Identification of novel major and minor QTLs associated with Xanthomonas oryzae pv. oryzae (African strains) resistance in rice (Oryza sativa L.).

Gustave Djedatin,Mathias Lorieux,Alain Ghesquiere,Valérie Verdier,Ambaliou Sanni,Marie-Noelle Ndjiondjop

doi:10.1186/s12284-016-0090-9

Abstract

BackgroundXanthomonas 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.ResultsThe 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.ConclusionWe 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.

Highlights

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
Most were of relatively small effect except on chromosomes 7 and 11. qBB-4, qBB-5, qABB-9 and qBB-12 mapped to genomic regions where BB resistance quantitative trait loci (QTL) and or Xa genes were previously characterized in other crosses, indicating that BB-resistance genes to Asian and African Xoo strains may be shared by several rice accessions
Xa34(t) resistance gene to Chinese Xoo races V co-localize with qABB-1, the resistance QTL induced by the African Xoo strain MAI1 on rice chromosome 1

Summary

Introduction

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. 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. 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. With the recent expansion and intensification of rice cultivation in Africa, rice diseases have concomitantly increased in most African rice growing areas (Sere et al 2005; Traoré et al 2009). More than 30 R genes, which are given the prefix Xa for Xanthomonas, have been identified so far (for a review see Verdier et al. Djedatin et al Rice (2016) 9:18

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