Qualitative resistance of Hevea to Phyllachora huberi P. Henn

Qualitative observations of Hevea spp. resistance to Phyllachora huberi were carried out on 200 clones in a collection and 21 full-sib progenies under natural conditions of infestation. A total of 42 clones, mostly originating from the natural range of the Hevea genus, and at least two species (H. brasiliensis and H. benthamiana) revealed total resistance to the parasite. For nine of the thirteen `resistant ×susceptible' and `resistant × resistant' progenies studied, the ratio of susceptible: resistant plants suggested the existence of a total resistance mechanism produced by a dominant allele at a single locus for the P. huberi race(s) present at the study site. For three of the progenies involving the same resistant parent, it was possible to locate the gene (called Phr) at 14.7 cm from the adhisozyme locus.