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14 pages, 1530 KiB

Open AccessEditor’s ChoiceArticle

Relationship between Delayed Leaf Senescence (Stay-Green) and Agronomic and Physiological Characters in Maize (Zea mays L.)

by Nadia Chibane, Marlon Caicedo, Susana Martinez, Purificación Marcet, Pedro Revilla and Bernardo Ordás

Agronomy 2021, 11(2), 276; https://doi.org/10.3390/agronomy11020276 - 02 Feb 2021

Cited by 13 | Viewed by 3096

Abstract

Stay-green (SG) is a term used to describe genotypes that have delayed leaf senescence as compared to reference genotypes. SG could be favorable for grain yield, silage yield and quality, double exploitation (grain for feed and stover for bioenergy), stress resistance, etc. However, [...] Read more.

Stay-green (SG) is a term used to describe genotypes that have delayed leaf senescence as compared to reference genotypes. SG could be favorable for grain yield, silage yield and quality, double exploitation (grain for feed and stover for bioenergy), stress resistance, etc. However, some studies show contradictory results regarding the influence of senescence or SG in the uptake and remobilization of nutrients and the yield and moisture of stover and grain. This experiment is aimed to study the impact of senescence in grain and stover yield and moisture in inbred lines of maize and assess the potential of SG genotypes for double exploitation. We also study the influence of senescence in the uptake of N and remobilization of dry matter and N from stover to grain. We evaluated 16 maize inbred lines with contrasting expression of senescence in the field at two locations in Galicia in 2017. We confirmed that SG is functional, meaning that the SG genotypes maintained photosynthesis activity for a lengthy period. Coordinated with a delayed senescence, the grain filling of the SG genotypes was 9 days longer than NSG genotypes. SG genotypes took up more N after flowering, although the remobilization of N and, in general, of dry matter from stover to kernels was less efficient. However, the higher uptake compensated the poor remobilization, and the final effect of SG on the N content of the kernels was favorable. SG was also favorable for kernel weight and the kernels of SG genotypes were 20% heavier than for NSG. The stover yield was also higher in the SG genotypes, indicating a potential of SG for breeding for double purpose (grain for feed and stover for bioenergy). Full article

(This article belongs to the Special Issue Maize Breeding for Alternative and Multiple Uses)

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19 pages, 1276 KiB

Open AccessArticle

Genetic Diversity for Dual Use Maize: Grain and Second-Generation Biofuel

by Eduardo D. Munaiz, Kenneth A. Albrecht and Bernardo Ordas

Agronomy 2021, 11(2), 230; https://doi.org/10.3390/agronomy11020230 - 27 Jan 2021

Cited by 3 | Viewed by 1830

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Maize Breeding for Alternative and Multiple Uses)

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13 pages, 1293 KiB

Open AccessArticle

Alternative Lime Pretreatment of Corn Stover for Second-Generation Bioethanol Production

by Iria Fírvida, Pablo G. del Río, Patricia Gullón, Beatriz Gullón, Gil Garrote and Aloia Romaní

Agronomy 2021, 11(1), 155; https://doi.org/10.3390/agronomy11010155 - 15 Jan 2021

Cited by 5 | Viewed by 2135

Abstract

In this work, a delignification process, using lime (Ca(OH)₂) as an alternative alkali, was evaluated to improve enzymatic saccharification of corn stover cellulose, with the final goal of obtaining second-generation bioethanol. For that, an experimental design was conducted in order to [...] Read more.

In this work, a delignification process, using lime (Ca(OH)₂) as an alternative alkali, was evaluated to improve enzymatic saccharification of corn stover cellulose, with the final goal of obtaining second-generation bioethanol. For that, an experimental design was conducted in order to assay the effect of temperature, lime loading, and time on the corn stover fractionation and enzymatic susceptibility of cellulose. Under conditions evaluated, lime pretreatment was selective for the recovery of cellulose (average of 91%) and xylan (average of 75.3%) in the solid phase. In addition, operating in mild conditions, a delignification up to 40% was also attained. On the other hand, a maximal cellulose-to-glucose conversion (CGC_MAX) of 89.5% was achieved using the solid, resulting from the treatment carried out at 90 °C for 5 h and lime loading of 0.4 g of Ca(OH)₂/g of corn stover. Finally, under selected conditions of pretreatment, 28.7 g/L (or 3.6% v/v) of bioethanol was produced (corresponding to 72.4% of ethanol conversion) by simultaneous saccharification and fermentation. Hence, the process, based on an alternative alkali proposed in this work, allowed the successful production of biofuel from the important and abundant agro-industrial residue of corn stover. Full article

