Abstract:The mutant nbc(t) was a brittle culm mutant of rice found in the offspring of 93112/IRBB21.The all tissues of plant of mutant nbc(t) are brittle during the whole growth.The main agronomic characters of the brittle mutant were investigated and gene mapping of brittle trait was initially made.The results showed that the main agronomic traits of nbc(t) were as similar as the parent 9311 except that its yield was low.The rice quality of nbc(t) was also similar to 9311 except of head rice rate.The yield and rice quality of hybrid between Guangzhan 63-4S and nbc(t) were as same as that of Yangliangyou 6.Comparing with 9311,the anti-booklet strength was similar,but stretching resistance was lower.The cellulose content in culm of nbc(t) was lower than that of 9311 by 17%.The genetic analysis showed that the brittle culm trait was controlled by two pairs of dominant genes,which were mapped on two loci of chromosome 9,namely,one locus was between the SSR marker RM3700 and RM24371 with the genetic distance of 1.3 cM and 3.1 cM ; another locus was outside of the INDEL marker CL062 and CL045 with the genetic distance of 1.6 cM and 6.0 cM.