Maize Accessions Research Articles

Determination of the Best Performing Sri Lankan Maize Accessions Based on the Photosynthetic, Biomass and Yield Traits

Maize (Zea mays L.) is one of the most widely cultivated cereal crops throughout the world and is extensively grown in Sri Lanka. Information on the photosynthetic, biomass and grain yield of local maize accessions are useful for plant breeding programs. However, due to the scarcity of such information, this study aimed to investigate the potentials of maize accessions to select the best performers utilizing the rank summation and selection index criteria. As the first step, the seeds from 14 maize accessions along with two varieties viz; Pacific-999 and Bhadra (control) were established in the field. The leaf-level photosynthetic and chlorophyll fluorescence traits were analyzed, while biomass and yield traits were obtained at harvest, by employing standard techniques. Our findings revealed that traits related to growth, photosynthesis, and biomass showed greater variations among the maize accessions tested. The number of days taken to 50% flowering (44d-60d), photosynthetic rates (19.7-30.45 μmol CO2 m−2 s−1), transpiration rates (2.45-4.52 mmol H2O m−2 s−1), water use efficiency (5.69-8.13 μmol CO2 mmol H2O-1), and maximum quantum yield (0.68-0.73) among the tested accessions. Additionally, the variations in biomass (111.0-459 g/plant) and final cob yield (38-232 g/cob) were also seen among the maize accessions. According to rank summation index analysis, the maize accessions SEU2, SEU16, SEU15, SEU9 and SEU10 were superior in terms of photosynthetic rates, biomass and yield compared exhibiting with the lowest RSI values of 71, 100, 101, 103 and 117, respectively, than the cv. Bhadra. Therefore, future crop development programs can make use of these five potential maize accessions identified through this study.

Large scale sampling of Mexican maize landraces for the presence of transgenes.

The presence and levels of transgenic maize in Mexico and the effect this could have on local landraces or closely related species such as teosinte has been the subject of several previous reports, some showing contrasting results. Cultural, social and political factors all affect maize cultivation in Mexico and although since 1998 there has been a moratorium on the commercial cultivation of transgenic maize, Mexico imports maize, mainly from the USA where transgenic cultivars are widely grown. Additionally extensive migration between rural areas in Mexico and the USA and customs of seed exchange between farmers may also play an unintentional role in the establishment of transgenic seed. A comprehensive study of all Mexican maize landraces throughout the country is not feasible, however this report presents data based on analysis of 3204 maize accessions obtained from the central region of Mexico (where permits have never been authorized for cultivation of transgenic maize) and the northern region (where for a short period authorization for experimental plots was granted). The results of the study confirm that transgenes are present in all the geographical areas sampled and were more common in germplasm obtained in the northern region. However, there was no evidence that regions where field trials had been authorized showed higher levels of transgene presence or that the morphology of seed lots harboring transgenic material was significantly modified in favor of expected transgenic phenotypes.

Lifetime of Corn Seeds in Long-Term Storage in the National Genetic Bank of Albania

Genetic banks manage seed collections for the conservation and utilization of plant genetic resources. AGB implements standards for genebank management recommending a temperature of -18 ± 3°C for long-term storage of the base collection and 5-10°C for medium-term storage of the active collection.The germination energy of the 12 maize accessions taken in the study has relatively low initial values. The values of germination energy, even after 20 years of seed storage, do not deviate much from the initial data (from 2000) and from those from 2010 (10 years of seed storage). The germination data for the three years of testing are somewhat small in the initial testing. The average capacity germination for all 12 accessions under study in the 2010 test is 4.2% lower than the initial test (year 2000), so there is a decrease in capacity germination. Whereas in the testing of 2020, i.e. after storing the seed for 20 years in the genetic bank, there was a decrease in capacity germination on average of 2.9%; that is, there was less decrease in capacity germination in the second 10 years of storage compared to the first 10 years. The reduction in germination is not to the same degree between accessions. Four pairs of correlations were found, three between energy germination indicators and one among capacity germination. The correlation coefficients are positive and related to the age of the seed.

