Identification of novel major and minor QTLs associated with Xanthomonas oryzae pv. oryzae (African strains) resistance in rice (Oryza sativa L.).
BACKGROUND
Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of Bacterial Leaf Blight (BB), an emerging disease in rice in West-Africa which can induce up to 50 % of yield losses. So far, no specific resistance gene or QTL to African Xoo were mapped. The objectives of this study were to identify and map novels and specific resistance QTLs to African Xoo strains.


RESULTS
The reference recombinant inbred lines (RIL) mapping population derived from the cross between IR64 and Azucena was used to investigate Xoo resistance. Resistance to African and Philippine Xoo strains representing different races was assessed on the RIL population under greenhouse conditions. Five major quantitative trait loci (QTL) for resistance against African Xoo were located on different chromosomes. Loci on chromosomes 1, 7, 9, 10 and 11 explained as much as 13 %, 37 %, 13 %, 11 % and 15 % of resistance variation, respectively. A major novel QTL located on chromosome 7 explained 37 % of the phenotypic variance to the African Xoo corresponding to race A3 whereas that on chromosome 11 is effective to all African races tested. Together with genes and QTLs for resistance to bacterial blight previously described, the QTLs described here were mapped onto the reference O. sativa subs japonica (var. Nipponbare) physical map.


CONCLUSIONS
We characterized new resistance QTLs. While some co-localize with known resistance genes/QTLs to Asian strains, others are specific to African strains. We result with new information on genes and QTLs for resistance to bacterial blight that will be useful for controlling the disease.
Université Polytechnique d'Abomey, BP 2282, Abomey, Benin. djedatingustave@yahoo.fr.
Gustave
G
Djedatin
Africa Rice Center (AfricaRice), 01 BP2031, Cotonou, Benin.
Marie-Noelle
MN
Ndjiondjop
Université d'Abomey Calavi, 01 BP526, Cotonou, Benin.
Ambaliou
A
Sanni
UMR Diversité, Adaptation et Développement des plantes (DIADE), Institut de Recherche pour le Développement, 911 Avenue Agropolis BP 64501, 34394, Montpellier Cedex 5, France.
Mathias
M
Lorieux
IPME Interactions Plantes Microorganismes, Environnement, IRD - Cirad - University Montpellier, 34394, Montpellier, France.
Valérie
V
Verdier
UMR Diversité, Adaptation et Développement des plantes (DIADE), Institut de Recherche pour le Développement, 911 Avenue Agropolis BP 64501, 34394, Montpellier Cedex 5, France.
Alain
A
Ghesquiere
Molecular mapping; Oryza sativa; QTL; Xanthomonas oryzae pv. oryzae; disease resistance