engleski

Characterization of NBS-LRR class resistance-gene analogs in faba bean and chickpea

A PCR approach with degenerate primers designed from conserved NBS-LRR (nucleotide binding site leucin-rich repeat) regions of known disease resistance (R) genes was used to amplify and clone homologous sequences from five faba bean (Vicia faba L.) lines and two chickpea (Cicer arietinum L.) accessions. Sixty-nine (44 from faba bean and 25 from chickpea) sequenced clones showed homologies to various R genes deposited on the GenBank database. Using 70% of amino acid sequence identities as a threshold value, these clones were grouped into ten classes of resistance gene analogs (RGA01 to RGA10). The number of clones per class varied from 1 to 30. RGA classes Nos. 1, 6, 8, and 9 were comprised solely by clones isolated from faba bean while classes Nos. 2, 3, 4, 5, and 7 included only chickpea clones. RGA10, showing 99% of within-class identity, was the only class consisting of both faba bean and chickpea clones. A phylogenetic tree based on the deduced amino-acid sequences of 12 representative clones from ten RGA classes and the NBS domains of six R genes (I2 and Prf from tomato, RPP13 from Arabidopsis, Gro1-4 from potato, N from tobacco, L6 from flax) clearly indicated the separation between TIR (Toll/Interleukin-1 receptor homology: Gro1-4, L6, N, RGA05 to RGA10) and non-TIR (I2, Prf, RPP13, RGA01 to RGA04) type NBS-LRR sequences. The development of suitable polymorphic markers based on cloned RGA sequences to be used in genetic mapping will facilitate the assessment of their potential linkage relationships with disease resistance genes in faba bean and chickpea.

disease resistance; resistance gene analog; Vicia faba L.; Cicer arietinum L.; resistance breeding

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