Nutritional properties of underutilized legumes and intercropped maize

Over the years, intercropping which is majorly carried out on legumes and cereal has been practiced to maximize the utilization of land resources and increase the productivity over a piece of land. Most studies on intercropping focus on the yield and yield parameters, leaving out other important aspects such as the nutritional value of the harvested crops. Underutilized legumes are crops which have very scanty information available on them which reduces their general acceptability and utilization. The effects of intercropping on the nutrient status of underutilized legumes and maize in an intercropping system are not well understood. Therefore, the objective of the research was to assess the effect of intercropping on the nutrient and antinutrient parameters of African Yam Bean (AYB), and Winged bean (WB) when monocropped and when intercropped with maize. Hence, this research sought to answer the following questions: (i) does intercropping with maize affect the nutrient and anti-nutrient properties of AYB and WB (ii) does intercropping with AYB and WB and the application of urea fertilizer affect the nutrient and anti-nutrient properties of maize. Five accessions each of AYB and WB were separately intercropped with two accessions of maize. The research was carried out on the research field of the International Institute of Tropical Agriculture, Ibadan, Nigeria. The field was laid out in a Randomized Complete Block Design in triplicates. The treatment consisted of sole and intercropped legumes and maize as well as maize planted with urea fertilizer. The result from the research revealed that intercropping had effects on the nutrient and anti-nutrient properties of AYB, WB and maize, even though each accession responded differently to the intercropping. For instance, in the legumes, intercropping with M2 led to a reduction in the moisture content of AYB accessions TSs4, TSs30, and TSs77, and an increase in the moisture content in winged bean accession Tpt51. Equally, a reduction in the protein content of African yam bean accessions TSs4 and 101 when intercropped with both maize accessions was observed (P ≤ 0.05). On the other hand, an increase was observed in the protein content of AYB accession TSs30 (intercropped with M2), as well as WB accession 15-4 (intercropped with M2) and Tpt51 (intercropped with M1). A reduced tannin content was observed in WB accession Tpt12 intercropped with both maize accessions, while an increased the tannin content was observed in AYB accessions TSs4, TSs101, and WB accessions 15-4, and Tpt32 when intercropped with both maize accessions (P ≤ 0.05). Finally, intercropping increased the fat content in both maize accessions, increased the tryptophan content of M1 when intercropped with Tpt32, and increased the carbohydrate content in M1 intercropped with Tpt51. In conclusion, the results from this experiment revealed that intercropping affected the nutritional and antinutritional properties of the maize and legumes. Of all the Accessions of the underutilized legumes used, AYB accession TSs30 responded better to intercropping by having a better nutritional value (an increased ash, protein, fat and carbohydrate contents as well as a reduced moisture content); it is therefore necessary to further explore this accession to ensure that the potentials embedded in itis maximally tapped into to enhance food security.

Scoring the number of B chromosomes in Zea mays L. using droplet digital PCR assay

BackgroundB chromosomes are classified as dispensable genomic components tolerated by cells, which are transmitted to progeny despite providing no benefit in most cases. They have been observed in over 2800 species of plants, animals and fungi, including numerous maize accessions. As maize is one of the most important crops worldwide, research on the maize B chromosome has been pioneering in the field. The characteristic of the B chromosome is its irregular inheritance. This results in offspring with a different number of B chromosomes compared to the parents. However, the exact number of B chromosomes in the studied plants is a crucial piece of information. Currently, assessing the number of B chromosomes in maize largely depends on cytogenetic analyses, which are laborious and time-consuming. We present an alternative approach based on the droplet digital PCR technique (ddPCR), which is faster, more efficient and provides the results within one day with the same level of accuracy.ResultsIn this study, we report a rapid and straightforward protocol for determining the number of B chromosomes in maize plants. We developed a droplet digital PCR assay using specific primers and a TaqMan probe for the B-chromosome-linked gene and a single-copy reference gene on maize chromosome 1. The performance of the assay was successfully verified by comparison with the results of cytogenetic analyses performed in parallel.ConclusionsThe protocol significantly improves the efficiency of B chromosome number assessment in maize compared to cytogenetic approaches. The assay has been developed to target conserved genomic regions and can therefore be applied to a wide range of diverged maize accessions. This universal approach can be modified for chromosome number detection in other species, not only for the B chromosome but also for any other chromosome in aneuploid constitution.

