A saturated genetic linkage map of rubber tree (Hevea spp.) based on RFLP, AFLP, microsatellite, and isozyme markers

The first genetic map for Hevea spp. (2n = 36) is presented here. It is based on a F1 progeny of 106 individuals allowing the construction of a female, a male, and a synthetic map according to the pseudo-testcross strategy. Progeny were derived from an interspecific cross between PB260, a H. brasiliensis cultivated clone, and RO38, a H. brasiliensis x H. benthamiana interspecific hybrid clone. The disomic inheritance observed for all the codominant markers scattered on the 2n = 36 chromosomes revealed that Hevea behaves as diploids. Homologous linkage groups between the two parental maps were merged using bridge loci. A total of 717 loci constituted the synthetic map; including 301 RFLPs, 388 AFLPs, 18 microsatellites, and 10 isozymes. The markers were assembled into 18 linkage groups, thus reflecting the basic chromosome number, and covered a total distance of 2144 cM. Nine markers were found to be unlinked. Segregation distortion was rare (1.4%). Average marker density was 1 per 3 cM. Comparison of the distance between loci in the parental maps revealed significantly less meiotic recombination in the interspecific hybrid male parent than in the female parent. Hevea origin and genome organisation are discussed.