Journal of Energy Bioscience 2025, Vol.16, No.3, 151-162 http://bioscipublisher.com/index.php/jeb 153 However, whether starch ferments well depends not just on how much starch there is but also on its structure. Certain genetic traits can make the starch easier to break down by enzymes, making it easier to convert. Some high-oil maize varieties accumulate more triglycerides in the kernels, which could be used to produce biodiesel. But these types of maize usually have less starch than regular maize (Li et al., 2022). Researchers are working on how to increase both oil and starch levels without affecting yield or plant health. They are using molecular markers and genomic prediction methods to find genes that help improve both starch content and fermentability (Gesteiro et al., 2023; Pratikshya et al., 2025). 3.2 Cell wall composition and lignin content for straw ethanol production Lignocellulose is mainly made of cellulose, hemicellulose, and lignin. Lignin makes plants harder to break down, so it’s harder to convert into sugar. Breeding efforts now focus on reducing lignin content or changing its structure to improve straw digestibility and saccharification efficiency (Barrière et al., 2016; Choudhary et al., 2020; Pratikshya et al., 2025). The brown midrib (bm) mutation is valuable because it has low lignin content, making it useful for increasing straw utilization (Choudhary et al., 2020). Different maize varieties have very different cell wall compositions. Some local varieties or inbred lines have more cellulose and less lignin in their straw, which makes them better for biofuel production. For example, QPM straw has these characteristics, which also lead to higher saccharification efficiency and ethanol yield (Pratikshya et al., 2025). Scientists have discovered some key regions and genes through GWAS and QTL mapping that are related to cell wall formation and digestibility, such as transcription factors such as ZmMYB and ZmNAC, and some enzymes that control lignin synthesis (Barrière et al., 2016). 3.3 Biomass yield and harvest index Maize biomass includes both kernels and straw. The harvest index (HI) is the proportion of total biomass that becomes kernels. To make ethanol from straw, it’s important to increase overall biomass without reducing kernel yield. In temperate maize, over time, both kernel yield and straw have increased, but the harvest index hasn’t changed much (Lorenz et al., 2010). Different types of maize vary greatly in biomass and harvest index. Hybrids usually have higher yields and a higher HI, while local varieties tend to have a lower HI (Munaiz et al., 2021). Some local varieties from Europe actually produce more straw and have better fiber quality. Kernel and straw yields are usually positively related, and because these traits are highly heritable, it’s possible to improve both traits through phenotypic selection and genomic prediction (Lorenz et al., 2010; Munaiz et al., 2021; Gesteiro et al., 2023). 3.4 Traits related to drought tolerance and nutrient use efficiency Some traditional maize varieties grow well in low-fertilizer and low-water environments, producing high biomass and energy content (Serrano et al., 2014). These drought-tolerant traits are important for biofuels because they can reduce costs and environmental pressure. In order to improve drought resistance and nutrient utilization efficiency, breeding mainly focuses on finding gene loci that can enhance water and fertilizer absorption and stress resistance. The development of genomics and phenomics has helped discover these key genes and molecular markers (Choudhary et al., 2020).
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