Abstract
Maize is the basis of nutrition of domesticated herbivores and one of the most promising energy crops. The presence of lignin in the cell wall, tightly associated to carbohydrates, prevents the physical access of enzymes such as cellulase, limiting the carbohydrate degradability and consequently the energy value. To increase the utilization of the biomass cellulose content, the challenge of breeding programs is to lower or modify the lignin components. In maize several mutations are able to modify the lignin content and in particular the mutation in brown midrib3 (bm3) gene appeared as one of the most promising in breeding programs. Unfortunately this mutation has several negative pleiotropic effects on various important agronomic traits such as stay green, lodging and susceptibility to several infections.The maize Brachyitic 2 (br2) gene encodes for a putative protein involved in polar movement of auxins. br2 mutant plants are characterized by shortening of lower stalk internodes, unusual stalk strength and tolerance to wind lodging, darker leaves persisting longer in the active green state in comparison to wild type plants, suggesting a possible utilization of br2 plants to counteract the negative effects of the bm3 mutation. In this work, we report the generation and a preliminary characterization of the double mutant bm3 br2, suggesting the potential use of this new genetic material to increase biomass cellulose utilization.
Highlights
Cellulose is a linear polymer of glucose units, joined by β-1,4 glycosidic linkages and organized in microfibrils by intra and intermolecular hydrogen bonds
With the aim of reducing the negative effects associated to the reduced lignin content in maize bm[3] mutant we generated the double mutant br2bm[3] and in this paper we present the phenotypical, molecular, histological and chemical characterization of this new genetic material
The pedigree selections were assisted by molecular genotyping of the plants using primers specific for br2/Brachytic 2 gene (Br2) and bm3/B3 alleles. 5 to 10 F2 plants were selected for each genotype and crossed with each other by pollen pooling for three generations and after 3 more cycles of self pollination we obtained the the 4 AI-RILs, the characterization of which is the object of this paper (Fig. 1)
Summary
Maize is the basis of nutrition of domesticated herbivores and one of the most promising energy crops. To increase the utilization of the biomass cellulose content, the challenge of breeding programs is to lower or modify the lignin components. The tight association of lignin to cellulose prevents the physical access of hydrolytic enzymes such as cellulase, and limits the use of cellulose as a glucose source. For this reason the challenge of breeding programs aimed at improving maize for silage and biofuel production is to lower or modify the lignin components. Lignin plays an important role in the plant’s life, reinforcing the structural integrity of cell walls, contributing to plant standability and resistance to biotic and abiotic stresses[3]
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