The Cluster of Local Maize Accessions Based on Seed Characteristics from North Sumatra

The Cluster of Local Maize Accessions Based on Seed Characteristics from North Sumatra

EVALUATION OF MAIZE ACCESSIONS FOR DROUGHT TOLERANCE THROUGH PRINCIPAL COMPONENT ANALYSIS

Drought is among the severe abiotic stresses that reduces crop yield. It greatly affects the growth and development at both vegetative and reproductive stages and the yield processes of crops. Maize is the third most important and widely distributed crop, suffering from drought stress, resulting in final kernel yield losses. The conduct of a screening experiment selected drought-sensitive and drought-tolerant maize accessions against water stress applied via calculating field capacity. This experiment used two treatments, T0 and T1 (T0 with 100% field capacity and T1 with 50% field capacity), in a completely randomized design (CRD) with a factorial arrangement and two replications at the wirehouse, Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, Pakistan. Recording data on seedling traits ensued. Drought-tolerant and drought-sensitive accessions’ selection resulted from principal component analysis, with a conclusion that the accessions H45C × H6B, H21 × H2B, H17 × H16, H23 × H21, H17 × H16A were drought tolerant, while H20 × H7C, H47A × H6C, and H9 × H21 were drought sensitive. This research will provide information in the future for comparing drought-sensitive and drought-tolerant accessions and help identify drought-tolerant maize accessions benefitting future breeding programs.

Will future maize improvement programs leverage the canopy light-interception, photosynthetic, and biomass capacities of traditional accessions?

Maize germplasm has greater latent potential to address the global food and feed crisis because of its high radiation, water and nutrient efficiencies. Photosynthetic and canopy architectural traits in maize are important in determining yield. The present study aimed to screen a subset of local maize accessions in Sri Lanka to evaluate their photosynthetic, biomass and yield related traits and to identify resource efficient germplasm. Experiments were carried out in the Ampara district of Sri Lanka. Eight maize accessions viz; SEU2, SEU6, SEU9, SEU10, SEU14, SEU15, SEU17 and SEU17 and two elite F1 cultivars (cv. Pacific-999 and cv. Bhadra) were analyzed under field conditions. Our results showed that maize genotypes produced a lower leaf area index (LAI) at the third and tenth week after field planting (WAP). However, the LAI was significantly increased in six WAP by Pacific-999, SEU2, SEU9, and SEU15. A similar trend was observed for percentage of light interception at three WAP (47%), six WAP (>64%), and decreased at 10 WAP. In addition, LAI maximum values were between 3.0 and 3.5, allowing 80% of the incident light to be intercepted by maize canopies. The estimated light extinction coefficient (k) remained lower (<0.5), suggesting that maize leaves are eractophilic canopies. Although fractional interception (f) varies, SEU2 and SEU9 had the highest values (0.57), and quantum yields of PSII (>0.73) in dark-adapted leaves. In addition, Pacific-999, SEU2, SEU9, and SEU17 had significantly higher rates of photosynthesis with minimal stomatal conductance and transpiration rates. As a result, they outperformed the control plants in terms of biomass, cob weight and grain yield. This suggests that native maize germplasm could be introduced as novel, less resource-intensive cultivars to sustain global food security.

