Rice Genetics IV - IRRI books - International Rice Research Institute

Box no. 1The saga of Xa21THE STORY OF BACTERIAL blight diseaseresistance gene Xa21 epitomizesnearly all the IPRB program componentsin Figure 1 and above all the extensionof the program goals from knowledge generationto production of improved rice varieties.The following is a brief “telegraphic”coverage of that voyage of discoveryand ultimate application for thebenefit of Asian rice farmers.1977 Oryza longistaminata linesoriginating from Mali, Africa,noted to carry broad-spectrumresistance to bacterial blight198? Xa21 transferred into O. sativabackground through interspecifichybridization (Khushet al 1991)1990 Xa21 locus RFLP mapped(Ronald et al 1992)1992-95 Map-based cloning via bacterialartificial chromosome libraryconstruction (Wang et al1995); Xa21 sequencing anddemonstration of engineeredresistance of a susceptiblegenotype (Song et al 1995,Wang et al 1996)1995 Patent filed and eventual U.S.Patent Number 5,859,339granted to Ronald et al, 12January 1999; innovativeinstitution founded (GeneticsResources Recognition Fund—University of California, Davis)to use license fees/royaltiesto assist science capacitybuilding in developing coun-tries (Ronald PC, personalcommunication, 28 September1997)1997 Xa21 pyramided with otherXa R genes via PCR-basedmarker-assisted selection(Huang et al 1997, Reddy etal 1997)1998 Xa21 experimentally transformedinto elite rice varieties(Tu et al 1998, Zhang et al1998)1999 Field trials of pyramidedXa genes, including Xa21,reported in China, India, Indonesia,and Philippines (RockefellerFoundation 1999)2000 Commercial hybrid restorerline genetically improved bymarker-assisted selection ofXa21 and resulting hybrid ricedemonstrates field-level efficacy(Chen et al 2000)Over the 17-year period of the IPRB, weestimate that four Predoctoral, fourPostdoctoral, and five Biotechnology CareerFellows took part in the above internationalresearch collaboration, transferringthe basic skills, knowledge, andother materials to their home institutions.In one prominent publication, Song et al(1995), the 12 authors represented fourresearch institutions in China, France,Korea, and the United States. The researchbackground for that publicationtruly represented unprecedented internationalcollaborative research, training,and capacity building spanning the globe.The Rockefeller Foundation's International Program on Rice Biotechnology 45