Recherche sur le riz : accès libre

Abstrait

Evaluation of Elite Rice Varieties Unmasks New Sources of Bacterial Blight and Leaf Streak Resistance for Africa

Issa Wonni

Background: Bacterial Leaf Blight (BLB) and Bacterial Leaf Streak (BLS) diseases respectively caused by Xanthomonas oryzae pv oryzae (Xoo) and X. oryzae pv oryzicola (Xoc) have become a real threat to rice production in West Africa. Genetic and pathogenicity studies revealed African X. oryzae (Xo) pathovars to be both fairly distant from their Asian counterparts. It is therefore mandatory to evaluate whether available major resistance genes are adapted for an efficient and durable control of BLB in Africa. As to BLS no resistance sources have been identified in rice so far. Results: We screened eleven upland and lowland elite rice varieties cultivated in Burkina Faso for resistance to bacterial blight and bacterial leaf streak. We show that all five upland varieties including three NERICAs are highly resistant to each of the three races of Xoo identified in Africa and generally susceptible to several strains from Asia. We next demonstrated that resistance is occurring independently of the plant developmental stage. Strikingly, phenotyping and in planta growth curves assays showed that the five varieties are also highly resistant to a set of Xoc strains representative of the diversity in West Africa. Finally, we show that resistance of the NERICA varieties to both Xoo and Xoc is likely to be inherited from the O. sativa ssp. japonica rather than the O. glaberrima parental lines. Conclusion: We identified and characterized rice accessions exhibiting new sources of resistance against African Xoo and Xoc strains specifically. These results provide important perspectives for the control of BLB and BLS in West Africa.