A molecular marker tightly linked to P, a gene required for flower and seedcoat color in common bean (Phaseolus vulgaris L.), contains the Ty3-gypsy retrotransposon Tpv3g

Abstract

In common bean (Phaseolus vulgaris L.), the expression of color in flower and seedcoat tissues requires the dominant allele of the P gene. The fully recessive p allele completely suppresses color expression in these tissues, whereas in specific genetic backgrounds, the p(gri) allele potentiates a grayish-white seedcoat and pale violet (nearly white) flowers with two violet dots on the banner petals. As a first step to gaining a better understanding of this important gene, we phenotypically scored an F2 population segregating for P and p(gri) and subsequently screened contrasting bulk DNA samples with oligonucleotide primers to uncover random amplified polymorphic DNA (RAPD) fragments. OU3(2300), an RAPD marker linked in coupling phase to the dominant allele, mapped 1.3 cM from P. The core 'BAT93' x 'Jalo EEP558' recombinant inbred population was scored, and the marker mapped to linkage group B7. The segregating fragment was cloned, sequenced, and shown to possess significant homology to the Ty3-gypsy class of retrotransposons. We have named the element Tpv3g. It is estimated that about 100 copies of the element are present in the common bean genome. Phylogenetic analysis placed Tpv3g in the class A group of plant retrotransposons.