(This article belongs to the Special Issue Maize Breeding for Alternative and Multiple Uses)

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18 pages, 6505 KiB

Open AccessArticle

A Global Screening Assay to Select for Maize Phenotypes with a High Tolerance or Resistance to Fusarium verticillioides (Sacc.) Nirenberg Rots

by Shamir Gabriel Román, Jesús Quiroz-Chávez, Miguel Villalobos, Vianey Urías-Gutiérrez, Eusebio Nava-Pérez, Eliel Ruíz-May, Rupesh Kumar Singh, Lav Sharma and Francisco Roberto Quiroz-Figueroa

Agronomy 2020, 10(12), 1990; https://doi.org/10.3390/agronomy10121990 - 18 Dec 2020

Cited by 3 | Viewed by 3299

Abstract

Fusarium verticillioides (Sacc.) Nirenberg (Fv) causes rots in maize around the world and produces mycotoxins that contaminate grains, making this species a significant health concern for both animals and humans. One of the best approaches to address rots is to identify [...] Read more.

Fusarium verticillioides (Sacc.) Nirenberg (Fv) causes rots in maize around the world and produces mycotoxins that contaminate grains, making this species a significant health concern for both animals and humans. One of the best approaches to address rots is to identify highly tolerant or resistant genotypes that can be used for genetic improvement. The aim of the study was to evaluate dose-response assays to tolerance or resistance for Fv rots throughout the maize life cycle. These tests assessed the effects of Fv during post-germination development and the seedling (V2) stage by seed infection, the plantlet (V4) stage by substrate infection, and in the reproductive phase in maize stalks (R2 stage) and ears (R6 stage) by R1 stage inoculation. In all assays, the doses were effective at distinguishing contrasting phenotypes. Severity, root fresh weight, and aerial length were the most informative parameters at the V2 and V4 stages. Evaluation of the stalk necrosis area between and within the internodes of susceptible genotypes revealed significant differences among doses, and a positive correlation between necrosis and conidia concentration was observed in internodes. Injecting eight million conidia in the ear was sufficient for selecting different phenotypes. A total of 85% of the genotypes conserved their same capacity to respond to Fv infection throughout the maize life cycle, so that screening at the early vegetative stage (e.g., V2) could be useful for distinguishing contrasting phenotypes in the reproductive stage. Implementing these screening assays in a maize breeding program could be valuable for classifying the degrees of resilience of maize germplasms to Fv rots. This global screening has the potential to be employed to select against other Fusarium species. Full article

(This article belongs to the Special Issue Maize Breeding for Alternative and Multiple Uses)

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16 pages, 2389 KiB

Open AccessArticle

A Whole-Slurry Fermentation Approach to High-Solid Loading for Bioethanol Production from Corn Stover

by Pablo G. del Río, Patricia Gullón, F.R. Rebelo, Aloia Romaní, Gil Garrote and Beatriz Gullón

Agronomy 2020, 10(11), 1790; https://doi.org/10.3390/agronomy10111790 - 15 Nov 2020

Cited by 18 | Viewed by 3266

Abstract

Corn stover is the most produced byproduct from maize worldwide. Since it is generated as a residue from maize harvesting, it is an inexpensive and interesting crop residue to be used as a feedstock. An ecologically friendly pretreatment such as autohydrolysis was selected [...] Read more.

Corn stover is the most produced byproduct from maize worldwide. Since it is generated as a residue from maize harvesting, it is an inexpensive and interesting crop residue to be used as a feedstock. An ecologically friendly pretreatment such as autohydrolysis was selected for the manufacture of second-generation bioethanol from corn stover via whole-slurry fermentation at high-solid loadings. Temperatures from 200 to 240 °C were set for the autohydrolysis process, and the solid and liquid phases were analyzed. Additionally, the enzymatic susceptibility of the solid phases was assessed to test the suitability of the pretreatment. Afterward, the production of bioethanol from autohydrolyzed corn stover was carried out, mixing the solid with different percentages of the autohydrolysis liquor (25%, 50%, 75%, and 100%) and water (0% of liquor), from a total whole slurry fermentation (saving energy and water in the liquid–solid separation and subsequent washing of the solid phase) to employing water as only liquid medium. In spite of the challenging scenario of using the liquor fraction as liquid phase in the fermentation, values between 32.2 and 41.9 g ethanol/L and ethanol conversions up to 80% were achieved. This work exhibits the feasibility of corn stover for the production of bioethanol via a whole-slurry fermentation process. Full article