Detection of pathogens to test seed health of some food crops in storage

The health condition of the seed, which is defined by the presence or absence of seed-borne microbes like fungi, bacteria, nematodes, or viruses, is one aspect that affects seed quality. The purpose of this study is to assess the health of some food crop seeds by looking for fungus and bacteria. The Pathogen Detection Laboratory, Division of Management of Genetic Resources (ICABIOGRAD), conducted this investigation in 2019. The Gen Bank collection and rejuvenation were the sources of the tested seeds. The use of moist blotter and agar procedures allowed for the detection of fungi and bacteria. 100 accessions of each of the following: rice, maize, soybeans, peanuts, sorghum, and cowpea had their seed health evaluated. Under a microscope, pathogens are observed growing, and their pathogenic properties are identified using the relevant literature. According to the findings, 12 maize accessions had fungal infections and 8 had bacterial infections. In peanuts, fungus and bacteria were found in 11 and 14 accessions, respectively. As opposed to 16 accessions of sorghum being infected with fungi and 18 accessions being infected with bacteria, nine accessions of soybeans had fungi and eleven accessions had bacteria. 18 accessions of the rice commodity had fungal infections, while 15 had bacterial infections. A total of 26 cowpea accessions had fungal infections, while 23 had bacterial infections. Even with relatively low infection rates (0–10%), fungus and bacterial infections on stored seeds are always present, with the exception of cowpea.

Embracing diversity: a genetic marker dataset with increased marker density facilitates association studies in maize

Embracing diversity: a genetic marker dataset with increased marker density facilitates association studies in maize

Syntenic Cell Wall QTLs as Versatile Breeding Tools: Intraspecific Allelic Variability and Predictability of Biomass Quality Loci in Target Plant Species

Syntenic cell wall QTLs (SQTLs) can identify genetic determinants of biomass traits in understudied species based on results from model crops. However, their effective use in plant breeding requires SQTLs to display intraspecific allelic variability and to predict causative loci in other populations/species than the ones used for SQTLs identification. In this study, genome assemblies from different accessions of Arabidopsis, rapeseed, tomato, rice, Brachypodium and maize were used to evaluate the intraspecific variability of SQTLs. In parallel, a genome-wide association study (GWAS) on cell wall quality traits was performed in miscanthus to verify the colocalization between GWAS loci and miscanthus SQTLs. Finally, an analogous approach was applied on a set of switchgrass cell wall QTLs retrieved from the literature. These analyses revealed large SQTLs intraspecific genetic variability, ranging from presence-absence gene variation to SNPs/INDELs and changes in coded proteins. Cell wall genes displaying gene dosage regulation, such as PAL and CAD, displayed presence-absence variation in Brachypodium and rapeseed, while protein INDELs were detected for the Brachypodium homologs of the rice brittle culm-like 8 locus, which may likely impact cell wall quality. Furthermore, SQTLs significantly colocalized with the miscanthus and switchgrass QTLs, with relevant cell wall genes being retained in colocalizing regions. Overall, SQTLs are useful tools to screen germplasm for relevant genes and alleles to improve biomass quality and can increase the efficiency of plant breeding in understudied biomass crops.

Characterization of Sri Lankan maize accessions using SSR markers associated with insect-resistant traits

Maize genetic diversity is utmost to develop new varieties conferred with favorable agronomic traits. Landraces are priceless resources that can serve to strengthen crop breeding programs. Hence, this study aimed to characterize 19 Sri Lankan maize landraces and one elite commercial variety Bhadra using SSR markers linked with insect-resistant traits. Using established procedures, genomic DNA extraction was done from immature maize leaves and PCR was performed utilizing bnlg1017, bnlg339, umc1021, umc1187, bnlg1346, bnlg1588, bnlg1556, umc1178, nc134, umc1688 and umc1045 primers. GenAlex and DARwin software were used for the data analysis. According to the results, a sum of 77 alleles was amplified with the maximum number of observed (13) and effective (11.28) alleles for bnlg1588. The highest gene diversity and PIC values were recorded in bnlg1588 (0.911 and 0.904 respectively), while the lowest was in umc1045 (0.640 and 0.581 respectively). Out of the total SSR primers used, bnlg1588, bnlg339, bnlg1346, and bnlg1017 linked with FAW-resistant traits were found to be more informative based on their genetic diversity parameters. The accessions SEU7, SEU11, SEU16, and SEU20 showed more genetic diversity compared to Bhadra, whereas SEU17 showed the lowest diversity. The dendrogram divided the 20 maize accessions into two main clusters with the mean similarity of 0.752. Similarly, the principle coordinate analysis explained 40.63 % of the genetic variation and grouped the maize accessions into two. Considering the genetic diversity parameters, the accessions SEU6 and SEU7 from cluster I and SEU9, SEU11, SEU16, and SEU20 from cluster II could be utilized for strategic maize breeding programs in Sri Lanka.

