Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/1997
Publication Date: N/A
Technical Abstract: Blast disease has been a common problem in most rice growing areas in the world and can result in 10-50 percent yield losses. Most blast epidemics have been attributed to a breakdown of major genes for blast resistance due to the new races of the pathogen and environmental conditions conducive to blast development. Some blast resistances are quantitative in nature and are known as partial resistance or field resistance. Partial resistance is characterized by a reduced rate of disease development and is usually polygenic, race non-specific, and presumably more durable. To locate genes for partial resistance, a population of F8 RILs from Lemont/Teqing was planted in single-row plots replicated three times. Plots were evaluated for partial resistance to rice blast using the Standard Evaluation System (SES) for rice blast rating, percentage diseased leaf area (percent DLA), and area under disease progress curve (AUDPC). Percent DLA and SES ratings were taken at weekly intervals for five weeks, allowing study of the temporal expression of the identified QTLs. QTLs affecting partial resistance were located by correlating phenotypic data with RFLP data on previously mapped markers. For all the detected QTLs, Teqing was the donor of the resistance allele. Loci identified from diverse populations and studies may prove to be more stable in expression and more useful. QTLs located at or alongside major resistance genes were expressed earlier and more consistently throughout the seedling stage than the QTLs that mapped to chromosomal regions not associated with major blast resistance genes. Our results suggest that strategic pyramiding schemes, where the temporal expression and race specificities of the genes and QTLs are considered, can indeed provide durable resistance to a broad spectrum of blast races.