(This article belongs to the Special Issue Maize Breeding for Alternative and Multiple Uses)

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14 pages, 4717 KiB

Open AccessArticle

22KD Zein Content Coordinates Transcriptional Activity during Starch Synthesis in Maize Endosperm

by Ada Menie Nelly Sandrine, Hailiang Zhao, Yao Qin, Qin Sun, Dianming Gong, Zhenyuan Pan and Fazhan Qiu

Agronomy 2020, 10(5), 624; https://doi.org/10.3390/agronomy10050624 - 28 Apr 2020

Cited by 6 | Viewed by 2393

Abstract

Starch, the main form of stored energy in plants, plays an important role in maize (Zea mays L.) kernel development. The Shrunken-2 (Sh2) gene encodes the large subunit of the rate-limiting starch biosynthetic enzyme ADP-glucose pyrophosphorylase (AGPase). The sh2 mutant [...] Read more.

Starch, the main form of stored energy in plants, plays an important role in maize (Zea mays L.) kernel development. The Shrunken-2 (Sh2) gene encodes the large subunit of the rate-limiting starch biosynthetic enzyme ADP-glucose pyrophosphorylase (AGPase). The sh2 mutant exhibits impaired AGPase activity, resulting in the partial or complete loss of starch synthesis. Here, we investigated the transcriptional regulatory framework of sh2 through transcriptome and co-expression network analysis using an F₂ population derived from the maize reference line B73 and sweet corn inbred line HZ508. We identified 5175 differentially expressed genes (DEGs), including 2878 upregulated and 2297 downregulated genes in sh2 mutant lines. DEGs are associated with various biological processes including nutrient reservoir activity, transferase activity, catalytic activity, water deprivation and glycogen metabolism. At the genetic level, 2465 DEGs, including 357 transcription factors, were involved in transcription. In addition, the maize floury and opaque mutant genes fl1, ndk2, o7 and o2, which regulate the biosynthesis of 22KD zein, were co-expressed with the differential expressed transcription factor genes, thus suggesting that zein content might be a key regulator coordinating the expression of genes determining starch accumulation in maize endosperm. Full article

(This article belongs to the Special Issue Maize Breeding for Alternative and Multiple Uses)

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Review

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49 pages, 598 KiB

Open AccessEditor’s ChoiceReview

Sweet Corn Research around the World 2015–2020

by Pedro Revilla, Calli M. Anibas and William F. Tracy

Agronomy 2021, 11(3), 534; https://doi.org/10.3390/agronomy11030534 - 12 Mar 2021

Cited by 53 | Viewed by 18757

Abstract

Modern sweet corn is distinguished from other vegetable corns by the presence of one or more recessive alleles within the maize endosperm starch synthesis pathway. This results in reduced starch content and increased sugar concentration when consumed fresh. Fresh sweet corn originated in [...] Read more.

Modern sweet corn is distinguished from other vegetable corns by the presence of one or more recessive alleles within the maize endosperm starch synthesis pathway. This results in reduced starch content and increased sugar concentration when consumed fresh. Fresh sweet corn originated in the USA and has since been introduced in countries around the World with increasing popularity as a favored vegetable choice. Several reviews have been published recently on endosperm genetics, breeding, and physiology that focus on the basic biology and uses in the US. However, new questions concerning sustainability, environmental care, and climate change, along with the introduction of sweet corn in other countries have produced a variety of new uses and research activities. This review is a summary of the sweet corn research published during the five years preceding 2021. Full article

(This article belongs to the Special Issue Maize Breeding for Alternative and Multiple Uses)

9 pages, 278 KiB

Open AccessReview

Maize Breeding in the Highlands of Ecuador, Peru, and Bolivia: A Review

by José Luis Zambrano, Carlos F. Yánez and Carlos A. Sangoquiza

Agronomy 2021, 11(2), 212; https://doi.org/10.3390/agronomy11020212 - 23 Jan 2021

Cited by 7 | Viewed by 3988

Abstract

Maize is one of the most important staple crops in the highlands of the Andean region of Ecuador, Peru, and Bolivia. Most seeds come from landraces, with their own kernel characteristics. The kernels are used for the elaboration of traditional dishes and other [...] Read more.

