Gene symbolization for the blast resistance was discussed in the RGC
Coordinating Committee meeting, which was held at Yokohama, Japan, on August
31, 1993 on the occasion of the 15th International Botanical Congress. The
committee noted that there is no uniformity in naming blast resistance genes.
Dr. S. Kiyosawa designated genes with the first one or two letters of a variety in which the gene was detected first. For example, the blast resistance genes from Aichi Asahi and Kanto 51 were symbolized as Pi-a and Pi-k, respectively. Chinese scientists continue to use this system. IRRI scientists have started using the numerals to designate blast resistance genes such as Pi-1, Pi-2, etc. Scientists at the Cornell University designate blast resistance genes with the symbol Br.
To avoid the confusion and to conform to the rules of gene nomenclature in the naming of blast resistance genes, the committee agreed to designate the genes with Pi followed by a numeral. However, the gene symbols assigned by Dr. Kiyosawa will be retained. When a blast resistance gene is identified, it should be designated with Pi followed by a numeral with suffix t (tentative). If the allelism tests reveal it to be allelic to one of the Kiyosawa genes, then the old gene symbol should be used. If the gene is found to be non-allelic to all of the Kiyosawa genes, then the gene symbol Pi with numeral would be retained and the suffix (t) is removed. Research workers are requested to follow these rules.