Exploring Genetic Diversity and Population Structure of Turkish Black Sea Region Maize (Zea mays L.) Germplasm using SSR Markers

Plant landraces are heterogeneous plant populations that have adapted to local environmental conditions and serve as a source of genetic variations that can be used for the breeding perspectives. Studies regarding genetic diversity assessment are very important as they provide an opportunity for the scientific community to investigate novel genetic variations for the genetic improvement of crops. Maize is one of the most important cereal crops and provides daily calories to millions of people all over the world. This study aimed to investigate the genetic diversity and population structure of 32 local maize genotypes collected from the Black Sea Region of Turkey using SSR markers. Molecular characterization was performed using the 14 most polymorphic primers that yielded a total of 42 bands. An average of 3 alleles per SSR primer was detected, and the number of alleles varied from 1 (phi022) to 6 (umc1571). The unweighted pair-group method with arithmetic means (UPGMA) clustering divided maize accessions into three main populations. According to Nei's genetic distances, DZ-M-145 (Corum) and DZ-M-20 (Trabzon) genotypes were the closest (0.03) genetically related populations, while DZ-M-68 (Artvin) and DZ-M-55 (Rize) were the most genetically distant (0.63) populations. The study identified molecular genetic diversity not mentioned for maize plants from the Black Sea. On this occasion, new opportunities have been created for hybrid maize products.

Genome‐wide association analysis of chilling‐tolerant germination in a new maize association mapping panel

AbstractMaize is a crop that is highly susceptible to the negative effects of low temperature. Low temperature can delay seed germination and cause a decrease in seed vigor, which seriously affects seedling emergence and yield. In this study, 190 maize accessions (inbred lines) with strong germination potential at normal temperature (25°C) were selected from more than 500 accessions to construct a new association mapping panel to further investigate germination under chilling stress (5°C). We re‐sequenced the genomes of the 190 diverse accessions and obtained 4,886,919 high‐quality SNPs. We then used this data to analyze population structure, perform principal components analysis, and construct a phylogenetic tree of the new maize panel. The relative germination rate (RGR) and relative germination index (RGI) are two traits that are significantly related to chilling‐tolerant germination. Genome‐wide association analysis showed that RGR and RGI shared a major QTL, and they also shared the top SNP. There were a total of 26 significant SNPs in common. These SNPs hit directly or indirectly within 37 candidate genes. Among these 37 gene candidates, eight are homologs of genes previously reported to be related to both germination and low‐temperature stress, and another 12 genes related to low‐temperature stress or other abiotic stresses such as drought, salinity, oxidative, and high light stress. In addition, RGR and RGI had another 15 and 26 significant SNPs, respectively, which were associated with 17 and 92 candidate genes, respectively. Further qRT‐PCR analysis using 26 chilling‐tolerant and 22 chilling‐sensitive accessions implied that Zm00001eb272370, Zm00001eb272390, and Zm00001eb272400 associated with the top SNP, may play different roles during cold‐germination. Thus, our study not only established a new association mapping panel suitable for investigation of germination at low temperature but also provided valuable genetic resources for future studies to improve chilling‐tolerant maize varieties.

