Ough durability of BB R genes is,in component,mainly because mutation of Xoo to overcome R genes (Vera Cruz et alrecent field and laboratory studies have also shown the influence of temperature on the interactions of rice R gene with Xoo. Higher temperatures are conducive to BB illness,and most BB R genes,including Xa,are significantly less productive at controlling BB disease at high temperatures (Vera Cruz et al. ; Webb et al Xanthomonas oryzae (Xo) is usually a diverse species,with distinct phylogenetic lineages comprising US Xo,Asian Xoo,African Xoo,and Xanthomonas oryzae pv. oryzicola (Xoc) (Triplett et al. ; Hajri et al A further lineage improperly named Xanthomonas campestris pv. leersiae (Xcl) comprises strains isolated on weeds (Wonni et al Earlier perform highlighted differences within the race structure amongst Asian and African Xoo strains (Cecropin B site Gonzalez et al Virulence assays revealed three races (A,A plus a) present in Mali,BurkinaFaso,Niger and Cameroon that do not represent any on the identified Xoo races characterized in Asia so far (Gonzalez et al. ; Triplett et al According to experiments carried out on BB isogenic lines (IRBB),BB resistance genes Xa,xa and Xa deliver resistance to some African Xoo strains (Gonzalez et al Despite the fact that in absence of a complete overview of Xoo race prevalence in Africa,we anticipated that Xa,xa and Xa could provide resistance against strains of Xoo in BurkinaFaso,Cameroun and Niger. Regardless of the increasing significance of BB in Africa,small is recognized around the genetic determinism of resistance. O. glaberrima and O. sativa accessions have been screened for resistance to African Xoo strains. The tropical japonica landrace Azucena is susceptible to all African Xoo strains. Few accessions,among them the indica cultivar IR,are extremely resistant to AfricanXoo strains. None of those accessions had the xa or Xa resistance alleles (Djedatin et al. suggesting that these accessions carry new resistance genes that could be fantastic targets for R gene discovery and further deployment. With all the completion of genome sequences for japonica and indica rice (Kawahara et al. and for O. glaberrima (Wang et al. a,b),it’s important to possess a improved image from the various Xa resistance genes and QTLs characterized so far and their positions in the rice genome. The objectives of this study are to: . Identify and analyse the genetic basis of rice resistance to African Xanthomonas oryzae pv. oryzae strains by developing a QTL strategy working with the reference mapping population created of recombinant inbred lines (RIL) derived in the cross between IR and Azucena. . Map novel and identified bacterial blight resistance genes and QTLs to Xoo strains and analyze their colocalization on the reference Nipponbare physical map. For the first time in history,we report on particular resistance QTLs to African Xoo strains.RIL Recombinant Inbred LinesDjedatin et al. Rice :Page ofThis continuous variation of lesion lengths indicates the existence of QTLs underlying the segregation of resistance. Each parents,IR and Azucena,are susceptible to Asian Xoo strain PXO with an average lesion length of . . and cm,respectively. Conversely,IR is resistant to PXO; the Philippines race ,with an typical lesion length of . . cm,whereas Azucena is susceptible with an average lesion length of . . cm. The lesion length from the RILs lines shows a continuous variation with an average PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/21710263 lesion length of . to . cm and . to . cm with PXO and PXO,respectively (Table,indicating the resistance to Asian strains is controlled by QTLs.Mapp.