Breeding Maize for Food and Nutritional Security

Maize occupies an important position in the world economy, and serves as an important source of food and feed. Together with rice and wheat, it provides at least 30 percent of the food calories to more than 4.5 billion people in 94 developing countries. Maize production is constrained by a wide range of biotic and abiotic stresses that keep afflicting maize production and productivity causing serious yield losses which bring yield levels below the potential levels. New innovations and trends in the areas of genomics, bioinformatics, and phenomics are enabling breeders with innovative tools, resources and technologies to breed superior resilient cultivars having the ability to resist the vagaries of climate and insect pest attacks. Maize has high nutritional value but is deficient in two amino acids viz. Lysine and Tryptophan. The various micronutrients present in maize are not sufficient to meet the nutritive demands of consumers, however the development of maize hybrids and composites with modifying nutritive value have proven to be good to meet the demands of consumers. Quality protein maize (QPM) developed by breeders have higher concentrations of lysine and tryptophan as compared to normal maize. Genetic level improvement has resulted in significant genetic gain, leading to increase in maize yield mainly on farmer’s fields. Molecular tools when collaborated with conventional and traditional methodologies help in accelerating these improvement programs and are expected to enhance genetic gains and impact on marginal farmer’s field. Genomic tools enable genetic dissections of complex QTL traits and promote an understanding of the physiological basis of key agronomic and stress adaptive and resistance traits. Marker-aided selection and genome-wide selection schemes are being implemented to accelerate genetic gain relating to yield, resilience, and nutritional quality. Efforts are being done worldwide by plant breeders to develop hybrids and composites of maize with high nutritive value to feed the people in future.

Assay system for mesocotyl elongation and hydrotropism of maize primary root in response to low moisture gradient

We designed and validated a test system that simulates a growth environment for Zea mays L. maize seedlings under conditions of low moisture gradient in darkness. This system allowed us to simultaneously measure mesocotyl elongation and the primary root hydrotropic response in seedlings before the emergence phase in a collection of maize hybrids. We found great variation in these two traits with statistically significant reduction of their elongations under the low moisture gradient condition that indicate the richness of maize genetic diversity. Hence, the objective of designing a new test system that evaluates the association between these underground traits with the potential use to measure other traits in maize seedlings related to early vigor was achieved.

Heterosis and Heterotic Grouping among Tropical Maize Germplasm

Maize (Zea mays L.) is the most important staple cereal cultivated in sub-Saharan Africa but its productivity is considerable low due to several factors. Development and deployment of maize hybrids have been reported as one of the crucial options in achieving sustainable maize production in sub-Saharan Africa. Information on the heterotic response among available genetic materials in a breeding program is valuable before commencement of any hybrid development program. Unlike the temperate germplasm, maize tropical germplasm is characterized with wide genetic base and genetic complexities and thus, proper organization of the pools, populations, varieties and inbreds that can serve as parental materials for hybrid development through identification of a distinct heterotic groups and patterns among tropical germplasm becomes very essential. This paper reviewed past research efforts at characterizing heterotic response among tropical maize genetic materials with a view to point out merits and demerits in the methods used and future direction towards achieving sustainable hybrid cultivation and enhancing food security in the sub-region.

SILAGE PRODUCTION, BROMATOLOGICAL COMPOSITION AND ECONOMIC VIABILITY OF INOCULATION OF VARIETAL MAIZES WITH

In the western region of the State of Goias family farmers that depend onthe raising of livestock as one of their main sources of income are predominant. These farmers periodically grow maize for the production of silage in order to compensate their incomes. Considering the high cost of hybrid seeds and nitrogen fertilization, technologies that contribute to the reduction of silage production costs are required. In this sense, the objective of this study was to evaluate the response of maize genetic materials (Feroz Hybrid VIP3 and varieties SCS 156 and SCS 154), regarding silage production, bromatological composition and economic viability when inoculated with Azospirillum brasilense. The experiment was carried out on strips using a completely randomized design with four replications. Each cultivar responded differently to inoculation. For the Feroz hybrid and SCS 156 variety, the use of Azospirillum provided increases of 13.1% and 42.1% in green stem mass and 11.2 and 30.3% in silage nitrogen content, influencing the nutritional composition of the bulky food produced. For the SCS 154 variety, there was no response to inoculation. As for the economic viability, the use of inoculated SCS 156 variety presents a better rate of rentability, proving to be more economically attractive and viable to farmers.