English

Purple-grain maize is a marginal cereal grown exclusively and consumed in the Central-North of C&ocirc;te d&#39;Ivoire. However, few studies have been done on the diversity of this cultivar. Whereas, the use of local genetic resources available for breeding purposes requires a good knowledge of their agronomic and morphological characteristics. Thus, 70 accessions of purple-grain maize collected in the Hambol region were subject to an agro-morphological characterization study. The test was carried out in an alpha-lattice device (10 &times; 7) and repeated three times. The observations focus on 18 variables which have been selected in the maize descriptor proposed by Bioversity International. Descriptive analyses revealed a high inter-accession variability for quantitative traits. The multi varied analyses (principal component analysis (PCA) and a hierarchical cluster analysis (HCA)) made it possible to structure this diversity into two groups. The semi-flowering cycles (FlMa and FlFe), the heights of the plants (HaPl and HiEp) as well as the length of maize cobs (LoEp) were the main discriminating characters between the groups, because they could be used as estimators of phenotypic diversity for this plant. In addition, the accessions from each group could be brewed in order to develop different populations with broad genetic base. This will permit to enhance and to conserve diversity. Key words: C&ocirc;te d&rsquo;Ivoire, agro-morphological diversity, purple-grain maize, marginal.

Genetic Diversity and Population Structure of Normal Maize Germplasm Collected in South Sudan Revealed by SSR Markers.

Maize is one of the leading global cereals, and in South Sudan maize cultivation occurs in nearly all of the country’s agro-ecological zones. Despite its widespread cultivation, farmers in South Sudan depend on undeveloped varieties, which results in very low yields in the field. In the current study, 27 simple sequence repeat (SSR) markers were used to investigate genetic diversity and population structures among 37 landrace maize accessions collected from farmers’ fields in South Sudan. In total, 200 alleles were revealed with an average of 7.4 alleles per locus and a range from 3.0 to 13.0 alleles per locus. The observed heterozygosity values ranged from 0.06 to 0.91 with an average of 0.35. High polymorphic information content (PIC) values were identified with a mean of 0.69, which indicates the informativeness of the chosen SSR loci. Genetic structure analysis revealed a moderate genetic differentiation among the maize populations with a fixation index of 0.16, while there was very high genetic differentiation within the groups of populations of three regions with a mean fixation index (F) of 0.37. An unweighted pair group method with an arithmetic mean (UPGMA) dendrogram clustered the 37 maize accessions into three groups with 43% genetic similarity. The clustering pattern of the maize accessions was moderately consistent with their collection area. The findings of this study will provide maize breeders with a better understanding of maize diversification as well as a reserve of genetic resources for use in the selection of advantageous and useful resources for the development of maize varieties in South Sudan.

Nitrogen fixation and mucilage production on maize aerial roots is controlled by aerial root development and border cell functions.

Exploring natural diversity for biological nitrogen fixation in maize and its progenitors is a promising approach to reducing our dependence on synthetic fertilizer and enhancing the sustainability of our cropping systems. We have shown previously that maize accessions from the Sierra Mixe can support a nitrogen-fixing community in the mucilage produced by their abundant aerial roots and obtain a significant fraction of their nitrogen from the air through these associations. In this study, we demonstrate that mucilage production depends on root cap and border cells sensing water, as observed in underground roots. The diameter of aerial roots correlates with the volume of mucilage produced and the nitrogenase activity supported by each root. Young aerial roots produce more mucilage than older ones, probably due to their root cap’s integrity and their ability to produce border cells. Transcriptome analysis on aerial roots at two different growth stages before and after mucilage production confirmed the expression of genes involved in polysaccharide synthesis and degradation. Genes related to nitrogen uptake and assimilation were up-regulated upon water exposure. Altogether, our findings suggest that in addition to the number of nodes with aerial roots reported previously, the diameter of aerial roots and abundance of border cells, polysaccharide synthesis and degradation, and nitrogen uptake are critical factors to ensure efficient nitrogen fixation in maize aerial roots.

A Combination of a Genome-Wide Association Study and a Transcriptome Analysis Reveals circRNAs as New Regulators Involved in the Response to Salt Stress in Maize.

