Identification of resistance gene analogs in Phaseolus vulgaris var. aborigineus

STENGLEIN S.A. & BALATTI P.A.

Salta, Salta

Simposio; Phaseomics IV: Genomics and Biotechnology of Phaseolus; 2005

Plants are always exposed to pathogens, while some of them are susceptible other ones are resistant, which is due to the absence/presence of resistance (R) genes. They belong to a large class of genes that code for large proteins, most of them with conserved motifs such as a nucleotide binding site (NBS) near the N-terminus, and a leucine¨Crich repeat (LRR) residue near the C-terminus. By means of primers complimentary to conserved sequences, homologues to R genes have been amplified and cloned and are known as resistance gene analogs (RGAs).  Considering that wild relatives of common beans can be a source of disease resistance genes and therefore of genetic diversity, the aim of this work was to isolate and characterize RGAs from wild common beans, P. vulgaris var. aborigineus (Burkart) Baudet. Among 22 putative P. vulgaris var. aborigineus RGA clones sequenced, 15 were homologues to RGAs from other plants species, mostly legumes and common bean as revealed by BLAST in the NCBI database. The sequences had high levels of identity (¡Ý 80%) with RGAs from the Ur-6, a gene that confers resistance to bean rust Uromyces appendiculatus, a QTL associated with resistance to anthracnose (Colletotrichum lindemuthianum) and angular leaf spot (Phaeoisariopsis griseola), and to an RGA that partially contributed to resistance against the Bean golden yellow mosaic virus (BGYMV) and anthracnose. Given the paucity of knowledge regarding molecular organization of R genes in P. vulgaris var. aborigineus, the RGAs described in this work might be useful probes to map, characterize, and manipulate R genes of bean genome. P. vulgaris var. aborigineus might be an important source of genes coding for resistance to diseases, since several RGAs were identified in a wild bean population, suggesting that wild beans possesses an array of resistance genes against a wide spectrum of diseases. This work is the first step aiming to the identification of R genes in P. vulgaris var. aborigineus, and demonstrates the potential importance of this wild common bean as a source of resistance genes.