetic s tudies.