Salinization seriously threatens the normal growth of maize, especially at the seedling stage. Recent studies have demonstrated that circular RNAs (circRNAs) play vital roles in the regulation of plant stress resistance. Here, we performed a genome-wide association study (GWAS) on the survival rate of 300 maize accessions under a salt stress treatment. A total of 5 trait-associated SNPs and 86 candidate genes were obtained by the GWAS. We performed RNA sequencing for 28 transcriptome libraries derived from 2 maize lines with contrasting salt tolerance under normal and salt treatment conditions. A total of 1217 highly expressed circRNAs were identified, of which 371 were responsive to a salt treatment. Using PCR and Sanger sequencing, we verified the reliability of these differentially expressed circRNAs. An integration of the GWAS and RNA-Seq analyses uncovered two differentially expressed hub genes (Zm00001eb013650 and Zm00001eb198930), which were regulated by four circRNAs. Based on these results, we constructed a regulation model of circRNA/miRNA/mRNA that mediated salt stress tolerance in maize. By conducting hub gene-based association analyses, we detected a favorable haplotype in Zm00001eb198930, which was responsible for high salt tolerance. These results help to clarify the regulatory relationship between circRNAs and their target genes as well as to develop salt-tolerant lines for maize breeding.

Genetic diversity and environmental influence on morphological and yield parameters of maize in Benin

Seeds are the most important input in agricultural production and its quality seed determines the yield of the crop. They contribute to nearly 30% of crop productivity. The present study aims at surveying, collecting and characterizing maize accessions from the North, Centre and South Benin. Thirty-two (32) accessions were collected from 11 townships of Benin. Four experiments (Bassila, Glazoue, N'Dali and Adjohoun sites) were carried out to evaluate the agro-morphological characteristics of the collected 32 accessions. Eighteen (18) quantitative parameters were measured at each site. The accessions were classified into 3 groups by the hierarchical ascending classification showing a very important variability among cultivars with very highly significant (P < 0.001) or highly significant (P < 0.01) differences. The observed diversity among the different cultivars were based on plant height, growth life cycle, ear height, yield and yield components. The collection consisted of 18 intermediate-maturing cultivars showing big corn size with the ears inserted at a great height (Group 1), 8 late-maturing cultivars with the best vegetative and reproductive traits (Group 2) and 6 early-maturing cultivars with the best reproductive growth and best ear and grain yields (Group 3). The phenotypic variability of the cultivars was more related to their agronomic and morphological traits than their origin. These diverse groups of accessions could be used to develop improved maize varieties with high yield potential and adapted to different agro-climatic conditions.

Maize dispersal patterns associated with different types of endosperm and migration of indigenous groups in lowland South America.

The lowlands of South America appear to be remarkably important in the evolutionary history of maize, due to new evidence that suggests that maize dispersed from Mexico and arrived in this region in a state of partial domestication. This study aimed to identify dispersal patterns of maize genetic diversity in this part of the continent. A total of 170 maize accessions were characterized with 4398 single nucleotide polymorphisms (SNPs) and analysed to determine if maize dispersal was associated with types of endosperm and indigenous language families. Four genetic groups were identified in the discriminant analysis of principal components and five groups in the cluster analysis (neighbour-joining method). The groups were structured according to the predominance of endosperm types (popcorn, floury, flint/semi-flint). Spatial principal component analysis of genetic variation suggests different dispersal patterns for each endosperm type and can be associated with hypotheses of expansions of different indigenous groups. From a possible origin in Southwestern Amazonia, different maize dispersal routes emerged: (1) towards Northern Amazonia, which continued towards the Caatinga and south-eastern Atlantic Forest (Floury); (2) towards Southern Brazil, passing through the Cerrado and Southern Atlantic Forest reaching the Pampa region (Floury); and (3) along the Atlantic Coast, following Tupi movements originating from two separate expansions: one (Tupinamba) from north to south, and the other (Guarani) in the opposite direction, from south to north (flint, floury and popcorn).