Characterization And Gene Mapping Of A Brittle Culm Mutant Nbc(t) Of Rice

Rice is one of the most important food crops in the world, it spreads over more than 120 countries, covering about 11% of the fields on the globe, and 600 million tons harvested each year. Rice feed half of the people in the whole world. Number of types, widely planted areas, high value with the small chromosomes form of rice made it the model crop of the unifacial leaf plant. In the 7000 years of rice evolutionary, it generated lots of mutants by natural and artificial selecting. Nagao and Takahashi (1963) found brittle culm rice mutant bcl. In past more than 40 years, the researches on several brittle culm mutants of rice were carried on. With studies of cell wall shape, molecular mechanism of the mechanical strength, signal control of cell growth, and the use as forage of brittle culm rice. The research on brittle culm rice is unceasingly thorough.In this paper, we studied a brittle culm mutant nbc(t) which was found out from the offspring of 9311/IRBB21. The object of this paper is to make an initial gene mapping of nbc(t), and study the differences of agronomic character and grain quality between the mutant and the wild type. This research will provide primary scientific evidence for deeply study and application of this brittle mutant.The main results are as follows:1. This brittle culm mutant nbc(t) was a natural dominant brittle mutant. nbc(t) has reduction in mechanical strength, but its height and plant types were similar to the wild type 9311, which was different from the other brittle mutants.2. The results of characterizing agronomic and grain quality traits showed that nbc(t) had same quantity with 9311 on main agronomic traits, but the yield of grain had a small lower than 9311; The grain quality of nbc(t) was not different from 9311, except the head rice percentage.3. Comparing of the mechanical strength between nbc(t) and 9311, including the tension stress and the bending strength showed that nbc(t)'s bending strength is equal to 9311, which means if you want to buckle the culm of rice, the force you imposed on the mutant is the same to the wild type, it's also the cause of this mutant to lodging resistance. The tension stress of nbc(t) was about 69% lower than the wild type, means the force you imposed to break the mutant was less than the wild type.4. At the same time, we measured the ingredient of the rice culm, it showed that the cellulose content of the mutant was 17% lower than the wild type, and the lignin content was 5% more than the wild type. 5. The cytological inspection indicated that the cell shape and cell number of nbc(t) were decreased than 9311; The sclerenchymatous cell layers and the shape of vessels were the same.6. Genetic analysis for the nbc(t) gene:Through investigations and genetic analysis in 12 F2 genetic populations and four BC1 genetic populations, we found that the brittle trait of nbc(t) was controlled by one or two pair of dominant genes.7. Initial map of nbc(t):in nbc(t)/KBLB67 and nbc(t)/yujing6 two F2:3 populations, nbc(t) was mapped on two loci of chromosome 9, one was between the SSR marker RM3700 and RM24371 with the genetic distance of 1.3 cM and 3.1 cM; the other was located near the INDEL marker CL062 and CL045 with the genetic distance of 1.6 cM and 6.0 cM.