Abstract
Maize biomass from agricultural residues can be a substrate for biofuel production. However, commercial breeding programs have focused on grain yield for food and feed, and whole plant yield and nutritive value for silage, with little attention paid directly to stover yield or composition. Enhancing the energy content of crop residues with higher quality cellulosic biomass for ethanol conversion should provide a complementary use to grain use. We also question whether there is maize germplasm predisposed to dual use as second-generation biofuel. Twenty genotypes, including landraces from Spain, Atlantic, and Mediterranean Europe and genotypes derived from Iowa stiff stalk synthetic, Lancaster, and commercial hybrids were studied in a randomized complete block design across environments in Galicia (Spain) in 2010 and 2011. Germplasm was evaluated for agronomic characteristics and fiber parameters. Results show high heritability for all characteristics and parameters, ranging from 0.81 to 0.98. Principal components analysis revealed clear differences among origin of the varieties studied. Hybrids had the highest grain yield values and B73xMo17 and PR34G13 had the highest grain yield overall, at 10133 and 9349 kg/ha, respectively. European landrace varieties had lower harvest indexes (HI) than the hybrid origin, with Faro and BSL having HI of 0.43–0.47, compared to hybrid PR34613 at 0.56. Fiber concentrations were significantly correlated with yield performance, with values ranging from 0.38 to 0.61 for cob fibers and between −0.14 to −0.57 for stover fibers. Fiber concentrations were significantly different, based on the origins, in cobs but not in stover, with the Atlantic European group showing a favorable trend for cob exploitation with low acid detergent lignin and high acid detergent fiber and neutral detergent fiber values. In summary, population origin showed a reservoir of genetic diversity for breeding to improve residue quality, suggesting that adaptation played a role for stover yield and quality. European landraces could be used in prebreeding programs with stover yield and fiber quality as target traits for dual-purpose maize.
Highlights
Fossil fuels are not renewable and contribute to the increment of CO2 concentration in the atmosphere
Elite maize varieties selected for grain yield may not be ideal for dual exploitation, as selection for grain may negatively affect some relevant characteristics for a dual purpose biofuel resource [23,39]
Our results showed that successful commercial maize breeding focused on grain yield [48], because the hybrids had higher grain yield than landraces, even though the later had higher grain moisture on average (Supplementary Table S2)
Summary
Fossil fuels are not renewable and contribute to the increment of CO2 concentration in the atmosphere. Biomass from agricultural residues could contribute to a sustainable or circular bioeconomy as a feedstock for bioenergy (biofeedstock) or high value bio-based products in integrated biorefineries [1,2]. The exploitation of residues could stimulate the economy in rural areas, which are being depopulated, by increasing the value of crops and by generating new jobs in biorefineries [5]. Local crop varieties have large genetic variability, which reduces the vulnerability to new stresses and could provide alleles to improve crop adaptation [6]. These local varieties can be a source of genes to increase adaptation to environmental change of elite germplasm [7] and contribute to a more sustainable agriculture. In low-input or organic farming, there is an interest in local varieties, whose seeds can be saved by farmers for the growing season, something that cannot be done with elite varieties, as for example maize hybrids, that must be purchased each growing season [8,9]
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