Biological Characterization Of Rice Brittle Culm Mutants And Analysis Of Their Biomass Enzymatic Digestibility

Bioenergy is increasingly considered as a sustainable energy for partial non-fossil energy supply and environmental care. Rice is a major food crop in China, and can provide abundant biomass residues. Thus, genetic selection of bioenergy crops could not only maintain a similar grain yield, but also provide the biomass residues with high enzymatic digestibility for lignocelluloses biofuels. In this study,18 rice brittle culm mutants were identified as the potential energy crop candidates including observation of biological phenotypes and analysis of biomass enzymatic digestibility. The main results were concluded as follows:1. Compared with wild type (NPB), all mutants displayed a slightly shorter plant height and lower tension stress.2. Cell wall chemical composition analysis indicated that rice brittle culm mutants contained significantly lower cellulose level and more hemicelluloses and lignin contents than that of wild type during the heading stage. In the mature stage, however, both mutants and wild type showed a similar lignin level.3. The rice mutants appeared to have a stronger resistance to lodging than NPB did, but mutants had higher number of panicles, unchanged single plant spike weight, seed setting rate and 1000-grain weight, suggesting that the mutants were not much affected with their seed yields. In addition, the mutants exhibited higher biomass product than that of wild type.4. With respect to the culm-brittle property, all mutants were detected with much higher biomass enzymatic digestibility upon various acid and alkali pretreatments in rice residues from both heading and mature stages.5. In addition, expression levels of the major genes involved in cell wall biosynthesis were determined in the six representative mutants. The RNA transcript levels were consistent with their cell wall composition alternation.In conclusion, the selected brittle culm mutants were of the normal agronomic traits, similar grain yield, high biomass product and efficient lignocellulosic enzymatic digestibility. The results suggested that the rice brittle culm mutants could be applied for energy crop breeding.