Maize is one of the most important staple crops in the highlands of the Andean region of Ecuador, Peru, and Bolivia. Most seeds come from landraces, with their own kernel characteristics. The kernels are used for the elaboration of traditional dishes and other elaborates for human consumption. In this region, maize breeding is conducted mainly by public institutions. In this review, we outline the methodology that has been used by the maize breeding programs (MBPs) of the National Institutes for Agricultural Research and other institutions in the highlands of Ecuador, Peru, and Bolivia during the last 20 years. The main objective of MBPs in the region has been to develop more uniform and productive open-pollinated varieties (OPVs) of floury maize (Zea mays L. var. Amylacea), which is the most important type of maize in the area. Participatory plant breeding, combined with half-sib, has been used to breed new maize varieties. At least 18 OPVs of floury maize have been released into the Andean region in the last 20 years. Breeding this type of maize has been very important to conserve diversity and promote consumption in the region, but they have had very little impact on yield. The yield of floury maize is around three times below that of dent or semident maize grown in the region. Therefore, there is a need to apply new breeding techniques in the region to accelerate the development of more productive floury-maize cultivars. Full article

(This article belongs to the Special Issue Maize Breeding for Alternative and Multiple Uses)

22 pages, 4685 KiB

Open AccessEditor’s ChoiceReview

Conservation and Use of Latin American Maize Diversity: Pillar of Nutrition Security and Cultural Heritage of Humanity

by Filippo Guzzon, Luis Walquer Arandia Rios, Galo Mario Caviedes Cepeda, Marcia Céspedes Polo, Alexander Chavez Cabrera, Jesús Muriel Figueroa, Alicia Elizabeth Medina Hoyos, Teófilo Wladimir Jara Calvo, Terence L. Molnar, Luis Alberto Narro León, Teodoro Patricio Narro León, Sergio Luis Mejía Kerguelén, José Gabriel Ospina Rojas, Gricelda Vázquez, Ricardo Ernesto Preciado-Ortiz, José Luis Zambrano, Natalia Palacios Rojas and Kevin V. Pixley

Agronomy 2021, 11(1), 172; https://doi.org/10.3390/agronomy11010172 - 18 Jan 2021

Cited by 45 | Viewed by 15797

Abstract

Latin America is the center of domestication and diversity of maize, the second most cultivated crop worldwide. In this region, maize landraces are fundamental for food security, livelihoods, and culture. Nevertheless, genetic erosion (i.e., the loss of genetic diversity and variation in a [...] Read more.

Latin America is the center of domestication and diversity of maize, the second most cultivated crop worldwide. In this region, maize landraces are fundamental for food security, livelihoods, and culture. Nevertheless, genetic erosion (i.e., the loss of genetic diversity and variation in a crop) threatens the continued cultivation and in situ conservation of landrace diversity that is crucial to climate change adaptation and diverse uses of maize. We provide an overview of maize diversity in Latin America before discussing factors associated with persistence of large in situ maize diversity, causes for maize landrace abandonment by farmers, and strategies to enhance the cultivation of landraces. Among other factors, maize diversity is linked with: (1) small-holder farming, (2) the production of traditional food products, (3) traditional cropping systems, (4) cultivation in marginal areas, and (5) retention of control over the production system by the farmers. On the other hand, genetic erosion is associated with substitution of landraces with hybrid varieties or cash crops, and partial (off-farm labor) or complete migration to urban areas. Continued cultivation, and therefore on-farm conservation of genetic diversity held in maize landraces, can be encouraged by creating or strengthening market opportunities that make the cultivation of landraces and open pollinated varieties (OPVs) more profitable for farmers, supporting breeding programs that prioritize improvement of landraces and their special traits, and increasing the access to quality germplasm of landraces and landrace-derived OPVs. Full article

(This article belongs to the Special Issue Maize Breeding for Alternative and Multiple Uses)

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