Genome assembly of the maize inbred line A188 provides a new reference genome for functional genomics

Heretofore, little is known about the mechanism underlying the genotype-dependence of embryonic callus (EC) induction, which has severely inhibited the development of maize genetic engineering. Here, we report the genome sequence and annotation of a maize inbred line with high EC induction ratio, A188, which is assembled from single-molecule sequencing and optical genome mapping. We assembled a 2,210 Mb genome with a scaffold N50 size of 11.61 million bases (Mb), compared to those of 9.73 Mb for B73 and 10.2 Mb for Mo17. Comparative analysis revealed that ~30% of the predicted A188 genes had large structural variations to B73, Mo17 and W22 genomes, which caused considerable protein divergence and might lead to phenotypic variations between the four inbred lines. Combining our new A188 genome, previously reported QTLs and RNA sequencing data, we reveal 8 large structural variation genes and 4 differentially expressed genes playing potential roles in EC induction.

INOVATION AND SPECIALTY MAIZE BREEDING FOR MARKET NICHES IN THE STATE OF SÃO PAULO

Maize is one of the most harvested cereals on the planet. In Brazil, it is the country’s second largest grain production after soybean, with a large portion of production destined for animal feed. During the 2019/2020 harvest, 35% of total maize production was exported, 9.5% was destined for industrial processing and only 1.1% for human consumption. Specialty maize are those grains that are not destined for the dry grain commodities market, but have various other uses and are destined exclusively for human consumption. Specialty maize are also considered as an alternative profit source for farmers. From a plant breeding standpoint, maize is greatest example of success when it comes to the exploitation of heterosis and therefore most of the investment in genetic breeding done by private companies is in the development of simple GMO single-cross hybrids. In today’s market, there are rarely any specialty maize cultivars available, creating a niche for public funded research and development centers to exploit with their conventional type cultivars. This article discusses the relevance of the specialty maize market niches and the role of the Maize Genetic Breeding Program of Instituto Agronomico (IAC) in the development of innovations in São Paulo through the launch of conventional cultivars aimed at small and medium producers and niches of specialty maize.

YIELD POTENTIAL AND GENETIC VARIABILITY OF SEMIEXOTIC MAIZE POPULATIONS AS A BASIS FOR SELECTION

In order to verify the genetic and agronomic value, yield potential and inbreeding depression of synthesized composites, as well as quantifying the population variability and incorporating new sources of semiexotic germplasm in maize genetic improvement programs, four populations, identified as NAP-FA x HG-71 (P1), NAP-FL x HG-49 (P2), NAP-FB x HG-49 (P3), and NAP-DB x HG-49 (P4), with two levels of inbreeding (S0 and S1), were evaluated in three locations. From the P1 and P4 populations, 100 full-sib progenies were evaluated in only one location. Plant and ear height, lodging, breakage, ear length and diameter, resistance to diseases, ears with chalky kernels and grain yield were evaluated. The grain yield of the S0 and S1 populations varied between 5.50 and 6.65 t ha-1 and 3.8 and 4.58 t ha-1, respectively, with an average inbreeding depression between 23.9% and 38.0%. Considering all the locations, the grain yields of the non-inbreeding populations varied between 64.4% and 78.0% in relation to commercial hybrids (witnesses), indicating a good yield potential for start of improvement program. In the P1 and P4 populations, sufficient genetic variability was identified in most of the characters, which accredits them for recurrent selection. Gains of 13.7% and 17.8% for grain yield and 31.64% and 29.9% for ears with chalky kernels were estimated.